January | 2018 | Old Machine Press

By William Pearce

Before devoting his life to engine development, Nicolaus Otto worked selling merchandise to grocery stores around Cologne, Germany, but he always had an interest in science and technology. Otto became entirely focused on internal combustion engines around 1860, after reading about Étienne Lenoir’s engine. He was so fascinated that he had an example built for experimentation in 1861.

Drawing of the Otto-Langen engine circa 1866. Note the piston (K) and its rack (X) in the cylinder (A). The drawing also shows an early version of the over-running clutch (S).

Otto tried a wide-range of modifications to the Lenoir atmospheric engine in search of better performance. One interesting finding was that when the engine’s cylinder and piston were used to compress the incoming air and fuel charge, the resulting power stroke had enough energy to rotate the crankshaft through several revolutions. While Otto had discovered a number of improvements for the Lenoir atmospheric engine, creating a compression engine was a bit beyond the contemporary technology. Otto had already spent his saving and what he had borrowed from friends. To continue his research and develop an atmospheric engine, he needed money.

For some time, Eugen Langen ran his family’s sugar refining business in Cologne, Germany, but, like Nicolaus Otto, his true passion was for science and technology. Langen had become a fairly wealthy man from the family business and from a few of his own ventures. In 1863, his business was running smoothly, and he was looking for a new enterprise. Langen had read of the Lenoir engine and contemplated how such a device could benefit industry.

A reproduction of the over-running clutch built by Wayne Grenning of Grenning Models. Counterclockwise movement of the gear brings the shoes to their stops and allows the gear to rotate free from the inner hub. When the gear rotates clockwise, the shoes slide on their rollers until they are wedged between the gear and the inner hub, locking the two together. The clutch was originally designed by Franz Reuleaux, and later clutches used on the Otto-Langen had three shoes. (Wayne Grenning image)

Exactly how Otto and Langen met is not known. Perhaps Otto sought out Langen as a financial backer, or perhaps they met through a third party. Regardless, Langen witnessed Otto’s unrefined atmospheric engine running on 9 February 1864. Langen saw potential in the engine and its inventor. Langen and Otto formed N.A. Otto & Cie on 31 March 1864 to develop and manufacture internal combustion engines.

Other reproduction parts built by Wayne Grenning. The piston with its rack attached are shown outside of the cylinder housing column. The piston and rack weigh around 80 lb (36 kg). The studs seen at the base of the column are where the slide valve mounts. (Wayne Grenning image)

Three years of experimentation and refinement occurred before N.A. Otto & Cie had a marketable engine that was superior to the competition. The Otto-Langen .5 hp (.37 kW), single-cylinder, atmospheric engine made its public debut at the 1867 International Exposition in Paris, France (Exposition universelle de 1867). Nothing about the engine appeared remarkable, but interest piqued when a demonstration showed that the engine consumed half the gas of other engines of the same power. The engine’s remarkably efficient performance won it the grand prize.

The Otto-Langen engine consisted of a vertical column that formed a single cylinder. A free piston was installed in the cylinder, with the piston head facing down. Attached to the upper part of the piston was a rack gear that extended out vertically above the engine. The rack engaged the one-way, over-running (sprag) clutch that was mounted on the engine’s main drive shaft. The clutch was the first of its type and was designed by Franz Reuleaux. The flywheel was mounted on one side of the main drive shaft, and the belt drive pulley was mounted on the other side. On the flywheel side of the main drive shaft was the main drive gear. The main gear engaged an accessory gear, which drove the accessory shaft. Typically, the accessory gear was larger and had more teeth than the main gear. The difference resulted in an accessory gear speed slower than that of the main gear, which helped reduce impact forces on the accessory gear drive.

Top view of the Otto-Langen engine at the Rough and Tumble Engineers Historical Association in Kinzers, Pennsylvania. It is the oldest internal combustion engine in the Americas. Installed on the main drive shaft (top) from left to right are the flywheel, main drive gear, over-running clutch, and belt drive. Installed on the accessory shaft (bottom) from left to right are the accessory drive gear, secondary eccentric, main eccentric, and ratcheting gear. (Rough and Tumble Engineers image)

The accessory gear was mounted on and drove the accessory shaft. Also on the accessory shaft were two eccentrics and a ratcheting gear. The ratcheting gear was attached directly to and turned with the accessory shaft. The two eccentrics operated independently of the accessory shaft and were mostly stationary. A pawl would engage the ratcheting gear and drive the main eccentric. This eccentric lifted the piston and rack assembly and also drove the second eccentric, which operated the hand-scraped slide valve at the base of the engine via a control rod. When the eccentrics raised the piston and slide valve, the air and fuel mixture was draw into the cylinder. The slide valve then aligned to a port with an internal flame that ignited the gaseous mixture in the cylinder.

On the power stroke, the free piston had unrestricted upward movement in the cylinder and took advantage of the complete expansion of gases during the combustion process. As the piston moved up, the rack attached to the upper side of the piston moved freely on the clutch. As atmospheric pressure and gravity pulled the rack and piston back down, the rack engaged the over-running clutch that drove the main drive shaft. A flyball governor was driven by the accessory shaft and controlled an exhaust valve. With a closed exhaust valve, the piston could not fully descend. As the speed of the accessory shaft decreased below the desired rpm, the governor opened the exhaust valve, which allowed the piston to descend. This movement of the piston and its attached rack assembly tripped an arm that engaged the pawl to the ratcheting gear, driving the eccentrics and subsequently firing the engine.

Grenning’s full-size reproduction of a .5 hp (.37 kW) Otto-Langen engine under power. The accessory shaft is in the foreground, and the pawl in the center of the image is about to engage the ratcheting gear. The ratcheting gear will then drive the eccentrics. (Wayne Grenning image)

The internal flame that ignited the gaseous mixture in the cylinder was extinguished on each power stroke. The internal flame was relit by an external flame via a port on the slide valve that aligned as the valve moved. The Otto-Langen engine was run on illuminating gas, which was typically distributed at around .07 psi (.005 bar). When firing, the engine needed more gas than the line could supply. An accumulator bag was used, which held a surplus of gas. The Otto-Langen engine would draw from the bag when firing, and the gas would be replenished between firings from the low-pressure supply line.

For cooling, an integral water jacket surrounded the cylinder. The Otto-Langen engine employed thermosyphon circulation. As the water was heated, it expanded out of a port in the upper part of the water jacket and flowed to an external reservoir. At the same time, cool water was drawn from the external reservoir and to the engine. The engine relied on manual, external lubrication, which could be (and was) supplied while the engine was in operation. The Otto Langen’s design and features allowed for a quick start and continuous running.

The base of Grenning’s Otto-Langen reproduction shows the safety slide valve (with brass connector) and the main slide valve behind it. The main slide valve was operated by the secondary eccentric. The rod with the coiled spring is the governor-controlled exhaust valve. Later engines did not have the safety slide valve, and the governor controlled the pawl’s engagement. (Wayne Grenning image)

Because of the free piston, cylinder firing was not directly linked to the rpm of the drive shaft. With a light load, the cylinder could fire once for every 25 revolutions of the main drive shaft. Under heavy loads, the cylinder could fire once for every two revolutions. The engine was typically operated with a main drive shaft speed of 90 rpm. However, the speed could be increased to 120 rpm or decreased to around 30 rpm. The high and low speeds were dictated by the mechanical limitations of the eccentrics and slide valve movement.

Grenning’s completed Otto-Langen reproduction is a fantastic display of a modern-day master-craftsman’s appreciation of old-world engineering. After spending years researching the Otto-Langen, it took Grenning 14 months to build his reproduction engine. (Wayne Grenning image)

The cylinder housing on the early Otto-Langen engines was fluted and resembled a Grecian column, but this expensive feature was not included on later engines. In addition, early engines did not have a governor and had a second slide valve. The secondary slide valve acted as a safety feature to cut the gas flow to the cylinder. Extensive engine operation showed that the safety slide valve was not needed, and it was eliminated to cut down on manufacturing costs.

The success at the International Exposition in Paris brought in a flood of orders that N.A. Otto & Cie could not fulfill due to a lack of existing capital. Ludwig August Roosen-Runge, a businessman from Hamburg, lent financial support, and the company was renamed Langen, Otto & Roosen in 1869. That same year, the factory was relocated to Deutz, Germany. More capital was sought and found, and a new company, Gasmotoren-Fabrik Deutz AG (Deutz), was established in January 1872. That same year, Gottlieb Daimler and his protégé, Wilhelm Maybach, joined Deutz.

Maybach was tasked with redesigning the Otto-Langen engine to simplify its construction and lower its production cost. The updated design eliminated the accessory shaft and ran everything from the main drive shaft. The governor controlled cylinder firing with the pawl and not with the exhaust valve. The updated engine was available at the end of 1873.

View of the accessory shaft on Grenning’s engine. The left side of the shaft drives the flyball governor. In the background are the black gas accumulator bag and copper water reservoir. (Wayne Grenning image)

The .25 hp (.19 kW) version was the smallest Otto-Langen, and it stood 7 ft (2.1 m) tall and weighed 900 lb (408 kg). To make more power, the engine was basically scaled-up to a larger size. However, the design of the Otto-Langen engine limited just how large the engine could be while still being practical. With its vertical cylinder and long rack attached to the piston, the Otto-Langen was a tall and heavy engine. There were practical limits on the engine’s height and weight. The vertical piston had a tendency to send significant vibrations through the ground with every stroke. This shook foundations, could damage nearby equipment, and made most above ground level installations unfeasible. The largest Otto-Langen engine was the 3 hp (2.24 kW) model. It was 12.7 ft (3.9 m) tall and weighed 4,450 lb (2,018 kg).

The .5 hp (.37 kW) Otto-Langen engine created its power at 110 rpm at the flywheel with 40 power strokes per minute. The cylinder had a 5.9 in (150 mm) bore and a 38.7 in (985 mm) maximum stroke. Maximum displacement was 1,062 cu in (17.4 L). The engine was 8.8 ft (2.65 m) tall and weighed 1,600 lb (725 kg). The piston and rack assembly of the .5 hp (.37 kW) engine weighed around 80 lb (36 kg).

The 2 hp (1.49 kW) engine operated at 90 rpm at the flywheel with 30 power strokes per minute. The cylinder had a 12.5 in (318 mm) bore and a 40.5 in (1,030 mm) maximum stroke. Maximum displacement was 4,992 cu in (81.8 L). The 2 hp (1.49 kW) engine was 10.7 ft (3.25 m) tall and weighed 4,000 lb (1,815 kg). The piston and rack alone weighed 116 lb (52.6 kg).

The first Otto-Langen engine is on display in the Deutz Technikum Engine Museum in Cologne, Germany. This engine has no governor, and the safety slide valve was removed sometime after the engine was built. The gas accumulator bag is on the right. (Wayne Grenning image)

By 1875, there was competition in the form of George Brayton’s Ready Motor and other engines. Otto felt that the atmospheric engine had reached its zenith, yet Daimler was still interested in pursuing the type. Tension existed between Otto and Daimler, and the men did not work well together. In 1876, Otto first ran his four-stroke, internal combustion engine using the combustion cycle that would revolutionize the world. Development of the Otto-Langen engine stopped around 1877, and production of the engine at Deutz stopped around 1878. Daimler and Maybach left Deutz in 1880 and formed a new company to develop engines and automobiles. The Deutz company is still in business designing and manufacturing internal combustion engines.

Between 1864 and 1882, Deutz and its predecessors built 2,649 Otto-Langen engines. Around 2,000 more engines were built by subsidiaries or under license in Austria (Langen & Wolf), Belgium (E. Schenck & Co.), Britain (Crossley Brothers), and France (Sarazin / Panhard). For a brief time, the Otto-Langen atmospheric engine led the industry, and it was the world’s first commercially successful internal combustion engine. Perhaps the Otto-Langen’s greatest achievement was to serve as a stepping stone to the four-stroke, Otto-cycle engine. Around 23 Otto-Langen engines survive, including the very first engine built, which won the grand prize in 1867. The over 150-year-old first engine is on display at the Deutz Technikum Engine Museum in Cologne, Germany, and it is run on special occasions.

Wayne Grenning of Grenning Models has built a number of reproduction Otto-Langen engines. He gives a detailed explanation of the engine’s operation in the video below.

Sources:
– Internal Fire by C. Lyle Cummins, Jr. (1989)
– Flame Ignition by Wayne S. Grenning (2014)
– Startup & Instructional Explanation of 1867 Otto Langen Engine Operation by Wayne Grenning (5 March 2017)
– https://sites.google.com/site/wgrenning/home
– “Improvements in Air-Engines,” US patent 67,659 by Eugen Langen and Nicol. Auguste Otto (granted 13 August 1867)
– “Improvements in Gas-Motor Engines,” US patent 153,245 by Gottlieb Daimler (granted 21 July 1874)
– https://collection.maas.museum/object/207174
– http://www.roughandtumble.org/ottolangen

By William Pearce

At the close of World War II, the United States Navy lacked the ability to carry out a nuclear strike. The nuclear bombs of the time were large and heavy, and no aircraft operating from an aircraft carrier could accommodate the bomb’s size and weight. The Navy did not want nuclear strikes to be the sole responsibility of the Army Air Force (AAF). In addition, the Navy felt that launching an attack with a medium-sized aircraft from a carrier that was hundreds of miles from the target offered advantages compared to large AAF bombers traveling thousands of miles to the target. On 13 August 1945, the Navy sponsored a design competition for a carrier-based, nuclear-strike aircraft. The competition was won by the North American AJ Savage.

Typical example of a production North American AJ-1 Savage, with its R-2800 engines on the wings and J33 jet in the rear fuselage. The intake for the jet was just before the vertical stabilizer and was closed when the jet was not in use.

First flown on 3 July 1948, the AJ Savage was a unique aircraft that spanned the gap between the piston-engine and jet-engine eras. The Savage was powered by two Pratt & Whitney R-2800 engines and a single Allison J33 turbojet that was mounted in the rear fuselage. The jet engine was used for takeoff and to make a final, high-speed dash to the target. In December 1947, before the AJ prototype had even flown, North American Aviation (NAA) proposed an improved version of the Savage that benefited from the continued advancement of turboprop engines. Designated NA-158 by the manufacturer, a mockup was inspected in September 1948, and the Navy ordered two examples and a static test airframe in October 1948—only three months after the AJ Savage’s first flight. The new aircraft was designated XA2J Super Savage, and the two prototypes ordered were given Navy Bureau of Aeronautics (BuAer) serial numbers 124439 and 124440.

Originally, the North American XA2J Super Savage was to be very different from the AJ Savage, but the jet engine in the rear fuselage would be retained. As the project moved through 1949, emphasis was placed on improving the XA2J’s deck performance over that of its predecessor. As a result, the XA2J became an entirely new aircraft but still resembled the AJ Savage. A mockup of the updated XA2J design, the NA-163, was inspected by the Navy in September 1949, and approval was given for NAA to begin construction.

Concept drawing of the XA2J Super Savage from April 1949. Note how the aircraft bears little resemblance to the AJ Savage. The intake for the jet engine can be seen just before the vertical stabilizer. The pilot sat alone under the canopy, and the co-pilot/bombardier and gunner sat in the fuselage, behind and below the pilot.

The XA2J had the same basic configuration as its predecessor but was a larger aircraft overall. The Super Savage was of all metal construction and utilized tricycle landing gear. The high-mounted, straight wing was equipped with a drooping leading edge and large trailing edge flaps. To be brought below deck on a carrier, the aircraft’s wings and tail folded hydraulically. The pressurized cockpit accommodated the three-man crew, which consisted of a pilot, a co-pilot/bombardier, and a gunner. The pilot and co-pilot/bombardier sat side-by-side, and the rear-facing gunner sat behind them. Cockpit entry was via a side door, and an escape chute provided emergency egress out of the bottom of the aircraft. The co-pilot/bombardier was responsible for the up to 10,500 lb (4,763 kg) of bombs stored in a large, internal bomb bay. The gunner managed the radar-equipped tail turret with its two 20 mm cannons and 1,000 rpg. The defensive armament was never fitted to the prototype.

The XA2J did away with the mixed propeller and jet propulsion of the earlier AJ Savage; instead, it relied on two wing-mounted Allison T40 turboprop engines. The T40 engine was made up of two Allison T38 engines positioned side-by-side and coupled to a common gear reduction for contra-rotating propellers. Either T38 power section could be decoupled from the gear reduction, and the remaining engine could drive the complete contra-rotating propeller unit. The engine produced 5,332 hp (3,976 kW) and 1,225 lbf (4.7 kN) of thrust, for a combined output equivalent to 5,850 hp (4,362 kW). The Aeroproducts propellers used on the XA2J had six-blades and were 15 ft (4.57 m) in diameter.

The XA2J Super Savage as built only had turboprop engines. In this image, the wide propellers installed on the aircraft have different cuff styles. Markings on the propeller installed on the right engine would seem to indicate that the propeller (rounded cuff) is being tested. Note the cockpit entry side door and open bomb bay doors.

The Super Savage had a 71 ft 6 in (21.8 m) wingspan and was 70 ft 3 in (21.4 m) long and 24 ft 2 in (7.4 m) tall. Folded, the wingspan dropped to 46 ft (14 m), and height decreased to 16 ft (4.9 m). The aircraft had an empty weight of 35,354 lb (16,036 kg) and a maximum takeoff weight of 61,170 lb (27,746 kg). Two fuel tanks at each wing root and two fuselage fuel tanks gave the aircraft a total fuel capacity of 2,620 gallons (9,918 L). The XA2J’s estimated top speed was 451 mph (726 km/h) at 24,000 ft (7,315 m), and its cruise speed was 400 mph (644 km/h). The aircraft had a ceiling of 37,500 ft (11,430 m) and a combat range of 2,180 miles (3,508 km) with an 8,000 lb (3,629 kg) bomb load.

NAA believed that the Super Savage airframe could be more than just a carrier-based medium bomber. The company developed designs in which various equipment packages could be installed in the aircraft’s bomb bay. The XA2J could be changed into a photo-recon platform with the installation of a camera package. Or the aircraft could become a tanker once it was outfitted with a 1,400 gallon (5,300 L) fuel tank in the bomb bay and a probe-and-drogue refueling system. A target tug system was also designed.

The Super Savage over the desert of California. The Allison T40 engine created trouble for every aircraft in which it was installed. The jet exhaust divider between the T38 engine sections can just be seen at the rear of the engine nacelle. Both propellers installed on the aircraft have square cuffs.

Construction of the first XA2J Super Savage prototype (BuAer 124439) began in late 1949 and progressed rapidly. However, Allison experienced massive technological problems developing the T40 engines, and they were not delivered until late 1951. The XA2J finally made its first flight on 4 January 1952 and was piloted by Robert Baker. The aircraft took off from Los Angeles International Airport and was ferried to Edwards Air Force Base (Edwards) for testing. By the time of the XA2J’s first flight, superior aircraft designs, namely the Douglas A3D (A-3) Skywarrior, were nearing completion. In addition, Allison never solved all of the T40’s issues, and the engines were limited to 5,035 hp (3,755 kW).

Testing at Edwards revealed some difficulties with the Super Savage. All aircraft powered by the complex T40 experienced numerous power plant failures, and the XA2J was no exception. The Super Savage was around 4,000 lb (1,814 kg) overweight and was never tested to its full potential. The highest speed obtained during testing was just over 400 mph (644 km/h). Even the aircraft’s estimated performance did not offer a significant advantage over that of the AJ Savage already in service. The XA2J project was cancelled in mid-1953, and the second prototype (BuAer 124440) was never completed.

The Super Savage had an aggressive appearance that gave the impression that the aircraft could live up to its name. However, it was outclassed by the Douglas A3D (A-3) Skywarrior and had performance on par with the AJ Savage it was intended to replace.

Sources:
– North American Aircraft 1934-1999 Volume 2 by Kevin Thompson (1999)
– Aircraft Descriptive Data for North American XA2J-1 (June 1953)
– American Attack Aircraft Since 1926 by E.R. Johnson (2008)
– The Allison Engine Catalog 1915–2007 by John M. Leonard (2008)
– “They didn’t quit… 5: Turbine-Driven Savage,” Air Pictorial Vol. 21 No. 12. (December 1959)
– https://www.secretprojects.co.uk/forum/index.php?topic=15792.0;all