Category Archives: Diesel Engines

cummins 1952 28 start

Cummins Diesel Indy 500 Racers

By William Pearce

Clessie Lyle Cummins was a self-taught engineer. In 1911, he served on the pit crew for Ray Harroun’s #32 Marmon Wasp racer, which won the inaugural Indianapolis 500 race. Clessie went on to start the Cummins Engine Company in 1919 and specialized in diesel engines. The Cummins company struggled in its early years. Initially, Cummins engines found success powering yachts, but the company made efforts to break into the automotive field.

cummins 1931 record dc

Clessie Cummins in Washington D.C. on tour after setting the diesel speed record at 100.755 mph (162.150 km/h) on 7 February 1931 in Dayton Beach, Florida. The car was slightly modified and entered in the 1931 Indianapolis 500 race. (Indiana Public Media image via flickr.com)

The Great Depression took its toll on Cummins and also affected auto racing. To increase race participation, Eddie Rickenbacker, then-owner of the Indianapolis Speedway and American Automobile Association Contest Board president, relaxed the racing rules to allow stock-block engines up to 366 cu in (6.0 L) in 1930. Cummins saw an opportunity to help fill the racing field and gain publicity in the Indianapolis 500 by fielding a diesel-powered racer in the 1931 race. Rickenbacker agreed to the plan and offered Cummins a provisional spot provided the racer could top 80 mph (129 km/h). However, the Cummins entry would not be entitled to any winnings, because of its guaranteed entry into the field.

Cummins contracted Augie Duesenberg to modify a Duesenberg Model A chassis and install a 4-cylinder Cummins Model U engine. The Model U was a marine engine with a 4.5 in (114 mm) bore, a 6.0 in (152 mm) stroke, and a displacement of 382 cu in (6.3 L). To make the engine conform to the displacement limit, the bore of the race engine was decreased by .125 in (3 mm), resulting in a bore of 4.375 in (111 mm). This resulted in a displacement of 361 cu in (5.9L). The engine had been modified with aluminum pistons and two intake valves but retained a single exhaust valve. The race engine produced 85 hp (63 kW) at 1,500 rpm and weighed about 1,600 lb (726 kg).

cummins 1931 8 indy

Clessie Cummins stands behind the Cummins Diesel Special #8 entered in the 1931 Indy 500. Dave Evans and Thane Houser are in the cockpit. Note the racer’s height. (IMS image)

To test the powertrain, Clessie drove the car to Daytona Beach, Florida and set a diesel flying-mile (1.6-km) speed record at 100.755 mph (162.150 km/h) on 7 February 1931. The racer was then driven to Washington D.C. and back to the Cummins factory, where it was modified in accordance with the Indy 500 rules. Its completed weight was a hefty 3,389 lb (1,537 kg).

For the Indy 500, the car was named the Cummins Diesel Special and given race #8. Dave Evans was the driver with Thane Houser as the riding mechanic / co-driver. The Cummins Diesel Special was regularly driven the 45 miles (72 km) from the Cummins factory in Columbus, Indiana to the Indianapolis Motor Speedway. The Cummins racer qualified at 96.871 mph (155.899 km/h), which was the 43rd fastest car. Since Rickenbacker had guaranteed a spot in the 40-car field, the Cummins Diesel Special was the slowest car in the 1931 Indianapolis 500. However, the Cummins team had a plan to pick up a few spots during the race.

cummins 1931 8 display

The restored #8 displayed in the Indianapolis Motors Speedway Museum. Note the engine’s four individual cylinders. (Doctorindy image via Wikimedia Commons)

On race day, 30 May 1931, the Cummins Diesel Special was driven from the factory to the raceway. The racer proved to be slow during the 500-mile (805-km) competition, but the fuel-efficient engine enabled the Cummins Diesel Special to run the entire race without stopping, the first and only racer to accomplish such a feat during the Indy 500. In those days, the race continued after the first-place car finished until each car that could finish had completed the 200 laps. The Cummins Diesel Special completed its 200th lap and finished the race 38 minutes after the race leader, which was enough to secure a 13th place finish. The diesel-powered racer averaged 86.170 mph (138.677 km/h) over the 500-mile (805-km) distance, and the amount of fuel used reportedly cost $1.40 ($23 in 2018 USD).

In 1932, Clessie Cummins and William G. Irwin (Cummins’ main financial backer) took the racer on a 5,000-mile (8,047-km) tour of Europe. This trip resulted in some modifications to the racer, such as the addition of a windshield and headlights. The Duesenberg-built Cummins Diesel Special was preserved by Cummins and restored to its Indy-race configuration. The car is often displayed in various museums and run on rare occasion at special events.

cummins 1934 6 indy

Dave Evans and Jigger Johnson in the four-stroke #6 at Indy in 1934. The Roots supercharger can just be seen at the front of the car. (IMS image)

The Cummins Team returned in 1934 to race in the Indy 500. Cummins fielded two Duesenberg-chassis cars for the race, each powered by an experimental, supercharged, aluminum, inline-four engine. The engine had a 4.875 in (124 mm) bore and stroke and displaced 364 cu in (6.0L). The difference between the cars was primarily a difference in engines, with one car using a four-stroke engine and the other car using a two-stroke engine. The Indy 500 race served as a test to compare the two different combustion cycle engines. The Roots-type supercharger was driven from the engine and installed at the front of the car. The supercharger in the four-stroke car took about 7 hp (5 kW) to run, compared with 37 hp (28 kW) for the two-stroke car, which also used the supercharger for cylinder scavenging. The four-stroke engine had one intake valve and one exhaust valve. The two-stroke engine had two exhaust valves and intake ports in the cylinder that were uncovered by the piston. Each engine produced approximately 135 hp (101 kW) at 2,500 rpm. The engines each weighed about 1,000 lb (454 kg), and each car weighed around 3,200 lb (1,451 kg).

cummins 1934 6 engine

The #6 car with the Roots supercharger passing induction air through the radiator and to the engine. (IMS image)

The four-stroke car, race #6, was driven by Dave Evans with John ‘Jigger’ Johnson as the riding mechanic. It qualified in 22nd place at 102.414 mph (164.819 km/h). During the race, #6 made its first pitstop after 200 miles (322 km). Unfortunately, engine torque damaged the transmission as the racer quickly accelerated to reenter the track. This forced Evans and Johnson to retire from the race, and #6 was awarded 19th place. The engine in #6 had operated flawlessly during the race. The car has been preserved by Cummins and is occasionally displayed for special events.

cummins 1934 6 display

The restored #6 car displayed in the Cummins Museum at the Company’s corporate headquarters in Columbus, Indiana. (Ricky Berkey image)

cummins 1934 5 daytona clessie

Clessie Cummins stands by the two-stroke #5 racer at Indy in 1934 with Stubby Stubblefield and Bert Lustig in the cockpit. The Roots supercharger can be seen through the car’s grille. The racer’s 12th place finish is the best for a diesel-powered car in the Indy 500. (Indiana Public Media image via flickr.com)

The two-stroke car, race #5, was driven by Stubby (Wilburn Hartwell) Stubblefield with Bert Lustig as the riding mechanic. The car qualified 29th at 105.921 mph (170.463 km/h). Although the two-stroke engine was temperamental, #5 went the distance and finished the 500-mile (805-km) race in 12th place, averaging 88.566 mph (142.533 km/h). Evans took over driving duties from Stubblefield around mid-race. Race #5 was the last car to complete the 200 laps—finishing the race trailing smoke and overheating. After the racer was shut down, the pistons seized in the cylinders. Some sources indicate that Clessie was so displeased with the two-stroke engine that it was tossed into a river as the team made its way back to Columbus. Because of the issues with the two-stroke engine, Cummins subsequently abandoned two-stroke development and focused on four-stroke engines.

cummins 1934 5 daytona

After Indy, a four-stroke, six-cylinder engine was installed in the #5 racer. Wild Bill Cummings set diesel speed records on Daytona Beach Florida in 1935 and is seen behind the wheel. The front of the car was stretched to accommodate the longer engine. Note the six-to-one exhaust manifold. (Cummins image)

Race #5 was subsequently modified (lengthened) to accommodate a four-stroke, six-cylinder engine. Wild Bill Cummings used the updated #5 to set a flying-mile (1.6 km) diesel speed record of 133.023 mph (214.080 km/h) on 1 March 1935. The following day, Cummings increased the record speed to 137.195 mph (203.200 km/h). Race #5 was preserved by Cummins in its record-setting form and is occasionally displayed in various museums.

cummins 1934 5 display

The restored #5 in its Daytona configuration with a four-stroke, six-cylinder engine. The car was displayed for a time at the Auburn-Cord-Duesenberg Museum on account of its Duesenberg chassis. (Henri Greuter image)

It was not until 1950 that Cummins returned to the Indy 500. The car was called the Cummins Diesel Special (just like the 1931 entry) and wore race #61. Because of its green color, driver Jimmy Jackson referred to the car as the Green Hornet. The racer consisted of a modified Kurtis Kraft chassis powered by a supercharged inline-six engine based on the Cummins JBS-600 truck engine. The car used disc brakes, which was a first at Indy.

cummins 1950 61 indy

Jimmy Jackson sits in the 1950 Cummins Diesel Special #61 at Indy. Although much more refined compared to the earlier racers, #61 was still a heavy brute compared to the rest of the field. Induction air was brought in via the front tunnel. The scoop on the engine cowling provided clearance for the cylinder head and airflow to help cool the engine, but overheating was still a problem. (IMS image)

The Roots-type supercharger was crankshaft-driven and mounted in front of the engine. The special engine had four-valves per cylinder and used an aluminum crankcase, cylinder block, and head. Two injectors delivered fuel into each cylinder, and the engine used an early design of what would become Cummins’ PT (Pressure-Timed) fuel injection. The engine had a 4.125 in (105 mm) bore and a 5.0 in (127 mm) stroke. It displaced 401 cu in (6.6 L) and produced 320 hp (239 kW) at 4,000 rpm. With the ram-air effect of the racer at speed providing additional boost, the engine’s output increased to 340 hp (254 kW) at 4,000 rpm. The engine weighed 860 lb (390 kg).

cummins 1950 61 engine

The uncowled #61 with Jackson in the cockpit. Note the crossflow head with the intake manifold on one side and the exhaust manifold on the other. The earlier Indy racers had the intake and exhaust manifolds on the same side (passenger) of the engine. The car’s independent front suspension was a first at Indy. (Motor Trend image)

Despite some difficulty, the diesel-powered Green Hornet eventually qualified for the Indy 500 at 129.208 mph (207.940 km/h), the slowest qualifying speed of the grid. During the race, the car was retired on lap 52, while in 29th place, because of issues with the engine’s vibration damper and supercharger drive. Repaired, and at the Bonneville Salt Flats on 11 September 1950, Jackson and the Green Hornet set six International diesel speed records: 163.82 mph (263.64 km/h) over 1 km (.6 mi), 165.23 mph (265.91 km/h) over 1 mile (1.6 km), 164.25 mph (264.33 km/h) over 5 km (3.1 mi), 161.92 mph (260.59 km/h) over 5 mi (8.0 km), 147.63 mph (237.59 km/h) over 10 km (6.2 mi), and 148.14 mph (238.41 km/h) over 10 mi (16 km). The Green Hornet was preserved by Cummins and is often displayed in various museums. On rare occasions, the car is run at special events.

cummins 1950 61 display

The 1950 racer was nicknamed Green Hornet on account of its paint. After Indy, #61 and Jackson set six diesel speed records at the Bonneville Salt Flats in Utah. The Green Hornet is pictured as displayed in the Indianapolis Motors Speedway Museum. (AutoDesign image)

In 1951, Cummins decided to make a serious attempt for the 1952 Indy 500. Clessie’s brother Don Cummins headed the team, with Nev Reiners as the chief engineer. Also on the team were Thane Houser (riding mechanic / co-driver for the 1931 Indy effort), Bill Doup, Mike Fellows, Art Eckleman, and Joe Miller. The Cummins Team worked directly with Frank Kurtis of Kurtis Kraft to design a low-slung chassis, and every opportunity was taken to exploit the chassis-engine combination.

cummins 1952 28 indy

Freddie Agabashian and crew with the 1952 Cummins Diesel Special #28 at Indy. The engine installed on its side made the car a low and sleek racer. Compare #28’s height with that of the earlier racers. (IMS image)

Powering the new racer was a further development of the JBS-600-based engine used in the Green Hornet. Since the new engine was turbocharged, it is often referred to as a modified JT-600. The engine consisted of a magnesium crankcase with an aluminum cylinder bank and head. Concepts from Cummins’ NHH-series engines (inline-six laid on its side) were applied to the race engine, and it was installed in the racer’s chassis laid over at an 85-degree angle—nearly on its side. This resulted in a very low engine cowling about 23 in (.58 m) above the ground. The turbocharger was installed in front of the engine on the right side of the car and provided up to 20 psi (1.38 bar) of boost. Like with the Green Hornet, a precursor to the Cummins’ PT fuel injection system was employed. The engine had a 4.125 in (105 mm) bore, a 5.0 in (127 mm) stroke, and a displacement of 401 cu in (6.6 L). The power produced was 380 hp (283 kW) at 4,000 rpm and 430 hp (321 kW) at 4,500 rpm. The engine weighed around 750 lb (340 kg).

The crankshaft, transmission, and driveline were on the left side of the car, putting 150 lb (68 kg) of weight bias on the left side of the car for better handling around the oval track. The cockpit was offset to the right, and the driver’s position was very low, only 4 in (102 mm) off the ground. The racer’s configuration resulted in a very low center of gravity, but the car was quite heavy at around 3,100 lb (1,406 kg). The turbocharger was a first at Indy, as was the offset drivetrain and the car’s independent front suspension. The aerodynamics of the chassis and bodywork were fine-tuned in a wind tunnel, which was reportedly another Indy first.

cummins 1952 28 no body

With the body removed, the compact nature of #28’s chassis is revealed. The turbocharger can just be seen between the front tires. On the left side of the car, note the underside of the crankcase and the driveline extending to the rear. (Cummins image)

The car was completed in late 1951, and testing began in November. Again christened as the Cummins Diesel Special, the car was given race #28 and was driven by Freddie Agabashian. Early testing indicated a very fast car, and Agabashian was careful not to reveal the racer’s full potential during practice sessions at Indy. Agabashian would not run full power for complete laps because there was some concern that the car would be banned had its true, competitive speed been reached. Fifteen minutes before the end of Pole Day qualifying, Agabashian took #28 out and set a one-lap record at 139.104 mph (223.866 km/h) and a
four-lap record at 138.010 mph (222.106 km/h). Agabashian and #28 had qualified in 1st place in a diesel. Agabashian had pushed the racer so hard that he tore the tread off some of the tires. The qualifying record was short-lived, as two cars later qualified with faster speeds, but it was still a major accomplishment for the Cummins Team.

On 30 May 1952, the Indy 500 was run. Agabashian in #28 found the diesel slower to accelerate than the other cars. Another problem cropped up with a buildup of tire rubber debris clogging the turbocharger intake. This issue ultimately caused the turbocharger to fail and forced #28 to retire on lap 71. At that point, Agabashian was in 5th place and had averaged 131.5 mph (211.6 km/h). The race was eventually won at a 130.843 mph (210.571 km/h) average, indicating #28 was keeping pace. Race #28 was credited with a 27th place finish. In short order, rules were changed, and the Cummins Diesel Special was the last diesel-engine racer to compete in the Indy 500.

cummins 1952 28 start

Agabashian and #28 set off from the pits at Indy for a practice run. Unlike racers of today, the smoke at the back of the car is diesel smoke exhaust and not tire smoke. Note the indentation ahead of the front tire. The body was so wide that body indentations were needed for full lock tire clearance. (Cummins image)

Race #28 was returned to the Cummins factory in Columbus, Indiana where it was preserved. A restoration in 1968 revealed that the crankshaft had cracked and would have failed completely had the turbocharger issues not brought a halt to #28’s race. The racer was occasionally run for special events until 1999. In 2016, the Cummins Diesel Special underwent a restoration and was run for the first time since 1999. The racer is often displayed at the Cummins Museum and run on rare occasion at special events.

In each of its four outings at Indy, Cummins took advantage of rules that enabled the displacement of diesels to be up to twice that of spark-ignition engines. While this did offer an advantage for diesels, nearly everything else about the engine was a disadvantage compared to the standard racers. Cummins used the Indy 500 to showcase its diesel engines, test new technology, and make a statement about diesel power.

A sponsorship agreement between Cummins and the Indianapolis Motor Speedway will provide for all five diesel Indy cars to make a parade lap before the 2019 Indy 500. The event, which coincides with Cummins’ 100-year anniversary, will be the first time that the five cars have run together.

cummins 1952 28 goodwood

After its 2016 restoration, #28 participated in the 2017 Goodwood Festival of Speed in Chichester, UK. Bruce Watson, a retired Cummins Engineer, is driving the racer and also led the car’s restoration. (Steve Siler / Car and Driver image)

Sources:
“Cummins at the Brickyard” by Karl Ludvigsen, Car Life (July 1969)
“Diesels at Speed” by Griffith Borgeson, Motor Trend (December 1950)
“The Triumph of the Diesel” Popular Mechanics (July 1934)
http://www.trucktrend.com/cool-trucks/0808dp-cummins-diesel-race-car/
http://www.trucktrend.com/news/1605-cummins-wakes-1952-diesel-special-indy-car-after-years-of-slumber/
http://triplettracehistory.blogspot.com/2016/01/the-1931-cummins-diesel-photo-by-author.html
https://www.allpar.com/corporate/bios/cummins.html
https://stevemckelvie.wordpress.com/2011/06/05/the-cummins-diesel-special-at-the-1952-indianapolis-500/
https://www.thetruthaboutcars.com/2015/10/clessie-cummins-made-diesels-king-road-almost-indy-part-one/
https://www.thetruthaboutcars.com/2015/10/clessie-cummins-made-diesels-king-road-almost-indy-part-two/
https://www.cummins.com/company/history/indianapolis-500
https://www.caranddriver.com/features/when-cummins-diesels-assaulted-indy-feature
https://www.conceptcarz.com/vehicle/z15198/duesenberg-cummins-diesel-indy-racer.aspx
https://www.hemmings.com/blog/index.php/2011/08/02/diesels-at-daytona/
https://cumminsengines.com/No-28-cummins-diesel-special-to-run-with-moto

SGP Sla 16 X-16 front

SGP Sla 16 (Porsche Type 203) X-16 Tank Engine

By William Pearce

In 1943, Simmering-Graz-Pauker (SGP) in Vienna, Austria was tasked by the Heereswaffenamt (HWA, German Army Weapons Agency) to develop a new main tank engine for the Heer (German Army). The requested engine was an air-cooled diesel that would only require minor modifications to be interchangeable with the existing engine installed in various German tanks. The existing engine was the liquid-cooled Maybach HL230 V-12 that produced 690 hp at 3,000 rpm and displaced 1,409 cu in (23.1 L). However, reliability issues with the HL230 limited the engine to 2,500 rpm and 600 hp (447 kW). The demand for an air-cooled diesel was dictated by Adolf Hitler, and SGP was to work closely with Porsche GmbH to develop the new engine.

SGP Sla 16 X-16 front

Front view of the basic Simmering-Graz-Pauker Sla 16 engine without the airbox, turbochargers, or cooling fans. The intake manifolds and some baffling can be seen in the 45-degee Vee formed by the cylinders. Note that the intake ports are on the top of the cylinders.

Led by Ferdinand Porsche, the Porsche design and consulting firm had experience with air-cooled engines and took on the brunt of the preliminary design work for the new engine. Ferdinand Porsche had been discussing tanks and diesel tank engines with Hitler since 1942. Designed by Porsche’s Paul Netzker, the new engine was an X-16 layout consisting of four banks of four cylinders. The cylinder banks were spaced 135 degrees apart on the top and bottom and 45 degrees apart on the sides. The engine was issued Porsche designation Type 203 and SGP designation Sla 16 (which will be used for the remainder of this article).

The Simmering-Graz-Pauker Sla 16 was made of a sheet steel crankcase and used a single crankshaft with four master connecting rods. Three articulating connecting rods attached to each master rod. The cylinders were comprised of a substantially finned aluminum cylinder head screwed onto a finned, steel cylinder barrel. At the front of each cylinder bank was an injection pump that fed fuel to that bank’s cylinders. The fuel injector was positioned in the cylinder head and angled toward the 135-degree side of the cylinder. At the base of each cylinder bank was a camshaft positioned on the 135-degree side. The four camshafts were driven from the rear of the engine and operated the two valves per cylinder via pushrods and rockers. The intake and exhaust ports were located on the 45-degree side of the cylinders, with the intake port on the top of the cylinder.

SGP Sla 16 X-16 section

Transverse cross section of the Sla 16 illustrates the engine’s X configuration and the drive for the cooling fans. Note the master and articulated connecting rods and the four exhaust manifolds in the left side of the drawing.

Induction air was drawn in through a large filter placed above the engine. The air then flowed through twin turbochargers located at the engine’s rear. Two separate intake manifolds branched out from each turbocharger, with one manifold supplying the upper cylinder bank and the other manifold supplying the lower cylinder bank. The exhaust from two cylinders was paired in a single manifold so that each side of the engine had four exhaust manifolds leading to the turbocharger. The turbochargers were made by Brown Boveri and spun at a maximum of 28,000 rpm. The boost from the turbochargers was conservative at 7.3 psi (.5 bar).

To cool the engine, a fan was placed above and outside each of the two upper cylinder banks. The fans extracted warm air out from between the tight, 45-degree cylinder bank sections, which were closely baffled. As a result, cool air was drawn in through the cylinders’ cooling fins and into the 45-degree Vee. Each fan was driven via a beveled gear shaft that extended from the cooling fan to the rear of the engine. Here, an enclosed drive shaft with two universal joints and beveled gears took power from the crankshaft at the extreme rear of the engine and powered the shafts that led to the fans. The cooling fans were developed by FKFS (Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart or Research Institute of Automotive Engineering and Vehicle Engines Stuttgart). The fans were 20.5 in (520 mm) in diameter and operated at 2.05 times crankshaft speed. Two oil coolers flanked each engine cooling fan.

SGP Sla 16 X-16 rear

Without all of the engine’s accessories, the drive for the cooling fans can be seen protruding from the back of the Sla 16 engine. The push rod tubes and fuel injectors are visible on the far cylinder bank. The four passageways in the rear baffle are for the exhaust manifolds.

Helical gears increased the speed of the Sla 16’s output shaft to 1.5 times crankshaft speed. The speed increase was needed because of the operating speed difference between the Sla 16 and the Maybach HL230. In order to be a direct replacement, the 2,000 rpm Sla 16 needed to have an output speed multiplier to match the 3,000 rpm HL230. Since the Sla 16’s crankshaft was in the middle of the engine’s X configuration, the step-up gears also lowered the output shaft to align with the existing transmission used with the V-12 HL230.

The Sla 16 had a 14.5 to 1 compression ratio, a 5.3 in (135 mm) bore, and a 6.3 in (160 mm) stroke. The engine’s total displacement was 2,236 cu in (36.6 L). The Sla 16 was forecasted to produce 750 hp (559 kW) at 2,000 rpm. With the cooling fans, the complete engine was approximately 5.5 ft (1.68 m) long, 8.2 ft (2.50 m) wide, and 3.8 ft (1.15 m) tall. The Sla 16 weighed 4,960 lb (2,250 kg).

By late 1943, a single-cylinder 140 cu in (2.3 L) test engine had been built and designated Type 192. The Type 192 engine passed a 48-hour test run on 6 November 1943. The single cylinder engine produced 47 hp (35 kW) at 2,100 rpm, which scaled to an output of 752 hp (561 kW) for the complete 16-cylinder engine. The listed output did not take into consideration the power needed to drive the cooling fans. With favorable results from the Type 192 tests, work moved forward on the full-size Sla 16 X-16 engine.

SGP Sla 16 X-16 fans rear

Rear view of the complete Sla 16. The airbox on the top of the engine fed air into the turbochargers via a bifurcated manifold. Note the oil coolers and cooling fans. The enclosed drive shafts for the cooling fans can been seen below the turbocharger exhaust outlets.

The first Sla 16 engine was tested in late 1944 and produced 770 hp (574 kW) at 2,200 rpm without the cooling fans. It took around 95 hp (71 kW) to drive the cooling fans, which reduced the engine’s output to 685 hp (511 kW). On 10 January 1945, two Sla 16 test engines had completed a combined 300 hours of test operation. Porsche’s involvement with the engine had essentially stopped by this time. Plans were made for Sla 16 production to start in June 1945 at the Steyr-Daimler-Puch factory in Austria. Steyr-Daimler-Puch was producing Daimler-Benz DB 603 engines (although the factory built DB 605s from October 1942 to October 1943), and production of the DB 603 would give way for the Sla 16. Some changes were incorporated into the Sla 16 production engines, such as the use of two fuel injection pumps rather than the four pumps used on the prototype engines. It is possible that the production engines carried the Porsche Type 220 designation. However, the Sla 16 engine never entered production because of the German surrender in May 1945.

A Sla 16 engine was reportedly installed in the chassis of the experimental Panzerjäger Tiger Ausf. B (Tank Hunter Tiger Variant B or Jagdtiger, Hunting Tiger) and underwent some feasibility tests. Initially, the lower cylinder banks ran hot, but modifications to the cooling fans and air baffles resolved the issue. In addition, a Panzerkampfwagen Tiger Ausf. B (Armored Fighting Vehicle Tiger Variant B), or Tiger II, was modified to accept a Sla 16 engine and waited for the engine’s installation. However, the installation was never completed. The engine was also proposed for the VK 45.02 P2 (Porsche Type 181C), which was never built. The majority of Sla 16 parts, tooling, and equipment were captured by the Soviet Union at the end of World War II.

SGP Sla 16 X-16 stand

The left image (engine inverted) shows the camshaft drives at the rear of the engine. In the center image (engine upright), the engine’s output can be seen below the crankshaft. The right image (engine almost inverted) displays the cylinder’s valves. The exhaust ports on the side of the cylinders are easily seen, while the intake ports on the top of the cylinders have been covered.

In late 1943, FKFS contemplated using the 140 cu in (2.3 L) cylinder from the Sla 16 as the starting point for a new tank engine to power the proposed Panzerkampfwagen Panther II. The FKFS engine consisted of two V-12 engines mounted 90-degrees apart on a common crankcase. The 24-cylinder engine would have displaced 3,354 cu in (55.0 L) and produced 1,100 hp (820 kW). Four engine-driven, FKFS cooling fans would have been installed, with two above each V-12 engine section. The FKFS 24-cylinder engine project did not progress beyond the drawing board, and the Panther II was never built.

A larger version of the X-16 engine was investigated under the Porsche Type 212 designation. This engine had a 5.9 in (150 mm) bore and a 6.7 in (170 mm) stroke. Total displacement of the Type 212 was 2,933 cu in (48 L), and the engine was forecasted to produce 1,500 hp (1,119 kW) at 2,500 rpm. A 183 cu in (3.0 L), single-cylinder test engine was evaluated as the Type 213, but it does not appear that the tests were completed or that a complete Type 212 engine was built. The Type 212 was proposed to power the Panzerkampfwagen VIII Maus (Porsche Type 205), but the engine was rejected by Albert Speer, the Minister of Armaments.

SGP Sla 16 X-16 test

The Sla 16 engine under test in late 1944 without cooling fans or turbochargers. However, the test equipment most likely provided forced induction.

Notes: Sources are split on the Porsche Type designation for the 750 hp (559 kW) Sla 16. Many refer to the engine as the Type 203, and just as many use Type 212. In addition, Type 180, 181, 192, and 220 are also used. Type 180 was a tank design (VK 45.02 P) that originally used Porsche’s Type 101 V-10 engine. Type 181 was the same tank reengined with the Sla 16 after the V-10 encountered problems. As mentioned in the article, Type 192 was a single-cylinder test engine for the Sla 16. Since Type 213 was a single-cylinder test engine for the larger X-16, it makes sense for the larger X-16 to be Type 212. This leaves Type 203 as the logical choice for the Sla 16. As stated in the article, Type 220 may have been the production version of the Sla 16.

Furthermore, a number of sources list the larger, 1,500 hp (1,119 kW) engine as an X-18. However, there can be no X-18 engine; to add up to a total of 18 cylinders, two banks would need to have five cylinders each, and two banks would need to have four cylinders each. Such an armament would be ill-advised. Most likely, “X-16” was either mistyped or misread as “X-18” on some scarce document captured at the end of World War II, and the misnomer stuck. However.

Lastly, the Porsche Type 181B (VK 45.02 P2) tank design was to be powered by two 16-cylinder engines. The 16-cylinder engine was an air-cooled diesel that produced 370 hp (276 kW) at 2,000 rpm. Reportedly, the design of this engine was a collaboration with Deutz. Some sources indicate the engine was a V-16, while others state it was an X-16. It is not clear whether the smaller 16-cylinder engine had anything in common with the Sla 16 or what its Type number was. The small 16-cylinder engine had a 4.3 in (110 mm) bore, a 5.1 in (130 mm) stroke, and a total displacement of 1,206 cu in (19.8 L). The small 16-cylinder engine was never built.

SGP Sla 16 X-16 general arrangement rear

General arrangement drawing of the Sla 16 engine.

Sources:
Professor Porsche’s Wars by Karl Ludvigsen (2014)
Der Panzer-Kampfwagen Tiger und seine Abarten by Walter J. Spielberger (1998)
AFV Weapons Profile: Elefant and Maus (+ E-100) by Walter J. Spielberger and John Milsom (October 1973)
Wunibald I. E. Kamm – Wegbereiter der modernen Kraftfahrtechnik by Jurgen Potthoff and Ingobert C. Schmid (2012)
Daimler-Benz in the Third Reich by Neil Gregor (1998)
https://vk.com/page-39215368_53036748
http://ftr.wot-news.com/2014/11/25/maus-engine-by-captiannemo/
http://www.alanhamby.com/maybach.shtml

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)

Sources:
“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)
http://www.deutsches-museum.de/en/collections/machines/power-engines/combustion-engines/diesel-engines/large-diesel-engines/marine-diesel-engine-1938/
http://www.deutsches-museum.de/en/collections/machines/power-engines/combustion-engines/diesel-engines/large-diesel-engines/marine-engine-l11z-1930-1939/
http://www.hermann-historica-archiv.de/auktion/hhm61.pl?f=NR_LOT&c=6902&t=temartic_M_GB&db=kat61_m.txt

mercedes-benz-mb-518-v-20-rear

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.

mercedes-benz-mb-501-v-20-rear

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.

mercedes-benz-mb-501-v-20-crackington

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 350z-uk.com)

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.

mercedes-benz-mb-502-v-16

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.

mercedes-benz-mb-507-v-12

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.

mercedes-benz-mb-511-v-20-aeronauticum

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.

mercedes-benz-mb-518-v-20-drawings

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.

mercedes-benz-mb-518-v-20-rear

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.

mercedes-benz-mb-518-v-20-assembly

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.

Sources:
http://alternathistory.com/dvigateli-nemetskikh-torpednykh-katerov-razrabatyvavshiesya-i-seriino-stroivshiesya-v-1920-1940-gody
https://de.wikipedia.org/wiki/Mercedes-Benz_MB_518
http://ftr.wot-news.com/2014/11/25/maus-engine-by-captiannemo/
https://ww2aircraft.net/forum/threads/opportunity-lost-db-16-cyl.21836/
http://www.german-navy.de/kriegsmarine/ships/fastattack/schnellboot1937/tech.html
http://www.german-navy.de/kriegsmarine/ships/fastattack/schnellboot1939/tech.html
http://www.german-navy.de/kriegsmarine/ships/fastattack/schnellboot1940/tech.html
http://www.wrecksite.eu/wreck.aspx?163703
http://www.shipspotting.com/gallery/photo.php?lid=1885985
http://s-boot.net/sboats-vm-forelle.html

daimler-benz-db602-zeppelin-museum

Daimler-Benz DB 602 (LOF-6) V-16 Diesel Airship Engine

By William Pearce

Around 1930, Daimler-Benz* developed the F-2 engine, initially intended for aviation use. The F-2 was a 60 degree, supercharged, V-12 engine with individual cylinders and overhead camshafts. The engine had a 6.50 in (165 mm) bore and an 8.27 in (210 mm) stroke. The F-2’s total displacement was 3,288 cu in (53.88 L), and it had a compression ratio of 6.0 to 1. The engine produced 800 hp (597 kW) at 1,500 rpm and 1,000 hp (746 kW) at 1,700 rpm. The engine was available with either direct drive or a .51 gear reduction, and weighed around 1,725 lb (782 kg). It is unlikely that the Daimler-Benz F-2 powered any aircraft, but it was used in a few speed boats.

The Daimler-Benz OF-2 diesel engine was very similar to the spark ignition F-2. Note the dual overhead camshafts in the Elektron housing above the individual cylinders. This was one of the OF-2’s features that was not incorporated into the LOF-6.

The Daimler-Benz OF-2 diesel engine was very similar to the spark ignition F-2. Note the dual overhead camshafts in the Elektron housing above the individual cylinders. This was one of the OF-2’s features that was not incorporated into the LOF-6.

In the early 1930s, Daimler-Benz used the F-2 to develop a diesel engine for airships. This diesel engine was designated OF-2 (O standing for Ölmotor, or oil engine), and it maintained the same basic V-12 configuration as the F-2. The individual cylinders were mounted on an Elektron (magnesium alloy) crankcase. Each cylinder had four valves that were actuated by dual overhead camshafts. The OF-2 had the same bore, stroke, and displacement as the F-2, but the OF-2’s compression ratio was increased to 15 to 1.

Fuel was injected into the cylinders at 1,330 psi (91.7 bar) via two, six-plunger injection pumps built by Bosch. The fuel was injected into a pre-combustion chamber located between the four valves in the cylinder head. This design had been used in automotive diesels built by Mercedes-Benz. Sources disagree on the gear reduction ratio, and it is possible that more than one ratio was offered. Listed ratios include .83, .67, and .58.

The Daimler-Benz OF-2 engine had a normal output of 700 hp (522 kW) at 1,675 rpm, a maximum output of 750 hp (559 kW) at 1,720 rpm, and it was capable of 800 hp (597 kW) at 1,790 rpm for very short periods of time. Fuel consumption at normal power was .392 lb/hp/hr (238 g/kW/hr). The engine was 74.0 in (1.88 m) long, 38.6 in (.98 m) wide, and 42.5 in (1.08 m) tall. The OF-2 weighed 2,061 lb (935 kg).

daimler-benz-lof-6-db602-diesel-rear

This view of a display-quality DB 602 engine shows the four Bosch fuel injection pumps at the rear of the engine. The individual valve covers for each cylinder can also be seen.

The OF-2 passed its type test in 1932. At the time, Germany was developing its latest line of airships, the LZ 129 Hindenburg and LZ 130 Graf Zeppelin II. These airships were larger than any previously built, and four OF-2 engines would not be able to provide sufficient power for either airship. As a result, Daimler-Benz began developing a new engine to power the airships in 1933. Daimler-Benz designated the new diesel engine LOF-6, but it was soon given the RLM (Reichsluftfahrtministerium or Germany Air Ministry) designation DB 602.

Designed by Arthur Berger, the Daimler-Benz DB 602 was built upon lessons learned from the OF-2, but it was a completely new engine. The simplest way to build a more powerful engine based on the OF-2 design was by adding two additional cylinders to each cylinder bank, which made the DB 602 a V-16 engine. The two banks of eight cylinders were positioned at 50 degrees. The 50 degree angle was selected over the 45 degree angle typically used for a V-16 engine. This gave the DB 602 an uneven firing order which helped avoid periodic vibrations.

The individual steel cylinders were mounted to the 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.

Daimler-Benz LOF-6 DB602 V-16 diesel engine

Originally called the LOF-6, the Daimler-Benz DB 602 was a large 16-cylinder diesel engine built to power the largest German airships. Note the three-pointed star emblems on the front valve covers. Propeller gear reduction was achieved through bevel planetary gears.

A single camshaft was located in the Vee of the engine. 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. Separate pushrods for the intake and exhaust valves rode on the camshaft and acted on duplex rocker arms that actuated the valves. Each cylinder had two intake and two exhaust valves. Four Bosch fuel injection pumps were located at the rear of the engine and were geared to the camshaft. Each injection pump provided fuel at 1,600 psi (110.3 bar) to four cylinders. Fuel was injected into the center of the pre-combustion chamber, which was situated between the four valves. For slow idle (as low as 300 rpm), fuel was cut from one cylinder bank.

The DB 602 engine was not supercharged and had a .50 propeller gear reduction that used bevel planetary gears. 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. Two water pumps were driven by a cross shaft at the rear of the engine. Each pump provided cooling water to one cylinder bank. The engine’s compression ratio was 16.0 to 1, and it was started with compressed air.

The DB 602 had a 6.89 in (175 mm) bore and a 9.06 in (230 mm) stroke, both larger than those of the OF-2. The engine displaced 5,401 cu in (88.51 L). Its maximum continuous output was 900 hp (671 kW) at 1,480 rpm, and it could produce 1,320 hp (984 kW) at 1,650 rpm for 5 minutes. The DB 602 was 105.9 in (2.69 m) long, 40.0 in (1.02 m) wide, and 53.0 in (1.35 m) tall. The engine weighed 4,409 lb (2,000 kg). Fuel consumption at cruising power was 0.37 lb/hp/hr (225 g/kW/hr).

lz-129-hindenburg

The ill-fated LZ 129 Hindenburg on a flight in 1936. The airship used four DB 602 engines housed in separate cars in a pusher configuration. Note the Olympic rings painted on the airship to celebrate the summer games that were held in Berlin.

Development of the DB 602 progressed well, and it completed two non-stop 150-hour endurance test runs. The runs proved the engine could operate for long periods at 900 hp (671 kW). Four engines were installed in both the LZ 129 Hindenburg and the LZ 130 Graf Zeppelin II. Each engine powered a two-stage compressor. Each compressor filled a 3,051 cu in (50 L) air tank to 850 psi (59 bar) that was used to start the engine and to manipulate the camshaft for engine reversing.

Plans for a water vapor recovery system that used the engines’ exhaust were never implemented, because the airships used hydrogen instead of the more expensive helium. The recovery system would have condensed vapor into water, and the collected water would have been used as ballast to help maintain the airship’s weight and enable the retention of helium. Without the system in place, expensive helium would have been vented to compensate for the airship steadily getting lighter as diesel fuel was consumed. With the United States unwilling to provide helium because of Germany’s aggression, the airships used inexpensive and volatile hydrogen, as it was readily available. The Hindenburg was launched on 4 March 1936, and the Graf Zeppelin II was launched on 14 September 1938.

Engines for the Hindenburg were mounted in a pusher configuration. In April 1936, the Hindenburg’s DB 602 engines experienced some mechanical issues on its first commercial passenger flight, which was to Rio de Janeiro, Brazil. The engines were rebuilt following the airship’s return to Germany, and no further issues were encountered. The Hindenburg tragically and famously burst into flames on 6 May 1937 while landing at Lakehurst, New Jersey.

daimler-benz-db602-musee-de-l-air-et-de-l-espace

Front view of the DB 602 engine in the Musée de l’Air et de l’Espace, in Le Bourget, France. Above the engine are the cooling water outlet pipes. In the Vee of the engine is the induction manifold, and the pushrod tubes for the front cylinders can be seen. Note the finning on the bottom half of the crankcase. (Stephen Shakland image via flickr.com)

The Graf Zeppelin II was still being built when the Hindenburg disaster occurred. Design changes were made to the Graf Zeppelin II that included mounting the DB 602 engines in a tractor configuration. The inability of Germany to obtain helium, the start of World War II, and the end of the airship era meant the Graf Zeppelin II would not be used for commercial travel. The airship was broken up in April 1940.

The DB 602 engine proved to be an outstanding and reliable power plant. However, its capabilities will forever be overshadowed by the Hindenburg disaster. Two DB 602 engines still exist and are on display; one is in the Zeppelin Museum in Friedrichshafen, Germany, and the other is in the Musée de l’Air et de l’Espace, in Le Bourget, France. Although the DB 602 was not used on a wide scale, it did serve as the basis for the Mercedes-Benz 500 series marine engines that powered a variety of fast attack boats (Schnellboot) during World War II.

*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 automobiles. However, both names were occasionally applied to aircraft engines in the 1930s.

daimler-benz-db602-zeppelin-museum

Rear view of the DB 602 engine on display in the Zeppelin Museum in Friedrichshafen, Germany. A water pump on each side of the engine provided cooling water to a bank of cylinders. (Stahlkocher image via Wikimedia Commons)

Sources:
Aircraft Diesels by Paul H Wilkinson (1940)
Aerosphere 1939 by Glenn D. Angle (1940)
Diesel Engines by B. J. von Bongart (1938)
High Speed Diesel Engines by Arthur W. Judge (1941)
Diesel Aviation Engines by Paul H Wilkinson (1942)
“The Hindenburg’s New Diesels” Flight (26 March 1936)
“The L.Z.129’s Power Units” Flight (2 January 1936)
https://en.wikipedia.org/wiki/LZ_129_Hindenburg
https://en.wikipedia.org/wiki/LZ_130_Graf_Zeppelin_II