The Evolution Of The Nobel Diesel Engine

(1898) Fig 1. The first Nobel Diesel Engin(e

(1903) Fig. 2. The first Marine Diesel Engine of the Motor Ship “ "Ssarmat".”

Fig. 3. Engine Room of Motor Ship “"Ssarmat"”

Nobel Diesel Fig 4

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Nobel Diesel Fig 10

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Nobel Diesel Fig 12

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Fig 20. 160 B.H.P. Nobel Diesel Engine of Submarine “Ssom”

Fig 21. 160 B.H.P. Nobel Diesel Engine of Submarine “Ssom”

Fig 22. Valve gear of 160 B.H.P Nobel Diesel Engine

Fig 23 120 B.H.P- Nobel Diesel Engine of Submarine “ Makrel.”

Fig 24. 120 B.H.P. Nobel Diesel Engine of Submarine “ Makrel.”

Nobel Diesel Fig 25

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Fig 30 The first Two-stroke Nobel Diesel Engine, 1903

Fig. 31. The first Reversible Two-stroke Engine, 1905.

Fig. 32. The first Reversible Two-stroke Engine, 1905.

Fig. 33. 350 B.H.P. Two-stroke Nobel Diesel Engine of Motor Yacht “Gradusichy”

Fig. 34. Valve Gear of 350 B.H.P. Two-stroke Nobel Diesel Engine.

Fig. 35. 450 B.H.P. Two-stroke Nobel Diesel Engine.

Fig. 36. 1360. B H P. Nobel Diesel Engine of Submarine “Kaguar”

Fig. 37 Arrangement of Machinery in Motorship “Imperatritza Alexandra"

Fig. 38. 600 B.H.P. Two-stroke Reversible Nobel Diesel Marine Engine.

Fig. 39. Air Compressor of 600 B.H.P, Two-stroke Nobel Diesel Marine Engine

Fig. 40. Scavenging pump of 600 G.H.P. Two-Stroke Nobel Diesel Marine Engine

Fig. 41. View showing relative position of Nobel Diesel Engines in Motorship “ Imperatritza Alexandra”

Fig. 42, 1600 B.H.P. Nobel Diesel Two-stroke Marine Engine.

Nobel Diesel Fig 43

Nobel Diesel

A key part of the Nobel system was diesel technology. In 1893, the German engineer Rudolf Diesel received a patent for the engine that would forever bear his name. He sold manufacturing licenses to companies in several countries, including Maskinfabrik Ludvig Nobel. The negotiations leading up to the deal were handled by Emanuel Nobel himself, “the cold Swede” as Rudolf Diesel called him.

The diesel engine was powered by fuel from Branobel’s own refineries. The engines powered the company’s tankers and power stations. Diesel engines were an important product for Maskinfabriken, which during the 1890s was the world’s largest diesel engine manufacturer. Advanced applications were also developed, such as portable diesel-powered power plants for the Russian army and diesel engines for the navy’s submarines.

After the revolution of 1917, the production of diesel engines ended up in Sweden. It was the only part of Nobel’s system that could be saved from the confiscation of all private property in Russia. In 1919, some of the brothers formed AB Nobel-Diesel in Nynäshamn. It was something of an attempt to re-establish what had only three years earlier been the engine department of Maskinfabriken Ludvig Nobel in St. Petersburg. One of the reasons for starting the company was to make use of the expertise of the many Swedes who had worked there but had been forced to flee the revolution.

One of the foremost diesel engine designers of the time was Anton Carlsund. He had been employed by the Nobel works in St. Petersburg and was personally acquainted with Emanuel Nobel. Carlsund lived in Sweden in 1919 and was employed as director of Nobel-Diesel. He is the one standing next to the first finished engine in Nobel-Diesel's workshop, a 1,600-horsepower reversible two-stroke diesel. The engine was one of the world's largest diesel engines in 1921, but it is still only a fragment of Nobel's enormous system.

The company AB Nobel-Diesel could not survive on its own, and was liquidated in 1926.

The Evolution of The Nobel Diesel Engine

By Baron George J. Steinheil, B.Sc., M.I.N.A., M.I.Mech.E, M.I.A.E. (Member).

READ Tuesday, November 14, at 6.30 p.m.

Chairman: Mr. P.B. Fielden (Vice-Chairman of Council).

From a publication from 1922 from Institute of Marine Engineers.

In July, 1897, Dr. Rudolf Diesel, of Munich produced in conjunction with the Maschinenfabrik Augsburg the first engine bearing his name.

The experimental work to produce a commercially possible engine from the original design took about eight years to accomplish, but by July, 1897, according to Dr. Diesel’s statement, the experimental stage was finished and drawings of the engine were sent to the drawing office of the Augsburg works, in order to start manufacture on a commercial scale.

There was a considerable amount of controversy in this country as well as in Germany, whether the Diesel engine was actually Dr. Diesel’s invention or not, and whether it should be called by any rival name or simply a “ high compression oil engine.”

It is not the subject of this paper to discuss the vexed question, as to do this, references would have to be made to patents, to transactions of various technical societies in this country and on the Continent, etc.

However, it is enough to say that the engine developed by Dr. Diesel bears in everyday engineering life his name, and therefore the author proposes to call it by such in the paper. As soon as the first commercially practical engine was ready, representatives of various engineering concerns came to Germany to witness the tests of that engine with a view of obtaining the manufacturing licences for that type of engine for their respective works.

Among those who saw the tests of this first engine was Mr. Anton Carlsund, at the time chief engineer of L. Nobel, Ltd., of Petrograd.

He immediately appreciated the great possibilities of the new prime mover, especially from the Russian point of view, as in Russia the natural oil supplies were very great and incidentally practically the whole of these were controlled by Nobel interests. On his return to Russia he persuaded Mr. Emanuel Nobel, the head of the Nobel concern to acquire a licence for Diesel engines for Russia.

In autumn 1897 all licence arrangements were completed and Nobels proceeded at once to build their first Diesel engine.

All this happened 25 years ago.

Thus the Nobel Works were among the very first firms in the world to take up Diesel engine manufacture, and among other pioneer firms may be mentioned such well-known concerns as Mirrlees, Watson, Co., Ltd., of Glasgow, now better known as Mirrlees, Bickerton and Day, Ltd., of Stockport; Maschinenfabrik Augsburg A.G.; Fr. Krupp, Germania Werft, Kiel; Carels fréres, Ghent; Sulzer Bros., Winterthur, and others. It must, however, be admitted that the German Diesel engine of 1897 was found to be in many details quite unsuitable for Russian conditions, and the Nobels had the heavy task of re-designing the engine to suit these local conditions. Of the most important alterations were those of the fuel pump and pulveriser. The German engine was designed to work on paraffin, but the abundance of cheap raw naphtha (crude oil) in Russia, made it necessary to make the Russian engine to work on that fuel, and therefore the fuel pump and pulveriser had to be altered accordingly.

In general outline, however, the Nobel engine followed closely the German design which was of the single cylinder stationary crosshead four-stroke cycle type, developing 20 b.h.p. at 200 r.p.m.. The cylinder dimensions of the engine were:-— Diameter 260 m/. and stroke 410 mm. Fig. 1).

Tests carried out on this engine by Professor G. Doepp, of Petrograd Institute of Technology, in 1899, showed that the engine easily developed as much as 25 b.h.p. at a fuel consumption (crude oil) of 220 grams (0,486 lbs.) per b.h.p. hour with a colourless exhaust. In 1900 a new type of 30 b.h.p. per cylinder crosshead engine was put on the market, built in one and two cylinders per shaft.

The first customers for Nobel engines were the Nobel Bros. Petroleum Production Co., and the Russian War Office, while the general public and even the majority of engineers of the time looked upon the new engine with considerable suspicion. Several engines were put in the Nobel Oil Refinery at Baku in 1900.

The management of the Caucasian Railways, who were then busy building the great pipe-line from Baku, on the Caspian Sea to Batum on the Black Sea, a distance of about 500 miles, for the conveyance of paraffin (kerosene), decided to install Diesel engines in their pumping stations on the pipe-line. Their decision was influenced by the great economy of a Diesel plant and also by the lack of suitable feed water for boilers of steam engines in the Baku district. The first pumping station at Baku was to be of three pumping sets of 100 b.h.p. each. If steam engines were to be installed the fuel oil consumption per station per annum (4,000 working hours) would have been about 650 tons, assuming 1,1 lbs. of oil per h.p. hour, whereas a Diesel plant of the same power would consume about half of that amount.

Owing to the lack of fresh water supplies in Baku, the question of cooling of Diesel engine cylinders presented certain difficulties, but eventually it was decided to use the cooling water in a closed circuit, the outlet water entering a special watercooler, from which it was pumped again into the water jackets of Diesel engines. The cooling medium for the circulating water was the paraffin, which was pumped by the engines through the pipe line, the cooler having been connected for the purpose with the main pipe. In the semi-tropical climate of Caucasia this arrangement was considered more efficient than ordinary cooling towers. A new type of Diesel engine was designed for the purpose of developing 100 b.h.p. in two cylinders. The crosshead was abolished and ordinary trunk pistons were used. Three such sets were installed at Baku pumping station in 1902, and gradually all the other pumping stations on the pipe line were lniilt and fitted with Diesel engines. By 1903 ten different sizes of Diesel engines were already marketed by Nobels in powers ranging from 10 to 100 b.h.p. per cylinder.

The 10 b.h.p. single cylinder stationary engine was specially brought out to meet the demands of farmers and small power users. Another interesting instalation of three sets of single cylinder trunk piston engines of 75 b.h.p. each was made in 1902 at the Tenteleff Chemical Works, of Petrograd. These engines were driving air compressors supplying air for the manufacture of sulphuric acid, and the nature of the work demanded continuous working of several davs’ running. To prevent excessive corrosion all exposed bright parts of the engines were coated with paint. It is quite possible that in future, rustless steel will be used by Diesel engine makers for this kind of work. In those early davs it was rather difficult to get Diesel engines t- I t o cv built on a manufacturing basis, as practically even* engine made was an improvement on the previous one. On the original 20 b.h.p. Diesel engine the injection air was sucked from the atmosphere and compressed to full blast pressure of 50-60 atm. (700-850 lbs. per sq. inch) in a single stage air compressor direct driven by a rocking lever from the engine.

This design gave fairly satisfactory results so long as the power output did not exceed 30-40 b.h.p. per cylinder, but when higher-powered engines were produced, considerable difficulties were experienced with this type of compressor. The volume of air to be compressed was so large, that the coolers could not cool the air well enough and not infrequently explosions occurred in the cooler coils and air supply pipes, due to ignition of oil present in the air. To overcome this defect it was suggested bv Dr. Diesel to make the compression of blast air in two stages, by by-passing the cylinder air during the compression period from the cylinder to the air compressor proper, where it was to be compressed to the blast pressure. The air from the cylinder was by-passed at a pressure of about 10 atm. (142 lbs. per square in.) into the air compressor by way of an intermediate cooler.

Thus the air compressor had to compress comparatively cool air from 10 atm. to 50 atm., instead of from 1 to 50 atm. This arrangement, though it partially did away with the danger of explosion, introduced drawbacks of its own, in the shape of particles of dirt and carbon deposit, which were carried by the by-passing air into the compressor cylinder, often causing seizure of compressor pistons. Dr. Diesel, Professor Mayer, and the German makers, were greatly in favour of the by-pass arrangement, considering it a great improvement over the single stage compression in spite of its drawbacks, which they said were purely accidental. The Nobel engineers were, however, of a different opinion, which was based on the difficulties experienced with both systems of air compression. With the trunk piston type of engines they introduced the two-stage compound air compression proper, in which the air was compressed in two separate air compressors, driven by links from the engine. In the case of multi-cylinder engines, the L.P. and H.P. air compressors were separate units, but in single cylinder engines the air compressors formed one unit and the two connecting rods were driven by a common link.

The atmospheric air entered the L.P. stage compressor and was then compressed to 7 atm. (100 lbs. per square in.) then, after passing through a cooler, it entered the H.P. stage cylinder and was compressed from 7 atm. to 50-60 atm. (700-850 lbs. per square in.). Eventually on large stationary engines a three-stage compression was introduced, the compressors being all separate units, driven by links. The German Augsburg Works, soon after Nobels, also dropped the by-pass compression and introduced two-stage, air compressors of the tandem type. As already mentioned, considerable prejudice existed among prospective customers- against Diesel engines. They were afraid of the high pressures used, and of occasional breakdowns and accidents, which were in most cases due to the inexperience of attendants. However, after some time, confidence was established, and the demand for Diesel engines in Russia became so great that the Nobel Works could not cope with the orders. Arrangements were accordingly made in the autumn of 1903 for the Kolomna Works in Golutwin to take up the manufacture of four-stroke Diesel engines under licence from Nobels, the Kolomna Works, securing, to begin with, a part of the contract for pumping sets on the Baku-Batum pipe-line.

The majority of orders for Diesel engines about that time were for engines suitable for belt drive of workshops, flour mills, textile mills, and small power stations for lighting purposes, etc. The electrical engineers were at the time of the opinion that a Diesel engine could not be made to run with enough cyclic regularity to be able to drive a dynamo direct coupled to the crankshaft, and especially a direct driven alternator running in parallel with engines of other types and speed (gas, steam, water turbines, etc). To prove the fallacy of that idea, the Nobel Works installed in the power station of the Petrograd Institute of Electrical Engineers in 1905 an 80 b.h.p. twin-cylinder Diesel engine direct coupled to a D.C. dynamo, which supplied current, in parallel with steam driven dynamos, for the lighting of the premises as well as driving of various electro-motors in the laboratories and buildings. In the same year later a 400 b.h.p. three-cylinder engine direct coupled to an alternator was installed in the power house of the Perm Ordnance Works in the Ural district, and this alternator was run in parallel with an alternator driven by a steam engine. After that successful experiment the demand for high power stationary engines became very great and most of the principal provincial towns in Russia, as well as various works and shipyards, put direct-driven Diesel generators into their power houses. The largest type of four-stroke stationary engine built by Nobels was that of 200 b.h.p. per cylinder at 150 r.p.m

The cylinder dimensions of that engine were: Diameter 600 m/m. and stroke 800 m/m. Three and four-cylinder sets of this size were built, developing 600 and 800 b.h.p. respectively. Two such 600 b.h.p. engines were installed in the steel rolling plant of Moscow Metal Works, Ltd., in 1907, one of these engines being direct coupled to the mills. Such work put very heavy stresses on the engine, as it had to work at a constantly variable load from practically 10% load to overload and vice versa. The fact that this engine has done this work already for fifteen years, only proves the reliability of the modern Diesel engine. Another interesting installation of an 800 b.h.p. engine was at the Tzaritzin Flour Mills. The engine was a four-cylinder set with a heavy flywheel pulley between the second and the third cylinders. The pulley was arranged for rope drive. The crankshaft was so designed that either pair of the cylinders could be uncoupled from the flywheel, the engine working then on two cylinders at lialf-power. The reason for such an arrangement was the doubt of the owners in the reliability of the Diesel engine, they preferring to have at least half the power than nothing at all in case of breakdown. It must be remembered that even a short stoppage of machinery in a flour mill entails considerable inconvenience and even loss to the millers, as most of the grain and flour in the middle of the process must he sent again from the start, and therefore the attitude of the Tzaritzin Mill owners was understandable, as to them at the time a Diesel engine installation was quite a novelty. However, it must be said to the credit of the builders of the engine that there never was an occasion to run the engine on two cylinders. Although the building of stationary Diesel engines formed a considerable branch of the Nobel Diesel business, it was for the designing and building of marine Diesel engines that Nobels spent most of their energies, and therefore the author will proceed to the description of a few interesting types of marine engines.

Four-Stroke Nobel-Diesel Marine Engines.

Not counting a small 20 b.h.p. French Diesel engine fitted into a small canal barge in France, it is to Nobels that belongs the credit of having built in 1903 the first marine Diesel engine and in which the speed could be varied by hand. That engine was a four-cylinder one of “A” frame trunk piston type and developed 180 b.h.p. at 240 r.p.m. The cylinder dimensions were: Diameter 320 m/m. and stroke 420 m/m. The outside view of the engine is shown in Fig. 2. Two such engines were fitted in 1904 into the motor-tank-ship "Ssarmat", of the Nobel Bros. Petroleum Co.

The ""Ssarmat"" was a ship of 800 tons D.W. capacity and therefore of very humble dimensions as compared with present-day tankers of 15,000 tons. Her hull dimensions were: length B-P 244ft. 6 in., breadth md. 31 ft. 9in., and draught fully loaded 6 ft. She was built at the Ssormovo Shipyard, on the River Volga, and was suitable for both river and sea navigation. The engines were non-reversible and the necessary astern motion of the propeller shaft was obtained on the Del-Proposto system. That system consisted of a dynamo direct coupled to the engine crankshaft and an electromotor coupled to the propeller shaft, between those two was interposed a friction clutch. For ordinary ahead running the clutch was coupled in and the propeller was direct driven by the engine. The dynamo and electromotor were not working, but rotating simply as additional flywheels and the speed of the ship was regulated by the speed of the engine.

For astern running the clutch was released, current switched on and the electromotor turned the propeller shaft in a direction opposite to that of the engine (Fig. 3). The engine was run at constant speed, whereas the electromotor could be run at variable speed, thus regulating the speed of the ship. The "Ssarmat" has been in commission for nineteen years, having- still the original engines (Fig. 4). A sister ship to the "Ssarmat", named Vandal, was built at the Ssormovo yard a year before the former, and was also fitted with four-stroke Diesel engines, but of the ordinary stationary type, the propeller shaft drive being purely Diesel-electric. These engines had direct coupled dynamos, which supplied current to electromotors on the propeller shafts. Three of such three cylinder engines, built by the works now owned by the New Atlas-Diesel Co., of Stockholm, were fitted into the Vandal.

The cylinder dimensions were: diameter 290 mm and stroke 430 mm., each engine developing 120 b.h.p. at 240 r.p.m. The "Vandal" and the "Ssarmat" were actually the two first motorships in the world, and, although comparatively little publicity was given as to their performance, it must be said that they played a very important part in the development of motor-shipbuilding in Russia.

The fact that the two motorships in those days could maintain a regular service for single voyages of over 3,000 miles long, year in and year out, carrying petroleum in bulk, set many Russian shipowners thinking, and the performance of these two ships was closely watched.

The behaviour of these two ships in service was so satisfactory that the Nobel Bros. Petroleum Production Company had decided then to convert the whole of their steam fleet into motor ships.

Such a conversion was probably the biggest one ever yet undertaken, as the tonnage of the fleet was over 650,000 tons D.W., and some of the tankers were of 10,000 tons D.W. capacity.

The programme was arranged for the gradual conversion of ships, starting with tugs and the smaller tankers first.

As the conversion could not be accomplished by the Nobel Works alone, because they were very busy with naval orders, part of the conversion work was given over to the Kolomna Works in Golutwin, who were Nobels’ licensees.

These two firms supplied the bulk of the engines for the fleet, but a few ships were fitted with engines purchased abroad.

In many cases quite good triple expansion steam engines had been removed and replaced by Diesels.

It was expected that by 1924 the conversion would have been completed, but unfortunately the outbreak of the war in 1914 and of the Russian revolution in 1917, completely upset the programme, as in 1918 the Bolsheviks had “nationalised ” the Nobel fleet, with the result that only a comparatively small number of old tankers are running at present.

It is of interest to note however, that of the two first marine Diesel installations, that of the "Ssarmat" with Del-Proposto drive, proved to be more reliable and economical than that of the "Vandal", which had a Diesel electric drive.

The "Vandal" was broken up in 1913.

The replacement of steam machinery in paddle tugs by Diesels required a considerable amount of ingenuity, as the speed of the paddles was so much below the slowest normal speed of Diesel engines and it naturally required the adoption of some sort of reduction gear.

It was out of the question, of course, to put slow speed land type engines, as they were much too heavy and cumbersome for the weak hulls of the river tugs. A special type of high-speed light multi-cylinder direct reversible engine had to be designed for the purpose.

In 1907 such an engine was already on the test bed at the Nobel Works and it developed 120 b.h.p. in three cylinders at 400 r.p.m. The cylinder dimensions were: diameter 275 m/m. and stroke 300 m/m. (Fig. 5).

It was of the enclosed crankcase type with a two-stage air compressor at the side of the engine, driven by rocking levers. This engine was the first direct reversible four-stroke Diesel engine ever built in the world.

Reversing was performed through the shifting of cams by means of forks fitted to a layshaft and actuated by the hand-wheel seen in Fig. 5 near the top of the vertical shaft.

Each cylinder had two sets of cams, and to allow for their shifting, the rocking levers of the valves had to be pressed down by means of the long hand lever seen on the top of the engine, so as to lift the rollers clear of the cams. This type of reverse gear is known as Carlsund’s gear.

The manoeuvring lever is seen near the middle of the vertical shaft, and it actuated the lower layshaft, which in its turn threw the starting and fuel valves in and out of gear when necessary.

The manoeuvring lever could he rotated round a dial.

The position of that lever shown in Fig. 5 is the “ Stop ” position, when the fuel and starting valves are out of gear. Two-stroke starting was provided, i.e., admission of starting air was on every downward stroke, as otherwise with a three-cylinder four-stroke engine at certain crank positions no starting valve may he open.

Turning the manoeuvring lever clockwise, there came the first “ Start” position, when the three cylinders were working on air, then came the second “ Start ” position, when the first cylinder was on fuel, and the other two on air, then the third “ Start ” position, when two cylinders were on fuel and the third on air and finally came the “Work” position when all the three cylinders were working on fuel.

This type of starting gear was the invention of Mr. Nordstroem, of Nobels (Nordstroem’s patent, Sweden, 1907). The fuel regulation could be performed in two ways, firstly by a small hand-wheel at the lower end of the vertical shaft, which could vary the tension of springs of the centrifugal governor and secondly by a small hand lever, which controlled the lift of the suction valves of the fuel pumps.

The lubrication of the engine was of three kinds: forced for cylinders and air compressors, by means of a mechanical lubricator and gravity for main bearings, which were watercooled, whereas the crankpins had banjo ring lubrication.

Two of such engines were installed in the Russian submarine "Minoga", in 1908, and it may be stated that the above submarine, though comparatively ancient as submarines go, did very good work during the great war. A number of these engines were built for naval purposes as well as merchant marine, and, in the non-reversible design as lighting sets in ships and as stand-by engines in power stations.

In Table I. are given results of official 120 hour trials carried out by Professor N. Bykoff, of Petrograd Institute of Technology upon “Minoga” engines in 1908. This type of engine, however, was too small and of too high a speed to work satisfactorily in the paddle tugs, and therefore a more powerful engine of similar design was brought out in 1908.

The design of that new engine was later standardised, and it was produced in three, four and six cylinder models. Besides river paddle tugs, that engine was fitted in 1909 into the Russian submarine "Akula" (three four-cylinder sets of 300 b.h.p. each at 3T5 r.p.m.) That engine in general appearance was similar to the “Minoga” engines, with the exception that in some of the later engines tandem air compressors were direct driven from the forward end of the crankshaft.

The reverse gear in that type of engine was simplified—the shifting of cams having been performed by a hand lever that actuated the layshaft, instead of by the handwheel as was on the “Minoga” engines.

On the later engines of the “Minoga” type the reverse gear was also altered to hand lever cam shifting and a tandem air compressor was fitted at the forward end of the crankshaft.

The paddle tugs had their engines placed transversely, i.e., parallel to the paddle shafts. In the case of larger tugs two direct reversible engines were fitted, driving the shafts through electro-magnetic clutches. The Nobel Bros, motor tug "Ssamoyed", was a typical example of this class of river tugs. She was built in 1909 for service on the upper reaches of the River Volga and Northern Canal system for the towing of oil barges. The hull dimensions were: length B-P. 132ft. 9ins., breadth md. 19ft., depth md. 8ft. 3ins., draught 3ft. 3ins., D.W. capacity 10 tons, and Cargo towing capacity 3,200 tons. She had two three-cylinder reversible four-stroke engines, developing each 140 b.h.p. at 260 r.p.m., whereas the paddles turned at 35 r.p.m.

The paddle shafts were separate, each engine driving through an electric-magnetic clutch one paddle only, which considerably added to the manoeuvring qualities of the tug. The necessary speed reduction was obtained through herringbone gears of the Citroen type (Fig. 6).

The cylinder dimensions of these engines were : diameter 330 mm and stroke 380 mm. Motor tug "Lesgin", built in 1910 for the same owners, had two four cylinder engines of the above type developing 200 b.h.p. each, as the size of the boat was larger (90 tons D.W., 4,800 tons tow L. 175ft., B. 27ft., 1). 8ft. and draught 2ft. 4ins.).

The drive from the engines to the paddle shafts was through Dohmen-Leblanc clutches and Citroen gears (Fig. 7).

Motor tug "Ossetin" (Fig. 8) of slightly smaller dimensions than the "Lesgin", was fitted also with two four-cylinder 200 b.h.p. engines, but these were placed longitudinally side by side, driving through Dohmen-Leblanc clutches two propeller shafts (Fig. 9).

The speed of the engines was 270 r.p.m. These two larger sized tugs and their sister ships were used for towing purposes on the lower reaches of the Volga. The first motor tug on the Volga was the "Belomor", built in 1908. She was smaller than the above-mentioned tugs, her dimensions being: eight tons D.W. capacity, 1,600 tons tow, L. 110ft. 6in., B. 17ft., D. 8ft., draught 3ft. 3ins.

Only one reversible three-cylinder engine of 140 b.h.p. was fitted, driving a paddle shaft common to both paddles through an electric-magnetic clutch and Citroen gears.

This arrangement of solid paddle shaft had the drawback that both paddles could only be turned in one direction at a time and therefore for the turning of the ship only the rudder was available. In 1911-1912 three slightly larger single engine paddle tugs were built for the service on the Vistula in Poland.

They were called the "Mazur", "Polia", and "Madjar" (Fig. 10). They were captured by the Germans during the war and used by them for army purposes, upon the signing of the Versailles peace treaty these tugs were returned to their rightful owners, and are now in service again.

In Fig. 11 is shown the engine of motor tug "Mazur".

It is interesting to note, as a special proof of the economy of the motorship, that the Nobel Bros. Petroleum Production Company found it cheaper to carry their oil from Baku on the Caspian Sea to Warsaw on the Vistula, via Astrakhan, Volga, Northern Canal System, Neva, Petrograd, Finnish Gulf, and the Baltic Sea into Vistula, a total distance of 3,200 miles, instead of using railways, the distance in the latter case being only 1,900 miles.

Considerable amount of trouble was experienced at the beginning with the above mentioned Citroen type of gear drive, the fault having been not with the gears themselves, but with the design of the arrangement of machinery in the ship.

The hulls and engine foundations of river paddle tugs and boats in general, were made very light as the water surface was usually smooth and the inertia forces of slow speed (25-40 r.p.m.) horizontal paddle steam engines were quite negligible.

With the adoption of Diesel propulsion the conditions become quite altered, as the comparatively high speed vertical Diesel engine with its heavy pistons and connecting rods was likely to set up considerable vibrations in the foundations and in the hull, especially if the inertia forces were not properly balanced and the period of engine vibrations synchronised with that of the hull.

Such vibrations were likely to cause deformations in the hull structure, so that the gears could get out of alignment, sometimes with disastrous results.

The author remembers having seen a breakdown of such gears in one of the earlier tugs, due to the abovementioned cause, when the teeth of the large wheel were stripped clean off.

This difficulty was eventually overcome by a suitable design of the hull and strengthened engine foundations, combined with a better system of balancing of engines.

It is not the intention of the author to go into the question of engine balancing and hull vibrations in this paper, as the subject is too important and voluminous, and it could easily form a paper by itself.

During the Russo-Japanese war of 1904-1905 the water communications of the Russian armies in the Far East were very much hampered by bands of lawless Khunghuses, who attacked defenceless tugs and barges on the River Amour, causing considerable delays in the delivery of supplies and munitions.

In order to bring these brigands to book the Russian Government commandeered several river steamers and converted them into some sort of river gunboats, by arming them with small naval guns and machins guns.

These boats helped a lot to stop looting, and even policed the river after the conclusion of war in peace time. But as these boats had log-fired boilers and only a limited supply of wood could be taken on board at a time, it was decided in 190G to build eight new river monitors, armed with two 6 in. Q.F. and four 4.7 in. Q.F. guns, and driven by Diesel engines, which would give them the ability of making long runs without replenishing their fuel tanks.

The total power of the engines per ship was estimated to be 1,000 b.h.p., which was to give the ship a speed of 11 knots. The order for all these engines was secured by Nobels, but as the Admiralty was in a hurry to get the ships ready as soon as possible, it was decided not to wait until the completion of the tests of the reversible engines, but fit in non-reversible engines with a Del-Proposto drive.

Every monitor got four engines of 250 b.h.p. each in four cylinders running at 350 r.p.m., the engine being similar in other respects to the tug engines of Nobel Bros. Co. As the whole contract of 32 engines could not be finished by Nobels in time, a half of that number was given over to the Kolomna Works, who built those engines from Nobels’ drawings.

The hulls of these eight monitors (known as “Shkwal” class) (Fig. 12) were built at the Baltic Shipyard in Petrograd, and were sent in pieces to an erecting yard on the River Amour, where they were assembled.

The first monitor, "Shkwal", was ready in 1908, and after having undergone her trials in the Gulf of Finland, she was shipped in pieces to the Far East.

Among the sea-going motor tankships can he mentioned Motorship "Robert Nobel", of Nobel Bros. Petroleum Co. (Fig. 13. She was originally a twin-screw tank steamer of 1,700 D.AV. capacity (L. 260ft., B. 34ft., D. 17ft., draught 14ft.) In 1909 she was to undergo a complete overhaul of engines and boilers, but instead of that it was decided to convert her into a motorship.

Two four-cylinder Nobel-Diesel engines of the enclosed crankcase type of 400 b.h.p. each were fitted in 1910, driving propeller shafts through Dohmen Leblanc clutches at 215 r.p.m. The engines had the following cylinder dimensions: diameter 450 mm and stroke 510 mm. and were direct reversible. The reverse gear, however, was different from Carlsund’s gear used on the smaller power engines, as it consisted of two set of rollers on the links of valve rocking levers.

Only one cam was required for every valve for both ahead and astern running, and the cams were fixed solidly on the camshaft, i.e., there was no shifting of cams for reversing, which was performed by placing the second roller against the cams through a suitable movement of the links. This type of reverse gear is known as Nordstroem’s gear (Nordstroem’s patent, Sweden, 1909).

The reason for the change of design in the reverse gear was that at the time it was considered that the shifting of cams by hand could only be performed on engines of comparatively small powers, and that in larger sizes it would be beyond the power of an ordinary man to shift the cams and thus a servo motor would have to be introduced.

The Nordstroem’s double roller reverse gear was so designed as to abolish the cam shifting and the whole of the reversing operation could be performed in 7-8 seconds. The idea about the impossibility of cam shifting by hand on large engines proved, however, to be false, and it will be shown later that all modern two-stroke Nobel-Diesel engines up to the very largest powers have hand camshifting, without the use of any servo motors whatever.

This Nordstroem’s double roller reverse gear, though not used at present by Nobels, has been revived lately by a well-known Swiss concern on their two-stroke engines.

In 1908 it became necessary to police the communications on the Caspian Sea and protect Russian shipping from assaults of Persian pirates, and therefore it was decided to build two sea-going gunboats of 680 tons displacement and 141/2 knots speed, armed with two 4,7 in. Q.F. guns and four 3 in. Q.F. guns.

Owing to the fact that these gunboats might be called to leave port at a moment’s notice, and also to the presence of local cheap supplies of oil, they were designed with Diesel engines as their propelling machinery, because to keep steam always up would have been too costly.

Tenders were invited from various Bussian (by that time two more firms got licences to build Diesel engines in Russia) and foreign firms for non-reversible engines with Del-Proposto drive.

Among these tendering firms were the Nobel Works, who sent in a tender for direct reversible engines of 500 b.h.p. each. The comparative simplicity and compactness of Nobel design with direct reversible engine installation as compared with a Del-Proposto plant, appealed considerably to the Russian Admiralty, with the result that new tenders were asked from various firms for direct reversible engines. A few of the firms sent in those new tenders for reversible engines, but without any guarantee.

This made the Technical Department of the Admiralty decide again in favour of Del-Proposto drive, as their own experience with direct reversible engines was at the time only with engines of submarines "Minoga" and "Akula", which in the latter case did not exceed 300 b.h.p. per shaft, and they were afraid to take the risk of installing reversible engines of nearly double the power per shaft.

After a lot of arguments the Nobel Works persuaded the Admiralty to adopt direct reversible engines, the Nobels installing them at their own risk, so that in case of failure they were to convert the engines to non-reversible type with Del-Proposto drive.

This was a rather daring proposition, as it meant to the engine builders a loss of at least £2,000 per ship, in case such a conversion would have been necessary. The hulls of these two twin-screw gunboats "Kars" and "Ardagan" (Fig. 14) were built by the Petrograd Admiralty Dockyard.

Every ship had two direct reversible six-cylinder engines, developing 500 b.h.p. per shaft and running at 310 r.p.m.

The cylinder dimensions were: diameter 375 m/m. and stroke 430 m/m. In general design these engines were similar to those of the Motorship "Robert Nobel", and had the Nordstroem’s twin-roller reverse gear (Figs. 15 and 16).

Two twin-cylinder auxiliary sets of 60 b.h.p. each were also provided. The cooling of the engines was with fresh water, which circulated in a closed circuit and was cooled before entering the cylinders in special coolers provided for the purpose. Such an arrangement was considered necessary, as at the time it was thought that the cooling of cylinders by seawater from the Caspian Sea, which contained a considerable percentage of salt, would be detrimental to the engines. In autumn 1909 the "Kars" was ready for trials, which took place in the Gulf of Finland. While turning under her own power in the River Neva the gunboat nearly dashed into the granite embankment of the river.

The situation was critical. The captain of the "Kars" having raised the Russian Naval Ensign before the trials, automatically took all the responsibility from the builders for the safety of the ship.

Common sense told him that to save the ship and his own job it was necessary to reverse the engines, but being a steam man, he had little experience with Diesel-driven ships, and naturally, mistrusting the new type of engine, was afraid to reverse them.

Seeing- the captain’s indecision, Mr. M. P. Seiliger, Manager of Nobels, who was standing on the bridge near the captain, took the matter in his own hands and pulled the engine room telegraph of both engines to “full speed astern.”

Before the usual reply came from the engineroom the ship stopped and started moving away from the shore. The captain, who was rather angry at first with the impudence of an ordinary “civilian” giving orders on a warship, did not know afterwards how to thank Mr. Seiliger for the saving of the ship.

In the early spring of 1910 the two gunboats "Kars" and "Ardagan" were to proceed to their stations on the Caspian Sea.

Originally it was intended to dismantle their machinery and armament and tow the hulls along the Northern Canal system and Volga to Astrakhan, where the machinery and guns were to be put in again. But by that time the captains and the crew became great Diesel enthusiasts, and it was decided to send the boats via the same route direct to Baku under their own power.

Having left Petrograd the gunboats encountered floating ice-fields in the Ladoga Lake, and had to work as ice-breakers in order to be able to proceed.

While under tow, negotiating some rapids on the River Svir, the tow rope of the "Ardagan" broke, and, if it were not for the instantly started Diesel engines, the ship would have got on the rocks.

During the journey on the Volga it was found that for continuous running at full speed the piston tops were likely to give trouble, as several cases of cracking were observed. This was quite a new experience, as up to that time the high speed engines were of a small enough diameter not to produce these troubles.

Two solutions offered to that problem, either to introduce piston cooling or re-design the piston tops and make them of some more suitable material.

The Nobel Works had chosen the latter course in the case of these engines, as the adoption of piston cooling meant too many alterations in the installation.

On the way from Astrakhan to Baku the gunboats got into a severe gale, which taxed their propelling machinery to the utmost.

In military operations of 1919, in the Caspian Sea, these gunboats took an active part. Two sets of similar engines were fitted in 1911 into the Black Sea Revenue Cruiser "Yastreb", whose hull was built at the Nicolaiett Shipyard (Fig. IT).

One set of such engines was built for the Admiralty icebreaker train ferry "Galerny", for the conveyance of railway goods trucks across the River Neva.

This latter ship had propellers at both ends, driven through friction clutches from each end of the engine, one propeller moving at a time. This arrangement was adopted in order to do away with the turning of the ship in the river (Fig. 18). Up to 1910 all tlie Russian submarines, with the exception of "Minoga" and "Akula" had petrol or paraffin engines; but owing to several fatal accidents due to petrol explosions, the Russian Admiralty decided in 1909 to replace these light petrol-paraffin engines by Diesels, as risks of fire in the latter case would be less.

This was no easy proposition, as the weight of marine Diesel engines of that time was in the neighbourhood of 40 kg per b.h.p., whereas the weight of petrol or paraffin engines was 20-25 kg per b.h.p.

Tenders were invited from various Russian and foreign firms for light high speed Diesel engines, and the most suitable tender showed a weight per b.h.p. of 25-30 kg. (55-65 lbs.), but unfortunately the overall dimensions of all these tendered engines were far too large to enable the engines to be put into those submarines.

Eventually, however, the Admiralty specially requested the Nobel Works to take the whole order for the conversion of fourteen submarines to Diesel power.

Owing to the lack of available space in the engine room the Diesel engines had to be designed of about the same overall dimensions as the petrol engines, and, in order to reduce their weight, resort had to be made to high grade materials, such as chrome, nickel steels, aluminium, etc.

All this meant considerable experimental work, before a suitable engine could be produced. With a view of coming nearer to the practical solution of that problem Nobels had built in 1909 a special experimental marine Diesel engine of extremely light weight. After exhaustive trials in the shops, that engine was fitted into Mr. L. Nobel’s motor yacht "Intermezzo", and tested under actual sea-going conditions. The engine was of the V type, the angle of V being 90°. There were eight cylinders of 200 m/m diameter and 220 m/m stroke, placed four on each side of the V.

At the end of each row of cylinders were placed the air compressors, the L.P. cylinder on one side and the H.P. cylinder on the other. Both compressors had no suction valves, the suction being through small ports. The engine developed 200 b.h.p. at 600 r.p.m. (Fig. 19).

The cylinders were of cast iron with copper water jackets. The crankcase was of aluminium and the connecting rods of alloy steel.

The crankshaft, which was made at Fagersta in Sweden from Swedish carbon steel and tough hardened by Brinell process had a diameter of 100 mm. The tensile stress of material was 80-90 k.g. per sq. mm. with an elongation of about 12%.

The ball bearing camshaft was on top of the crankcase between the cylinders, the reversing being performed by the shifting of the camshaft bodily endwise.

The valve gear and the general appearance of that engine resembled very much those of the present-day aero engines.

The lubrication was forced. The weight of that Diesel engine was only 2,000 kg or 10 kg per b.h.p., which made it the lightest Diesel engine ever produced.

Very valuable experience was obtained with the running of that engine, and many points of its design were embodied in the new engines specially built for the conversion of submarines.

These fourteen submarines were of three different types and sizes: Ssom class, six boats of Lake type of 110 tons displacement had petrol engines of 160 b.h.p.: Makrel class, seven boats of Holland type, and 115 tons displacement, with engines of 120 b.h.p. and the Delphin class (one boat) was of Russian design with petrol engines of 200 b.h.p. Therefore, owing to the difference in size and shape of engine room, three entirely different types of engines had to be produced.

The conversion began in 1910 with the Lake type boats first, and instead of the old petrol engine was installed in each boat one six-cylinder 160 b.h.p. non-reversible Nobel-Diesel engine, giving the boat a surface speed of 9½ knots. In general appearance these engines resembled also very much the present-day aero engines, as can be seen from Figs. 20 and 21.

The cylinder dimensions were: diameter 225 m/m and stroke 300 mm, and the engine developed its full power of 160 b.h.p. at 440 r.p.m. The weight of the engine was only 2,900 kg. (6,400 lbs.), which worked out at 18,1 kg per b.h.p. In order to get such light weight combined with necessary strength and stiffness, the usual orthodox design of Diesel engines had to be departed from, and the engine designed on entirely novel lines.

Thus the bedplate consisted of two parallel longitudinal girders with four cast iron box shaped cross beams carrying the main bearings.

A very light cast iron crankcase did not take any vertical stresses as special run through bolts held it down to the cross girders of the bedplate.

The three cast-in-pairs blocks of cylinders were bolted down to the crankcase top by the usual studs. The size of the main bearings was kept as small as possible, and in order to allow for their efficient working their lower halves were watercooled and had forced lubrication by an oil gear pump driven from the lower end of the vertical shaft at the front part of the engine.

All the four box girders of main bearings were connected together by water pipes at the level of the side members of the bed plate.

The pipes connecting the first with the second, and the third with fourth main bearing were on the off side of the engine, whereas the pipe between the second and third bearings was on the near side of the engine.

The whole of the cooling water circulated through the bearings before entering the water jackets of the cylinder. Means were also provided for the cooling of the lubricating circulating oil in the forced system. For that purpose the delivery pipe from the oil pump passed through the water pipe between the first and second main bearings. The lubrication of all the crankpins including that of the compressor overthrow at the forward end of crankshaft, was of the banjo ring type, part of the oil from the main bearings dropping into the rings.

The lubrication of the cylinders, air compressors and gudgeon pins was by a mechanical lubricator. To collect the oil at the bottom of the bed plate a thin sheet steel undershield was provided with a sump at the forward end containing the oil strainer and oil pump. To prevent splashing of oil the large openings in the crankcase were covered with detachable sheet steel covers.

In the design of the cylinders racing motor car practice was followed in many respects. Each block was of cast iron with heads and liners forming an integral part of the cylinder. But the water jackets were of thin sheet copper screwed to the flanges on the cylinder walls. Each cylinder had the usual assortment of valves (inlet, exhaust, starting and fuel valves), actuated from an overhead ball-bearing camshaft driven from the vertical shaft already mentioned. The inlet and exhaust valves were directly below their respective cams, and therefore had no rockers or levers of any kind, the cams actuating these valves through the usual type of motor car tappets (Fig. 22).

The starting valve situated vertically between the inlet and exhaust valves on one side of the cylinder, was actuated by a bell crank rocking lever, while the inclined fuel valve had two bell crank rockers connected by a link. The design of the pulveriser of the fuel valve required special study, so as to obviate one-sided injection of fuel into the cylinder, and means were provided to push the fuel by blast air in the direction opposite to that it had the tendency to take. The fire plate had a horizontal fan-shaped opening, so as to spread the fuel right across the combustion chamber towards the centre of the piston top. It is a known fact that in high speed engines, owing to the inherent restriction in the size of valves, the exhaust valve works under very unfavourable conditions, as exhaust gases of very high velocity and of considerably high temperature go past it, causing the usual overheating of the exhaust valve. To obviate this drawback, small exhaust ports were provided in the lower part of the cylinders of that engine, which ports were uncovered by the piston at the lower part of tlie stroke, so that the hot exhaust gases could escape through the ports, leaving comparatively cooled exhaust products at a much lower pressure to be expelled through the exhaust valve. The water cooled exhaust pipe was connected with both the exhaust valves and exhaust ports. There was one fuel pump for each pair of cylinders, and the three pumps were combined in one group driven from the rear end of the camshaft. A flywheel centrifugal governor controlled the speed of the engine by altering the lift of the suction valves of the fuel pumps. As the engine was driving the submarine on the Del-Proposto system, a hand regulation for the fuel pump was also necessary for ahead running, a handwheel at the rear end of the engine having been provided for the pur­ pose. The starting and fuel valves were put in and out of the action by the usual eccentric shaft arrangement controlled by the starting lever. The whole of the camshaft, rockers and tappets were enclosed in an aluminium casing containing the four ball bearings of the camshaft and the thrust bearing taking the end thrust of the skew gear of the vertical shaft.

That casing had three detachable covers and was hinged, so that in case valve inspection was necessary, only four pins and the coupling at the upper part of vertical shaft had to be taken away and the whole of camshaft could be swung clear of the valves. The engines of that type had a two-stage air compressor driven from the forward end of the crankshaft, but in the two first engines the L.P. stage had only one delivery (ring type) valve, the suction air entering from the inside of the crankcase into the compressor cylinder through ports at the lower end of the cylinder. The high pressure stage had a combined suction delivery ring type valve. This design considerably simplified the compressor, but it had also its drawbacks which soon made themselves felt in service. The air drawn into the L.P. stage was not clean atmospheric air, but air mixed with an oil vapour, which usually was contained inside an enclosed crankcase of a high speed Diesel engine.

Admission of such oily mixture into the compressor was very undesirable as the oil was likely to ignite inside the air receivers between the stages and cause a possible explosion in the coils. To counteract partially this drawback there was a drain provided at the lowest point of the intermediate cooling coil, which, combined with the downward path of air in the cooler, was supposed to clean the air enough to obviate the likelihood of an explosion. However, such an explosion occurred in service, and therefore new compressors were fitted to all these engines, having L.P. suction valves connected direct with the atmosphere and the air cooling coils were removed from the compressor jackets into a separate box fixed at the side of the engine.

The copper jackets also proved to be slightly leaky in service, and the last three engines were built with thin cast iron jackets cast integral with cylinder block in the usual motor car style. Gradually all engines of that type had their copper jacketed cylinders replaced by those of new design. The fuel consumption at full load of these engines was 215 gram (0-475 lbs.) per b.h.p. hour at normal speed. Beside submarine use four of such engines were fitted as auxiliary sets into the Russian steam driven transport "Xenia" (mother-ship for submarines of Ssom class), the reason for this being to have identical engines in the whole of the flotilla, so as to facilitate replacement of spare parts.

The submarines of the Makrel class had four-cylinder non-reversible Diesel engines of 120 b.h.p. installed to replace the old petrol engines. The short length of engine room prevented the installation of the six-cylinder engines of 160 b.h.p., in order to give a higher speed and therefore the old h.p. was retained, giving the boat a speed of 6½-7 knots on surface. These 120 b.h.p. engines were of a slightly different and heavier design than the six-cylinder engines described above. The cylinders were cast in pairs, the heads and water jackets forming an integral part of them. Large inspection doors on both sides of the jackets were provided to facilitate cleaning of water spaces. The two blocks of cylinders were fastened by studs to a light cast iron crankcase having detachable aluminium covers to prevent oil splashing. The bedplate was also of cast iron with three cross members containing the water-cooled main bearings (Figs. 23 and 24.) The crankcase was relieved of tensile stresses in a manner similar to the 160 b.h.p. type, and also had a light sheet steel undershield.

The lubrication of the cylinders and air compressor was by means of the usual mechanical lubricator, whereas that of the main bearings and crank pin was similar to the engines of the Ssom class boats; the circulating oil was cooled bv a cooler placed alongside the bedplate of the engine. The cooling water was circulated through the main bearings and cylinder water jackets by means of a gear driven from the forward end of camshaft.

The camshaft was enclosed in the crankcase and was driven from the crankshaft by spur gearing at the rear end of the engine. The cylinder diameter of these engines was 250 m/m and stroke 300 m/m, the full power of 120 b.h.p. being developed at 450 r.p.m. The two-stage air compressor was similar in design and method of drive to the improved type of 160 b.h.p. compressor. The two air coolers were separate and bolted to the off side of the engine. The four valves were on the top part of the cylinder, the inlet and exhaust opening vertically downwards, whereas the starting and fuel valves were inclined at 45° to the vertical. All these valves were actuated from the camshaft by means of the usual motor car type tappets and push rods. Auxiliary exhaust ports were also provided with an exhaust manifold similar to that of the Ssom class engines. The two eccentric shafts controlling the throwing in and out of action of the starting and fuel valves were on top of the cylinder, and each shaft controlled two cylinders by means of a small hand lever, seen near the top between the cylinder blocks. In order to assist the ventilation of the crankcase, part of the cylinder suction working air was taken from the crankcase, suitable baffle plates having been provided to prevent lubricating oil being- sucked into the cylinders.

For this purpose three copper pipes having a number of slots, connected the inlet valve chambers with the crankcase. A similar arrangement was also provided in the 160 b.h.p. engines of the Ssom type. The four fuel pumps were grouped together between the two cylinder blocks above the camshaft from which they were driven. A band lever at the rear end of the engine controlled through suitable gearing the amount of fuel delivered by the fuel pumps to the cylinders.

To prevent racing of the engine a centrifugal governor of the Jahns’ type was driven from the rear end of the engine. In the case of both types of engines (120 b.h.p. and 160 b.h.p.) the uncooled pistons were of cast iron, having five piston rings and no scraper rings at the lower end of the piston skirt. The connecting rods of I. section were forgings of nickel steel, machined all over, while the chrome-nickel steel crankshafts were machined from the solid.

The fuel consumption of that 120 b.h.p. engine was 215 gram (0-475 lbs.) per b.h.p. and the weight of the complete engine 3220 kg. (7,100 lbs.) or 26,8 kg. (59 lbs.) per b.h.p. Besides submarines, this size of engine was put in several small minelayers, tugs and in the revenue cruiser Control of the Baku Custom House. The overall dimensions of that ship were: length B.P. 72ft., breadth md. 14ft., depth md. 6ft. 6ins., and loaded draught 3ft. 3ins. The engine of the submarine "Delphin" was a combination of designs of the 160 b.h.p. and 120 b.h.p. types.

It was a six cylinder non-reversible set of the same cylinder dimensions as the 120 b.h.p. type D=250 m/m x S=300 but of slightly higher piston speed, the r.p.m. being 500, which gave it a power output of 220 b.h.p. (Figs. 25 and 26). The cylinder design as well as that of the bedplate, crankshaft, connecting rods, piston and compressor was similar to the 120 b.h.p. type, but the valves, though in arrangement similar to the above-mentioned type, were actuated by rockers from an overhead camshaft driven from an inclined shaft at the rear of the engine. This camshaft was not of the hinged type, but was supported on ball bearings by four brackets bolted to the cylinder tops, the cams working in an oil bath. The eccentric shaft was in one piece actuated from a hand lever at the front end of the engine, thus putting all six cylinders on fuel at once during the starting operation. A centrifugal governor was mounted on the inclined shaft and the fuel lever, placed near by, controlled the fuel pumps, six in number, grouped together at the rear of the crankcase and driven by bevel gearing from the inclined shaft. The crankcase was of very light scantlings and of cast iron with large aluminium inspection doors, which were easily detachable. The weight of the engine was 4275 kg. (9,440 lbs.) or 19,4 kg per b.h.p. The duty of the governor was to prevent excessive racing of the engine when the clutch was released or when the dynamo was running at no load. During tests of instantaneous throwing off the load from full to no load, the engine speed increased momentarily to 565 r.p.m. and then settled down to 545 r.p.m., which was the speed for no load running of the engine. In table II. are given the principal results of the official 12 hours non-stop trials of that engine made in 1912.

Owing to the shallow and undulating coast line of Russia in the Baltic Sea, it was necessary to have small size submarines, which could navigate those waters, and that explains the reason why the submarines of the Ssom and Makrel class were retained during the war when most other nations built only quite large sea-going submarines.

The Russian Navy had a good number of large submarines also, fitted mostly with, two-stroke engines, but even the small submarines were often operating near the coast of Germany, as could be instanced by the case of submarine "Oltun" (Makrel class) which sank a German battleship off Danzig in 1916. The abovedescribed Diesel engines were not the smallest type submarine engines built by Nobels.

In 1914-three 50 b.h.p. four-cylinder non-reversible Diesel engines were made, running at 500 r.p.m. These engines were fitted in three 35-ton submarines, giving them a speed of 6 knots. These submarines were designed for the defence of the approaches to Cronstadt, and, if necessary, could be taken on board ship for transportation. The crew of these submarines consisted of five men all told, and the headroom available was so small that a tall man had to move inside the boat in a bent position. The cylinder dimensions of these small engines were: diameter 170 m/m and stroke 220 m/m. In general design they were a copy of the 120 b.h.p. type on a smaller scale. The weight of these engines was 910 kg. (2,000 lbs.) or 18-2 kg. (40-2 lbs.) per b.h.p.

A slightly modified type of such engines using six cylinders in three blocks of two, the cylinder diameter being 180 m/m and stroke 230 m/m. (9 1 16th ins.) and developing 80 b.h.p. at 450 r.p.m., was fitted into several minelayers during the war (Fig. 27). Reverse gears were provided for astern motion. A very important point in connection with the design of these small and medium size high speed Diesel engines was that of crankcase ventilation. During the working of the engine, inside the crankcase an oil vapour accumulates, and if it is not expelled from the crankcase, an explosion may occur due to the ignition of that oil vapour when coming in contact with the underside of the hot uncooled piston head.

To overcome this defect, part of the necessary suction air for the cylinders is drawn through the crankcase, thus sucking that vapour into the cylinders, and incidentally cooling the pistons by air. But this again has its disadvantages, because inside the crankcase, especially in forced feed lubricated engines, oil splashes all over the place and particles of such oil are drawn into the air suction pipe. The engine in such a case runs partially on fuel oil and partially on lubricating oil, with the result that the fuel oil consumption is considerably reduced, while the lubricating oil consumption is correspondingly increased.

Besides the financial drawback, such running entails considerable risks, as, when there would be too much lubricating oil sucked into the cylinder, the engine might get out of control and race away, with consequent disastrous results. A system of carefully designed baffle plates should be fitted into the suction pipe, so as to arrest the particles of oil on their way up that pipe.

A purely Diesel electric drive for warship propulsion was also made by Nobels in the case of the small converted cruiser liynda. The reason for the adoption of the purely electric drive was that at the time the order was placed (1910) the Admiralty had many doubts as to the advisability of having reversible engines of 1,000 b.h.p. per shaft, considering that for a six-cylinder engine the cylinder dimensions would be prohibitive.

This was contrary to Nobels ideas, who urged the Admiralty to adopt one reversible engine of 1,000 b.h.p., as the ship was single screw. This, however, would have meant too many alterations in the engine room, which was very short, as a compound steam engine was there previously, and the boiler space could not be allotted for the Diesel installation, as it was to be used for other purposes.

Eventually it was decided to put two high speed Diesel engines of 600 b.h.p. each direct coupled to 400 kw. D.C. generators, these generators supplying current to one slow speed electro-motor on the propeller shaft. In cylinder dimensions, D=450 m/m. and and S=510 m/m. and general appearance the engines were similar to those of motor ship Robert Nobel, hut in order to get the necessary power output their piston speed was increased to 5,45 m/sec (1,070 ft./min.) or 320 r.p.m. and the engines were of course not reversible. Owing to the adoption of the electric drive the weight of the engine had to be kept as low as possible, so as to come within reasonable total weight figures, and the main cast parts of the engines were steel castings with the exception of cylinder liners and pistons, which were of cast iron (Fig. 28). No flywheels were fitted, as the armature of the dynamo, weighing 4,850 kg. (4¾ tons) served as such.

The weight of each engine proper was 23,750 kg. (23½ tons) or 39,6 kg. (87-5 lbs.) per b.h.p. Owing to the high power output per cylinder (150 b.h.p.) piston cooling had to be resorted to, and this was effected by circulating the forced feed oil in the piston heads via hollow connecting rods, the returning oil having been cooled in special separate coolers provided for the purpose below the engine room floor.

The exhaust valves were water-cooled, as well as the exhaust pipe and main bearings. Two plunger circulating water pumps were driven from the forward end of the crankshaft, from which also was driven a two-stage tandem air compressor. The dimensions of that compressor were D-HP 90=mm D-LP=290 m/m and stroke 280 m/m. and the air cooler was separate and bolted to the side of the crankcase. Considerable trouble due to overheating of air was experienced with that type of compressor, so that it was replaced by a three-stage double tandem air compressor of the following dimensions: D-HP=55 m/m. D-IP=125 m/m.; D-LP=290 m/m and a common stroke of 280 m/m. After that alteration the compressor troubles disappeared.

It was the first time, in Russia at least, that a double tandem three-stage air compressor was applied to Diesel engines, but since then all Nobel Diesel marine engines, having compressors driven direct from the crankshaft, are fitted with such double tandem three-stage compressors. In table III. are given results of non-stop 100 hours duration official trials of these Rynda type engines.

In 1912-1913 great extensions were made in the Naval Port of Sebastopol, on the Black Sea, including the building of a large dry dock to accommodate the new Russian battleships, then under construction. A pumping station of considerable power was built at the Dockyard. To prevent any damage to machinery by enemy fire, the plant was placed underground in casemates, protected by ferro-concrete and armour plates.

Owing to this the space was limited, of course, and the power station of the plant was designed to have high speed Diesel engines, driving the various pumps by electricity. The Russian Admiralty expected war in the Black Sea, and therefore was anxious to have the pumping station in working order as soon as possible. As no firm could give quick enough delivery of a high speed Diesel electric plant of about 750 kw. aggregate output, the Admiralty sacrificed for the purpose the Rynda engines, which were put into that power station in 1914, with all their electric gear, without any alteration.

The cruiser Rynda was broken up just before the war. When the foiir Russian battleships of the Gangout class were designed it was decided to provide some Diesel generating sets, which could run in parallel with the steam turbine driven sets and supply current to various parts of the ship, including the electromotors for turning the gun turrets. The steam auxiliary plant consisted of four 320 KW. DC. dynamos fitted with A.C. stop rings and driven by De Laval steam turbines. The Diesel plant was of two sizes : the lighting plant and the power plant. The lighting plant consisted of three sets of 180 b.h.p. six-cylinder, four-stroke Diesel engines built by Felser Works of Riga. These engines were direct coupled to 120 I(W. DC. generators. The power plant consisted of two 320 KW. DC. generators, with A.C. slip rings, direct driven through a Voigt elastic coupling by a 480 b.h.p. Nobel Diesel engine

(Fig. 29). The reason for the adoption of Voigt coupling was that the engine and dynamo bedplates were separate castings, not bolted together. These engines were placed in one engine room just in front of the rear gun turret and under the main protected deck. The cylinder dimensions were: diameter 375 m/m. and stroke 430 m/m and the normal output of 480 b.h.p. was obtained in six cylinders at 320 r.p.m. The fuel consumption of the engines at full load was 195 grams (0-43 lbs.) per b.h.p. hour. The engines were non-reversible and in general outline followed the usual Nobel Diesel high speed medium power practice.

A double tandem air compressor of equal dimensions to that of "Rynda" engines, but of slightly shorter stroke 270 m/m was direct driven from the forward end of the crankshaft. The pistons were water-cooled bv means of a telescoping gear and the exhaust valves and exhaust pipes, silencers, and bearings were also water-cooled. The telescoping- gear consisted of a tubular bridge piece bolted to the piston skirt by the middle and having at the ends two vertical steel pipes well polished externally.

These steel pipes moved up and down in gunmetal water receivers, the leakage of water was prevented by a gland. During navigation in the Baltic Sea, ordinary seawater was used for piston cooling, as the salt contents in the water was small, but during ocean voyages, the pistons were to be freshwater cooled, while the cylinder jackets, etc., had seawater cooling. The above-mentioned telescopic gear proved to be troublesome in services, as the tightness of the gland depended upon the perfectly vertical motion of the piston, i.e., without any side play whatever. In practice this was impossible of achievement as the piston had to have some small play inside the cylinder, and that small play was large enough to loosen the glands, so that water used to spout past these glands into the bedplate. This was very undesirable, as the water was mixing with the circulating oil at the bottom of the bed plate and the emulsion was taken by the oil transfer pump to the day circulating oil tank and hence sent through the oil cir­culating system, with results which can easily be guessed.

The author remembers such a case, while he was in charge of these auxiliary sets on board the battleship Sebastopol in 1S14 in the Baltic. The engines were supplying current for the turning of 12in. gun turrets, and after some time it was observed that emulsion got into the drip feeds. The situation was rather an unpleasant one, as the engines could not be stopped on any account. To continue the running of the engines on emulsion for some considerable time was also out of the question, therefore the only possible solution at that moment was to stop the circulating principle of lubrication and lubricate the bearings with fresh oil all the time, using the oil transfer pump to convey the emulsified oil from the bottom of the bedplate to an empty reserve oil tank near by, to which a suitable connection was improvised on the spot.

After the emulsified oil had settled in that tank it was filtered, transferred to the day oil tank and used over again. After this experience it was decided to change over from the telescopic principle to the grasshopper type, which was later fitted to ail the eight engines and proved to be practically immune from trouble. After this reconstruction the ordinary circulating lubrication of bearings was again resorted to.

The author had another interesting experience with these engines on hoard of all the four ships, and that was the effect of resonnance or vibrations of foundations due to minor unbalanced forces in the engines. It was found that when the two engines were running together at the same speed, vibrations of certain amplitude were set up in their foundations, and when the two amplitudes synchronised, the vibrations became so pronounced that it was quite unpleasant to stand on the engine room floor. The remedy for it was found in the running of engines at different speeds (one at 323 r.p.m. and the other at 318 r.p.m.), when these vibrations disappeared.

With the description of this type of engine closes the chapter of the four-stroke Nobel Diesel engines, as no more new types of four-stroke engines were built by Nobels after those, all the new types being of the two-stroke cycle; to the description of which engines the author will proceed at next meeting, as it is considered more desirable to do so and invite discussion on each.

The Chairman: The paper to-night is historical. Some of those present will probably find points for discussion, particularly those who are opposed to the four-stroke type of engine. I notice that in the last paragraph the author states that Messrs. Nobel have given up the manufacture of the four-stroke engine in favour of the two-stroke.

Mr. W. Hamilton Martin: Mr. Steinheil’s paper has given us some interesting historical facts about the early achievements of the Nobel firm on the Diesel engine. What the author tells us does not readily invite discussion, but it certainly leads one back to the days when the marine Diesel engine was in its infancy. Many were the difficulties met and overcome, and great was the prejudice encountered by Dr. Rudolf Diesel and his assistants while devoting untiring energy and capital to the perfecting of his engine for both land and marine use.

Thanks to the wide circle of friends which my father had, and the way in which I was always taken by him to join in the discussions on matters of future interest, I had the privilege of meeting the late Dr. Diesel several times. My father was one of the engineers who took out an early licence for building the two-cycle marine Diesel engines at the Flushing Royal Dockyard, Holland, of which lie was the Engineering Manager from its foundation in 1875.

We had many very interesting conversations with Dr. Diesel before deciding to take up the building of his engines, now nearly 15 years ago, and I recollect how even then Dr. Diesel repeatedly referred to the fine results obtained by the Nobel firm in Russia.

If I may make a slight digression, I would like to mention here that three 1,000 K.W. dynamos, driven by six-cylinder Diesel engines, were some time after installed at the Flushing Dockyard by my father instead of the old steam plant for driving the entire yard. This was just prior to the war, and when soon after we had the coal famine in Holland, our yard with its plentiful oil supply, thanks to foresight, could carry on where others had to slow down on close altogether. This power house has proved a great success. I may add that my father made several suggestions, which were gratefully accepted, for converting tlie inherently somewhat stationary type of Diesel engine into a more suitable marine job. He very soon substituted solid drawn steel tubing and conical unions for copper piping with brazed joints for the fuel injection line, which was always giving out, not being able to stand the vibration. He also did away with silencers altogether, and substituted a light water-cooled valve which has since been adopted as standard in a certain Continental Navy’s Submarine Service; he devised a. simple fuel injection pump which allowed of close speed regulation and assured equal fuel supply to all working cylinders, and made various other practical improvements.

In consequence of our relations with Dr. Diesel I had the privilege of working for some time at the M.A.N. Works at Nurnberg, as assistant in their testing department for highspeed marine Diesels, which were then mostly fitted in submarines or gunboats in sizes from 200 to 1,200 B.H.P., of three, four, or six cylinders, all two-cycle. These people were continually carrying out costly experiments for Dr. Diesel on cylinder and piston head formations, scavenge, exhaust, and fuel valves, cast iron mixtures for cylinders, etc.

I went through many of their marine engine “teething” troubles with them, and gradually saw most of these cured on severe endurance tests. Later on I saw several of these engines giving satisfactory service, also during war service. The Nobel people had by then, however, already passed i through most of their troubles, and had actually been successfully running reversible units in Russian tugs and submarines.

Speaking of tugs, we arranged with the makers to have a 300 h.p. six-cylinder two-cycle engined tug boat, the .Xirrnberg, in use some time in the dockyard at Mushing. She had 110 magnetic clutch as the Nobel’s fitted in theirs, and consequently, when picking up a string of barges on a river or tidal basin with current, this job often proved a more profitable one for the tow-rope suppliers than for the tug owners.

The cushioning effect of steam when taking up the tow-strain will take a lot of beating, but the idea of fitting a magnetic or friction clutch ought to solve the question of gradually picking up the load. Without a clutch one could best compare the flexibility at starting of oil and steam power with a horse which jerks, when starting a loaded cart, and a span of oxen which slowly but steadily lean, as it were, against their yoke when commencing to move.

This tug was eventually sold to the German Navy at Kiel for instruction purposes of their submarine engineers, for which it has no doubt proved eminently suitable.

While at Numberg I met an engineer officer of the Russian Navy who was taking delivery there of some 1,100 B.H.P. two-cycle Diesel engines made presumably for Russian gunboats. Through the outbreak of war, however, these went into German submarines. His wonderful experience in the running of Diesel engines in those early days I have always envied. The inevitable result was, however, that this officer proved a relentless inspector. I remember his examining all finished cylinders and piston heads minutely with a strong lens, for hair-cracks or small flaws, after which they had to be kept for 24 hours under hydraulic preassure twice the working preassure.

I understood these were the Russian Admiralty’s test standards. Batches of a dozen or so fully finished cylinders or piston heads were rejected by him at a time, many of which would probably have been good enough for an appreciable amount of running. I did not envy the builders having that inspector!

These requirements no doubt led to the fact that the M.A.N. people soon made the finest cylinder head castings, and many of their later licencees preferred to order these parts from them. Their foundrymen were at the time earning as much as 90 to 100 marks a week, then £5, which in those days was very high pay indeed for such work. If Messrs. Nobel have had to contend with similar rigorous inspections in Russia and still managed to get such success in those days, it speaks all the more for their pluck and determination to have achieved all the work which has just been shown to us so ably by Mr. Steinheil.

Before ending, the following observation may be of interest; I just happened to notice in the Motorship year book of this year that from 1904 to 1911, out of the existing twenty-one motorships of the world, nineteen were Nobel and Kolomna engined.

The other two were—one in 1910, the tugboat "Nurnberg", which I mentioned, fitted with M.A.N. engines, and the other the "Vulcanus", fitted with Werkspoor engines.

Mr. Windeler: May I first of all thank you for inviting me to be present to-night. I have had the pleasure of knowing Mr. Steinheil for many years, and in 1912 in a paper read before the Liverpool Engineering Society I referred to the very astonishing fact that we had to turn to Russia for experience in the design and running of marine Diesel engines. Russia did not strike one as being an industrial country which was likely to develop such a modern type of prime mover.

I recently had the pleasure of seeing one of Messrs. Nobel’s latest type of marine Diesel engine made in their works in Sweden, and I think I may say that it is one of the latest productions in marine internal combustion engines.

With all due appreciation of the progress and pioneer work made by Mr. Steinheil’s firm in Russia, I would like to remind him that there has been a great deal of pioneer work done in this country. Messrs. The Mirrlees Watson Company took out a licence and built an engine in 1897, and the experience gained from this engine laid the foundation of the work which has been since done in this country on the Diesel engine. I think my firm was the first to fit a high speed Diesel engine in a battleship at a time when Continental makers had not had any experience with high speed enclosed Diesel engines. They also made at that time a high speed Diesel engine for propelling pinnaces for H.M. Navy, and Mr. Steinheil’s experience with the captain of the ship which nearly ran into the jetty reminds me of the unsatisfactory operation of reversing gears available in those days. They were very cumbersome and most unsatisfactory.

You can, as Marine Engineers, imagine the condition of a comparativly small boat being caught out in an equinoctial gale in the Channel with engines which could not be reversed. However, the results were in the end quite satisfactory, and at that time it was considered a triumph for British engineering.

My firm has specially developed engines for power production and a large number have been installed for driving electric-generating plant.

At first there was some mistrust of the reliability of Diesel engines, but experience proved that they were exceedingly reliable and ran satisfactorily, even with alternators in parallel. You Marine Engineers are used to calling upon your engines to deal with widely fluctuating loads, and one realises that marine Diesel engines must satisfy these conditions. I am quite sure that as experience is gained you will find there will be 110 difficulty in this respect. As an instance of the widely varying loads which it is possible for a Diesel engine to deal with, my own firm installed an engine which is driving a rolling mill, in which the power varies from 15/200 B.H.P. every four or five minutes.

Mr. Steinheil referred to compressor difficulties. I can assure you that was one of the most serious difficulties in the early days and experience has since taught us that it was largely due to inefficient lubrication. It is not desirable to have an air compressor arranged so that its internal parts are supplied with forced lubrication, as excess quantities of oil are likely to pass up the pistons and cause deposits of carbon to be formed which ultimately result in overheating.

My firm quickly realised that a multi-stage compressor was desirable and proved a great advance on the arrangement suggested bv Dr. Diesel, i.e., a single-stage compressor.

The lubrication of the air compressor is best carried out by mechanically-operated controllable lubricators, as by this means you are able to observe and control the precise quantity of oil which is to be supplied to the various working parts.

Much trouble was experienced with copper coils deteriorating but this difficulty has also been reduced to a negligible quantity by this attention to the lubricating arrangements, but even now it is recommended that the cooling coils should have their weights stamped upon them when they are first installed and that they should be periodically examined and when the weight has been reduced by 25% they should be rejected and a new one installed.

With regard to the point raised by the last speaker in connection with copper pipe joints. At the outset my firm decided that brazed joints would not be satisfactory, and we developed a joint which was formed by flanging the copper pipe in a conical form and arranging for a suitably shaped ring to slide on the back of the cone so that the tightening operation would not cut the copper pipe. This joint proved most satisfactory up to the highest pressures, and was approved of by the Admiralty for use on the Diesel engines which were manufactured for H.M. ships.

Since the war the development of the internal combustion engine (in particular the liquid fuel engine) has been very rapid, and much progress has been made in what is known as the solid injection type of engine. In one ship which I recently had the pleasure of inspecting, in which an engine was installed having a power of over 2,000 horsepower, the working pressure for injecting the fuel oil was as high as 9,000 lbs. per square inch, a great advance on any pressures which had hitherto been used for injecting fuel into the combustion chamber of the engine.

With reference to the efforts which are being made to eliminate compressed air for injecting the fuel into the combustion chamber, I think Mr. Steinheil will agree with me that so far none of the modifications which have been proposed have shown any great improvement over air injection. The old idea that the air compressor was a source of danger has passed away and there is no difficulty to-day in designing a suitable air compressor to deal with the conditions.

One point I would mention and that is that it is not necessary, as is commonly thought, to use high air injection pressures at starting. 550/600 lbs. per square inch is ample, and the same may be said of the starting pressures. One important point in connection with the marine oil engine is that it should be able to run at very slow speeds with regular combustion. In this particular connection, great progress has been made and on some trials which I recently witnessed of a Doxford ship, fitted with opposed piston engines, they were able to reduce the engine speed down to 15 R.P.M., and run at that speed for considerable periods.

As far as I know, this is the best results which have been obtained on a Diesel driven ship, and goes to prove that the oil engine can be made as flexible as other prime movers which have been used.

I would like to take this opportunity of congratulating Marine Engineers on the courage they have displayed in taking up the Diesel engine. As we all know it is a very different matter to go to sea with a prime mover which is comparatively new to the work, but judging by the large number of motorships which are being built today and the great interest which Marine Engineers are taking in the internal combustion engine, as a propelling motor, proves that at least a very considerable amount of success has been obtained. My own feeling about the marine oil engine is that up to a certain power we shall use four-stroke engines: beyond that, two-stroke single-acting engines and for high powers or for special purposes, double-acting two-stroke engines.

Miss V. Holmes, B.Sc. (Women’s Engineering Society): I have been particularly interested in following Mr. Steinheil’s paper, and also in what Mr. Windeler has just told us. On the subject of solid injection, however, I should like to point out that such high fuel pressures as 10,000 lbs. per square inch are not necessary. Vicker’s marine engines use only 4,000 lbs. and I understand that Doxford’s have recently reduced the pressure in their engines to 3,000 lbs. In some land engines the pressures are even lower; for example, Crossley’s use only 1,000 lbs., and Ruston and Hornsby’s about 1,500 lbs. I think it must be admitted that there is a great deal to be said in favour of solid injection. In addition to the obvious advantages of simplicity and low first cost owing to the elimination of the air compressor, there is the saving in space which should appeal to Marine Engineers. Another advantage which is not often mentioned is that of greater safety. There are dangers connected with the air injection system from which the solid injection engine is free. I refer to the dangers of the spray valve leaking, of the compressor bursting through over-lubrication, and of the inter-cooler coils of the compressor becoming worn and bursting.

Mr. W. McLaren : Mr. Steinheil is to be congratulated on the great amount of information he has imparted to us in this paper. It is particularly a paper for the young men, as may be gathered from the preceding part of the discussion, in which a lady has now taken part. I am sure it will be gratifying to our President to know that we have had such a paper and discussion, which appeal especially to the younger generation of engineers, who are being called upon to deal with the new types of Diesel engines at sea. I am glad to hear of the great advances which are being made in the efficient working of the Diesel engine, but I cannot help saying that I still consider the steam engine is superior in flexibility.

Mr. R. Jolly : I have been struck with the fact that most of Messrs. Nobel’s problems which have been described so fully by Mr. Steinheil have been in the nature of conversions from steam or other type of machinery to Diesel engines. I think it is all the more creditable that they have made a success of each of these problems, which are far more difficult than the installation of Diesel engines in new vessels which have been designed specially to suit the type of engine in question.

I have at times found that the ship’s sides—the constructive department — have little sympathy with the difficulties of the engineer who is called upon to arrange a totally different type of machinery so as to fit it into the space occupied by a steam plant which has been removed for replacement. From the figures given in the paper, and from a rather hurried impression, I think the builders of the Nobel engine have been aiming all along at reduction in weight of the engine, and I shall be very interested to hear the paper on the two-stroke engine in order to see to what extent that object has been achieved in the later type. A great many people have been discussing the merits of steam versus Diesel ships in the Press. Many of them seem to have overlooked the saving in space, in the case of the Diesel engine due to there being no need for coal bunkers. I think that soon we shall see a Diesel engine which will show a greater saving in weight than with present types, as compared with steam plant. That is the greatest field for improvement in the Diesel engine.

Mr. Thom : The younger generation of engineers are more in touch with the developments of the Diesel engine, and I think the paper to-night is one which gives them the chance to give us a brief account of their experience. I hope the discussion will not close without some further contribution from the young members present, and I would particularly urge them to ask any questions which may occur to them.

The author has not told us half of what he knows, and I am sure he will be pleased to answer any questions on the subject. I emphasise this, as we have several thousand members—the number present tonight is only a tiny portion of the membership—and it is on behalf of those who are not privileged to be here tonight that I urge you to bring out in the discussion all the information possible, so that it may be passed on to absent members through the medium of the Transactions.

There is just one point I should like to mention with regard to the dangers which are present in Diesel engine work when you are compressing air in pipes, valves, etc. It occurred to me tonight that there is a means of removing the source of danger from the metallic surfaces, and that is by passing a blast of C02 through the system. You will find that this has a purging effect provided it is passed through very quickly.

With regard to compression pressure for solid injection, I certainly think 9,800 lbs. is very high. It may not be necessary except in the case of high speed engines. Before concluding I would refer to a point mentioned regarding the reduction of weight of the Diesel engine; I think there is a limit to that under the rules and regulations of certain registration societies.

The Chairman : Mr. Thom is referring to the Board of Trade regulations in regard to tonnage. As this is a point which may have come more within my experience than that of the author perhaps I may answer it. The deduction from the gross tonnage for space occupied by propelling machinery is fixed by the Merchant Shipping Act.

If the space occupied is between 13 and 20 per cent, of the gross tonnage a deduction of 32 per cent, is made from the gross tonnage. There is an alternative wav for deduction on account of machinery space, but this need not be quoted now as it is usual to design the ship to get the 32 per cent, deduction.

Space is saved by fitting Diesel engines, but the greatest gain is in the saving of weight. If we assume the consumption of a Diesel ship is one-fourth of a coal-burning steamship and the Diesel ship requires 500 tons of fuel for a certain voyage, then the steamer will require 2,000 tons, and the difference (1,500 tons) shows the amount of extra cargo which can be carried on account of the difference in consumptions.

A Visitor: Miss Holmes referred to compression pressures used on land engines, including the Crossley. I think the Crossley pressure is 450 lbs., and even with that low pressure they obtain high efficiency. Another point regarding the Ruston engine is the practical absence of cams. Most marine engineers do not like cams. The Ruston engines of the higher powers employ eccentrics instead of cams.

Capt. A. F. C. Timpson, M.B.E. : Mr. Steinheil refers to the telescopic tube arrangement of piston cooling as having been found unsatisfactory by him. On engines designed with cylinders open to the crankpit at the bottom the necessity for fitting the cooling tubes inside the frame undoubtedly placed the telescope system at a disadvantage, as any water leak found its way into the oil in the crankpit. On more modern engines the cylinders are sometimes mounted with a few inches clearance from the top of the engine frame, the piston rod working through a gland. With this arrangement telescopic tube cooling can be used satisfactorily as the end of the female tube, fitted with a gland, can be brought outside the frame and any leak will drain off into the bilges.

Mr. G. B. Plows: In connection with piston cooling, I was concerned with some large four-stroke engines in 1914 fitted with a grasshopper type of piston cooling, which proved most unsatisfactory and was scrapped in favour of a lubricating oil cooling system via the crosshead. This also proved unsatisfactory as the oil from the pistons caused excessive wear on the journals, loss of oil pressure, continual filter trouble and a high lubricating oil consumption. Finally the telescopic gear with water cooling was adopted with reasonably good results. I was pleased to hear from Mr. Windeler that most of the air compressor troubles have now been eliminated, for I agree that 30% or more of the trouble with large marine Diesel installations in the earlier days was in connection with the air compressors, and in this connection the quality and distribution of the lubricating oil always demands serious attention. With regard to the author’s remarks in the last paragraph on the vibrations of certain amplitudes synchronising and causing pronounced vibrations when the engines were run at the same speed, I have had a similar experience with large twin reciprocating engines and as stated the vibrations ceased as soon as the speeds differed.

Mr. Windeler : May I correct the impression which seems to have been erroneously formed by some of the speakers regarding compression pressures which are used on Diesel engines. Speaking for my own firm, all engines are turned out having a compression pressure of not more than 475 lbs. per square inch. Experience has shown that there is no appreciable gain in carrying compression pressures beyond this, and it is needless to point out that any additional pressures add to the stresses on the working parts. In regard to the question of air compressors. Modern-designed air compressors can run for long periods without any necessity for cleaning the valves and without any difficulty being experienced. In our own power-house we have an engine fitted with a three-stage air compressor which has run for over 15 months without being opened out in any way. I should like to congratulate the author on the interesting information he has given us in his Paper.

Mr. G. J. Steinheil : I must thank Mr. Martin for his complimentary remarks. He mentioned that his father used solid drawn tubing with copper taper unions instead of the brazed joints which used to break in service. This is exactly the same experience Nobels had with these joints in their earlier types of engines. The brazed joints were later replaced by Nobels by taper ring joints, which work quite satisfactorily.

With regard to tug work, the clutch seems to be of great help, but I think that the skill of the skipper has a lot to do with the proper handling of tow ropes. It is useless to attempt to pick up a string of barges having sagging tow ropes with the engine running at a good speed. In such a case one should turn the engine slowly and stop it or de-clutch before the nearest tow rope draws taut, merely allowing the inertia of the tug to tighten the rope. Then start up the engine again and pull the first barge until the second tow rope is nearly tight, then stop or de-clutch again and so on. I admit that such a procedure may seem tedious to describe, but in practice it gives quite good results.

I was also pleased to note Mr. Windeler’s remarks about the driving of alternators. As he remarked there is no difficulty whatever in running Diesel driven alternators in parallel, provided the flywheels were designed with the necessary coefficient of speed fluctuation. As rightly mentioned by Mr. Windeler, most of the compressor troubles, especially in the early days, were due to over lubrication. It is absolutely necessary to keep the amount of lubricating oil supplied to its minimum, consistent of course with the proper functioning of the compressor.

A mechanical sight feed lubricator in which the amount of oil supplied can be regulated is preferable to the old method of hand pressure oilers and similar appliances.

The question of solid (airless) injection, versus air injection, was raised by several speakers. In this country the solid injection has found a certain amount of footing and the advocates of it make particular claims as to its simplicity as compared with the air injection, also lower fuel consumption, etc. Let us consider the question from the simplicity point of view: it is true that for a solid injection engine no high pressure injection air compressor is required, but still for starting purposes, compressed air is used by most of the makers. This air must be supplied by some sort of a medium pressure compressor, which for arguments sake can be assumed to be separately driven, thus not affecting the mechanical efficiency of the engine.

As far as weight is concerned the gain will be comparatively small, when the two plants are compared. In the solid injection engine one gets rid of the high pressure air piping and joints, only to have those replaced by high pressure fuel piping with its joints, which have to withstand pressures varying from 2,000 lbs. to 9,000 lbs. per sq. inch, according to the type of engine.

An important point to remember is the combustion of fuel inside the cylinder. Most solid injection engines run with a smoky exhaust, causing deposits to set on to the cylinder walls, valves and exhaust passages, requiring frequent cleaning of the engine parts. In the case of an air injection engine the combustion is practically perfect, resulting in a clean exhaust and clean internal engine organs and consequently in a low fuel consumption.

Again it is said that a solid injection engine can work at a lower compression pressure than an air injection engine, but the maximum working pressure is higher, ranging from 550 to 550 lbs. per sq. in., whereas in the air injection engine the maximum pressure rarely exceeds 500 lbs. per sq. in.

The higher maximum pressures are detrimental to the smooth running of an engine and require therefore special design of engine in order to withstand the high stresses set up, and this entails a bulkier and heavier engine. Mr. Windeler mentioned the slow running and manoeuvring capabilities of the Doxford engine, which being of the opposed piston type of four units is, in reality, an eight piston engine having eight cranks, therefore, it may be considered as an eight cylinder single acting engine. The two outside cranks of each unit, belonging to the upper piston can be reckoned as one crank as far as the turning moment is concerned. The engine in question runs normally at 75-77 revs. per min., and a minimum speed of 15-17 r.p.m. was obtained at sea.

This is a remarkably low speed, as it is only about 20% of the normal speed. The Nobel-Diesel two-stroke single acting four-cylinder engine of 1600 B.H.P. can run at 24% of normal speed without any difficulty whatever.

I would like to thank Mr. McLaren for his kind remarks. The next speaker spoke about weights. I presume he meant weight per H.P. Through suitable design the weight per B.H.P. can be reduced considerably, as is instanced for example by the Nobel-Diesel 200 B.H.P. V-type engine of the M.Y. "Intermezzo". I do not think any engines of the high compression type have been built lighter than the above. I understand that the aviation people are now beginning seriously to consider the application of Diesel engines for aeroplanes and airships on account of greater safety when using oil fuel.

I have heard recently that a firm in Scotland is experimenting with a very light high speed Diesel engine intended for aviation purposes, though for obvious reasons, further particulars of the above engine are not yet available for the technical press. Regarding these light weight engines, one cannot expect them to run continuously at full load at the high speeds for which they are necessarily designed. It is not feasible for instance to aim at a reduction in weight of an engine for the mercantile marine on the scale of an engine to be used in a submarine. Rigidity and reliability have to be taken into account as well as low speed to suit the propeller in case of merchant ships.

However recent experience shows that the weights of Diesel engines can be reduced considerably and that is where the two-stroke cycle shows a particular gain. The weights of two-stroke Diesel engines of similar power and r.p.m. are about 65-75% of the weights of four-stroke engines.

Regarding Mr. Thom’s remarks about the slow running of steam engines I do think that the Diesel engine can compete with the steam engine in this respect, because speeds of 20-25 r.p.m. are about the slowest speeds one gets with condensing steam engines driving their own vacuum pumps and these speeds are those of Diesels also. I do not know the particular reason why a fuel injection pressure of over 9000 lbs. per sq. in. had been adopted in the Doxford engine, but other makers of solid injection engines use for marine work injection pressures of 2500-3000 lbs. per sq. in. (mercantile type) and 4000-6000 lbs. per sq. in. (submarine type).

As the Doxford engine runs at 77 r.p.m. only, it scarcely could be called a high speed engine. I think high injection pressures that are now used are an attempt to obtain a better atomisation of the fuel, and, as the problem of solid injection is still in its infancy, naturally a great variety of systems are being tried in the endeavour to obtain satisfactory working results. With regard to relative space required by the engine room in a motor ship and a steam ship, I consider it unfair to compare the former with the latter on hull dimensions.

If one puts into two sister hulls steam machinery in one and Diesels (especially two-stroke) in the other, the two ships will have still practically the same D.W. capacity because their engine rooms will have to be equal for reasons explained by Mr. Fielden. This will mean that in case of the motorship there will be plenty of spare space in the engine room which will not be available for cargo. When designing a motorship as such, which is to compete with the steamer of same D.W. capacity, the hull of the motorship can be made much smaller. The 13% engine room space can thus be esaily obtained, giving in the same time an engine room of ample but not excessive dimensions.

Talking about the carrying of fuel in double bottoms instead of bunkers, the motorship has the advantage of being able to bunker at the cheapest oil supply port and take fuel for the round voyage. I have heard t hat this is done by many Swedish motor ships ; they buy their oil in the cheapest market, retain as much of it as is required for the round voyage and sell the surplus in Sweden at the local market price. By such means their fuel bill is practically nil.

One speaker referred to the use of eccentrics instead of earns for valves, saying that marine engineers do not like cams. I am not aware of any modern type of marine Diesel engine having eccentrics for actuating the valves, but on land gas engines, the practice is fairly common. I can only recollect a few cases of obsolete marine Diesel engines of the two-stroke type in which the eccentrics were used to actuate certain valves only, but not all of them (Nobel, Fiat, Tosi, etc.)

Personally, I think there is nothing to be afraid of a cam and when clearances are properly adjusted and the cams covered up by detachable shields, the arrangement is as neat, reliable, simple and silent as could be desired. An eccentric gear is a far more complicated and costly piece of mechanism than a cam gear.

With reference to Mr. Timpson’s remarks about the tele­ scopic piston cooling gear, there are several types of such gear, some having glands and some glandless pipes (Sulzer, etc.). In case of crosshead engines the cooling gear of the telescopic type is generally so designed that any leakage of water is prevented. With regard to the grasshopper or link type of cooling gear, the trouble was always at the joints, which are liable to leak if they are of the ordinary surface friction type. The main point in the design of the link type of gear is to get rid of the surface friction joints. Our firm (Nobels) use now rubber joints and they work quite satisfactorily. I think I have covered the principal points raised, and in conclusion, I would wish to express my thanks to Miss Holmes and the gentlemen present for the kind reception of the paper.

A hearty vote of thanks was accorded to the author.

The Evolution of The Nobel Diesel Engine. (Part II.)

By Baron George J. Steinheil, B.Sc., M.I.N.A., M.I.Meeh.E., M.I.A.E. (Member).

READ Tuesday, November 21, at 6.30 p.m.

Chairman: Mr. P. B, FIELDEN (Vice-Chairman of Council).

The two-stroke cycle always appealed to Nobel engineers, because it possessed too many advantages over the four-stroke cycle in spite of all the practical difficulties of its application at the time of the adoption of that cycle by Nobels in 1901.

In that year a 13 ½, b.h.p. horizontal single-cylinder two-stroke hot bulb engine with crankcase compression and solid injection of fuel was produced. This type of engine was largely used for projector lighting sets in the Russian artillery, the engine being direct coupled to an 8 KW. generator.

The whole plant, including switch board, automobile type radiator, tanks, etc., was mounted on a carriage frame, suspended on semi-elliptical rear and elliptical front springs over respective road axles, which had artillery wheels.

The carriage was horse driven, seats for two men (coachman and mechanic) were provided in the front part of the carriage. The weight of that early type of 8 KW carriage was 3 ½ tons complete, overall length 12ft. 9ins., width 6ft. 6in. Fuel consumption (Russian kerosene sp. gr. 0,826, Cal. value 11,000 cal/kg.) was 510 grams per b.h.p. hour. In later years two and three cylinder vertical engines of 8 KW. and 12 KW. respectively were produced for similar purposes, the weight of complete 12 KW. carriages having been reduced to 2½ tons and fuel consumption to 393 grams per b.h.p. hour at 500 r.p.m.

From the experience gained with the running of these two-stroke hot. bulb engines, very valuable information was obtained and it was made use of when the first Nobel Diesel two-stroke engine was designed in the autumn of 1902. In the summer of 19’03 that first two-stroke Diesel engine was ready for tests in the shops and it underwent a series of exhaustive trials on the test bed.

The engine was a vertical single cylinder stationary engine with crankcase compression (Fig. 30). The cylinder diameter was 185 m/m and stroke 290 m/m and it developed 20 ,b.h.p. at 300 r.p.m., giving a brake mean effective pressure pe = 3,85 kg/cm². The fuel consumption of the engine was 215 grams per b.h.p. hour at full load. During the tests the engine was often run for long intervals at an overload of 15%, developing 23 b.h.p. at 300 r.p.m. with a pe = 4,43 kg/cm². This fuel consumption was very good for an engine of that size and even then compared favourably with four-stroke Diesel engines of similar dimensions and piston speed.

In order to study the reliability of the engine it was put to drive the transmission of one of the Nobel munition shops during the Russo-Japanese war, which duty it performed for three years, having daily runs of 10 hours.

Such running of the engine under actual working conditions gave a good opportunity to study its behaviour and defects and it must be said that comparatively very little trouble was experienced with that engine when considering its novelty of design at the time.

After the completion of the war work, the engine was presented by Mr. Emanuel Nobel to the Petrograd Institute of Technology for experimental purposes in the Engineering Laboratory.

The peculiarity of that engine was in the method of scavenging adopted. Experience with ordinary crankcase compression hot bulb engines had shown, that a volume of air, not exceeding the swept cylinder volume, could only be sucked into the crank-chamber.

This meant, that the working cylinder was starved of air, as considerable loss of air occurred through the exhaust ports, because of the small height of the inlet ports. All this led to a small power output per unit of cylinder volume or otherwise to a small M.E.P. It was considered very desirable to have an excess of scavenging air, so that the cylinder after the closing of the exhaust ports would contain a good charge of air.

The present day method of doing this is through the adoption of the scavenging pump: but at the time, especially taking into consideration the small size of the engine, the scavenging pump was considered a luxury and unnecessary complication.

In the engine mentioned, the function of the scavenging pump was performed by the underside- of the pistons of the working cylinder and air compressor.

For this purpose the lower part of the compressor was connected with the inside of the crank-chamber and the two stage tandem air compressor was driven by links from the main connecting rod in such a way that the upward and downward motions of both pistons coincided.

The volume swept by the scavenging sides of the pistons was greater than the working cylinder swept volume by the amount of compressor piston swept volume. There were ten automatic suction valves, five on each side of the crankchamber. These valves were of round steel plate type with a central spindle and spiral spring. To prevent excessive hammering, the valve lift was very small (2 m/m.—3/32in.) and the side of the plate that came in contact with the valve seat was covered with fibre.

The scavenging air was admitted to the cylinder through a single row of upwardly inclined inlet ports placed all round the lower part of the cylinder and the exhaust gases were expelled upwards through two exhaust valves in the cylinder head, which also contained the fuel and starting valves.

All these valves were actuated from the camshaft near the top of the cylinder in the usual way. Theoretically such an arrangement possessed many advantages, as it allowed a low velocity of scavenging air while passing through ports and gave thus practically a solid air column which entered the cylinder and pushed out the exhaust products in front of it without mixing with them. In service during prolonged runs, a certain amount of valve trouble was experienced at the beginning, owing to over-heating of the exhaust valves until a suitable material was found to make the valves from.

For larger powers it was doubtful whether such ail arrangement would prove successful, especially as the exhaust valves would require water cooling, and the cylinder heads would he likely to give trouble due to the heat stresses set up in the complicated castings of the heads. But nevertheless such an engine with 67 b.h.p. per cylinder output was built by Nobels in 1905, i.e., two years after that first engine. As already mentioned the motor tanker "Ssarmat" had a Del-Proposto drive, and the Nobel Bros. Petroleum Production Co. had decided on the conversion of the whole of their fleet into motorships.

From a commercial point of view tlie Del-Proposto drive was too heavy, too complicated and consequently too costly. The need for a direct reversible marine Diesel engine was urgently felt, and the Nobel Works were requested to design such an engine.

That was no easy proposition as the problem of direct reversing involved too many unknown factors. The question of the cycle had to be considered first. The peculiarities of the four-stroke cycle were fairly well known by the time, but for marine purposes the four-stroke engines of those days were too heavy and bulky; lighter and cheaper engines were wanted.

Experience with the "Vandal" and "Ssarmat" was proving this. All these considerations led Mr. Anton Carlsund (then Chief Engineer of the Nobel Works) to believe in the advisability of adopting the two-stroke cycle for marine propulsion. A three cylinder vertical crankcase compression direct reversible experimental engine was therefore designed.

In August, 1905, the first trial of that engine was made and a few hours after the first start, the engine was reversed, which operation was performed in 18 .seconds, without any difficulty whatever.

Many reversing tests were made afterwards and the reverse gear operated always quite satisfactorily. That fact is of great historical interest as this engine was thus the first direct reversible Diesel engine in the world. The engine besides the reverse gear possessed many novel features, some of which proved successful and were adopted in later types of two and four-stroke engines, whereas some proved to be a failure and were consequently abandoned. The three cast iron cylinders of 260 m/m diameter and 300 m/m stroke were bolted to three separate .crankcases mounted on a common cast iron bedplate. The engine was rated to develop 200 b.h.p. at 400 r.p.m., with a brake mean effective pressure pe = 4,73 kg/cm² (67 lbs./in.2) (Figs. 31 and 32). The. scavenging arrangement of that new engine was .similar to that of the 20 b.h.p. engine, as far as the main cylinder was concerned.

The inlet ports were placed on the lower part of the cylinder liner and the exhaust gases were ejected through exhaust valves in the cylinder head, which also had the usual fuel and starting valves.

The crankcase arrangement was quite different from that of the small engine. In the case of the 200 b.h.p. engine, an attempt was made to do away with automatic suction valves and with the excess air. Instead of the automatic valves in the crankcase, there were slots in the lower part of the cylinders, which connected the inside of the crankcase with the atmospheric air, when the lower part of the piston skirt would uncover these slots, while the piston would be approaching the end of the upward stroke. This upward motion of the piston would create a vacuum in the crankchamber, and, as soon as the suction ports would be uncovered, the air from the outside atmosphere would rush to fill the crankcase.

There it would be slightly compressed and by-passed in the usual way into the working cylinder at the right moment through the inlet ports.

This arrangement though being very simple mechanically had the inherent drawback of all ordinary crankcase compression engines of starving the cylinder of air. It was soon found out that the expected power output of 200 b.h.p. could not be obtained, as the brake mean effective pressure at the actual full load of the engine was only 3,3 kg/cm² (47 lbs./sq. in.) which corresponded to 140 b.h.p. at 400 r.p.m. A two-stage tandem air compressor was placed at the forward end of the engine on a separate “A” frame and driven from the forward end of the crankshaft.

The design of the crankcase in three separate units did not give the engine frame the desired stiffness, which was particularly necessary as the engines of that type were proposed to be installed into boats having very light scantlings. Consequently a new design of one unit totally enclosed crankcase was adopted, as shown in Figs. 31 and 32. This design of crankcase proved very successful and became standard lor Nobel Diesel marine engines. In order to silence the suction air, the cylinders were enveloped by light sheet steel jackets (Fig. 31). The cast iron cylinder heads contained the two exhaust valves, also the fuel, starting and safety valves.

The valves were actuated by levers from the camshaft supported on brackets cast integral with the heads and driven from the usual vertical shaft. No governor was fitted, the speed regulation having been obtained by a hand lever actuating the fuel pump. The latter had only one plunger for all three cylinders, the fuel before entering the fuel valves passed through a distributor which regulated the equality of fuel supply to the cylinders. Forced lubrication was used for cylinders, compressor, and main bearings, which were watercooled. The crank-pin bearings were lubricated by banjo rings. The exhaust pipe was also water-cooled, which was an innovation at that time, but the exhaust valves were uncooled.

Considerable trouble was experienced with overheated exhaust valves and cylinder heads during continuous runs. Owing to the complicated casting of the head, severe heat stresses were set up and heads used to crack. The reverse gear consisted of threegroupsof cams, the cam being in duplicate, for ahead and astern running, and could slide sideways, when actuated by forks from a layshaft.

The displacement of that layshaft could be controlled by a hand lever seen on the right of the engine below the camshaft (Fig. 31). The three eccentric shafts, flexibly connected together, were so designed, that through partial rotation of the master lever the valve rocking levers could be lifted, so that the rockers could allow a free sliding of cams. Then all the cylinders could be put on starting air by placing the master lever in the suitable notch and then one by one on fuel. This sliding cam type of reverse gear is generally known as Carlsund’s Reverse gear.

It must be admitted, however, that as far as the two-stroke cycle part of the engine went, it was a failure, but the reverse gear and other details proved to be quite successful. Therefore it was decided to adopt this type of gear to a four-stroke engine. In order to reduce the weight of the four-stroke type engines then available, a special design had been prepared embodying an enclosed crankcase and high r.p.m.

In 1907 the first reversible engine of that type was completed, and, as already mentioned, two such engines were fitted into the Russian Submarine "Minoga. Experience gained with the second experimental two-stroke engine clearly showed that the presence of exhaust valves in the head ivas undesirable and that probably an opposite arrangement (scavenging valves in head and exhaust performed through ports) would prove more successful.

In 1909 the Russian Admiralty was pressing Diesel engine makers to supply for submarines very light compact 'engines with a high (for those days) power output. The weight specified was 25 kg or 55 lbs. per b.h.p. and the power 500-400 b.h.p. The small engine-room space available forced Nobels to adopt the two-stroke cycle again; the new engine was of the high speed valve scavenging type with open crankcase and it developed 850 b.h.p. in six cylinders at 400 r.p.m. The general design of that engine was very peculiar, and although it is jnucli out of date nowadays, a certain amount of historical interest is attached to it, and therefore I may be permitted to say a few words about it.

The eight-throw crankshaft of the engine was supported by nine journal bearings on a cast iron bedplate (Fig. 33) The cylinders, or to be more correct, the cylinder covers only were supported by steel rods, which took all tension stresses. These tie rods had transverse diagonal bracing to give rigidity to the engine. The cast iron cylinder liners were suspended from the cylinder heads, each being bolted to the latter by twelve studs. The thin cast iron water jackets were bolted round the liner, special means for expansion having been provided (Fig. 34).

The cylinder heads were steel castings, of a rather complicated design as they contained not less than four valves, of which only one was stationary during the working of the engine, and it was the starting valve, the remaining valves were two scavenging and one fuel valve.

All the six heads were bolted together at the sides, thus forming one solid entablature on the top of the engine, which added wery much to the rigidity.

The sylinder dimensions of that engine were: Diameter 250 mm, and stroke 300 mm. which at a piston speed of 4 meter pr second gave a brake mean effective pressure of 4,45 kg/cm². The cast iron piston were of the trunk type and oil cooled by means of a rocking gear.

The pistons could be withdrawn downwards without disturbing cylinder heads and high pressure joints. The exhaust products were expelled into the exhaust pipe through exhaust ports om the lover part of the liner placed all round the circumference of the latter. All the above mentioned valves were actuated by a camshaft driven from a vertical shaft at the rear end of the engine and supported on brackets from the cylinder heads. To prevent the splashing of oil the engine frame was covered with easily detachable thin sheet steel shields.

The crankshaft lubrication was forced, whereas the gudgeon pins were lubricated with the piston cooling oil. The governor was of the Hartung type, acting as a cut-out when revolutions exceeded a pre-determined limit.

The air compressor and two water pumps were situated at the forward end of the engine and were direct driven from the crankshaft. The most interesting part of that engine was the method of scavenging. A double acting scavenging pump, with a cylinder diameter 520 m/m and stroke of 300 m/m, the piston having a trunk guide of 130 m/m, was placed between the compressor and the first cylinder.

The valves of the scavenging pump were automatic and a cooler was provided for the scavenging air so as to cool it before it entered the air receiver which was placed alongside the cylinder on the off side of the engine. The air filling the cylinder of a two-stroke Diesel engine after the scavenging process has been completed, must be compressed to a pressure of 31-35 atm (450-500 lbs./in.2) so as to obtain the necessary combustion for the fuel.

The air pressure inside the cylinder at the end of the scavenging period is proportional to the pressure in the air receiver and therefore the final compression pressure, depending upon the initial pressure inside the cylinder, is also proportional to the receiver pressure.

The periods during which the processes of scavenging and exhaust take place are functions of time and therefore of r.p.m. The arc. of opening of the exhaust ports and scavenging valves being constant, the time they remain open is inversely proportional to the revolutions per minute of the engine.

Therefore at slow speeds these valves and ports remain open longer than normally, and a certain amount of scavenging air escapes past the exhaust ports together with the exhaust gases, and the lower the speed the greater the loss of scavenging air.

Due to this the pressure inside the receiver naturally drops, as the scavenging pump is usually designed to supply a certain constant quantity of air corresponding to a given speed, and the ratio of pump volume to cylinder volume (usually about 1,25—1,5) is generally chosen to give best results at full speed and normal load.

The reduction of the receiver pressure brings forward the reduction of initial pressure in the cylinders and consequently a reduction in the final compression pressure, which may become low enough not to ignite the fuel. It is a known fact,'that the difficulty of quick starting ot ordinary two-stroke engines is due to tlie slow acceleration of the engine under starting air, with the result that the engine has to be put on fuel at a much lower speed than is desirable, and often starting fails, especially in cold weather, owing to the low compression.

To overcome this defect it is usual to run the engine for several revolutions, so that it would speed up and the pressure in the receiver would approach nearer to that of normal, but this of course entails a considerable consumption of starting air which in many, cases, such as in submarines for instance, cannot be afforded and other means must be provided.

Very often in cold weather resort has to be made to electric heaters in the suction pipe of the scavenging pump. In the case of the .above described engine Nobels tried to overcome these inherent drawbacks of two-stroke Diesel engines, by controlling the length of scavenging period.

For this purpose an intermediate oscillating butterfly valve A and slide valve B (Fig. 34) were introduced on each cylinder between the air receiver and scavenging valve. This combined valve was actuated by a link and two eccentrics (one for ahead and another for astern) mounted on the camshaft.

The moment of opening of the valve A and with it of the admission of scavenging air, could he varied at will by the rotation of sleeve B, whereas the end of the scavenging period always occurred when the exhaust ports were covered by the piston.

At slow speed the oscillating valve A was made to open later, thus giving a. shorter period of scavenging, i.e., one approaching in length that of full speed ; therefore the drop in initial pressure was obviated and compression kept normal.

A lever actuated all the sleeves B simultaneously, and the working position for that lever was such that the pressure in the receiver under any speed was to be equal to that of full speed.

Considerable economy in starting-air was thus obtained. The valve gear of the engine easily led to the adoption of the so-called “ Supercharge,” i.e., admission of extra air into the cylinder after the exhaust ports were closed by the piston.

This was obtained by fitting specially shaped cams to the scavenging valves allowing them to remain open for some time after the exhaust ports were closed.

Comparative trials with and without supercharge showed no particular advantages of same.

The reversing gear of the Carlsund type consisted of double sets of cams for each cylinder mounted on a sleeve which could slide on the camshaft proper, when actuated by forks connected to the layshaft which was parallel to the camshaft.

The layshaft was actuated by a hand lever. Besides the endwise motion due to tlie hand lever the layshaft was capable of a slight rotary motion given by the starting lever. The layshaft was connected through suitable mechanism with the valve gear and the rotation of the layshaft threw in and out of gear the starting and fuel valves as well as fuel pumps during manoeuvring.

The starting gear was of Nordstroem’s type and the engine cylinders were divided in three groups of two for starting purposes.

By rotating the starting handle clockwise from the “ STOP ” position to the first notch, all cylinders were put on air, further rotation brought first one pair of cylinders on fuel, and subsequently the second and third pairs.

There were six fuel pumps divided in three .groups and each group was actuated by an eccentric from the camshaft.

The amount of fuel supplied to the cylinders was regulated by a fuel lever, which lifted by means of suitable links the suction valves of fuel pumps.

The fuel consumption og that engine at full load and normal speed vas 235 gr. pr b.h.p. hour.

The weight of the engine complete with all accessories and flywheel was nine tons or 25,7 kg. (58 lbs.) per h.h.p. In order to test this engine under actual seagoing conditions, the engine was fitted into Mr. L. Nobel’s motor yacht Gradustchy. She was a boat of' 80 tons displacement, 120ft. length B.P., 13ft. breadth and 4ft. draught, and a speed of 13* knots. Exhaustive trials were carried out at sea with this boat in all sorts of weather, and the running’ of the engine proved quite satisfactory. However, the sea experience also showed that a complicated engine of that kind could be run only by very well trained engineers and was likely to give trouble in the hands of ordinary naval crews such a.s were then obtainable for submarines. Therefore this type of engine was abandoned and Nobels proceeded to design a. two-stroke submarine engine on a, modified principle. By 1911 the design of that new engine was ready and early in 1912 a two-cylinder experimental set was completed and ready for tests.

That experimental set had the two cylinders cast in block with separate cast iron liners. The two separate Cylinder heads were steel castings bolted to the cylinders (Fig. 35).

The cylinder dimensions were: Diameter 450 m/m, by stroke 480 m/m, and it developed 450 b.h.p. at 320 r.p.m. In reality, this engine was a part, so to speak, of a six cylinder submarine engine of the same cylinder dimensions. The cylinders were mounted on a thin cast iron crankcase, and the tension stresses were taken up by through bolts anchored in the bedplate. The double acting scavenging pump, having a piston valve, and a three stage air compressor were direct driven from the forward tend of the crankshaft. The peculiarity of that engine was in the method of scavenging- it had the so-called controlled port scavenging, now adopted as standard by Nobels.

In that engine a part of the circumference at the lower end of the liner contained a number of scavenging ports, and the remaining part—exhaust ports.

All ports were of the same height. The scavenging ports of both cylinders had a common piston valve which controlled the moment, of admission of the scavenging air into the cylinder and was actuated by an eccentric from the camshaft supported on brackets above the cylinder heads.

The design of the cylinder head was much simpler than in previous types of two-stroke engines, as only one working valve, the fuel valve, was in the head; the other two valves, starting valve and safety valve were stationary, while the engine was running. The two fuel pumps were driven from the camshaft and a ball governor was mounted on the vertical shaft.

The lubrication of cylinders, gudgeon pins -and air compressor was forced by means of a mechanical lubricator, whereas the main bearings were gravity fed and big ends had centrifugal lubrication (banjo ring type). In order to study the reliability of this engine, it was put into the power station of Nobel Works in Petrograd in the summer of 1912, where it ran in parallel with ordinary stationary engines for five years.

During the war years this engine was regularly running non-stop for six days a week.

In summer 1917 the engine was removed from the power-house to the test shop again, rebuilt and further research work was carried out on it until the virtual closing of Nobel’s Russian Works in 1918. From the experience gained with that engine an 8-cylinder submarine engine was designed and a large number of such engines was built in 1914-1918, and fitted into all the large twin screw Russian submarines of the Kayuar class.

These engines had four pairs of cylinders of diameter 390 m/m, by stroke 430 m/m. the pairs were cast en-bloc and had a common piston valve for the control of scavenging ports similar to those of the experimental engine (Fig. 36). The engines developed 1,360 b.h.p. at 350 r.p.m. The eleven throw crankshaft was supported in a cast iron bedplate. A cast iron crankcase acted as housing only because all the tensile stresses were taken up by through, bolts which supported the cylinders. The cylinder covers were steel castings and each cylinder had its own cover bolted to the cylinder block proper.

In general design it followed the experimental set although it differed from its details. The ports were of equal height. At the forward tend of the engine were placed two double acting scavenging pumps, the upper part of their trunk guides serving as the L.P. stage of' the air compressor. The remaining two stages (I.P. and H.P.) of the compressor were in tandem and driven from the very foremost crank.

The fuel valves were inelined ,so as to reduce the height of the engine. All the valves with the exception of safety valves were actuated by push rods and rockers from the camshaft, which was placed near the top of the crankcase. A centrifugal governor of the Jalms type acted as a cut out, and prevented racing of the engine. The first two engines were made reversible and they were fitted into the submarine "Kaguar". The remaining engines were non-reversible, as practice had shown that even with such large submarines the reverse motion could easily be given by the electromotors usually provided for underwater propulsion. All the control gear was at the reair end of the engine as is usual with submarine engines in general. A point of peculiar interest in connection with this engine is the method ,of lubrication. The cylinders gudgeon pins and air compressors were supplied with oil under pressure from mechanical lubricators, but the main bearings, which were water cooled, had ordinary gravity feed and the orankpins had centrifugal lubrication (banjo ring). No bearing trouble was experienced with this kind of lubrication in spite of the high speed of the engine and this only goes to prove, that with careful design such method of lubrication can be made as effective as the forced lubrication usually adopted for high speed engines. The fuel consumption of this engine at full load and normal speed was 228 gr. (0'504 lb.) per b.h.p.

The further development of submarine Nobel Diesel engines went in two ways: engines of higher power than the above and engines of lower power.

The lover power engines were of the six cylinder type with cylinders cast in pairs. They developed 550 b.h.p. at 350 r.p.m. The cylinder diameter was 300 m/m and stroke 400 m/m. The scavenging ports were controlled by horizontal rotary distributors mounted on a common shaft. Four such engines were to be placed in a submarine: two engines driving propellers direct (cruising condition) whereas the remaining two, coupled to dynamos, could charge the accumulators in the meantime, and supply additional power for full speed by driving the electromotors on the propeller shafts. Thus each propeller shaft at full speed would have had two engines driving it, one directly and the other indirectly. This method of propulsion was a modification of the Del-Proposto system.

The larger engines were eight cylinders sets with cylinders cast separately and developing 2,500 b.h.p. at 250 r.p.m. These latter were of the cross-head type and were destined for the large Russian submarine twin-screw cruisers.

Besides submarine engines, high power two-stroke auxiliary sets were built for the four Russian battle cruisers of the Navarin class. Each ship was to have two such engines direct coupled to 320 K.W. dynamos. The engines developed 480 b.h.p. ,at 320 r.p.m. in six cylinders of 320 m/m diameter and 350 m/m stroke, they were of the crosshead type.

The cylinders were cast in pairs, with separate steel-casting heads for each cylinder. Each pair had a mechanically operated piston valve which controlled the inlet ports on the near side of the engine, while the air receiver or scavenging air pipe wais bolted to the off side of the engine above the exhaust pipe and communicated with the corresponding scavenging valve -by internal passages in the cylinder blocks. A double acting scavenging pump and three stage double tandem air compressor (intermediate stage was below the L.P. stage) were in line with the cylinders and direct driven from the forward end of crankshaft. The pistons were oil cooled, whereas the cylinders had sea water cooling.

No flywheels were provided, the dynamo armatures acting as such. A particular feature of these engines was the compactness of their design, their overall dimensions were, length of bedplate 5450 m/m length, overall (including dynamo 7750 m/m, width of bedplate 1,100 m/m, height above centre of crankshaft 2400 m/m, maximum height (above floor) 2940 m/m.

Several sets of the three above mentioned types were under construction in 1917-1918, but their fate is unknown to the author, as he, together with many other engineers was obliged to leave the Russian Nobel Works, when these were “ nationalised ” by the Bolsheviks.

The activities of the Nobel Works did not rest with submarine and Naval type engines, as notwithstanding the handicap of war work, commercial types of two-stroke Diesel engines were also developed and built. A successful type of such engine was built in 1915 for the twin screw passenger motorship Irmperatritza Alexandra, of the Kawkaz and Mercury Steamship Co., for their mail service between Baku and Krasnovodsk on the Caspian Sea. These engines and their trials were fully described by the author in “Engineering” of 22nd December, 1916, and therefore only a little additional information will he given about them.

The ship, which originally was a passenger steamer and was converted to Diesel power, had the following leading dimensions: Length B.P. 243ft., breadth md. 34ft., depth md. 16ft. 9ins., and draught fully loaded 10 ft., displacement 1700 tons and cargo capacity 500 tons, speed 13 knots.

There was accomodation for 1000 passengers. Two four cylinder engines developed 600 b.h.p. each at a normal speed of 210 r.p.m.