Category Archives: Diesel Engines

Junkers Jumo 223 front

Junkers Jumo 223 Aircraft Engine

By William Pearce

In 1892, Hugo Junkers began experimental development of two-stroke, opposed-piston, gas engines. By 1910, Junkers had combined the opposed-piston principal with the diesel combustion cycle (compression ignition). Junkers investigated adapting this style of engine for aircraft use, but World War I and its aftermath prolonged development. In 1923, Junkers formed the Junkers Motorenbau (Jumo) to construct aircraft engines. Jumo’s first two-stroke, opposed-piston, diesel aircraft engine was commercially available in 1930. Originally known as the Jumo 4, the engine’s designation was changed in 1932 to Jumo 204.

Junkers Jumo 223 front

The 24-cylinder Junkers Jumo 223 two-stroke, opposed-piston, diesel aircraft engine was one of the most unusual engines ever built. The engine’s coolant exit ports can be seen by the upper crankshaft. The two starters at the front of the engine engaged the propeller shaft.

Throughout the 1930s, Junkers developed a number of two-stroke, opposed-piston, diesel aircraft engines. There is no cylinder head on an opposed-piston engine. Rather, each cylinder has two pistons that move toward the center of the cylinder during the compression stroke. Ports in the cylinder wall allow the admission of air and expulsion of exhaust. These ports are covered and uncovered by the pistons as they move. The Junkers opposed-piston diesels were six-cylinder, inline engines with two crankshafts—one at the top of the engine and one at the bottom. Each crankshaft had a complete set of six pistons.

For installation in aircraft, there were practical limits to the Junker’s inline, opposed-piston engine configuration. Its double piston design made it a very tall engine, adding more cylinders to the Junkers diesels would have created a very long engine with a long crankshaft susceptible to torsional stresses. Increasing the engine’s bore and/or stroke would result in a larger engine with a lot of rotating mass, necessitating relatively low rpm. Engines capable of a continuous 2,000 hp (1,490 kW) output were needed for proposed large transoceanic aircraft, but an inline, opposed-piston aircraft engine able to produce 2,000 hp (1,490 kW) of continuous power was simply not feasible.

Junkers Jumo 204

The Jumo 204 was the first diesel aircraft engine commercially available from Junkers. Its basic configuration was repeated in later Jumo diesels—collectively the most successful diesel aircraft engines produced.

By 1936, Junkers engineer Dr. Johannes Gasterstädt had come up with an opposed-piston engine configuration that would enable 2,000 hp (1,490 kW) in a compact package suitable for aircraft use. The configuration consisted of four cylinder banks positioned 90 degrees to each other so that they formed a rhombus—a square balanced on one point (◇). The pistons for two adjacent cylinder banks were connected to a crankshaft positioned at each corner of the rhombus. Each cylinder bank had six cylinders. The complete engine had four crankshafts, 24 cylinders, and 48 pistons.

Junkers’ rhombus-configured engine investigation was designated P2000. Dr. Gasterstädt passed away in 1937, and Prof. Otto Mader and Manfred Gerlach took over the P2000 project. By the end of 1937, a single cylinder test engine and a complete six-cylinder block had been built and run. In April 1938, the RLM (Reichsluftfahrtministerium or German Ministry of Aviation) redesignated the P2000 engine as the Jumo 223. By December 1939, a full-scale Jumo 223 engine was completed, and that engine was run-in by a dyno (the dyno turning the engine) in January 1940.

Junkers Jumo 223 split case

This picture of the separate castings that made up the Jumo 223 helps to illustrate the engine’s complexity. Note the scuffing and carbon deposits on the pistons, indicating they have been run.

The Jumo 223 was one of the most unusual engines ever built. The engine was constructed from two large and complex aluminum castings—one for the front of the engine and one for the rear. Each casting had four banks of three-cylinders. A large central gear was at the center of the engine where the two castings joined. Each crankshaft was made up of two main sections bolted together via a gear at its center. The gear on each crankshaft meshed with the central gear to transfer power from the crankshafts to the central gear. Drive shafts extended through the center of the engine from the front and rear of the central gear. The rear shaft powered the engine’s blower (weak supercharger) and accessories via a series of other gears. The front shaft led to the propeller. The central gear provided a .26 reduction in engine speed. At the front of the engine were two starters that engaged the propeller shaft to start the engine.

Junkers Jumo 223 cranks gear

The Jumo 223’s central gear was powered by gears at the center of the engine’s four crankshafts. Note the fork-and-blade connecting rods.

The left and right crankshaft gears each drove separate camshafts for an upper and lower row of fuel injection pumps. These camshafts and the injection pumps were located near the left and right crankshafts. Cast directly under each row of injection pumps was a square port that ran along the engine. This port took air from the blower and delivered it to a small chamber around each steel cylinder liner. Air entered the cylinders via a series of holes around the cylinder liner’s circumference. The fuel injectors were located in the center of the cylinder. As the pistons moved toward each other, the intake holes were covered and the air was compressed. Diesel fuel was injected and ignited by the heat of compression. The expanding gases forced the pistons away from each other, uncovering the intake holes (for scavenging) and then the exhaust ports, which were located near the upper and lower crankshafts. Exhaust gases flowed out the ports in the cylinder liner into a small chamber surrounding the liner. The exhaust gases for each cylinder bank were collected by a manifold that led to a turbocharger at the rear of the engine. It is not clear if the turbocharger was ever tested, but there is one photo that shows a Jumo 223 with the turbocharger or a mockup of it. The pistons were connected to the crankshaft via fork-and-blade connecting rods. Each crankshaft was secured in the crankcase by eight main bearings.

A triangular port for coolant was cast on both sides of the engine near the upper and lower crankshafts. Coolant flowed from the coolant pump located on the bottom rear of the engine and into the lower triangular ports. The coolant circulated throughout the engine and exited near the upper crankshaft via the coolant ports at the front of the engine.

Junkers Jumo 223 central gear

The central gear and front half of the engine is shown in this picture. Note the gears for the fuel injection pump camshafts by the left and right crankshafts. Coolant flowed through the triangular ports near the upper and lower crankshafts. Air flowed through the square ports near the left and right crankshafts.

The Jumo 223 engine had a 3.15 in (80 mm) bore and a 4.72 in (120 mm) stroke x 2 (for the two pistons per cylinder). Total displacement was 1,767 cu in (28.95 L). Without the propeller, the engine was 81.5 in (2.07 m) long, 48.8 in (1.24 m) wide, 53.0 in (1.345 m) tall, and weighed 3,086 lb (1,400 kg). The opposed pistons created a compression ratio of 17 to 1. With its planned intercooled turbocharger, the Jumo 223 was designed to produce 2,500 hp (1,860 kW) at an astonishing 4,400 rpm. That rpm would yield a fairly high average piston speed of 3,465 fpm (17.6 m/s). The Jumo 223 had a critical altitude rating of 1,800 hp (1,340 kW) at 16,404 ft (5,000 m) with the possibility of increasing the altitude to 32,808 ft (10,000 m) as the engine was further developed. Specific fuel consumption was .391 lb/hp/hr (238 g/kW/hr). The engine was contemplated for use in the four-engine Messerschmitt Me 264 long-range bomber, the six-engine Junkers EF100 commercial airliner, and other military aircraft projects.

The Jumo 223 engine ran for the first time on 27 February 1940. Without the turbocharger, the only boost came from the engine’s blower that was just intended to scavenge the cylinders. Peak high temperatures of 2,552 degrees F (1,400 degrees C) were encountered in the cylinders during combustion and caused pitting and seizure of the pistons. The issue was caused by the asymmetrical injection of fuel, a result of locating the injectors only on the outside of the engine, for ease of service, rather than having additional injectors inside the engine’s “square.”

Junkers Jumo 223 rear

The blower at the rear of the Jumo 223 can clearly be seen in this picture. The pipes leading away from the blower provided air to the passageways cast in the engine. The coolant pump is at the bottom of the engine.

Fuel injectors were modified, and tests continued throughout 1940. Three engines had been built by early 1941. In February 1941, the second engine was run for 100 hours and achieved a peak of 1,830 hp (1,360 kW) at 3,810 rpm. On 20 March 1941, the Jumo 223 passed the 2,000 hp (1,490 kW) mark by producing 2,040 hp (1,520 kW) at 3,980 rpm. During a 100 hour engine run in July 1941, crankshaft bolts and crankshafts were broken, indicating resonance vibration issues. In October 1941, the third engine completed a 100 hour test run at 1,500 hp (1,115 kW). The engine was run at a lower power because of the issues encountered when the Jumo 223 engine produced more power. The second engine was back in the test cell for a short run on 23 December 1941. The run set the mark for the highest power achieved by the Jumo 223 engine, producing 2,380 hp (1,770 kW) at 4,200 rpm.

Tests continued into 1942, but the engine’s reliability was a concern. The vibration issues seemed to be a result of the two-piece crankshafts and crankcase and the high rpm needed to produce the desired power. Along with the Jumo 223, Junkers was developing the Jumo 222—a 24-cylinder, spark ignition engine close to the same power and physical size as the Jumo 223, but lighter and of greater displacement. The Jumo 222 engine had more than its share of problems, and it made little sense to develop two engines in the same power class at the same time. In addition, developmental engines capable of more power than the Jumo 223 were needed.

Junkers Jumo 223 with turbo

This photo shows a Jumo 223 with a turbocharger. The exhaust manifolds can be seen leading to the turbocharger at the rear of the engine. Unfortunately, no information has been found regarding tests of this engine. It is possible that the turbocharger was only a mockup.

Development of the Jumo 223 as a production engine was halted in mid-1942. However, work on the engine continued, as it would serve as a model for a new, larger engine—the Jumo 224. By October 1942, six Jumo 223 engines were completed and two more were under construction. The eighth and last Jumo 223 prototype engine was run up to 2,200 hp (1,640 kW) on 28 February 1943. While this run was intended to be the last, Soviet forces had different ideas after the war. The Junkers factory was in Dessau, Germany and was part of the territory occupied by Soviet troops. The Soviets were interested in the Jumo 223 engine. The eighth example was run again on 23 March 1946 and for the last time on 4 April 1946. The last run was for a Soviet delegation and lasted 73 minutes. The run was halted after two pistons failed. Reportedly, at least one of the Junkers Jumo 223 engines was taken to State Factory No.500 in Tushino (now part of Moscow), Russia for further research, but no Jumo 223 engines are known to exist.

Note: There is no doubt that the Junkers Jumo opposed-piston engines in some way inspired the Napier Deltic, especially since Napier purchased licenses to build the Jumo 204 and 205 engines (to be built as the Culverin and Cutlass) in the 1930s. However, there is no indication that information on the Jumo 223 or 224 engines was applied to the design of the Deltic. In fact, the Deltic possessed many unique design characteristics, such as one crankshaft rotating the opposite direction compared to the other two.

Junkers Jumo 223 test run

The first Jumo 223 engine running on a test stand at the Junkers works in Dessau, Germany in early 1940.

Junkers Flugtriebwerke by Reinhard Müller (2006)
Flugmotoren und Strahltriebwerke by Kyrill von Gersdorff, et. al. (2007)
Opposed Piston Engines by Jean-Pierre Pirault and Martin Flint (2010)

GM EM 16-184 x section

General Motors / Electro-Motive 16-184 Diesel Engine

By William Pearce

GM EM 16-184 maintenance

This image shows an Electro-Motive-built 16-184A engine (since the triangular access ports have flanges around them). The top of the cylinder barrels, each with four exhaust valves, can be seen in the middle cylinder bank. The engine’s coolant manifolds are still in place. Note the two water pumps.

In 1937, the United States Navy visited the General Motors Research Laboratories (GMRL) in Detroit, Michigan. Since 1934, GMRL had been involved in experimental, single-cylinder testing of a new light-weight diesel engine. The Navy was interested in a light and powerful diesel and contracted GMRL to develop an engine that would produce 1,200 hp (895 kW). With an output of around 75 hp (56 kW) per cylinder, an engine with 16 cylinders would be needed. However, a V-16 would be too long and too heavy. Led by Charles Kettering, the GMRL designed the unique 16-184 engine to meet the Navy’s needs. The 16-184 engine designation stood for 16 cylinders, with each displacing 184 cu in (3.0 L).

The two-stroke 16-184 diesel had four banks of four cylinders situated at 90 degrees around the crankshaft. A unique feature of the engine was its vertical configuration in which the rows of cylinders were stacked above one another. Because of the stacked cylinder arrangement, this engine configuration was called a “pancake.” A centrifugal blower to feed air into the cylinders sat on top of the engine, and the engine was mounted on top of its right angle gear reduction for the propeller shaft. The 2 to 1 gear reduction was achieved by a pinion on the end of the crankshaft engaging a ring gear mounted on the propeller shaft. No reversing gear was incorporated, because the engine was used in conjunction with variable-pitch propellers.

The 16-184’s crankcase was constructed of steel plates welded together to form a single structure. It was built-up of four “X” elements, each consisting of four cylinders. A static strength report on two of the crankcases noted that they were “…truly remarkable pieces of engineering, and they will well repay careful study by anyone whose work involves mechanical design, welding design, welding techniques and weight saving.

GM 16-184 crankcase

This image of a General Motors 16-184 crankcase undergoing a stress test reveals many unique aspects of the engine. An exhaust housing has been installed on the upper cylinder bank. The top of the engine is on the left side. The intake passageway can be seen in the upper Vee. The camshaft housing can be seen in the lower Vee. The cylinder liners are not installed. Note that the triangular access ports do not have flanges, making this a General Motors-built crankcase.

The crankshaft was supported in and attached to the crankcase by four main bearing carriers and the timing gear housing at the top of the engine. The connecting rods were of the slipper type, which allowed for equal articulation for each cylinder’s rod and reduced the load on the individual crankpins. Each forged-steel piston was attached to its connecting rod by two trunnions positioned on either side of the connecting rod and bolted to the piston.

The blower on the top of the engine fed air into two crankcase passageways on opposite sides of the engine. The blower spun at ten times crankshaft speed and delivered around 4,000 cu ft (113.27 cu m) of air per minute at 6 psi (0.4 bar). The air flowed through ports in each cylinder barrel that were uncovered by the piston. The top of the cylinder barrel was enclosed by a housing for the fuel injector (at center) and four exhaust valves (surrounding the fuel injector). This housing made up the cylinder’s combustion chamber. The exhaust valves opened into a space above the cylinders where exhaust flowed into an exhaust manifold. The exhaust manifold was positioned in the engine’s Vee and above the intake passageway. The cylinders used uniflow scavenging, in which fresh air would flow through the intake ports in the lower cylinder barrel and push the exhaust gases out the open valves at the top of the cylinder.

GM EM 16-184 x section

A sectioned view of one of the 16-184 X cylinder groups. The propeller shaft drive is at the top of the image. Note the camshaft in the upper and lower Vees. The dark areas in the left and right Vees are the intake air passageways. The cylinder ports can be seen in the lower left cylinder.

Two camshafts were geared to the crankshaft via an idler gear in the timing gear housing at the top of the engine. One camshaft was situated in each non-intake/exhaust engine Vee. The camshafts controlled three pushrods for each cylinder via roller cam followers. One pushrod controlled the fuel injector while the other pushrods each controlled two exhaust valves. The pushrods articulated rocker arms that were bolted to the top of a cast iron exhaust housing attached over each cylinder bank. The top of the cylinder barrel assembly passed through the exhaust housing. This configuration allowed exhaust gases from the cylinder to be collected by the exhaust housing and delivered to the exhaust manifold via three ports for each cylinder.

Each piston was cooled by a jet of oil impinging on its underside. Two centrifugal water pumps were driven by the lower accessory section. The upper pump circulated coolant through each exhaust housing. The upper part of the cylinder barrel had a welded sheet metal water jacket. Via a special connection, coolant flowed from the exhaust housing into the cylinder barrel water jacket. The lower pump circulated sea water through the jacketed exhaust manifolds.

The 16-184 engine had a 6.0 in (152 mm) bore and 6.5 in (165 mm) stroke, giving a total displacement of 2,941 cu in (48.2 L). The complete engine was roughly 11 ft (3.4 m) tall, 4 ft (1.2 m) wide, and weighed 4,800 lb (2,177 kg). The 16-184 developed 1,200 hp (895 kW) at 1,800 rpm.

GM EM 16-184 installed

This view of an installed 16-184A engine shows the three pushrods for each cylinder. The middle pushrod controlled the fuel injector. Note the pedal and lever in the Vee. The pedal engaged a clutch and the lever connected the engine to or disconnected the engine from the propeller shaft.

By 1938, single cylinder test engines were operating reliably and achieving the design goals necessary for a complete, 1,200 hp (895 kW) engine. The design for the complete 16-cylinder engine had been completed and prototype construction was underway. The 16-184 was first run in June 1939, and it completed the Navy’s 168-hour endurance test on 31 October 1940. In 1941, two test engines were installed in an experimental submarine chaser: USS PC-453 designed by Captain A. Loring Swasey. PC-453 served as the prototype for a class of wooden submarine chasers during World War II. The boat was re-designated SC-453 and transferred to the Coast Guard after the war.

In 1941, 16-184 engine production was undertaken by the Electro-Motive Division of General Motors. Electro-Motive originally produced railcars and was purchased by General Motors in 1930 as the latter looked to expand into the diesel engine and rail marketplaces. The production engines built by Electro-Motive were designated 16-184A and had some minor changes to their crankcases, including welded-in cylinder liners where the prototype’s were screwed-in. In addition, triangular access ports on the General Motors 16-184 crankcase did not have flanges, while the Electro-Motive 16-184A crankcase did. The Electro-Motive 16-184A engines were built in La Grange, Illinois, and the first engine started test runs on 11 October 1941. The Navy accepted the first 16-184A engine on 5 February 1942.

Two pancake engines were installed in each of the 253 110-foot (33.5 m) submarine chasers built during World War II. After the war, several of these boats were sold to other nations. The 16-184A engines were noted for their reliable operation and good service life. Some of these engines continued to operate (occasionally) into the year 2000. Approximately 544 16-184A engines were built.

GM 16-338

This image shows the intake side of the General Motors 16-338 engine installed on its generating unit. This arrangement led to issues, for any liquids that leaked from the engine would drain down into the generator.

The 16-184A engine design was used as the basis for the General Motors 16-338 engine built in the late 1940s. The 16-338 had the same bore and stroke as the 16-184A and produced 1,000 hp (746 kW) at 1,600 rpm. Four 16-338 engines were installed in the Tench- and Tang-class submarines, and two were installed in the USS Albacore—the Navy’s first “teardrop” hull submarine, which paved the way for modern sub design.

The 16-338 engines sat atop a generator to provide power to electric motors that drove the ship’s propellers. The engine also had a different intake and exhaust arrangement in which the manifolds were situated in separate Vees of the engine. The 16-338 engines proved somewhat unreliable in service and required excessive maintenance. Some of the 16-338’s issues were due to the Navy using standard diesel lubricating oil rather than the special oil specified for use in the engine. Ultimately, the Tench- and Tang-class submarines were re-engined and their 16-338 parts were used as spares to keep the USS Albacore running until it was withdrawn from service in 1972.

– “Development of a Light Weight Diesel Engine” by J. C. Fetters, Diesel Power & Diesel Transportation (August 1942)
Parts Book GM Diesel Engine, Model 16-184A by Electro-Motive Division (1944)
Static Strength Tests of Diesel Engine Crankcases GMC 16-184 and EMC 16-184-A for 110-Foot Patrol Boats by J. W. Day (August 1943)
Diesel War Power by Electro-Motive Division, General Motors (1944)
Engines Afloat Volume II by Stan Grayson (1999)

Michel 3-cylinder

Michel Opposed-Piston Diesel Engines

By William Pearce

Hermann Michel* of Voorde, Germany was a foreman at the Krupp Germania shipyard in Kiel, Germany. Through his work, he experienced the common problems of two-stroke submarine engines. Seeking to avoid the disadvantages of conventional engines, Michel designed a unique, new engine. He believed his engine would be particularly well suited for marine use. His design was for an opposed-piston, two-stroke, diesel engine. Beyond the use of opposed pistons, the Michel engine was unique in that it was a crankless cam engine. With minor changes in the basic engine design, the cylinder group could either be stationary or rotate like a rotary engine.  Michel filed a patent application for his engine configuration in Germany on 20 July 1920 and in the United States on 23 August 1921.

Michel Cam engines

Drawings from Hermann Michel’s original patent show two- and three-cylinder cam engines. In the drawings, the cylinder group was stationary and the cam ring rotated. The upper cylinder in the three-cylinder engine drawing had the exhaust ports. Note that it was angled slightly different than the other cylinders to facilitate scavenging.

Michel’s engine design was for either two pistons in a common cylinder or three pistons in three cylinders. Regardless of the number of pistons used, the cylinder group possessed a common combustion chamber in which the pistons moved toward each other on the compression stroke. The movement of opposite pistons covered or uncovered intake and exhaust ports that were in the cylinder walls. This configuration eliminated the use of valves and a head gasket. The intake and exhaust port locations allowed scavenging air to flow through the cylinder and completely evacuate any exhaust gases when the ports were open.

The engine did not have a crankshaft. The pistons’ movement was controlled by a comparatively large cam ring that surrounded the cylinder group. The rod for each piston had rollers in an annular cam track that formed an undulating path. This path determined the pistons’ movement in the cylinder and facilitated the compression stroke. When configured with stationary cylinders, the cam ring rotated around the cylinder group. For a rotary configuration, the cylinder group rotated inside the stationary cam ring.

Unlike a crankshaft that is directly tied to the cycle of the engine, the cam ring could be made with several compression and power cycles for each revolution. For example, if the cam ring had six cycles, the cylinder group would go through six compression and six power strokes for each revolution of the cam ring. Likewise on a rotary configuration, the cylinder group would go through six compression and six power strokes each revolution.

Michel cam rings

This Michel patent drawing from 1923 illustrates the axillary cam (21) and axillary piston rod rollers (20) on a two-cylinder opposed-piston engine. The main roller (7) rode on the main cam track (15).

Michel took out at least five other patents relating to and further detailing his engine design. A patent filed on 27 October 1923 detailed the use of an auxiliary cam ring. In this design, the cam track was widened and the piston rod’s main roller rode on the track’s main outer edge during normal engine operation. The power stroke forced the main roller against the main track, and the main track was forced against the main roller during the compression stroke. As a result, the main roller was always in contact with the main cam track during normal operation.

Coaxial with the main rollers were smaller auxiliary rollers. During engine start or if a piston began to seize, the auxiliary roller would come into contact with the inner, auxiliary edge of the cam ring track. During the power stroke, if the cylinder lacked compression or there was too much friction between the piston and cylinder, the main roller would lose contact with the main cam track and the inner cam track would come into contact with the auxiliary roller. This action would result in a rattling nose emanating from the engine, alerting the (astute) operator that something was amiss.

A two-piston cam engine of Michel’s design was built in 1921 at the Krupp shipyard. For this engine, the cylinder group was stationary and the cam ring rotated. The engine had a bore and stroke of 5.9 in (150 mm), and the total displacement was 324 cu in (5.3 L). Reportedly, the engine produced 62.5 hp (46.6 kW) at 110 rpm. A larger two-piston engine followed with a 6.9 in (175 mm) bore and stroke; its total displacement was 514 cu in (8.4 L). This engine produced 120 hp (89.5 kW) at 110 rpm. Because of the six piston cycles per each revolution, it was noted that the Michel engine running at 110 rpm was equivalent to a standard engine operating at 660 rpm.

Michel 2-cylinder rotary B

Section drawings of the Michel 2-cylinder engine that was built in 1921. Like the patent drawings, the cylinder group was stationary and the cam ring rotated. Attached to the front of the cam ring housing was a drive shaft mounted in bearings.

After encouraging results with his two-piston engine, Michel went on to build a three-cylinder engine. For this engine, the cylinder group rotated within the stationary cam ring. The two intake cylinders were spaced 120 degrees apart, but the exhaust cylinder was at slightly different angle to allow that cylinder’s piston to lead the others. This arrangement uncovered the exhaust port first and improved cylinder scavenging. The three-cylinder engine had a 6.5 in (165 mm) bore and a 6.3 in (160 mm) stroke. The engine’s total displacement was around 626 cu in (10.3 L), and it produced 250 hp (186 kW), which seems high. Michel’s basic design allowed the addition of multiple cylinder groups (or stars) to create engines of increased power.

Michel continued his development of the three-cylinder opposed-piston engine design and reverted back to the use of a crankshaft, albeit three of them. The three cast iron cylinders were arranged in a Y configuration, and all the cylinders were spaced 120 degrees apart. Air was fed into the upper two cylinders via ports in the cylinder walls. The exhaust ports were in the wall of the lower cylinder, and exhaust gases were expelled through the side of the lower cylinder bank. The lower piston had a 24 degree lead time over the upper pistons to ensure good cylinder scavenging. The exhaust ports alone were uncovered for 32.6 degrees of crankshaft rotation. For the next 76.3 degrees, both the exhaust and intake ports were uncovered, followed by another 15.8 degrees where only the intake ports were unobstructed.

Michel section

Section view of the Michel three-crank opposed-piston engine. The crankshafts are marked A, B, and C. Clearly seen are the liquid-cooling (W), scavenging air (S), and exhaust (E) passageways. Note the unique piston head shape that creates a combustion chamber.

The three-cylinder engine had a 15 to 1 compression ratio. The engine’s three pistons converged on a common combustion chamber where a fuel injector was positioned vertically between the upper two cylinders. The piston heads were specially designed to create a combustion space when the pistons came together. Fuel injection started 19 degrees before the exhaust piston reached top dead center and continued for 21 degrees. The engine’s configuration resulted in very efficient combustion due to the high degree of turbulence and thorough mixing of air and fuel.

All three crankshafts rotated in the same direction. There was an additional, projecting crank at the end of each crankshaft. Attached to this crank was a triangular casting that connected the crankshafts together at the rear of the engine. This triangular member drove the generator and the water, oil, and Bosch fuel injection pumps. The fuel injection pump was positioned in the upper V of the engine.

Michel 3-cylinder section

Front and rear section view of the Michel three-cylinder opposed-piston engine. Note on the rear view, the triangular member connecting the three crankshafts and the rectangular scavenging air pump at its center.

A scavenging air pump was situated at the rear of the engine. This air pump was a rectangular frame formed integral with the triangular member that joined the crankshafts. The air pump took advantage of the frame’s rotary motion. The rectangular frame was sealed except for strategically placed passageways. A slide valve formed a partition within the frame and was fixed so that it could only move up and down. As the engine ran, the space within the frame on either side of the slide valve partition alternately expanded and contracted, creating a pumping action. Air was fed from the slide valve at 21-25 psi (1.4-1.7 bar) to the cylinders via internal passageways. Power from the engine was taken from the lower crankshaft.

In the early 1930s, Michel relocated to Hamburg, Germany and built a few of his redesigned, three-cylinder, opposed-piston engines. Like the cam engine, the cylinder group was somewhat modular, and additional groups could be added to the design. The engine with the smallest cylinder size had a 1.9 in (47 mm) bore and a 3.1 in stroke (80 mm). This engine had four three-cylinder groups and a total displacement of around 102 cu in (1.7 L) from its 12 cylinders. It produced 60 hp (45 kW) at 2,000 rpm and weighed 616 lb (279 kg).

Michel 3-cylinder

A Michel 3-cylinder group and its engine. This engine has one cylinder group. Note its short length and the single exhaust port of the lower cylinder..

A larger three-cylinder engine was built with a 2.6 in (67 mm) bore and a 4.7 in stroke (116 mm). Each three-cylinder group would displace around 75 cu in (1.2 L) and had an output of around 45 hp. A one cylinder group and a four cylinder group were made. The four cylinder group engine had a displacement of 299 cu in (4.9 L). This engine produced 180 hp (134 kW) at 2,000 rpm and weighed 1,188 lb (539 kg).

Although the engine’s size was not stated, a Michel engine was extensively run in a truck testbed and reportedly gave good results. However, the engine never entered production. The Michel line of engines was supposed to be made under license in the United Kingdom by Tekon Development Ltd and called the Stellar. However, it does not appear that any engines were made.

*Please note, the Hermann Michel discussed in this article is not the Nazi war criminal with the same name.

Michel 12-cylinder opposed piston engine

A Michel engine with four groups of three opposed-piston cylinders. This engine had a total of 12 cylinders. Note the four square exhaust ports on the lower cylinder bank.

– “Two-Stroke-Cycle Internal-Combustion Engine” US patent 1,603,969 by Hermann Michel (granted 19 October 1926)
– “Engine, and Particularly Internal Combustion Engine” US patent 1,568,684 by Hermann Michel (granted 5 January 1926)
– “Comments on Crankless Engine Types” NACA Technical Memorandum No. 462, May 1928 (Translated from “Motorwagen” 20 November 1927) 12.8 MB
High Speed Diesel Engines by Arthur W. Judge (1941)
The Modern Diesel fourth edition no date Illiffe & Sons Ltd
New Motoring Encyclopedia (complete work 1937)
Ungewöhnliche Motoren by Stefan Zima and Reinhold Ficht (2010)

Nordberg 12-cylinder radial diesel

Nordberg Radial Stationary Engine

By William Pearce

In 1889, Bruno V. Nordberg founded the Nordberg Manufacturing Company (Nordberg) in Milwaukee, Wisconsin to build various industrial machines. In the 1910s, the company entered the heavy-duty diesel engine market. Over the years, Nordberg expanded its stationary engine catalog to include engines from 10 hp (7.5 kW) to over 10,000 hp (7,457 kW). To further expand its market, Nordberg developed a line of stationary radial engines in the 1940s.

Nordberg 12-cylinder radial diesel

A 12-cylinder Nordberg diesel radial engine. This engine displaced 29,556 cu in (484.3 L) and produced around 2,000 hp (1,500 kW). Note the fuel injector in the center of the cylinder head.

The Nordberg radial offered several advantages over the stationary inline engines that were the current standard. With its cylinders horizontal, the Nordberg radial’s output shaft was in a vertical position. Although the engine was built primarily to generate power for the electrolytic reduction of aluminum, its arrangement was perfect for pumping applications. In addition, the configuration of the radial made it more compact and much lighter than a comparative inline engine. The Nordberg radial took up about half the space of an equally powerful inline engine and could be installed on a much lighter foundation.

The Nordberg radial was first introduced in 1947. The first engines were spark-ignition natural gas burning units that quickly established themselves as reliable and economical. These engines had two spark plugs located in the cylinder head. A single cam on the crankshaft actuated a gas valve for each cylinder. This gas valve allowed the natural gas into the incoming scavenging air for the cylinder.

Nordberg continued to develop the radial as its use spread to central power stations and various pumping applications, primarily for flood control and at sewage treatment plants. Nordberg soon developed a diesel version of the engine and a version that could run on a mixture of diesel and natural gas, which Nordberg dubbed Duafuel. The Duafuel engine could run on 100% diesel or as little as 5% diesel and 95% natural gas. This flexibility allowed the engine to operate with the most economical fuel mixture possible. In the diesel and Duafuel engines, the single cam now actuated a fuel pump for each cylinder, and the diesel fuel injector was in the center of the cylinder head.

Nordberg 12-cylinder radial spark ignition

A number of Nordberg 12-cylinder spark-ignition radial engines are loaded into a barge in Milwaukee, Wisconsin. Note the two spark plugs in the cylinder head. This image also shows the base of the engine that would extend under the operating floor.

A later development was the addition of two turbochargers and intercoolers that increased the engine’s thermal efficiency while decreasing its fuel consumption. It is not clear whether or not the turbochargers were available for all engine types or just for the spark-ignition engines.

The Nordberg radial was a two-stroke engine with a 14 in (356 mm) bore and a 16 in (406 mm) stroke. Each cylinder displaced 2,463 cu in (40.4 L). There was an 11-cylinder (RTS 1411) and a 12-cylinder (RTS 1412) version of the radial engine, displacing a total of 27,093 cu in (444.0 L) and 29,556 cu in (484.3 L) respectively. The 11-cylinder engine was 12.125 ft (3.70 m) in diameter while the 12-cylinder was 13 ft (4.96 m). The engines had an operating speed of 400 rpm. Output varied depending on the engine’s configuration. A 11-cylinder spark-ignition engine was rated at 1,340 hp (1,100 kW), an 11-cylinder diesel was rated at 1,655 hp (1,235 kW), and a 12-cylinder diesel was rated at 2,125 hp (1,585 kW).

The 11-cylinder and 12-cylinder engines both had a crankshaft cast of high tensile alloy iron. The crankshaft had upper and lower main bearings. Neither engine had a master connecting rod; all connecting rods were of the articulated type.

Nordberg 11-cylinder radial crankshaft

The crankshaft arrangement of the 11-cylinder Nordberg radial engine. All the connecting rods are attached to the master gear, which is not labeled in the image.

Each of the 11-cylinder engine’s connecting rods was attached to a large master gear via a knuckle pin. The master gear sat just above the connecting rods and was mounted on the crankshaft’s single crankpin. The master gear did not rotate, being restrained by two pinions and a stationary gear. The lower pinion rode on the master gear opposite the crankpin. The lower pinion was mounted on the same shaft as the upper pinion, which engaged a stationary gear at the top of the engine. Since the master gear was mounted on the crankpin, it moved in a circular motion with the crankshaft, and each knuckle pin subsequently moved in a circular motion. This design eliminated the need for a master connecting rod and provided good balance.

The 12-cylinder engine did not employ a master gear like the 11-cylinder engine. Instead, each connecting rod was attached to a master bearing via a knuckle pin. The master bearing was mounted on the crankshaft’s single crankpin. Two opposing connecting rods were rigidly connected to extended knuckle pins. Each of these extended knuckle pins carried a small restraining crank. The two restraining cranks were connected via a larger restraining link. This linkage prevented the master bearing from rotating but allowed it to move in a circular motion, like the master gear in the 11-cylinder engine. The 12-cylinder’s crankshaft arrangement was designed by Donald I. Bohn and awarded US patent 2,584,098 on 29 January 1952.

Nordberg 12-cylinder radial crankshaft

The crankshaft arrangement of the 12-cylinder Nordberg radial. Compare with the image of the 11-cylinder’s crankshaft.

The Nordberg radial engine had a single-piece cast iron crankcase and sub-base. Each cylinder was drawn to the crankcase by four long studs. The cylinders had intake ports positioned on the top side of the cylinder wall and exhaust ports on the lower side. The exhaust ports were closer to the head than the intake ports to allow for good cylinder scavenging. Either an electric or a geared blower pressurized the intake air and aided cylinder scavenging. The exhaust was expelled into a manifold located under the operating floor. The cylinders fired one right after another in successive order.

By the mid-1950s, the Aluminum Company of America (Alcoa) had 220 normally scavenged and 22 supercharged Nordberg radial engines installed in its Port Lavaca, Texas aluminum plant. Combined, these engines could produce 475,000 hp (354,207 kW). The engines were arranged in seven powerhouses, consisting of around 40 engines each. Kaiser Aluminum used 80 Nordberg radial engines in its reduction plant in Chalmette, Louisiana, accounting for 150,000 hp (111,885 kW).

Various smaller engine installations occurred in municipal power plants and pumping stations. In 1956, a 12-cylinder Nordberg radial engine was put into service at the municipal power plant in Winterset, Iowa. This engine is still in service as of 2016. In 1957, three 11-cylinder Nordberg radials were installed in the South Florida Water Management District Pump Station S-9, just west of Southwest Ranches, Florida. Each of these engines powered a pump with a 143,625 gpm (543,679 L/m) capacity. These Nordberg radials were retired in 1989 because of the scarcity of spare parts. One of the engines is currently on display at John Stretch Park in Lake Harbor, Florida. Nine 12-cylinder engines were installed in the Wastewater Treatment Plant at Deer Island (Boston), Massachusetts in 1968. Over five years, each engine had averaged 22,315 hours of operation. This equates to the engines running 12.25 hours a day, every day, for five years.

Nordberg 11-cylinder radial engines Alcoa

Forty Nordberg 11-cylinder spark-ignition radial engines in one of seven powerhouses at the Aluminum Company of America plant in Port Lavaca, Texas.

Over time, the engines did have problems. Because the cost to inspect the crankshaft was practically as much as replacing it, Alcoa adopted a policy to forgo inspections and run the engine until the crankshaft broke—and break it would. A number of other operators followed suit. Another issue was with excessive piston wear. The Deer Island installation had constant issues with various parts breaking, resulting in engines being off-line for extended periods. Since Nordberg was the sole supplier of parts and it could take some time for replacement parts to be supplied, cannibalism of engines occurred when more than one unit was down.

In 1970, the Nordberg Manufacturing Company was purchased by the Rexnord Corporation, also of Milwaukee, Wisconsin. In 1973, Nordberg/Rexnord stopped manufacturing diesel engines and parts. This, combined with the difficulties experienced by several operators, led to the phase out of the Nordberg radial engine. In 1987, Rexnord was purchased by Banner Industries of Cleveland, Ohio, and Nordberg was renamed Nordberg Inc. In 1989, Nordberg Inc was sold to the Finish company, Rauma-Repla Oy. At his time, Nordberg Inc manufactured mining equipment, mainly rock crushers. Through mergers, Rauma-Repla Oy became the Metso conglomerate in 1999. Nordberg Inc was renamed Metso Minerals Milwaukee, and continued to manufacture equipment until the factory was shut down on 30 June 2004. The closure ended 115 years of industrial machine manufacture.

Nordberg 11-cylinder radial engine FL

An 11-cylinder Nordberg diesel radial engine retired from pumping duties and now on display at John Stretch Park in Lake Harbor, Florida. (Image by Daniel Holth via Wikimedia Commons)

Diesel and High Compression Gas Engines – Fundamentals by Edgar J. Kates (1954)
Nordberg Radial Engines (1958)
– “Radial Engine,” US patent 2,584,098 by Donald I. Bohn (awarded 29 January 1952) and sub-pages

Beardmore Tornado Mk III

Beardmore Tornado Diesel Airship Engine

By William Pearce

In the early 1920s, William Beardmore & Company Ltd. began to design a series of high-power, low speed, direct-drive aircraft engines. From this line of engines and the company’s experience with diesel locomotive engines, Beardmore experimented with diesel aircraft engines. One of these engines was the compression ignition Typhoon. Designed by Alan Chorlton, the Typhoon was an inverted, water-cooled, straight-six engine with a 8.625 in (219 mm) bore and a 12 in (305 mm) stroke, giving it a total displacement of 4,207 cu in (68.9 L). In 1924, the British Air Ministry ordered compression ignition Typhoons to be used in the hydrogen-filled R100 and R101 airships. This decision was largely influenced by the fact that diesel (a low volatility fuel) did not have the quick ignition tendencies of normal fuel, thus reducing the fire risk.

Beardmore Tornado Mk I

The Beardmore Tornado Mark I engine. Note the circular intake ports and access covers on the crankcase.

The R100 and R101 airships were part of the British Imperial Airship Scheme: a plan to improve communication with the far corners of the British Empire by establishing air routes. Both the R100 and R101 had a gas bag volume of over 5,100,000 cu ft (144,416 cu m), were over 710 ft (216 m) long, and had a maximum diameter of around 132 ft (40 m). The R100 was to be mostly designed and built by private industry using existing technology, while the R101 was to be designed and built by the government using experimental technology. After tests, the best aspects of both airships would be incorporated into later airships.

By 1926, with the airships under construction, the Air Ministry felt the Typhoon had reached its development potential. Beardmore offered a new Chorlton-designed six-cylinder engine that used steam-cooling and was not inverted. This engine was known as the Hurricane, but there was concern that it would not be powerful enough. Chorlton modified the Hurricane’s design by adding two additional cylinders. This engine was known as the Tornado and was expected to produce 700 hp (522 kW) at 1,000 rpm and 720 hp (537 kW) at the engine’s maximum rpm of 1,100. The Air Ministry ordered five Tornado engines for use on the R101, plus one additional engine as a spare. Tornado engines were also to be used on the R100. However, the R100 switched to standard fuel engines (Rolls-Royce Condors) because of developmental delays with the Tornado.

Beardmore Tornado Mk III section

Sectional view of the Beardmore Tornado Mk III. Note the two plain main bearings that sandwiched double Michell thrust bearings on the propeller shaft.

The Beardmore Tornado was a straight, eight-cylinder engine with a 8.25 in (210 mm) bore and 12 in (304 mm) stroke, giving a total displacement of 5,132 cu in (84.1 L). The engine’s compression ratio was 12.25 to 1. Each cylinder had its own aluminum-alloy head with two intake and two exhaust valves. The valves were actuated by rockers and short pushrods from a single camshaft that ran along the side of the engine, just below the head. One fuel injector for each cylinder was placed in the center of the head, between the valves. The fuel pump was positioned at the rear of the engine along with the water pump, oil pumps, and other accessories.

The Tornado utilized steam cooling. Water in the engine was allowed to boil; the steam was then condensed in radiators attached to the airship’s hull and circulated back into the engine. For starting, a decompressor opened one inlet valve to allow the engine to be spun over and primed. A 40 hp (30 kW) starting motor was used to start the Tornado through a 20 to 1 reduction.

During testing, the Tornado was revised three times (Mark I, II, and III) in an attempt to cure various issues, including problems with torsional vibrations. The crankcase / cylinder block was of monobloc construction and cast in aluminum for the Mark I engine. The aluminum did not have sufficient strength, and cast iron was used, adding substantially to the engine’s weight. The cylinder heads were prone to cracking until heads specially made in Switzerland of cast steel resolved the issue. A series of large access holes with aluminum covers were provided along the crankcase. An aluminum sump was bolted to the bottom of the crankcase. With the steel crankcase, the Tornado Mark III had a dry weight of 4,200 lb (1,905 kg)—much heavier than the 3,000 lb (1,361 kg) of the Mark I engine.

Beardmore Tornado Mk III

Beardmore Tornado Mk III engine. Note how the access covers are now oblong. No doubt the access holes were enlarged to help offset some of the weight of the cast steel crankcase.

The vibration issues of the Tornado were exacerbated by the long crankshaft. Effort was undertaken to strengthen the crankshaft by increasing the ten (two were at the propeller end) main journals from 5 in (127 mm) in diameter to 5.75 in (146 mm) in diameter. In addition, the crankshaft webs were increased to 8.5 in (216 mm). The Crankpins remained at 4.25 in (108 mm) in diameter. Other work to dampen vibrations included adding a flywheel to the rear of the engine and a spring coupling between the crankshaft and propeller. However, vibration issues persisted, being most evident at idle and at cruising engine speeds of 950 rpm. As a result of the issues, the Tornado had a continuous rating of only 585 hp (436 kW) at 890 rpm and a maximum of 650 hp (485 kw) at 935 rpm. Utilizing the permissible speed range, the engine was run 225 hours non-stop without issues. Fuel consumption was .385-.40 lb/hp/hr (234-243 g/kW/h).

On the R101, two of the Tornado engines were to be fitted with reversible pitch propellers to aid maneuvering, but these propellers failed during testing. As a stopgap measure, one engine was fitted with a propeller of reverse pitch; this would mean that only four engines provided forward thrust, and one engine was used as a reversing motor only. Later, two of the engines were fitted with a reversing gear that allowed them to be stopped and then run in the opposite direction, but all five engines could be used for forward thrust.

Beardmore Tornado in R101 car

Beardmore Tornado in the engine car for the R101 airship. The propeller flange on the right was at the rear of the car. Note the varying lengths of exhaust pipes on the far side. Also, the intake ports have changed from circular, as seen on the Mark I engine, to oblong. In the front of the car (left side of image) was a generator.

Each Tornado engine was installed in an enclosed engine car on the R101. The cars hung below the airship and allowed for easy servicing and maintenance of the engines while on the ground or in flight. The cars could also be removed and replaced as a unit. Each car contained the Tornado’s starting motor. As installed on the R101, each pod weighed a portly 8,580 lb (3,892 kg).

Reportedly, the Tornado engines were installed on the R101 by 24 September 1929. Its first flight, which was over 5 hours, was on 14 October. After a series of flights, the R101 was found to be very overweight, and modifications to lighten the airship started on 30 November. Some of the modifications were to increase the size of the gas bags in the R101, despite the possibility that they could rub on the airship’s framework. An additional gas bag was installed in a new midsection of the R101. While the ship was down, a Tornado engine in a complete engine car was test run the equivalent flight time from London to Karachi, British India (now Pakistan) and back without any issues. The R101 returned to the air in June 1930 but still experienced issues: hydrogen leaked from the gas bags, and its outer skin covering had deteriorated and was prone to ripping. The R101 was down for repairs again.

Beardmore Tornado-powered R101

The 777 ft (237 m) long R101 airship moored at RAF Cardington. Four of the five Tornado engine cars can clearly be seen. The one at the rear of the R101 also provided airflow over the rudder to aid maneuvering.

Following the repairs, the R101 made its first trial flight (of almost 17 hours) on 1 October 1930. This would be the airship’s last flight before setting off for Karachi on 4 October. The R101’s spare Tornado engine had been shipped ahead, in case it was needed. On the evening of 4 October, the R101 started its voyage. About eight hours later, the airship was caught in a storm over Beauvais, France. The airship began to nose down out of control. It impacted the French countryside and burst into flames, ultimately killing 48 of the 54 people on board.

A board of inquiry investigated the R101 tragedy to determine the probable cause. They believed that skin in the front of the airship ripped during the storm and caused a gas bag to rupture. With the hydrogen escaping, the nose of the R101 became heavy and dropped toward the ground; the airship was doomed. Despite being overweight and under-powered, the Tornado engines did not play a role in the airship’s demise. After the R101’s crash, the R100 was grounded and later scrapped even though it had operated without major issues, even completing a flight to Canada and back. Eventually, the accident put an end to Britain’s airship programs. One of the R101’s Tornado engines was salvaged and returned to the United Kingdom. It is currently on display as a partial cutaway at the Science Museum in London.

During World War II, a British soldier deployed in India stumbled upon the last of the Tornado engines. The spare engine that had been shipped ahead of the R101 had been installed in a train and pressed into service. Harkening back to its origins, apparently the Tornado made a good diesel locomotive engine.

Beardmore Tornado from R101 at SM

The salvaged Beardmore Tornado engine from R101 airship. This engine is currently on display at the Science Museum in London. (Andy Dingley image via Wikimedia Commons)

Beardmore Aviation 1913-1930 by Charles Mac Kay (2012)
Aeroshpere 1939 by Glenn Angle
Jane’s All the World’s Aircraft 1931 by C. G. Grey
The Modern Diesel fourth edition no date Illiffe & Sons Ltd
An Account of Partnership – Industry, Government and the Aero Engine by George Bulman and edited by Mike Neale (2002)
– “The Latest Beardmore Aero Engine,” Flight, 16 February 1928
– “R.101,” Flight, 11 October 1929

KHD Dz 710 test stand crop

Klöckner-Humboldt-Deutz (KHD) Dz 700, Dz 710, and Dz 720

By William Pearce

The German engine manufacturer Deutz AG can trace its roots back to the inventor of the four-stroke internal combustion engine, Nicolaus Otto. Gottlieb Daimler, Wilhelm Maybach, Rudolf Diesel, Robert Bosch, and Ettore Bugatti all worked for progenitors of Deutz at one time or another. In 1935, the company, then known as Humboldt-Deutz, was commissioned by the RLM (Reichsluftfahrtministerium or German Ministry of Aviation) to develop experimental two-stroke diesel engines.

KHD Dz 700 front

The eight-cylinder KHD Dz 700 two-stroke diesel before the engine was returned to Germany. Note the manifolds in between the cylinders for the incoming fresh air and the exhaust ports on the front of the cylinders. (Joe Gertler/Memaerobilia image)

This new line of engines was, in part, to compete with Junkers’ Jumo two-stroke diesels. The Junkers engines used two opposed pistons in the same cylinder which moved toward each other for the compression stroke. These pistons also covered and uncovered the intake and exhaust ports. Dr. Ing (Engineer) Adolf Schnürle, who was employed by Humboldt-Deutz, had earlier developed a new method for two-stroke cylinder porting. Schnürle’s method became known as Schnürle porting (or Schnuerle porting) and used reverse loop scavenging. In the cylinder, the exhaust port was positioned in between and slightly higher than the two intake ports. When the piston uncovered the ports, the charge of fresh air would enter and flow to the back of the cylinder. The fresh air would then reverse direction and push all remaining gases out the exhaust port. Being higher on the cylinder, the exhaust port was uncovered longer than the intake ports; this allowed the incoming fresh air charge to fully evacuate the exhaust gases from the cylinder.

Schnürle was put in charge of the new Humboldt-Deutz diesel engine project. Preliminary tests were conducted in Cologne, Germany on small single-cylinder and two-cylinder engines. In 1937, the Dz 700 was built. It was an eight-cylinder, two-stroke, air-cooled, diesel engine. The engine had a 3.15 in (80 mm) bore and a 3.94 in (100 mm) stroke, giving a total displacement of 245 cu in (4.0 L). The Dz 700 produced 158 hp (118 kW) at 2,800 rpm. The Dz 700 had a diameter of around 38 in (1 m) and weighed only around 120 lb (55 kg). A blower (weak supercharger) forced air through manifolds in between and then into the cylinders. Utilizing Schnürle porting, the two intake ports were positioned slightly lower in the cylinder than the two exhaust ports, and all were covered and uncovered by the piston.

KHD Dz 710 side

The 16-cylinder KHD Dz 710 two-stroke diesel. Note the blower at the end of the engine with the coolant pump below and the fuel injection pumps under the engine.

In 1938, a six-cylinder engine was designed for use in training aircraft. A merger occurred in 1939, and the company became Klöckner-Humboldt-Deutz (KHD). The diesel engine projects were relocated to Oberursel, Germany. Shortly after, development of the six-cylinder engine and the Dz 700, which was then under tests, was abandoned. With the start of World War II, the RLM was interested in engines of higher power.

In 1939, Schnürle began work on the Dz 710—a 16-cylinder, liquid-cooled, engine. The original design was a fuel injected, spark ignition engine, but the design was developed into a two-stroke diesel. The Dz 710 was a horizontally opposed (or boxer/flat) engine with two banks of eight cylinders. Again, the cylinders were equipped with Schnürle’s reverse loop scavenge porting, but the system was doubled with four intake ports and two exhaust ports for each cylinder. The intake ports were 2.02 in (51.2 mm) tall and the exhaust ports were 2.65 in (67.2 mm) tall. Intake air came through a blower geared to the crankshaft at the rear of the engine that charged the air to 7.4 psi (.51 bar). The air then flowed through passageways into both sides of the cylinders. Exhaust gases were expelled both above and below the cylinder banks.

KHD Dz 710 test stand

The horizontally opposed 16-cylinder KHD Dz 710 engine on a test stand in Oberursel, Germany. Note the exhaust pipes both above and below the cylinder bank.

The Dz 710 had a bore and stroke of 6.30 in (160 mm), giving a total displacement of 3,141 cu in (51.5 L). Direct fuel injection at 400 psi (27.58 bar) was used, and the compression ratio was 15 to 1. The engine also had a 0.4 to 1 propeller gear reduction. Recorded dimensions for the Dz 710 were a length of 94.5 in (2.40 m), a width of 53.1 in (1.35 m), and an estimated height of 39.4 in (1.00 m). The engine weighed 2,866 lb (1,300 kg).

Completed in 1943, the Dz 710 had a planned output of around 2,700 hp (2,013 kW), but development and testing was delayed by other war priorities; KHD was involved in the production of diesel truck engines. Two Dz 710 engines were built with a third partially completed. In 1944, a Dz 710 test engine achieved 2,360 hp (1,760 kW) at 2,700 rpm, and both engines had accumulated a total of about 150 hours of operation. A very good specific fuel consumption of 0.34 lb/hp/hr (207 g/kW/hr) was recorded at cruise power. However, the Dz 710 had trouble with its pistons and ultimately used a bolted steel plate piston crown. In addition, two crankshafts failed due to torsional vibrations.

A turbocharged version of the Dz 710 was planned with an estimated output of 3,060 hp (2,280 kW). Either a mockup or actual parts for the turbocharger installation were built, but it is not clear if this engine ran. The turbocharger would have increased the intake air pressure to 23.5 psi (1.6 bar).

KHD Dz 720 front

The 32-cylinder KHD Dz 720 was quite literally two Dz 710 stacked on top of each other with the upper engine inverted. This arrangement formed an H-32 engine with an estimated max output of 5,900 hp (4,400 kW) with turbocharging.

By 1944, in the quest for more power, the two Dz 710 engines were stacked to form the Dz 720 (KHD actually referred to this engine as the Dz 710 P2). This 32-cylinder H engine had a displacement of 6,282 cu in (102.9 L). The turbocharged H-32 had an estimated output of 5,900 hp (4,400 kW) while the engine blower version was forecasted to produce 4,600 hp (3,430 kW). With a .3125 to 1 gear reduction for a single propeller, the engine was originally intended for use in large, long-range aircraft. However, the German Navy showed interest in utilizing it for high-speed boats. While the Dz 720 should have similar length and width as the Dz 710, the actual recorded dimensions were a length of 106.3 in (2.70 m), a width of 65.0 in (1.65 m), and an estimated height of 78.7 in (2.00 m). Perhaps the extra 11.8 in (0.3 m) length of the Dz 720 incorporated a combining gear converting the two Dz 710 power sections to a single output shaft. Dz 720’s weight was documented as 5,732 lb (2,600 kg) with engine blowers and 6,393 lb (2,900 kg) for the  turbocharged version.

Schnürle was very committed to the Dz 710 engine. At the end of World War II, he made it clear to the Army Air Force that he was willing to go to the United States with his engines and continue their research and development. While the Dz 700 and the two Dz 710 engines were taken to the United States, it was not for Schnürle to continue their development. The ultimate disposition of the Dz 710 engines has not been found, but the eight-cylinder Dz 700 radial engine ended up in a private collection in Florida. Around 1998, it was purchased by a private collector in Germany and returned to that country.

KHD Dz 720 side

Side view of the KHD Dz 720. Note the spacer placed in between the Dz 710 power sections to provide clearance for the blowers on the left of the image. The Dz 720 was a very tall engine which would have made installation in an aircraft difficult.

The Historical Society of the Motorenfabrik Oberursel is looking for any information regarding the KHD Dz 710 engines and their disposition in the United States. Please click here for details and contact information (PDF file).

– Correspondence with Helmut Hujer, Motorenfabrik Oberursel Historian
– Correspondence with Joe Gertler of Memaerobilia and The Raceway Collection
Flugmotoren und Strahltriebwerke by von Gersdorff, Schubert, and Ebert (2007)
The Development of Piston Aero Engines by Bill Gunston (1993/2001)
Jane’s All the World’s Aircraft 1945-46 by Leonard Bridgman (1946)

Clerget 16 H Diesel Aircraft Engine

By William Pearce

In 1936, the French Air Ministry issued a specification for a flying boat able to carrying at least 40 passengers and 1,100 lb (500 kg) of cargo 3,725 miles (6,000 km) against a 37 mph (60 km/h) headwind. This large passenger aircraft was to be used on transatlantic service for both the northern and southern routes. In 1938, three projects were selected for prototype construction: the Potez-CAMS 161, the Lioré et Olivier H-49 (which became the SNCASE SE.200), and the Latécoère 631.

Clerget 16 H front

The 2,000 hp Clerget 16 H with four Rateau turbosuperchargers atop the engine. In between the cylinder banks is the camshaft housing.

The new transatlantic airliner would be a large aircraft, necessitating powerful engines. Pierre Clerget felt an entirely new engine was needed to power this aircraft. Clerget, an aircraft engine pioneer who had already designed and built a few diesel aircraft engines in his long career, decided to capitalize on the inherent safety and efficiency of a diesel engine. Diesel fuel offered an increase in fuel efficiency and was far less prone to accidental ignition, eliminating much of the fire risk common in early aviation.

Clerget spent much of 1937 designing the engine, and what emerged was a powerful V-16 diesel engine known as the Clerget 16 H. Because of its 16 H designation, the engine is often assumed to be of an H configuration. However, the “H” most likely represented “Huile,” a French word for oil, as diesel fuel is a type of fuel oil. The four-stroke 16 H engine was first displayed at the Paris Salon de l’Aviation (Air Show) in late 1938. The 16 H had a bore of 7.09 in (180 mm) and stroke of 7.87 in (200 mm). The engine’s total displacement was 4,969 cu in (81.43 L). The 16 cylinders were arranged at a 45 degree angle in two banks of eight cylinders. The compression ratio was 14 to 1. The direct drive engine had individual aluminum cylinders with a steel barrel for the aluminum piston. The exposed four valves per cylinder were actuated by roller rocker arms and short pushrods from the camshaft, that was situated in the Vee of the engine. The camshaft was driven from the crankshaft via a vertical drive shaft at the rear of the engine.

Clerget 16 H rear

The diesel Clerget 16 H showing the fuel injection pumps along the side of the engine and various accessories at the rear of the engine.

Fuel injection for each cylinder was provided by two Clerget injection pumps and two Clerget hydraulically-operated injectors. Groups of four pump units (to supply two cylinders) were arranged on the outside of the engine, with a total of four such groups on each side. The pumps along each side of the engine were driven by a camshaft running at half-engine speed. One complete set of pumps could be shut off for operating the engine at low speeds. Fuel was injected into the cylinder at a maximum of 8,500 psi (586 bar).

The 16 H used a two-piece aluminum crankcase. The single-piece crankshaft had eight throws and was supported by nine main bearings. Connecting rods were of the master and articulated rod type. Pressure lubrication was provided by a dry-sump system, and each bank of cylinders had its own water-cooling circulation system. Starting was achieved by an air-starter unit attached to the rear of the engine. The engine was 31.5 in (.8 m) wide, 49.2 in (1.25 m) tall, and 112.6 in (2.86 M) long. The 16 H weighed 3,750 lb (1,700 kg).

Four Rateau turbosuperchargers sat atop the Clerget 16 H engine. Each turbocharger served four cylinders (two on each side of the engine). The turbine spun by exhaust gases from the cylinders was at the top of the turbocharger, and the compressor that supplied air to the cylinders was at the bottom of the turbocharger. The turbochargers allowed the 16 H engine to maintain power up to 16,400 ft (5,000 m).

Clerget 16 H side

An early image of the Clerget 16 H without turbochargers.

First run on 17 May 1939, the 16 H could produce 1,500 hp (1,119 kW) without the turbochargers. With the turbochargers, the engine produced 2,000 hp (1,491 kW) at 2,200 rpm for takeoff and 1,600 hp (1,193 kW) at 1,800 rpm for continuous cruise. At cruise power, fuel consumption was 0.375 lb/hp/hr (228 g/kW/hr), and oil consumption was 0.020 lb/hp/hr (12 g/kW/hr).

With the German invasion of France on 10 May 1940, engine development and the transatlantic passenger seaplane were put on hold. The sole Clerget 16 H engine was destroyed during a bombing raid on Paris in 1940. There were some rumors that the engine was moved to Germany before the bombing, but nothing ever came of this. In October 1940, there was interest in building another 16 H, but no further development was undertaken. Pierre Clerget continued to work on other aircraft engine designs but was found dead in the Canal du Midi in Moissac, France on 22 June 1943—a sad end for a remarkable man. The cause of his death has never been explained.

The Germans restarted the transatlantic passenger seaplane program in March 1941, and an example of each prototype had been completed and flown by the end of 1942. These aircraft were subsequently destroyed in Allied bombing raids. After World War II, ten examples of the Latécoère 631 were built, each powered by six 1,600 hp (1,193 kW) Wright R-2600 engines. The aircraft entered service in 1947 but would not last long. After four of the Latécoère 631s had crashed in separate incidents, the remaining aircraft were banned from flying in 1955.

Latecoere 631 Lionel de Marmier

The inspiration for the Clerget 16 H: the transatlantic flying boat airliner. This Latécoère 631, named Lionel de Marmier after the French ace who served in WWI and WWII, disappeared over the South Atlantic with all 52 on board on 1 August 1948.

Diesel Aviation Engines by Paul H. Wilkinson (1942)
Aircraft Engines of the World 1941 by Paul H. Wilkinson (1941)
Pierre Clerget: Un motoriste de génie by Gérard Hartmann (2004)
Flying Boats & Seaplanes by Stephane Nicolaou (1998)

Beardmore Cyclone, Typhoon, and Simoon Aircraft Engines

By William Pearce

In the early 1920s, William Beardmore & Company Ltd. began to design a series of high-power aircraft engines. One of the major problems facing aircraft designers at that time was converting the relatively high rpm of the engine to the low speed needed for a fixed-pitch propeller. Adding a propeller gear reduction increased the engine’s weight, complexity, and potential points of failure.

The 4207 cu in (68.9 L), straight-six Beardmore Cyclone.

The 4,207 cu in (68.9 L), straight-six Beardmore Cyclone.

Alan Chorlton, head of the Beardmore engine department, sought an alternative to the propeller reduction gear by having a relatively slow turning engine. In order for an engine to generate high power at low rpm, its cylinder must have a very large displacement.

Beardmore’s first high-power, low rpm aircraft engine designed by Chorlton was really two engines, the Cyclone and the Typhoon, whose development ran parallel. The Beardmore Cyclone was a water-cooled, straight-six engine with a 8.625 in (219 mm) bore and a 12 in (305 mm) stroke, giving it a total displacement of 4,207 cu in (68.9 L). The Beardmore Typhoon was essentially the same engine but in an inverted configuration. Almost all parts were interchangeable between the two engines.

The Beardmore Typhoon inverted engine.

The Beardmore Typhoon inverted engine.

Both the Cyclone and Typhoon used an aluminum crankcase that also formed the cylinder block. Thin steel Cylinder liners were inserted into the crankcase toward the crankshaft. The cylinder liners were supported by a flange toward the cylinder head and sealed by a ring toward the crankshaft. Each cylinder had its own detachable head. The four valves per cylinder were actuated via rockers and short pushrods from the single camshaft, which ran along the side of the engine just below the head. For the Cyclone, the camshaft was on the right side of the engine but, being rotated 180-degrees to the inverted position, the camshaft was on the left side of the Typhoon (both when viewed from the rear).

Two spark plugs were fitted to the top of each cylinder and fired by two Watford C6SM magnetos. The magnetos along with the water, oil, and fuel pumps were driven off the rear of the engines by a series of intermediate gears. Aluminum pistons with three compression rings and one oil-scrapper ring were used. The compression ratio was 5.25 to 1.

The Cyclone I was first run in 1922 and generated 700 hp (522 kW) at 1,220 rpm. Development continued, and by 1927, the Cyclone II was producing 850 hp (634 kW) at 1,350 rpm but could produce 950 hp (708 kW) at the same rpm with a larger carburetor. Fuel consumption was .48 lb/hp/hr (292 g/kW/h), and the engine weighed 2,150 lb (975 kg). The Cyclone was 80.3 in (2 m) long, 35 in (.9 m) wide, and 61.125 in (1.55 m) tall. Reportedly, only one Cyclone II was built, and it was sold to Heinkel Flugzeugwerke in Germany.

The Typhoon in the Avro 549C Aldershot IV during an engine run.

The Typhoon in the Avro 549C Aldershot IV during an engine run.

As already mentioned, the Typhoon was an inverted version of the Cyclone. The date the engine was first run is not clear, but the Typhoon was mentioned along with the Cyclone in a Beardmore brochure from 1924. The Typhoon I (some say Typhoon II) originally produced 800 hp (597 kW) at 1,350 rpm but was developed to 925 hp (690 kW) at the same rpm by 1926. Fuel consumption was .46 lb/hp/hr (280 g/kW/h), and the engine weighed 2,233 lb (1,013 kg). The Typhoon was 80.3 in (2 m) long, 38.5 in (.98 m) wide, and 59.3 in (1.5 m) tall. The Typhoon was installed in an Avro 549 Aldershot (J6852), replacing the Napier Cub engine. The Typhoon-powered aircraft, re-designated Avro 549C Aldershot IV, first flew on 10 January 1927. After a demonstration flight on 24 January 1927, pilot Bert Hinkler reported that the Typhoon engine was remarkably smooth.

The Beardmore Typhoon-powered Avro 549C Aldershot IV flown by Bert Hinkler during a flight demonstration on 24 January 1927. The inverted engine allows a good view from the cockpit.

The Beardmore Typhoon-powered Avro 549C Aldershot IV flown by Bert Hinkler during a flight demonstration on 24 January 1927.

Reportedly, this image is of the 750 hp (559 kW), semi-diesel Beardmore Typhoon.

Reportedly, this image is of the 750 hp (559 kW), compression ignition Beardmore Typhoon.

A low-speed, large displacement engine design was very suitable for compression ignition, and another Typhoon engine was built as a diesel. Some sources report this engine as the Typhoon I, while others simply refer to it as the Typhoon C.I. In addition, the engine was sometimes noted as a semi-diesel (surface ignition). However, the power output of 750 hp (559 kW) at 1,400 rpm suggests that it was a true compression ignition diesel. Regardless, the diesel Typhoon was dimensionally the same as the standard Typhoon. The engine was under development along with the Cyclone and standard Typhoon and is mentioned in some of the articles regarding those engines. Some sources state that this engine was installed in the Avro 549 Aldershot, but that does not seem to be the case. No evidence has been found that this engine ever flew. However, in 1924, the Air Ministry ordered nine compression ignition Typhoons to be used in the R101 airship under construction. By 1926, the Air Ministry felt the Typhoon had reached its development potential and changed the order to the Beardmore Tornado engine, then under development.

The 1,100 hp (820 kW), 5528 cu in (90.6 L), inverted, straight-eight, Beardmore Simoon aircraft engine.

The 1,100 hp (820 kW), 5,528 cu in (90.6 L), inverted, straight-eight, Beardmore Simoon aircraft engine.

The Beardmore Simoon engine was a further development of the standard Typhoon but was designed at the same time. Compared to the Typhoon, the Simoon’s bore was reduced to 8.5625 in (217.5 mm), but the stroke remained the same at 12 in (305 mm). However, two additional cylinders were added. This gave the inverted, straight- eight Simoon engine a total displacement of 5,528 cu in (90.6 L). The Simoon maintained the 5.25 to 1 compression ratio of the previous engines, and fuel consumption was .48 lb/hp/hr (292 g/kW/h). Normal output was 1,100 hp (820 kW) at 1,250 rpm, but 1,200 hp (895 kW) could be achieved at 1,350 rpm. The Simoon was 98 in (2.5 m) long, 37.6 in (.96 m) wide, and 72.6 in (1.84 m) tall. The Simoon’s height increase over the Cyclone and Typhoon was due to an additional sump protruding from the lower rear of the engine. The engine weighed 2,770 lb (1,256 kg). The Simoon was installed in the second Blackburn T.4 Cubaroo (N167), replacing a Napier Cub engine. The Simoon-powered Cubarro first flew early in 1927.

None of these large, low-speed, high power engines were a success, and only a small number were made.

Aerosphere 1939 by Glenn Angle (1940)
Beardmore Aviation 1913-1930 by Charles Mac Kay (2012)
Jane’s All the World’s Aircraft 1928 by C.G. Grey (1928)
British Piston Aero Engines and their Aircraft by Alec Lumsden (1994/2003)
Avro Aircraft since 1908 by A J Jackson (1965/1990)
Blackburn Aircraft since 1909 by A J Jackson (1968/1989)
– “The Beardmore “Cyclone’ Aero Engine,” Flight (4 November 1926)
– “The Beardmore ‘Typhoon’ Mark I Engine,” Flight (27 January 1927)
– “The Beardmore Cyclone and Typhoon,” Flight (5 July 1928)
– “British Aero Engines,” Flight (29 May 1924)

Inside the Cylinder of a Diesel Engine – by Harry Ricardo

Sir Harry Ricardo as seen in 1955 at age 70.

Sir Harry Ricardo as seen in 1955 at age 70.

Sir Harry Ricardo (26 January 1885 – 18 May 1974) was one of the foremost engine designers and researchers of the internal combustion engine. During the First World War, Ricardo designed significantly improved engines for early British tanks. Between the wars, he researched the physics of internal combustion and the design of combustion chambers. This work led to the use of octane ratings, stratified charge, and intake swirl (vortex). Ricardo was instrumental in the development of the sleeve valve engine, particularly for aircraft use. His work and research contributed greatly to the high-power aircraft engines of World War II. After the war, he continued to develop the Diesel pre-combustion chamber (Comet), originally designed in the 1930s, which made high-speed diesel engines possible.

The following excerpt is from a lecture Harry Ricardo gave to the Royal Society of Arts on 23 November 1931.

I am going to take the rather unconventional course of asking you to accompany me, in imagination, inside the cylinder of a diesel engine. Let us imagine ourselves seated comfortably on the top of the piston, at or near the end of the compression stroke. We are in complete darkness, the atmosphere is a trifle oppressive, for the shade temperature is well over 500 Celsius – almost a dull red heat – and the density of the air is such that the contents of an average sitting-room would weigh about a ton; also it is very draughty, in fact, the draught is such that, in reality, we should be blown off our perch and hurled about like autumn leaves in a gale. Suddenly, above our heads, a valve opens and a rainstorm of fuel begins to descend. I have called it a rainstorm, but the velocity of droplets approaches much more nearly that of rifle bullets than of raindrops.

For a while nothing startling happens, the rain continues to fall, the darkness remains intense. Then suddenly, away to our right perhaps, a brilliant gleam of light appears, moving swiftly and purposefully; in an instant this is followed by a myriad others all around us, some large and some small, until on all sides of us the space is filled with a merry blaze of moving lights; from time to time the smaller lights wink and go out, while the larger ones develop fiery tails like comets; occasionally these strike the walls, but, being surrounded by an envelope of burning vapour, they merely bounce off like drops of water spilt on a red hot plate.

Right overhead all is darkness still, the rainstorm continues, and the heat is becoming intense; and now we shall notice that a change is taking place. Many of the smaller lights around us have gone out, but new ones are beginning to appear, more overhead, and to form themselves into definite streams shooting rapidly downwards or outwards from the direction of the injector nozzles.

Fuel being burnt as it is injected into a diesel cylinder. (Bosch image)

Fuel igniting as it is injected into a diesel cylinder. (Bosch image)

Looking round again we see that the lights around are growing yellower; they no longer move in a definite direction, but appear to be drifting listlessly hither and thither; here and there they are crowding together in dense nebulae, and these are burning now with a sickly, smoky flame, half suffocated for want of oxygen. Now we are attracted by a dazzle, and looking up we see that what at first was cold rain falling through utter darkness, has given place to a cascade of fire as from a rocket. For a little while this continues, then ceases abruptly as the fuel valve closes.

Above and all around us are still some lingering fire balls, now trailing long tails of sparks and smoke and wandering aimlessly in search of the last dregs of oxygen which will consume them finally and set their souls at rest. If so, well and good; if not, some unromantic engineer outside will merely grumble that the exhaust is dirty and will set the fuel valve to close a trifle earlier.

So ends the scene, or rather my conception of the scene, and I will ask you to realise that what has taken me nearly five minutes to describe may all be enacted in one five hundredth of a second or even less.

– Harry Ricardo

View of a diesel combustion chamber showing the combustion sequence (ASOC: After Start of Combustion).

View of a diesel combustion chamber showing the combustion sequence (ASOC: After Start of Combustion).

More on Sir Harry Ricardo:
Engines & Enterprise: The Life and Work of Sir Harry Ricardo by John Reynolds (1999)

Deschamps V 3050 Diesel Aircraft Engine

By William Pearce

In the late 1920s, Desire Joseph Deschamps moved forward with his vision of an inverted, two-stroke, high-speed, diesel aircraft engine. Deschamps had immigrated to the United States from Belgium, where he had worked for the Minerva Company. Reportedly, Deschamps had a hand in designing Minerva’s first aircraft engine, which was also the first aircraft engine to incorporate Knight sleeve-valves (two sleeves).

Deschamps rotary valve as outlined in U.S. patent 2,064,196. On the left is a transverse sectional view of the cylinder with the rotary valve below (inverted engine) and feeding to the combustion chamber. On the right is a side view of the rotary valve for two cylinders revealing the various ports in the valve.

Working out of St. Louis, Missouri, Deschamps began the design of an inverted, liquid-cooled, straight six-cylinder, diesel aircraft engine. Outlined in U.S. patent 2,064,196, what was unique about this diesel engine was the use of a rotary sleeve valve. This rotary valve was essentially a cylindrical tube that ran the length of the engine below (inverted engine) the combustion chamber. Induction air flowed through the tube that rotated at half crankshaft speed. As the tube rotated, ports in the tube aligned with a port to the cylinder, allowing fresh air to force the exhaust gases out of the cylinder and provide air for the next combustion cycle. The exhaust ports were around the cylinder wall and covered/uncovered by the piston.

From all accounts, the rotary valve engine was never built. A more conventional valve arrangement was adopted, utilizing poppet-valves, rather than the rotary valve, for the intake . A two-cylinder test engine was built and run in the early 1930s. The test engine engine developed 174 hp (130 kW) at 1,600 rpm. This two-cylinder engine was expressly for the development of the Deschamps inverted V-12 diesel, having the same bore, stroke, and general configuration of the larger engine to come.

Deschamps V 3050 inverted V-12 aircraft diesel engine of 1934.

The Deschamps V 3050 was an inverted, 12-cylinder, diesel aircraft engine of all aluminum construction. The engine was built by the Lambert Engine and Machine Company in Moline, Illinois and completed in 1934. The cylinder banks were arranged in a 30-degree Vee to minimize the engine’s frontal area. With a 6.0 in (152 mm) bore and 9.0 in (229 mm) stroke, the engine had a total displacement of 3,053 cu in (50.0 L). The liquid-cooled, direct drive engine produced 1,200 hp (895 kW) at 1,600 rpm for takeoff and 950 hp (708 kW) at 1,500 rpm for cruise. Fuel consumption was 0.41 lb/hp/hr (249 g/kW/h). When built, it was one of the largest and most powerful diesel aircraft engines in the world.

The compression ratio of the V 3050 was 16 to 1, and air was forced into the cylinders by two gear-driven GE superchargers. The centrifugal superchargers were driven at 13.5 times crankshaft speed (21,600 rpm) and provided air at 12 psi (0.83 bar). Cylinder scavenging for the two-stroke cycle required eight psi, leaving four psi for boost. A small portion of the air entering the superchargers was taken from the crankcase to provide ample ventilation and burn away any fuel vapors. Sea-level power could be maintained to an altitude of 10,000 ft (3,048 m).

Each bank of cylinders had an intake manifold on the inside of the Vee to deliver air from the superchargers to the cylinders. The compressed air entered each cylinder via two poppet valves actuated simultaneously by an overhead camshaft driven at crankshaft speed.

Rear view for the Deschamps diesel highlighting the two GE superchargers. The glow plugs are also visible on the right cylinder bank.

A ring of 12 exhaust ports was located in the cylinder wall and exposed by the piston. To prevent excessive oil consumption and exhaust smoke, a small horizontal groove was cut in the cylinder wall just below each of the 12 exhaust ports. The grooves in the cylinder liner aligned with an annular groove in the cylinder casing wall. The annular grooves for all 12 cylinders were connected to a vacuum pump that scavenged oil from the pistons. The amount of oil stripped from the pistons was controlled by the amount of vacuum.

The superchargers and camshafts were driven from the crankshaft via separate vertical shafts with bevel gears. A Lanchester type torsional vibration damper was incorporated on the rear of the crankshaft to protect the gear drives. The damper was combined with a torque limiter clutch that would slip momentarily under sudden changes in torque.

Each bank of cylinders had independent intake delivery, exhaust, liquid-cooling connections, oil connections, oil and fuel pumps, and fuel injectors. In theory, each bank could be operated independently of the other bank, sharing only a common crankshaft. At 1,600 rpm, oil was circulated at 80–100 psi (5.5–6.9 bar) while coolant circulation was at 230 gpm (871 l/m).

Sectional view of the Deschamps V 3050 diesel with the glow plug detailed on the lower left.

Fuel was injected directly into each cylinder via two Deschamps-designed (U.S. patent 2,020,302) fuel injectors operating at 3,500 psi (241.3 bar). The two injectors per cylinder alternated supplying fuel into the cylinder, each firing every-other compression stroke. For slow rpm operation, one injector was shut off, essentially making the engine a four-stroke. This kept the engine running smoothly and the cylinders warm for instant application of more power. One fuel pump for each engine bank was used and supplied fuel at 15 psi (1.0 bar) with a maximum flow of 150 gph (9.4 l/m).

The engine was air-started by a compressor charged to 850 psi (58.6 bar). For staring the engine in cold weather, glow plugs were provided in the right cylinder bank while the left bank’s intake valves were kept open with the fuel shut off. A reversing gear could be fitted for utilizing the engine in airships. The V 3050 was 26.5 in (0.67 m) wide, 49.5 in (1.26 m) tall, and 99 in (2.52 m) long. It weighed 2,400 lb (1,089 kg) with all accessories, giving it 2.0 lb/hp (1.2 kg/kW).

After completing the engine, no funds remained for testing. Deschamps met with the Army Air Corps Power Plant Laboratory in June 1934, but it seems no further testing was done on the engine. Deschamps went on to work for various aviation corporations, patenting a number of fuel injectors and pumps along the way. Amazingly, the Deschamps V 3050 diesel engine survives and is in storage at the National Air and Space Museum’s Garber Facility in Silver Hill, Maryland.

Deschamps Diesel in storage at the National Air and Space Museum’s Garber Facility in Silver Hill, Maryland. (Fred van der Horst image via the Aircraft Engine Historical Society)

Aircraft Diesels by Paul H. Wilkinson (1940)
Aerosphere 1939 by Glenn Angle (1940)
Diesel Aviation Engines by Paul H. Wilkinson (1942)
Jane’s All the World’s Aircraft 1934 by C. G. Grey (1934)
– “A 1,200 H.P. Diesel Engine.” Flight. May 24, 1934
– “Internal Combustion Engine” U.S. Patent 2,064,196 by Desire J. Deschamps (1930) pdf