Category Archives: Marine

MAN 6-cyl WWI

MAN Double-Acting Diesel Marine Engines

By William Pearce

Maschinenfabrik Augsburg-Nürnberg (MAN) was involved with diesel engines since their inception. From 1893 to 1897, MAN* worked with Rudolf Diesel to develop his combustion cycle and build the first diesel engines. When Diesel’s engine first ran in 1894, it produced around 3 hp (2 kW) at 88 rpm. Just 15 years later, MAN was contracted to develop a diesel engine capable of 12,000 hp (8,948 kW) at 120 rpm.

MAN 6-cyl WWI

The MAN six-cylinder, double-acting, two-stroke, 12,000 hp, diesel marine engine under construction. The three workers provide a good reference as to the engine’s size.

The remarkable rise of diesel power caught the eye of many militaries. Anton von Rieppel, general manager of MAN at Nürnberg (Nuremberg), felt that diesels had matured enough to power the latest battleships. In August 1909, Rieppel proposed a new engine to the Reichsmarine (Germany Navy). By late 1909, a development contract was issued to MAN for the construction of a 12,000 hp (8,948 kW), six-cylinder diesel engine. Six of the engines would be needed to produce the 70,000 hp (52,199 kW) required for the latest German battleships. Given the uncharted territory MAN was traversing, a three-cylinder engine would be built first to prove that a six-cylinder engine could meet the desired specifications. Other companies were also contracted to build competing engines.

MAN’s design was an inline, two-stroke engine that used double-acting cylinders. Each of the closed cylinders had a combustion chamber at its top and bottom. Originally, each combustion chamber had four intake valves, four fuel valves, and two safety valves that were also used for air-starting the engine. The safety valves were located at the center of the combustion chamber. The locations of the remaining valves were split between passageways that branched off from either side of the upper combustion chamber. With the exception of the safety valves, the valves for each side of each combustion chamber were actuated by a single underhead camshaft. This configuration had a total of 20 valves for each cylinder and four camshafts for the engine. The final (seventh) combustion chamber design retained the four intake valves but had only two fuel valves and one safety valve (located in the upper combustion chamber). The changes lowered the number of valves per cylinder to 15. Exhaust ports were located in the middle of the cylinder and were covered and uncovered by the piston.

MAN 6-cyl section

A drawing of the final cylinder design of the World War I engine. Fuel valves are on the left of the drawing, and intake valves are on the right. The exhaust manifold is positioned at the center of the cylinder. Note how the two piston halves are bolted together.

The double-headed piston was constructed of two parts. The lower part was connected to a non-articulating piston rod, and the upper part of the piston was bolted to the lower part. The piston rod was connected to the connecting rod via a cross head. The cross head slid in vertical channels on both sides of the inner crankcase. Oil was circulated through the piston to cool it. The oil flowed up through passageways in the piston rod and into the lower part of the piston. The oil then flowed to the upper part of the piston and down the center of the piston rod. The upper and lower combustion chamber sections were bolted to the center section of the cylinder, and the assembly was attached to the crankcase. A water jacket surrounded the cylinder. The center section of the cylinder and of the upper combustion chamber were made of cast iron. The crankcase, piston, lower combustion chamber, and many other components were made of cast steel. Each complete cylinder assembly was around 12 ft (3.5 m) tall, and the engine was over 24 ft 3 in (7.4 m) tall.

Each cylinder had a 33.4 in (850 mm) bore and a 41.3 in (1,050 mm) stroke. Since the piston was double-acting and there was a lower combustion chamber, each cylinder’s displacement was nearly doubled, as if it were two conventional cylinders. The upper combustion chamber displaced 36,359 cu in (595.8 L). However, the connecting rod passing through the lower combustion chamber took up around 3,021 cu in (49.5 L) of volume. Displacement for the lower combustion chamber was approximately 33,337 cu in (546.3 L). The cylinder’s total displacement was around 69,697 cu in (1,142 L). The three-cylinder test engine displaced 209,094 cu in (3,426 L), and the six-cylinder engine displaced 418,187 cu in (6,853 L). The engine drove three double-acting air pumps to scavenge the engine. Each air pump had a 52.0 in (1,320 mm) bore and a 31.5 in (800 mm) stroke.

The three-cylinder engine was first run on 12 March 1911. Severe delays occurred as technological issues were encountered. In January 1912, a failure caused the intake manifolds to explode, killing ten workers. By June 1913, the three-cylinder engine had met its requirement by producing 5,400 hp (4,027 kW) at 90% power. Construction of a six-cylinder engine followed.

The six-cylinder engine was first run on 23 February 1914. By September 1914, the engine was producing 10,000 hp (7,457 kW) at 130 rpm. By this time, World War I was underway; priorities shifted, and shortages were encountered. A single cylinder made a five-day run at over 2,000 hp (1,491 kW) in April 1915. On 24 March 1917, the six-cylinder engine produced 12,200 hp (9,098 kW) at 135 rpm for 12 hours. In April 1917, the engine passed its five-day acceptance test, running at 90% power and producing 10,800 hp (8,054 kW) at 130 rpm.

MAN M9Z 42-58

One of the MAN M9Z 42/58 engines built for installation in a Deutschland-class cruiser. At least 24 of the engines were made. The fuel injection pumps for each cylinder can be seen above and below the housing along the engine’s side.

By mid-1917, it was obvious that due to delays and the war, the engine would never be used, and the other five engines would never be built. MAN decided to test the engine to its limits. The engine test stand at MAN could not absorb the maximum anticipated power of the complete six-cylinder engine, so just one cylinder was run. On 16 October 1917, a single cylinder produced 3,570 hp (2,662 kW) at 145 rpm. If all six cylinders could match that performance, the complete engine would produce 21,420 hp (15,973 kW). The engine was later scrapped as a result of the Treaty of Versailles.

After World War I, Germany entered a period of economic ruin. It was not until 1926 that MAN designed the first engine in a new series of double-acting, two-stroke diesels. Overseen by engineer Gustav Pielstick, the new engines were similar in concept to the double-acting engine built during World War I, but they incorporated many new features. Pielstick had developed MAN submarine engines during World War I but did not work on the large double-acting engine.

MAN MZ42-58

Sectional drawings of a MAN M9Z 42/58 engine. The rotary exhaust valves are positioned in a runner between the cylinder and the exhaust manifold. Note the long through bolts that pass through the entire engine.

The main structure of the new engines was made of steel plates welded together. This construction kept the engine rigid, but made it lighter than using cast components. Pairs of very long through bolts were positioned between the cylinders. They held the center part of the cylinder, crankcase, and crankshaft together and allowed for the disassembly of individual cylinders without compromising the integrity of the overall engine. The double-headed pistons were again made in two parts. From the top, the piston rod passed through the lower part of the piston, which was threaded to a shoulder on the rod. The upper part of the piston was threaded to the top of the piston rod. The skirt of the upper part of the piston slid into the skirt of the lower part. A sealed gap between the skirts allowed for the differential expansion of the individual piston halves. The piston was oil-cooled, like the World War I engine. The lower part of the piston rod was threaded into the cross head. Unlike the World War I engine, the cross head of the new series slid in a mount attached only to one side of the crankcase.

The new engine had no valves in the cylinder. In the middle of the cylinder were two rows of intake ports. The top row serviced the upper combustion chamber, and the bottom row serviced the lower combustion chamber. Air was forced into the cylinder by an auxiliary “pumping” engine. Fuel entered the cylinder via a single injector in the upper combustion chamber and two injectors on each side of the piston rod in the lower combustion chamber. The injectors were water-cooled and provided fuel to each cylinder at 3,625–4,350 psi (250–300 bar). Mounted to the side of the engine was a camshaft that drove the fuel injection pumps. Each cylinder had an upper and lower injection pump that respectively provided fuel to the upper and lower combustion chambers. Both pumps for each cylinder were controlled by a single lobe on the camshaft.

MAN LZ 19-30 section

Sectional view of the MAN L11Z 19/30 shows that the rotary exhaust valves have been placed inside of the exhaust manifold to conserve space. Otherwise, the engine and cylinder are very similar to the larger engines.

Each combustion chamber had its own exhaust ports which led to separate manifolds for the upper and lower combustion chambers. The intake and exhaust ports were on the same side of each cylinder, and their relative positions allowed the cylinder to be loop scavenged. Rotary valves inside of the exhaust manifolds closed off the exhaust port before the piston and allowed the cylinder to be charged with incoming air. The valve itself was supported by a hollow tube through which water was circulated to keep the valve cool. Otherwise, the intake and exhaust ports were covered and uncovered by the piston. All the engines of the new series used the same basic cylinder design, but the engines differed in their bore, stroke, and number of cylinders.

After cylinder testing, the first complete engine built of this type was the D4Z 23/34. In MAN nomenclature, “4” represents the number of cylinders per bank and “23/34” the bore/stroke in cm. With its 9.1 in (230 mm) bore and 13.4 in (340 mm) stroke in a double-acting cylinder, the engine displaced around 6,591 cu in (108 L). The D4Z 23/34 produced 1,000 hp (746 kW) at 800 rpm. The D4Z 23/34 was run in 1927, and tests went well.

On 27 March 1928, the Reichsmarine contracted MAN to develop a larger engine for what would become the cruiser Leipzig. Four M7Z 30/34 engines powered the middle shaft in the Leipzig, while two other shafts were powered by steam turbines. The seven-cylinder M7Z 30/34 engine had a 11.8 in (300 mm) bore and a 13.4 in (340 mm) stroke. Each engine displaced around 19,624 cu in (321.6 L) and produced 3,100 hp (2,312 kW) at 800 rpm, giving a total of 12,400 hp (9,247 kW) for the four engines.

Compared to a steam turbine, the diesel engine took up less space, was simpler to operate, had nearly instant power, and could suffer damage without disastrous consequences. Shrapnel passing through a diesel engine would shut down the engine, most likely one of several. Shrapnel passing through a steam boiler would cause the boiler to explode, most likely killing some of the crew in the room.

MAN LZ 19-30

Front view of the MAN L11Z 19/30. The camshaft ran to the side of the cylinders and controlled the fuel injection pumps. The handle on the front of the camshaft was used to adjust the camshaft when the engine was run in reverse. (Hermann Historica image)

The Reichsmarine decided to use only diesel-power for the Deutschland-class Panzerschiffe (armored ships) cruisers: Deutschland (later renamed Lützow), Admiral Scheer, and Admiral Graf Spee. In these ships, four nine-cylinder engines powered each of two propeller shafts. Engines were ordered in October 1928 for the Deutschland, on 9 January 1930 for the Admiral Scheer, and on 14 March 1931 for the Admiral Graf Spee. The engine type for these ships was the M9Z 42/58. With a 16.5 in (420 mm) bore and a 22.8 in (580 mm) stroke, the nine-cylinder, double-acting engine displaced 84,359 cu in (1,382 L). Each engine produced 7,100 hp (2,494 kW) at 450 rpm and weighed around 110 tons (100 tonnes). Combined, the eight engines provided a total of 56,800 hp (42,356 kW).

The artillery training ship (Artillerieschulschiff) Bremse was ordered in 1931. Powering the ship were eight M8Z 30/44 engines—four engines on each of the two propeller shafts. The M8Z 30/44 was the same engine used in the Leipzig but with an additional cylinder. The eight-cylinder M8Z 30/44 engine had a 11.8 in (300 mm) bore and a 13.4 in (340 mm) stroke. It displaced 22,427 cu in (367.5 L) and produced 3,350 hp (2,498 kW) at 600 rpm, giving a total of 26,800 hp (19,985 kW) for the eight engines.

The light cruiser Nürnberg was ordered in 1933 and used a combination of diesel engines and steam turbines, like its sister ship, the Leipzig. Four M7Z 32/44 engines powered the ship’s center shaft. The engines were larger than the ones used on the Leipzig but appear to have the same rated output. The M7Z 32/44 engine had a 12.6 in (320 mm) bore and a 17.3 in (440 mm) stroke. The seven-cylinder engine displaced 28,894 cu in (473 L) and produced around 3,100 hp (2,312 kW) at 600 rpm, giving a total of 12,400 hp (9,247 kW) for the four engines.

MAN piston rods

The piston, piston rod, connecting rod, and crankshaft section for a M9Z 65/95. The piston halves were threaded onto the piston rod, which was threaded to the cross head. An oil line can be seen attached to the cross head. The assembly is displayed in the Deutsches Museum in Munich. (enwo image)

Around 1933, the Reichsmarine looked to steam turbines to fulfill their power needs, so the funding for MAN’s large diesel marine engines was severely cut. At the same time, a new engine was needed to power the latest German airships, the LZ 129 Hindenburg and LZ 130 Graf Zeppelin II. Pielstick adapted the basic design of the double-acting diesel to create a lighter, smaller engine, the L7Z 19/30. After the Daimler-Benz DB 602 engine was selected to power the airships, MAN added four cylinders to the L7Z engine to create the 11-cylinder L11Z 19/30 for marine use. The L11Z 19/30 used an engine-driven blower to provide intake air and cylinder scavenging. The engine had a 7.48 in (190 mm) bore, a 11.81 in (300 mm) stroke, and a total displacement of around 10,979 cu in (179.9 L). The L11Z 19/30 had a maximum output of 2,000 hp (1,491 kW) at 1,050 rpm and a continuous output of 1,400 hp (1,044 kW) at 900 rpm. The engine was approximately 157 in (4.0 m) long, 39 in (1.0 m) wide, and 98 in (2.5 m) tall. It weighed around 8,378 lb (3,800 kg) and was reversible. L11Z 19/30 engines were used in torpedo boats, with three engines installed in each Schnellboot S 14 to S 17 (S 14 was launched in January 1936) and four engines installed in the Versuchs Schnellboot VS 5 (launched in January 1941). The three L11Z 19/30 engines from S 15 survived. One engine is in the MAN Museum in Augsburg; one is in the Deutsches Museum in Munich, and one is in a private collection.

In 1935 and under Nazi leadership, the Reichsmarine was renamed Kriegsmarine. That same year, the Kriegsmarine initiated the design of new H-class battleships. The first of the ships would be powered by diesel engines. In 1938, the Kriegsmarine showed a renewed interest in large diesel marine engines, and MAN’s developmental funding was substantially increased. MAN developed the M9Z 65/95 engine for the H-class battleships in 1938. Four of these engines would power each of three shafts. The nine-cylinder engine had a 25.6 in (650 mm) bore, a 37.4 in (950 mm) stroke, and a total displacement of approximately 330,945 cu in (5,423 L). The M9Z 65/95 weighed around 248 tons (225 tonnes) and had a continuous output of 12,500 hp (9,321 kW) at 256 rpm and an emergency output of 13,750 hp (10,253 kW) at 265 rpm. The 12 engines gave a total of 150,000 hp (111,855 kW) for continuous operation and 165,000 hp (123,040 kW) for emergencies. In early 1939, 24 M9Z 65/95 engines were ordered by the Kriegsmarine, followed later in the year by another order for 24 engines. However, the orders were cancelled in late 1939, and only one test engine was built. This engine was tested in 1940 but was destroyed during an Allied air raid. A piston and rod assembly survived and is displayed in the Deutsches Museum in Munich. No H-class battleships were completed.

MAN V12Z 32-44 section

Sectional view of the MAN V12Z 32/44 engine illustrates a cylinder design similar to that used on the inline engines but with a completely different manifold arrangement. The large upper manifold was the intake, and the three other manifolds were for exhaust. Note the camshaft and fuel injection pumps on the outside of the cylinder banks.

By 1939, Pielstick used the basic cylinder design of previous engines to create larger and more powerful engines in a V configuration with 24 cylinders. The V-24 engines had a 45 degree bank angle and a new manifold arrangement, but the cylinder design and other components were similar to the previous inline engines. Positioned in the Vee of the engine was a lower exhaust manifold that collected the exhaust gases from the lower combustion chambers. Above this manifold was the intake manifold that serviced all the cylinders. Each cylinder bank had an upper exhaust manifold that collected the exhaust gases from the upper combustion chambers. These manifolds were positioned between the intake manifold and the respective cylinder bank. The fuel injection camshaft and pumps were located on the outer side of the cylinder banks. An engine-driven blower was positioned at the rear of the engine and fed air into the intake manifold.

The first V-24 was designated V12Z 42/58, and the engine was designed for the German O-class battlecruisers, with four engines powering each of two shafts. A third shaft was powered by a steam turbine. The V12Z 42/58 had a 16.5 in (420 mm) bore, a 22.8 in (580 mm) stroke, and displaced around 224,957 cu in (3,686 L). The 150.5-ton (136.5-tonne) engine produced 15,600 hp (11,633) at 450 rpm. The eight engines planned for use in the O-class would have produced a total of 124,800 hp (93,063 kW), but the O-class was cancelled, and no ships were built. One V12Z 42/58 engine was built and completed a 200-hour test run, generating a continuous 10,000 hp (7,457 kW) at 243 rpm.

A second, smaller V-24 engine was the V12Z 32/44 (sometimes called the V24Z 32/44). This engine was designed in 1940 for the Zerstörer 1942, of which one was built, the Z 51. Most sources state that the Z 51 was powered by six engines, with two engines powering each of three shafts. Other sources claim the center shaft had four engines and that the outer shafts had one engine each. The V12Z 32/44 had a 12.6 in (320 mm) bore and a 17.3 in (440 mm) stroke. The engine displaced around 99,066 cu in (1,623 L) and produced 10,000 hp (7,457 kW) at 600 rpm. A turbocharged version was planned that would increase output to 16,000 hp (11,931 kW). The V12Z 32/44 weighed 56.0 tons (50.8 tonnes), and the turbocharged version weighed 66 tons (60 tonnes). The Z 51 destroyer was nearly complete when it was sunk during an allied attack on 21 March 1945. Sources state that either four or six V12Z 32/44 engines were built. One engine was preserved and is on display in the Auto & Technik Museum in Sinsheim.

MAN V12Z 32-44 construction

The MAN V12Z 32/44 engine under construction. The blower was mounted to the rear of the engine. Note the many access panels incorporated into the engine’s crankcase.

In the early 1950s, MAN again offered their double-acting, two-stroke diesel engines. The largest of these post-war engines was the D8Z 70/120. With a 27.6 in (700 mm) bore and a 47.2 in (1,200 mm) stroke, the eight-cylinder engine displaced 430,953 cu in (7,062 L) and produced 8,000 hp (5,966 kW) at 120 rpm. More efficient engines that required less maintenance overtook the double-acting, two-stroke power plants. Today, MAN continues to build diesels for automotive, industrial, and marine use.

*Maschinenfabrik Augsburg AG worked with Rudolf Diesel. The company merged with Maschinenbau-AG Nürnberg in 1898 to become Vereinigten Maschinenfabrik Augsburg und Maschinenbaugesellschaft Nürnberg (United Machine Factory Augsburg and Machinery Construction Company Nuremberg). In 1908, the company was renamed Maschinenfabrik Augsburg-Nürnberg (MAN).

MAN V12Z 32-44

The 24-cylinder MAN V12Z 32/44 engine as displayed in the Auto & Technik Museum in Sinsheim. The cars behind the engine give an indication of the engine’s size. Note the large blower housing attached to the engine. Six of these engines were to power the Z 51 destroyer. (Technik Museum Sinsheim und Speyer image)

“Multicylinder Combustion Engine” US patent 1,836,498 by Gustav Pielstick (granted 15 December 1931)
“Internal Combustion Engine” US patent 1,887,661 by Gustav Pielstick (granted 15 November 1932)
“Fuel Valve” US patent 1,919,904 by Gustav Pielstick (granted 25 July 1933)
“Piston for Double Acting Internal Combustion Engines” US patent 1,922,393 by Gustav Pielstick (granted 15 August 1933)
“Internal Combustion Engine” US patent 1,962,523 by Gustav Pielstick (granted 12 June 1934)
“Housing for a Vertical Combustion Power Engine” US patent 1,969,031 by Gustav Pielstick (granted 7 August 1934)
Diesel’s Engine by Lyle Cummins (1993)
Ungewöhnliche Motoren by Stefan Zima and Reinhold Ficht (2010)
Pocket Battleships of the Deutschland Class by Gerhard Koop and Klaus-Peter Schmolke (2014)

Engelmann VS 5 side

Versuchs Schnellboot 5 (VS 5) Semi-submersible Attack Boat

By William Pearce

In the early 1930s, Rudolf Engelmann of Berlin, Germany began investigating designs to improve the hull shape of seagoing ships. Engelmann felt that a new hull shape could be devised that would significantly improve how efficiently a sea-going ship plowed through the water. At the time, the fastest ocean liners and destroyers were capable of around 35 mph (56 km/h) and 46 mph (74 km/h) respectively. Engelmann’s goals were to increase speed to 46–58 mph (74–93 km/h) with the same amount of power and enable ships to maintain higher speeds through rough seas.

Engelmann patent drawings

Rudolf Engelmann’s original concept of a semi-submersible ship is illustrated in Fig 3 and Fig 4 from his first patent (651,390). Fig 10 shows the updated design from his second patent (651,892), with the exception of line 14. Line 14 indicates the chines that were added in the third patent (651,893).

Engelmann used models to test various hull shapes. On 25 March 1934, Engelmann applied for a German patent (no. 651,390) that outlined his design. Engelmann’s ship had a shape that was very similar to a modern-day submarine—a cigar-shaped (fusiform or spindle-shaped) hull with a propeller at its end and a superstructure in the middle. However, Engelmann’s ship was not fully submersible. The hull traveled beneath the water’s surface, but the superstructure sat above the waterline. The hull’s cross section was pear-shaped, with the narrow part in the middle positioned at the waterline. The submerged hull increased the ship’s efficiency and improved the ship’s stability in rough seas. The superstructure had a streamlined form to cut through the water and slice through waves.

After the first patent, Engelmann continued to develop the semi-submersible design. He applied for two other patents in 1935 that detailed an updated hull shape. The difference between the two later patents was detailed in German patent 651,893, which included a chine added to the superstructure. Tests indicated that in rough seas, the superstructure of the previous designs had a tendency to build up a bow wave. In addition, the design’s minimal reserve buoyancy caused the ship to plow under waves. To correct these issues, the thickness of the leading edge of the superstructure was reduced, and chines were added above the waterline. The chines tapered back and were blended into the sides of the superstructure. They directed water down from the superstructure rather than over it. The additional area created by the chines increased the ship’s displacement and buoyancy with the wave action.

Engelmann VS 5 drawing

A drawing of the Versuchs Schnellboot 5 (VS 5) shows the ship’s profile as very similar to what was depicted in Engelmann’s second and third patents. Note how the ship narrowed at the waterline, which is where the hull and superstructure joined.

Engelmann’s experiments caught the attention of the Kriegsmarine (German Navy), which felt the hull design had military applications. Having the superstructure as the only part of the ship above the water decreased the ship’s detection range and also presented a small target for an enemy to hit. Combined with its high speed, a ship of Engelmann’s design could get very close to an enemy ship undetected, launch torpedoes, and then quickly retreat to a safe distance. Around 1938, the Kriegsmarine ordered a proof-of-concept prototype be built.

The prototype was designated Versuchs Schnellboot 5 (Experimental Fast Boat 5 or VS 5) and was also referred to as the Engelmann-Boot. The ship was a semi-submersible, fast-attack torpedo boat for use in coastal waters. The VS 5 was built along the lines specified in Engelmann’s third patent. Rudders and stern planes at the rear of the ship provided control. The VS 5’s armament consisted of two forward-firing, 21 in (533 mm) torpedo tubes in the bow of the hull and two 20 mm cannons atop the superstructure. However, it is not clear if the weapons were ever installed in the prototype.

Engelmann VS 5 front

The VS 5 in dry-dock, most likely before it was launched in January 1941. The completed ship looked very much like a submarine with an odd sail. Note the chines on the superstructure. Engelmann stated in his patents that the top of the superstructure could be built with an overhang so that its leading edge was angled back to the hull. This configuration would further reduce the tendency of waves to pass over the superstructure.

Power was provided by four MAN (Maschinenfabrik Augsburg-Nürnberg) L11Z 19/30 diesel engines. The L11Z 19/30 was an 11-cylinder, double-acting, two-stroke, inline engine capable of reverse operation. Each of its closed cylinders had a combustion chamber at the top and bottom of the cylinder. A single intake manifold brought air into the cylinders, where the air was directed either above or below the double-sided piston, depending on its stroke. Separate exhaust manifolds collected exhaust gasses from the upper and lower combustion chambers. The engine had a 7.48 in (190 mm) bore and a 11.81 in (300 mm) stroke. Since the piston was double-acting and there was an upper and lower combustion chamber, the engine’s displacement was nearly doubled, as if it had 22 cylinders. However, the connecting rod passing through the lower combustion chamber took up around 40 cu in (.66 L) of volume. Total displacement for the upper combustion chambers was 5,710 cu in (93.56 L). Total displacement for the lower combustion chambers was approximately 5,269 cu in (86.35 L). The L11Z 19/30’s total displacement was around 10,979 cu in (179.91 L). The engine had a maximum output of 2,000 hp (1,491 kW) at 1,050 rpm and a continuous output of 1,400 hp (1,044 kW) at 900 rpm. The four L11Z 19/30 engines were installed in two rows in the middle of the VS 5 and were connected to a common gearbox that drove a single propeller.

MAN LZ 19-30 engine side

The VS 5 was powered by four MAN L11Z 19/30 double-acting, two-stroke, 11-cylinder engines. Note the upper and lower exhaust manifolds separated by the single intake manifold. The gap under the lower exhaust manifold is where the two fuel injectors for the lower combustion chamber were installed. A covered connecting rod passed through the center of each gap. (Hermann Historica image)

The VS 5 was 160 ft 3 in (48.84 m) long and 9 ft 3 in (2.82 m) wide. The keel sat about 11 ft 10 in (3.6 m) under the waterline. The superstructure was around 66 ft (20 m) long and rose about 12 ft 6 in (3.8 m) out of the water. The VS 5 displaced some 292 tons (265 tonnes) and had a forecasted top speed of 58 mph (93 km/h). The ship had a full crew of 17. Some sources state the VS 5 could sink in shallow water to hide from enemy ships. Once submerged, it could not move (other than surfacing), as the ship did not have batteries or the capability to run its engines while underwater. However, the ability to intentionally sink is not mentioned by all sources.

Engelmann VS 5 side

For normal operation, the hull of the VS 5 was completely submerged, and only the superstructure sat above the waterline. The 12 ft 6 in (3.8 m) tall and 66 ft (20 m) long superstructure was a small target for enemy ships to detect and hit.

Construction of the VS 5 started on 1 April 1940, and the ship was built by Deutsche Schiff- und Maschinenbau Aktiengesellschaft (Deschimag) in Bremen, Germany. Deschimag was a conglomerate of eight German shipyards. The VS 5 was launched on 14 January 1941, and trouble was encountered soon after testing began. Despite the changes in Engelmann’s design, the VS 5 still had a tendency to plow under waves in heavy seas. In addition, torque from the single propeller caused the whole ship to list around 14 degrees as full power was applied. The issue was so severe that a speed of 32 mph (52 km/h) could not be exceeded because of the tilt.

The VS 5 project was apparently abandoned in 1942, and what happened to the ship is not known. Plans for a larger 661-ton (600-tonne) ship were cancelled. Twin propellers were planned for the larger ship, and their configuration would have cured the list issues caused by the single-propeller. Engelmann’s design concept was passed over as the Kriegsmarine focused on submarines and fast boats, rather than a combination of the two.

Engelmann VS 5 rear

The chine on the superstructure can easily be seen in this image of the VS 5. The VS 5 had a severe list under full power, an issue that would have been corrected if other ships of the same type had been built. The VS 5 combined elements of both a fast boat and a submarine but did not really offer any advantages over other types of ships.

“Schiff” German patent 651,390 by Rudolf Engelmann (granted 23 September 1937)
“Schiff” German patent 651,892 by Rudolf Engelmann (granted 30 September 1937)
“Schiff” German patent 651,893 by Rudolf Engelmann (granted 30 September 1937)
“Improvements relating to the construction of Ships” GB patent 455,466 by Rudolf Engelmann (granted 21 October 1936)
“Improvements relating to the Construction of Ships” GB patent 470,907 by Rudolf Engelmann (granted 20 August 1937)
“High Speed Seagoing Ship” US patent 2,101,613 by Rudolf Engelmann (granted 7 December 1937)


Mercedes-Benz 500 Series Diesel Marine Engines

By William Pearce

Daimler-Benz was formed in 1926 with the merger of Daimler Motoren Gesellschaft and Benz & Cie. Prior to their merger, both companies produced aircraft engines under the respective names Mercedes and Benz. After the merger, the Daimler-Benz name was used mostly for aircraft engines, and the Mercedes-Benz name was used mostly for automobile production. However, both names were regularly applied to marine engines. For clarity in this article, the name Daimler-Benz will refer to aircraft engines, and the name Mercedes-Benz will refer to marine engines.


The MB 501 shows the close family resemblance to the DB 602, but the engines had Vees of different angles and completely different valve trains. The tubes for the pushrods can be seen on the outer side of the cylinders. Note the two water pumps on the rear sides of the engine.

As Germany began its rearmament campaign in the 1930s, high-performance marine diesel engines were needed to power various motorboats. The Kriegsmarine (German Navy) turned to Mercedes-Benz to supply a series of high-speed diesel engines. These engines were part of the MB 500 series of engines that were based on the Daimler-Benz DB 602 (LOF-2) engine developed to power the LZ 129 Hindenburg and LZ 130 Graf Zeppelin II airships. The 500 series diesel engines were four-stroke, water-cooled, and utilized a “V” cylinder arrangement.

The first engine in the 500 series was the MB 500 V-12. The engine’s two cylinder banks were separated by 60 degrees. The MB 500 used individual steel cylinders that were attached to an aluminum alloy crankcase. About a third of the cylinder was above the crankcase, and the remaining two-thirds protruded into the crankcase. This arrangement helped eliminate lateral movement of the cylinders and decreased vibrations. The crankcase was made of two pieces and split horizontally through the crankshaft plane. The lower part of the crankcase was finned to increase its rigidity and help cool the engine oil.


The crankcases of the wrecked MB 501 engines on Crackington Haven Beach have completely dissolved over the years from constant exposure to salt water. Only the engine’s steel components remain. Note the fork-and-blade connecting rods. The engine’s gear reduction can be seen on the left side of the image. (gsexr image via

Each cylinder had two intake and two exhaust valves. The camshaft had two sets of intake and exhaust lobes per cylinder. One set was for normal operation, and the other set was for running the engine in reverse. The fore and aft movement of the camshaft to engage and disengage reverse operation was pneumatically controlled. Bosch fuel injection pumps were located at the rear of the engine and were geared to the camshaft. Each injection pump provided fuel to the cylinders at 1,600 psi (110.3 bar). Fuel was injected into the center of the pre-combustion chamber, which was in the center of the cylinder head and between the four valves. For low-speed operation, fuel was cut from one bank of cylinders.

The MB 500 had a compression ratio of 16.0 to 1. The engine used fork-and-blade connecting rods that rode on roller bearings fitted to the crankshaft. The camshaft also used roller bearings, but the crankshaft was supported by plain bearings. Speed reduction of the engine’s output shaft was achieved through the use of bevel planetary gears. Two water pumps mounted to the rear sides of the engine circulated water through the cylinder banks. Each pump provided cooling water to one cylinder bank. The pumps were driven by a cross shaft at the rear of the engine. The engine was started with compressed air.


With the exception of the different intake manifolds, the MB 502 was nearly identical to the DB 602. Note the Mercedes-Benz emblem on the rear of the V-16 engine.

The MB 500 had a 6.89 in (175 mm) bore and a 9.06 in (230 mm) stroke. This cylinder size directly corresponded to the cylinder size used on the DB 602. The MB 500’s displacement was 4,051 cu in (66.39 L). The engine had a continuous output of 700 hp (522 kW) at 1,460 rpm and a maximum output of 950 hp (708 kW) at 1,630 rpm. Fuel consumption was .397 lb/hp/hr (241 g/kW/hr). The MB 500 was 9.6 ft (2.93 m) long, 3.2 ft (.98 m) wide, and 5.7 ft (1.73 m) tall. The engine weighed around 4,784 lb (2,170 kg). MB 500 engines were installed in Schnellboote that Germany built for Bulgaria. A Schnellboot, or S-boot, was a fast attack boat and was referred to as an E-boat (Enemy boat) by the Allies.

For more power, the MB 501 was built with two rows of ten cylinders, creating a V-20 engine. The MB 501 was similar to the MB 500, but it also had a number of differences. A 40 degree angle separated the cylinder banks, and the engine used two camshafts positioned in the upper crankcase, one on each side of the engine. Rollers on the lower end of the pushrods rode on the camshaft. Two pushrods for each cylinder extended up along the outer side of the cylinder bank to operate a set of duplex rocker arms for the two intake and two exhaust valves. The fork-and-blade connecting rods were attached to the crankshaft with plain bearings.


The MB 507 was based on the DB 603 inverted V-12 aircraft engine. Although the engine’s architecture was similar, the MB 507 had a completely different crankcase and reduction gear than the DB 603, and it was not supercharged.

The MB 501’s bore and stroke were increased over the MB 500’s to 7.28 in (185 mm) and 9.84 in (250 mm) respectively. The engine displaced 8,202 cu in (134.40 L). The MB 501 had a continuous output of 1,500 hp (1,119 kW) at 1,480 rpm and a maximum output of 2,000 hp (1,491 kW) at 1,630 rpm. Fuel consumption was .397 lb/hp/hr (241 g/kW/hr). The engine was 12.7 ft (3.88 m) long, 5.2 ft (1.58 m) wide, 5.6 ft (1.71 m) tall, and had a weight of 9,303 lb (4,220 kg). Three MB 501 engines were installed in each 1937 class Schnellboot. Six engines were installed in each of the U-180 and U-190 submarines. However, the MB 501 engines proved unsuitable in the submarines, and they were soon replaced by MAN diesels. The remains of three MB 501 engines can be found on Crackington Haven Beach in southeast Britain. The engines belonged to Schnellboot S-89, which was surrendered to the British after World War II. S-89 slipped its tow on 5 October 1946 and was wrecked upon the shore.

The MB 502 was essentially a Daimler-Benz DB 602, except it had water jacketed intake manifolds that protruded above the engine’s Vee. The rest of the MB 502’s specifics mirrored those of the DB 602. The MB 502 was a 50 degree V-16 with a single camshaft located in the Vee of the engine. The engine had a 6.89 in (175 mm) bore and a 9.06 in (230 mm) stroke. The MB 502 displaced 5,401 cu in (88.51 L) and had a continuous output of 900 hp (671 kW) at 1,500 rpm and a maximum output of 1,320 hp (984 kW) at 1,650 rpm. The engine was 9.9 ft (3.02 m) long, 4.0 ft (1.22 m) wide, and 6.2 ft (1.90 m) tall. The MB 502 weighed 5,952 lb (2,700 kg) and had a fuel consumption at cruising power of 0.37 lb/hp/hr (225 g/kW/hr). Three MB 502 engines were installed in each 1939 class Schnellboot.


The MB 511 engine on display in the Aeronauticum museum in Germany. Note the finning on the lower half of the crankcase. On the front of the engine (left side of image) is the gear reduction with the supercharger above. The square connection above the engine is for the induction pipe. (Teta pk image via Wikimedia Commons)

The MB 507 was based on the Daimler-Benz DB 603 inverted V-12 aircraft engine, but some features from the DB 602 were incorporated. The normally aspirated MB 507 was an upright V-12 diesel engine that used monobloc cylinders and had a compression ratio of 17 to 1. A new finned crankcase was fitted that was similar to those used on other MB 500 series diesel engines. For the initial MB 507 engines, the bore was decreased from the 6.38 in (162 mm) used on the DB 603 to 6.22 in (158 mm). The stroke was unchanged at 7.09 in (180 mm). This gave the MB 507 a displacement of 2,584 cu in (42.35 L). The DB507 weighed 1,834 lb (850 kg). The engine had a continuous output of 700 hp (522 kW) and a maximum output of 850 hp (634 kW) at 2,300 rpm. An updated version of the engine, the MB 507 C, reverted back to the 6.38 in (162 mm) bore, which increased its displacement to 2,717 cu in (44.52 L). The MB 507 C produced 750 hp at 1,950 rpm and 1,000 hp at 2,400 rpm. The engine was 6.0 ft (1.83 m) long, 2.6 ft (.79 m) wide, 3.5 ft (1.06 m) tall, and had a weight of 1,742 lb (790 kg). Two MB 507 engines were used in a few LS boats (Leicht Schnellboot or Light Fast boat), and the engine was also installed in some land vehicles, such as the Karl-Gerät self-propelled mortar.

The MB 511 was a supercharged version of the MB 501 V-20 engine. The bore, stroke, and displacement were unchanged, but the compression ratio was decreased to 14 to 1. The supercharger was positioned at the front of the engine, above the gear reduction. With the supercharger, output increased to 1,875 hp (1,398 kW) at 1,480 rpm for continuous power and 2,500 hp (1,864 kW) at 1,630 rpm for maximum power. The MB 511 was 13.1 ft (4.00 m) long, 5.2 ft (1.58 m) wide, and 7.6 ft (2.33 m) tall. The engine weighed 10,406 lb (4,720 kg). Three MB 511 engines were installed in each 1939/1940 class Schnellboot. An MB 511 engine is on display in the Aeronauticum maritime aircraft museum in Nordholz (Wurster Nordseeküste), Germany. Also, the MB 511 engine was built by VEB Motorenwerk Ludwigsfelde as the 20 KVD 25 in East Germany in the 1950s. Two 20 KVD 25 engines were installed in an experimental torpedo boat.


The sectional and cylinder drawing are for the MB 518 but were basically the same for the MB 501 and MB 511—all were 40 degree V-20 engines with individual cylinders. Note the pre-combustion chamber, valve train, and two camshafts.

The MB 512 was a supercharged version of the MB 502. Its compression was decreased to 14 to 1, but its output increased to 900 hp (1,398 kW) at 1,500 rpm for continuous power and 1,600 hp (1,864 kW) at 1,650 rpm for maximum power. The MB 512 was 10.0 ft (3.05 m) long, 4.2 ft (1.28 m) wide, and 6.3 ft (1.92 m) tall. The engine weighed 6,834 lb (3,100 kg). MB 512 engines replaced MB 502s in some Schnellboot installations.

The MB 517 diesel engine was a supercharged version of the MB 507. Returning to its DB 603 roots, the engine was inverted, but it retained the 6.22 in (158 mm) bore and 7.09 in (180 mm) stroke of the early MB 507. The supercharger boosted power from the 2,584 cu in (42.35 L) engine to 1,200 hp (895 kW) at 2,400 rpm. The MB 517 was installed in the Panzer VIII Maus V2 tank prototype.


The MB 518 was the last development of the V-20 engines. This image shows the large intercooler installed on the engine’s induction system.

The MB 518 was a continuation of the MB 511 and featured an intercooler. The large intercooler was positioned in the intake duct, above the engine and between the supercharger at the front of the engine and the intake manifolds in the engine’s Vee. The first MB 518s had a continuous output of 2,000 hp (1,696 kW) at 1,500 rpm and a maximum output of 3,000 hp (2,237 kW) at 1,720 rpm. After World War II, updated versions of the engine went into production starting in 1951. The MB 518 B had a continuous output of 2,275 hp (1,696 kW) and a maximum output of 3,000 hp (2,237 kW). The MB 518 C had a continuous output of 2,500 hp (1,864 kW) and a maximum output of 3,000 hp (2,237 kW). A turbocharger was added to create the MB 518 D. It had a continuous output of 2,900 hp (2,163 kW) and a maximum output of 3,500 hp (2,610 kW). The MB 518 engine was 14.8 ft (4.52 m) long, 5.2 ft (1.58 m) wide, and 8.0 ft (2.44 m) tall. The engine weighed around 11,332 lb (5,140 kg). MB 518 engines were used to power several different vessels for the German Navy and were also exported to 35 countries. Some of the engines are still in use today.

Schnellboot S-130, the only remaining German S-boot from World War II, was originally powered by three MB 511 engines. After the war, S-130 was reengined with two MB 518s, and one MB 511 was retained. S-130 is currently part of the Wheatcroft Collection and undergoing restoration. Four MB 518 C engines for the restoration were obtained from the Arthur of San Lorenzo, formerly known as the S39 Puma and originally built as a German Zobel Class fast patrol boat in the early 1960s.


A number of MB 518 engines under construction show many different details. The lower crankcase half is on the floor, while the upper half is in the engine cradle; note the two camshaft tunnels. The crankshaft and its fork-and-blade connecting rods can be seen. Farther down the line is an engine with cylinder studs installed, and farther still is an engine with studs and pushrod tubes installed.



Brayton Ready Motor Hydrocarbon Engine

By William Pearce

With the proliferation of steam power in the late 1800s, many inventors looked to create a simpler and more efficient engine. Rather than having combustion occur outside the engine, as with a steam engine, designers sought to create an internal combustion engine, in which the piston was driven by the expansion of a volatile gas mixture after it was ignited. George Brayton of Boston, Massachusetts was one such inventor, and while his designs would forever influence the internal combustion engine, he never achieved the same level of recognition as many of his contemporaries.


Patent drawings of George Brayton’s 1872 engine. Gas and air was drawn into cylinder C, compressed by piston D, and stored in reservoir G. The mixture was then released into cylinder A and ignited as it passed through wire gauze e. As the mixture combusted and expanded, it acted on piston B.

Brayton was an inventor, engineer, and machinist who had experience with steam engines. Some of his internal combustion engine experiments date back to the early 1850s, but he began serious development around 1870. In 1872, Brayton patented a new type of engine, the first in a series that became known as the Brayton Ready Motor. The name “Ready Motor” described the fact that the engine was immediately ready for operation, unlike a steam engine. The Brayton engine was also called a “Hydro-Carbon Engine.” The engine used fuel (hydrocarbons) mixed with air as the working fluid that directly acted on the piston, rather than the fuel heating some other working fluid, as with a steam engine. The theoretical process by which the Brayton engine worked became known as the constant-pressure cycle or Brayton cycle. The Brayton cycle in a piston engine involves the pressure in the engine’s cylinder being maintained by the continued combustion of injected fuel as the piston moves down on its power stroke. The constant-pressure Brayton cycle is used in gas turbines and jet engines and is also very similar to the Diesel cycle.

Brayton’s 1872 patent engine was a two-stroke that had two pistons mounted to a common connecting rod. The smaller of the two pistons acted as an air pump, compressing the air to around 65 psi (4.5 bar). A gaseous fuel, such as illuminating gas or carbureted hydrogen, was mixed with the air entering the compression cylinder. Alternatively, an oil fuel, such as naphtha, could be vaporized and added to the air entering the compression cylinder. The air/fuel mixture was then compressed, passed through a valve, and stored in a reservoir. An engine-driven camshaft opened a valve that allowed the pressurized air/fuel mixture to flow from the reservoir and into the large combustion cylinder. Before entering the cylinder, the air/fuel mixture passed through layers of wire gauze where a small pilot flame constantly burned. The pilot flame was kept lit by a continuous, small supply of the air/fuel mixture. As the charge passed through the wire gauze and entered the cylinder, it was ignited by the pilot flame. The combusting and expanding gasses created around 45 psi (4.1 bar) of pressure that forced the large piston back in its cylinder, creating the power stroke. At the same time, the small piston was moved toward top dead center in its cylinder, compressing another charge of air for continued operation.


Brayton’s 1874 patent illustrating a double-acting engine. The upper side of piston B compressed air as the lower side was exposed to the combustion process of air and fuel being mixed and ignited in chamber H. Reservoir C only stored compressed air.

Brayton’s experience with steam engines and how steam expands into the cylinder to smoothly act on the piston probably influenced his desire to have the fuel burn in the cylinder. Gas expansion created by burning fuel acts smoothly on the piston, whereas the sudden ignition of fuel by a spark creates more of an explosion that exposes the piston and other engine components to high stresses. The combustion (motor) cylinder was about twice the volume of the compression (pump) cylinder, and the reservoir was no more than twice the volume of the combustion cylinder. The pressure in the reservoir was always greater than the pressure in the combustion cylinder. A water jacket surrounded the combustion cylinder to provide engine cooling.

The 1872 patent clearly illustrates a single-acting engine in which only one side of the piston acts on the working fluid. Brayton explains in the patent that the same principles of his engine could be applied to a double-acting engine. In a double-acting internal combustion engine, one side of the piston compresses the working fluid, while the other side of the piston is used for combustion of the working fluid. The patent drawing also shows a flywheel mounted to the camshaft. Engine power would be distributed from a driving pulley on the opposite end of the flywheel. However, images of early Brayton engines show an articulated rod mounted to the connecting rod that drove the flywheel and drive pulley.


Brayton Ready Motor vertical engine with a double-acting cylinder. The air reservoir was housed in the rocking beam support column. Note the ball governor.

Around 1873, Brayton installed a 4 hp (3.0 kW) engine in a streetcar in Providence, Rhode Island. The streetcar could obtain a speed of 15 mph (24 km/h), but it would barely move with a full load and had difficulty climbing an incline. A larger 12 hp (8.9 kW) engine was substituted, as it was the most powerful Brayton engine that fit in the space available. The engine took up the space of one passenger and enabled the streetcar to climb a 5 percent grade. All total, the streetcar was tested for 18 months. However, the tests indicated issues with wheel slip on the rails, especially in snow or ice, and financial issues brought an end to the experiment.

A drawback to the 1872 engine was the storage of the volatile gas mixture in the reservoir. If any flame were to get past the wire gauze and continue to burn back to the reservoir, the contents of the reservoir would explode. A safety valve prevented damage to the engine, but such an event was very disconcerting to anyone near the engine. The use of light, gaseous fuel exacerbated the issue. In 1874, Brayton switched to a heavy petroleum oil fuel and patented a refined engine in which only air was stored in the reservoir. A small supply of petroleum fuel was pumped into absorbent, porous material contained in a chamber that surrounded the induction pipe. The top of the chamber formed what was basically a burner. As the liquid fuel was heated by the engine and vaporized, it joined with the air charge being admitted into the cylinder via a camshaft-driven valve. The mixture was then ignited as it flowed through the burner section and into the cylinder. The burner stayed lit by residual fuel from the absorbent material mixing with a small amount of air from the reservoir that constantly passed through the burner.


Engine speed was controlled by an admission valve that regulated the amount of air passing into the cylinder. Although the fuel quantity supplied to the chamber was metered and dependent on engine speed, making changes to engine speed proved to be difficult. Any change in the amount of air supplied meant that there was a brief period of either too much or too little fuel, and this would occasionally extinguish the burner flame. By 1876, this issue had been resolved by implementing a new fuel injection process. The incoming air passed through the absorbent, porous material that was saturated with injected fuel. A jet of air coincided with the injection of fuel and helped distribute the fuel throughout the absorbent material. This injection technique proved more responsive than the earlier vaporization process.

Other changes incorporated in the 1874 engine were the use of both sides of the piston, making the engine double-acting. A rod connected to the compression side of the piston extended out of the engine. The rod decreased the volume of the compression cylinder to less than that of the combustion cylinder. The rod also provided a means to harness power from the reciprocating movement of the piston. Although the rod was mounted on the compression side of the piston, it was the power stroke of the combustion side that provided the motive force.


Circa 1876 Brayton inverted rocking beam engine. The combustion cylinder is on the left, and the smaller compression cylinder is at the center of the engine. Two air reservoirs made up the engine’s base; one was used for operating the engine, and the other was used for starting. The engine is currently in storage at the Smithsonian. (Paul Gray image via John Lucas /

Development of the Brayton Ready Motor continued, and by 1875, the compression cylinder was completely separate from the combustion cylinder. Both cylinders had the same bore, but the stroke of the compression cylinder was about half that of the combustion cylinder. A number of different engine styles, both vertical and horizontal, were built, and the engines used different ways to harness the power of the compression cylinder. Some engines used the compression cylinder to actuate a rocking beam; other engines had the compression cylinder connected to a crankshaft that turned the power wheel.

By 1875 (and possibly as early as 1873), the Pennsylvania Ready Motor Company in Philadelphia had been established to sell Brayton’s engines, but the engines were built in the Exeter Machine Works in Exeter, New Hampshire. The Brayton Ready Motor may have been the first commercially available internal combustion engine. Engines based on the Brayton cycle were also sold by a number of other companies, including the New York & New Jersey Motor Company (by 1877) and Louis Simon & Sons, in Nottingham, England in 1878.


Drawing of the 10 hp (7.5 kW) vertical Brayton Ready Motor displayed at the Centennial Exposition in Philadelphia, Pennsylvania in 1876. This is the same engine that inspired George Selden. The compression cylinder was mounted above the combustion cylinder. The column supporting the rocking beam also contained the reservoir.

In 1878, John Holland used a 4 hp (3.0 kW) vertical Brayton engine in the first submarine powered by an internal combustion engine, the Holland I. While functional, this submarine was not a true success. Holland’s second submarine, the Fenian Ram, used a 15 hp (11.2 kW) horizontal Brayton engine and was launched in 1881. This submarine has been preserved and is displayed in the Paterson Museum in Paterson, New Jersey.

Also in 1878, a vertical engine was tested in an omnibus in Pittsburgh, Pennsylvania, but local authorities would not permit its use to transport passengers. Scottish engine pioneer Dugald Clerk converted a 5 hp (3.7 kW) Brayton engine to spark ignition. This engine was the first two-stroke, spark ignition engine ever built. Horizontal engines were installed in a few boats that operated on the Hudson River. In 1880, the USS Tallapoosa was fitted with a Brayton engine capable of 300 rpm. Other Brayton engines were used for industrial purposes such as powering pumps, cotton gins, or grinding mills. These Brayton engines were the first practical oil engines and were noted for their ease of starting and steady operation.


George Selden and Ernest Samuel Partridge in the Selden automobile in 1905. The vehicle was built in 1903 to prove the viability of Selden’s patent design. Between the front wheels is a three-cylinder Brayton-style engine, which ultimately led to Selden’s patent claims being dismissed.

George Selden was inspired by the 10 hp (7.5 kW) Brayton engine he saw at the 1876 Centennial Exposition in Philadelphia and felt the engine could be adapted to power a practical wheeled vehicle (automobile). In 1879, Selden applied for a patent on his three-cylinder Road Engine, which powered a four-wheel carriage. Selden continued to delay his patent with minor modifications until 1895, when the patent was finally granted despite the fact that Selden had never built the actual vehicle. That did not deter Selden from claiming he invented the automobile and demanding royalties from all automobile manufactures—suing those who refused to pay. Henry Ford led the rebellion against Selden and lost the court case in 1909. However, that ruling was overturned on appeal in 1911. For the successful appeal, Ford demonstrated that Selden’s automobile used an engine based on the Brayton cycle (two-stroke and a constant-pressure cycle), while Ford and others used engines based on the design of Nicolaus Otto (Otto cycle: four-stroke and a constant-volume cycle). No automobiles were built with a Brayton cycle engine; therefore, the automobile manufacturers were not infringing on Selden’s patent.

By the late 1880s, it was becoming clear that the Brayton cycle for piston-driven internal combustion engines was outclassed by the more efficient Otto cycle. The main issue facing the Brayton engine was its relatively low pressure (60–80 psi / 4.1–5.5 bar) combined with excessive friction, pumping, and heat losses between the compression and combustion cylinders.


Horizontal Brayton Ready Motor marine engine that was very similar, but not identical, to the engine used in the Fenian Ram submarine. The combustion cylinder is in the foreground, and the compression cylinder is in the background. The bevel gear powered the propeller shaft.

Brayton continued to develop his engine and applied for a patent in 1887 that outlined a horizontal, fuel injected, four-stroke engine. The cylinder was closed at both its combustion (hot) and non-combustion (cool) sides. Exhaust from the hot side of the cylinder passed through a water-cooled condenser that opened to the cool side of the cylinder. As the piston moved up on the exhaust stroke, the vacuum created in the cool side of the cylinder helped draw exhaust gases out of the hot side of the cylinder. An exhaust valve on the cool side of the cylinder was sprung to open at just above atmospheric pressure. As the piston moved toward the cool side of the cylinder on the intake stroke, the exhaust valve opened to expel the products of combustion. When the intake valve was opened, it brought fresh air into the cylinder and sealed the condenser. The intake valve then closed, and the piston moved toward the hot side of the cylinder to compress the air. Brayton stated in his patent that the cylinder’s cycle provided an abundance of fresh air to increase the engine’s power and efficiency.

Once the air was compressed, fuel was injected into the cylinder. The act of injecting the petroleum oil under pressure converted the fuel to a fine spray that was easily ignitable. The fuel injection pump was controlled by a follower riding on an engine-driven camshaft, and engine speed was controlled by the quantity of fuel injected. Once injected, the fuel was ignited by an incandescent burner made from a coil of platinum wire. This concept is very similar to a hot bulb in a much later semi-diesel engine. Brayton’s fuel injection was ideally suited for the use of heavy fuels. This engine was built with a 7 in (179 mm) bore and a 10 in (254 mm) stroke, displacing 385 cu in (6.31 L). Running at 200 rpm and driving a 30 in (762 mm) fan at 1,500 rpm for 10 hours, the engine only consumed 3.5 gallons (13.2 L) of kerosene.


Patent drawing showing the cylinder of Brayton’s horizontal, four-stroke engine of 1887. Passage d was used for both intake and exhaust. Passage d1 harnessed the vacuum created under the piston to help draw the exhaust gases out of the cylinder and through the condenser (C). The exhaust was expelled via valve g1. Fresh air was admitted via valve e1, which sealed the condenser. Fuel was injected via “Oil-jet” F and ignited by a platinum coil.

In 1890, Brayton patented his last engine, a vertical four-stroke that featured fuel injection. As the piston moved down on its intake stroke, a valve in the piston head opened and allowed the slightly pressurized air in the crankcase to enter the vacuum in the cylinder. As the piston moved up on the compression stroke, the exhaust valve opened for a short time to evacuate any remaining products of combustion. With all valves closed, the remaining air was compressed, and fuel was injected in a combustion chamber space above the piston. A connecting rod attached the piston to an inverted rocking beam, and the opposite end of the rocking beam was connected to a crankshaft. A small air pump was driven from a rod connected to the rocking beam. The air pump provided the pressure for the fuel injection system, enabling a blast of air to disperse the fuel into a fine spray as it was forced into the combustion chamber. The fuel was ignited by an incandescent burner and continued to burn as more fuel was injected and the piston moved down on the power stroke. Brayton’s last engine worked through a similar process as the engines Rudolf Diesel began developing in 1893, but Diesel used much higher cylinder pressures.

While traveling in England and still experimenting with engines, Brayton passed in 1892 at the age of 62. Production of his engines had already decreased by the time of his death but may have continued until the early 1900s. While names like Otto and Diesel are known to many today, Brayton’s is relatively unknown despite his pioneering work. Brayton’s engines were used in land vehicles, boats, and submarines before Otto’s or Diesel’s engines successfully ran. Undoubtedly, Brayton’s engineering contributions helped pave the way for many who followed. Out of the hundreds of Brayton Ready Motors that were made, only around six original engines are known to survive today.


Patent drawing illustrating Brayton’s 1890 inverted rocking beam (D) engine. Air slightly pressurized in the crankcase (A) passed through a valve (b1) in the piston to fill the cylinder (B). Fuel was injected (via g) and ignited by a burner (G) in a combustion chamber space (B1) at the top of the cylinder. A smaller cylinder (J) acted as a pump to power the fuel injector.

Correspondence with John Lucas
“Improvement in Gas Engines” US patent 125,166 by George B. Brayton (granted 2 April 1872)
“Gas Engines” US patent 151,468 by George B. Brayton (granted 2 June 1874)
“Gas and Air Engine” US patent 432,114 by George B. Brayton (applied 15 September 1887)
“Hydrocarbon Engine” US patent 432,260 by George B. Brayton (granted 15 July 1890)
Internal Fire by C. Lyle Cummins Jr. (1976/1989)
The Gas and Oil Engine by Dugald Clerk (1904)
A Text-Book on Gas, Oil, and Air Engines by Bryan Donkin Jr (1894)
Pioneers, Engineers, and Scoundrels by Beverley Rae Kimes (2005)
“The Brayton Ready Motor or Hydrocarbon Engine” Scientific American (13 May 1876)
“Brayton’s Hydrocarbon Engine” Scientific American Supplement, No. 58 (10 February 1877)
“Selden Patent Not Infringed” The Automobile (12 January 1911)
“Road Engine” US patent 549,160 by George B Selden (applied 8 May 1879)
“Events Which Led Up to the Formation of the American Street Railway Association” by D. F. Longstreet The Street Railway Journal (November 1892)

Zvezda M503 Rear

Yakovlev M-501 and Zvezda M503 and M504 Diesel Engines

By William Pearce

Just after World War II, OKB-500 (Opytno-Konstruktorskoye Byuro-500 or Experimental Design Bureau-500) in Tushino (now part of Moscow), Russia was tasked with building the M-224 engine. The M-224 was the Soviet version of the Junkers Jumo 224 diesel aircraft engine. Many German engineers had been extradited to work on the engine, but the head of OKB-500, Vladimir M. Yakovlev, favored another engine project, designated M-501.

Zvezda M503 front

Front view of a 42-cylinder Zvezda M503 on display at the Technik Museum in Speyer, Germany. Unfortunately, no photos of the Yakovlev M-501 have been found, but the M503 was very similar. Note the large, water-jacketed exhaust manifolds. The intake manifold is visible in the engine Vee closest to the camera. (Stahlkocher image via Wikimedia Commons)

Yakovlev and his team had started the M-501 design in 1946. Yakovlev felt the M-224 took resources away from his engine, and he was able to convince Soviet officials that the M-501 had greater potential. All development on the M-224 was stopped in mid-1948, and the resources were reallocated to the M-501 engine.

The Yakovlev M-501 was a large, water-cooled, diesel, four-stroke, aircraft engine. The 42-cylinder engine was an inline radial configuration consisting of seven cylinder banks positioned around an aluminum crankcase. The crankcase was made up of seven sections bolted together: a front section, five intermediate sections, and a rear accessory section. The crankshaft had six throws and was supported in the crankcase by seven main bearings of the roller type.

Each cylinder bank was made up of six cylinders and was attached to the crankcase by studs. The steel cylinder liners were pressed into the aluminum cylinder block. Each cylinder had two intake and two exhaust valves actuated via roller rockers by a single overhead camshaft. The camshaft for each cylinder bank was driven through bevel gears by a vertical shaft at the rear of the bank. All of the vertical shafts were driven by the crankshaft. The pistons for each row of cylinders were connected to the crankshaft by one master rod and six articulating rods.

Zvezda M503 Rear

Rear view of a M503 on display at Flugausstellung L.+P. Junior in Hermeskeil, Germany. The upper cylinder gives a good view of the exhaust (upper) and intake (lower) manifolds, and the engine’s intake screen can just be seen between the manifolds as they join the compounded turbosupercharger. The exhaust gasses exited the top of the turbine housing. (Alf van Beem image via Wikimedia Commons)

Exhaust was taken from the left side of each cylinder bank and fed through a manifold positioned in the upper part of the Vee formed between the cylinder banks. The exhaust flowed through a turbosupercharger positioned at the extreme rear of the engine. Exhaust gases expelled from the turbosupercharger were used to provide 551 lbf (2.45 kN / 250 kg) of jet thrust.

The pressurized intake air from the turbosupercharger was fed into a supercharger positioned between the turbosupercharger and the engine. The single-speed supercharger was geared to the crankshaft via the engine’s accessory section. Air from the supercharger flowed into a separate intake manifold for each cylinder bank. The intake manifold was positioned in the lower part of the Vee, under the exhaust manifold, and connected to the right side of the cylinder bank.

The M-501 had a 6.30 in (160 mm) bore and a 6.69 in (170 mm) stroke. The engine displaced 8,760 cu in (143.6 L) and produced 4,750 hp (3,542 kW) without the turbosupercharger. With the turbosupercharger and the thrust it provided, the engine produced 6,205 hp (4,627 kW). The engine weighed 6,504 lb (2,950 kg) without the turbocharger and 7,496 lb (3,400 kg) with the turbocharger.

Zvezda M503 Bulgaria

This partially disassembled M503 at the Naval Museum in Varna, Bulgaria gives some insight to the inner workings of the engine. The turbine wheel can be seen on the far left. Immediately to the right is the air intake leading to the compressor wheel, which is just barely visible in its housing. From the compressor, the air was sent through the seven outlets to the cylinder banks. The exhaust pipe can just be seen inside the water-jacketed manifold on the upper cylinder bank. Note the studs used to hold the missing cylinder bank. (Михал Орела image via Wikimedia Commons)

By 1952, the M-501 had been completed and had achieved over 6,000 hp (4,474 kW) during tests. The program was cancelled in 1953, as jet and turbine engines were a better solution for large aircraft, and huge piston aircraft engines proved impractical. The M-501 was intended for the four-engine Tupolev 487 and Ilyushin IL-26 and was proposed for the six-engine Tupolev 489. None of these long-range strategic bombers progressed beyond the design phase.

The lack of aeronautical applications did not stop the M-501 engine. A marine version was developed and designated M-501M. The marine engine possessed the same basic characteristics as the aircraft engine, but the crankcase casting were made from steel rather than aluminum. The M-501M was also fitted with a power take off, reversing clutch, and water-jacketed exhaust manifolds.

The exact details of the M-501M’s history have not been found. It appears that Yakovlev was moved to Factory No. 174 (K.E. Voroshilov) to further develop the marine engine design. Factory No. 174 was founded in 1932 and was formerly part of Bolshevik Plant No. 232 (now the GOZ Obukhov Plant) in Leningrad (now St. Petersburg). Factory No. 174 had been involved with diesel marine engines since 1945, and Yakovlev’s move occurred around 1958. Early versions of the marine engine had numerous issues that resulted in frequent breakage. In the 1960s, the engine issues were resolved, and Factory No. 174 was renamed “Zvezda” after the engine’s layout. Many languages refer to radial engines as having a “star” configuration, and “zvezda” is “star” in Russian. Zvezda produced the refined and further developed 42-cylinder marine engine as the M503.

Zvezda M503 cross section

Sectional rear view of a 42-cylinder Zvezda M503. The cylinder banks were numbered clockwise starting with the lower left; bank three had the master connecting rod. Note the angle of the fuel injector in the cylinder and that the injector pumps were driven by the camshaft (as seen on the upper left bank).

The Zvezda M503 retained the M-501’s basic configuration. The engine had a compounded turbosupercharger system with the compressor wheel connected to the crankshaft via three fluid couplings. The compressor wheel shared the same shaft as the exhaust turbine wheel. At low rpm, the exhaust gases did not have the energy needed to power the turbine, so the compressor was powered by the crankshaft. At high rpm, the turbine would power the compressor and create 15.8 psi (1.09 bar) of boost. Excess power was fed back into the engine via the couplings connecting the compressor to the crankshaft. Air was drawn into the turbosupercharger via an inlet positioned between the compressor and turbine.

The M503’s bore, stroke, and displacement were the same as those of the M-501. Its compression ratio was 13 to 1. The M503’s maximum output was 3,943 hp (2,940 kW) at 2,200 rpm, and its maximum continuous output was 3,252 hp (2,425 kW) at the same rpm. The engine was 12.14 ft (3.70 m) long, 5.12 ft (1.56 m) in diameter, and had a dry weight of 12,015 lb (5,450 kg). The M503 had a fuel consumption of .372 lb/hp/h (226 g/kW/h) and a time between overhauls of 1,500 to 3,000 hours.

Zvezda M503 Dragon Fire

Dragon Fire’s heavily modified M503 engine under construction. Each cylinder bank is missing its fuel rail and three six-cylinder magnetos. The turbine wheel has been discarded. The large throttle body on the left has a single butterfly valve and leads to the supercharger compressor. Note that the cylinder barrels and head mounting studs are exposed and that each valve has its own port. (Sascha Mecking image via Building Dragon Fire Google Album Archive)

M503 engines were installed in Soviet Osa-class (Project 205) fast attack missile boats used by a number of countries. Each of these boats had three M503 engines installed. Engines were also installed in other ships. A heavily modified M503 engine is currently used in the German Tractor Pulling Team Dragon Fire. This engine has been converted to spark ignition and uses methanol fuel. Each cylinder has three spark plugs in custom-built cylinder heads. The engine also uses custom-built, exposed, cylinder barrels and a modified supercharger without the turbine. Dragon Fire’s engine produces around 10,000 hp (7,466 kW) at 2,500 rpm and weighs 7,055 lb (3,200 kg).

For more power, Zvezda built the M504 engine, which had seven banks of eight cylinders. Essentially, two additional cylinders were added to each bank of the M503 to create the 56-cylinder M504. The M504 did have a revised compounded turbosupercharging system; air was drawn in through ducts positioned between the engine and compressor. The intake and exhaust manifolds were also modified, and each intake manifold incorporated a built-in aftercooler. At full power, the turbosupercharger generated 20.1 psi (1.39 bar) of boost. The M504 engine displaced 11,681 cu in (191.4 L), produced a maximum output of 5,163 hp (3,850 kW) at 2,000 rpm, and produced a maximum continuous output of 4,928 hp (3,675 kW) at 2,000 rpm. The engine had a length of 14.44 ft (4.40 m), a diameter of 5.48 ft (1.67 m), and a weight of 15,983 lb (7,250 kg). The M504 had a fuel consumption of .368 lb/hp/h (224 g/kW/h) and a time between overhauls of 4,000 hours. The engine was also used in Osa-class missile boats and other ships.

Zvezda M504 56-cyl

The 56-cylinder Zvezda M504 engine’s architecture was very similar to that of the M503, but note the revised turbocharger arrangement. Wood covers have been inserted into the air intakes. Just to the right of the visible intakes are the aftercoolers incorporated into the intake manifolds.

In the 1970s, Zvezda developed a number of different 42- and 56-cylinder engines with the same 6.30 in (160 mm) bore, 6.69 in (170 mm) stroke, and basic configuration as the original Yakovlev M-501. Zvezda’s most powerful single engine was the 56-cylinder M517, which produced 6,370 hp (4,750 kW) at 2,000 rpm. The rest of the M517’s specifications are the same as those of the M504, except for fuel consumption and time between overhauls, which were .378 lb/hp/h (230 g/kW/h) and 2,500 hours.

Zvezda also coupled two 56-cylinder engines together front-to-front with a common gearbox in between to create the M507 (and others) engine. The engine sections could run independently of each other. The 112-cylinder M507 displaced 23,361 cu in (383 L), produced a maximum output of 10,453 hp (7,795 kW) at 2,000 rpm, and produced a maximum continuous output of 9,863 hp (7,355 kW) at the same rpm. The engine was 22.97 ft (7.00 m) long and weighed 37,699 lb (17,100 kg). The M507 had a fuel consumption of .378 lb/hp/h (230 g/kW/h) and a time between overhauls of 3,500 hours for the engines and 6,000 hours for the gearbox.

Zvezda engineer Boris Petrovich felt the 56-cylinder M504 engine could be developed to 7,000 hp (5,220 kW), and the M507 (two coupled M504s) could be developed to over 13,500 hp (10,067 kW). However, gas turbines were overtaking much of the diesel marine engine’s market share. Today, JSC (Joint Stock Company) Zvezda continues to produce, repair, and develop its line of M500 (or ChNSP 16/17) series inline radial engines as well as other engines for marine and industrial use.

Zvezda M507 engine

The M507 was comprised of two M504 engines joined by a common gearbox. The engine sections had separate systems and were independent of each other.

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