tips-1917-18-cylinder-rotary-engine

Tips Aero Motor Rotary Aircraft Engines

By William Pearce

From a very early age, Maurice A. Tips and his younger brother Earnest Oscar were interested in aviation. By 1908, the Belgian siblings had built their first aircraft: a canard-design, pusher biplane. The first engine installed in the aircraft proved underpowered and was replaced with a Gnome rotary. The engine was geared to two shafts, each driving a two-blade pusher propeller. Although the aircraft made some flights, its handling was unsatisfactory, and the design was not developed further. The aircraft did possess unique concepts, a theme continued in Maurice’s subsequent designs.

tips-1908-biplane

Rear view of Maurice and Earnest Oscar Tips’ 1908 biplane pusher. The aircraft was unable to fly with its original Pipe V-8 engine, but the lighter Gnome rotary enabled the aircraft to takeoff. Note the central gearbox that provided power to the shafts that turned the propellers via right-angle drives.

After the 1908 aircraft, Maurice refocused his efforts on aircraft engines. By 1912, Maurice had designed a 25 hp (19 kW), seven-cylinder, “valveless,” rotary engine. The engine had a 2.76 in (70 mm) bore, a 4.33 in (110 mm) stroke, and a displacement of 181 cu in (3.0 L). Hollow “suction tubes” took the air/fuel mixture from the engine’s crankcase and delivered it to the cylinders. Each suction tube was geared to the engine’s fixed crankshaft. The suction tubes would spin at half the speed of the crankcase as it rotated. The top of the suction tube had two passageways. Each passageway would align with a common port near the top of the cylinder once every two revolutions of the crankcase. One passageway aligned to allow the air/fuel mixture to flow from the suction tube and into the cylinder. The second passageway aligned to allow the exhaust gases to flow from the cylinder out into the atmosphere.

Two larger versions of the seven-cylinder engine were planned. One had a 4.33 in (110 mm) bore, a 4.72 in (120 mm) stroke, a displacement of 487 cu in (8.0 L), and produced 50 hp (37 kW). The largest engine had a 4.41 in (112 mm) bore, a 5.12 in (130 mm) stroke, a displacement of 547 cu in (9.0 L), and produced 70 hp (52 kW). It does not appear that either of the larger engines were built.

tips-1912-7-cylinder-rotary-engine

Drawings of the 25 hp (19 kW) Tips engine of 1912. Air was drawn through the rotating suction tubes (5) which enable the intake port (14) and exhaust port (13) to align with the cylinder. The suction tubes were geared (9 and 10) to the stationary crankshaft (4).

Maurice worked to refine his “valveless” rotary engine throughout 1913 and 1914. The most obvious change was that the suction tube was moved to be parallel with the cylinder, rather than at an angle as seen in the 1912 engine. The newer engine design had an updated drive for the suction tubes, and the air/fuel mixture no longer passed through the crankcase; rather, it was delivered through a hollow extension of the crankshaft to a space under the suction tubes.

tips-engine-ad-1913

A 1912 advertisement for the Tips seven-cylinder engines. The ad is titled “The new rotary engines without valves,” and includes the more powerful 50 hp (37 kW) and 70 hp (52 kW) models.

A 25 hp (19 kW) Tips valveless rotary engine was installed in a monoplane built by Henri Gérard in 1914. However, it is not clear if the engine was the 1912 design or later. In addition, the results of the engine’s and aircraft’s performance have not been found. When World War I broke out, Maurice and Earnest Tips fled Belgium. Earnest made his way to Britain, where he worked with Charles Richard Fairey and helped start the Fairey Aviation Company in 1915. Earnest would return to Belgium in 1931 to start the Fairey subsidiary, Avions Fairey. He also produced the Tipsy series of light aircraft.

Maurice Tips traveled to the United States and continued to design aircraft engines. In 1917, The Tips Aero Motor Company was founded in Woonsocket, Rhode Island. That same year, Maurice applied for patents covering his new engine design, which incorporated many concepts from the earlier engines. The new Tips engine was an 18-cylinder, twin-row, rotary engine housed in a stationary frame. The new engine employed both water and air cooling. The cylinders were arranged in pairs, with one in the front row of the engine and the other in the rear row. The crankshaft had only one throw, and the pistons for both cylinders in a pair were at top dead center on their compression strokes at the same time. The engine’s compression ratio was 5.25 to 1. Each cylinder had one spark plug at the center of its combustion chamber. The spark plugs were fired by two magnetos mounted to the front of the engine and driven from the propeller shaft.

tips-1913-and-1914-rotary-engines

The 1913 (left) and 1914 (right) versions of the Tips rotary engine. The major changes were to the suction tube drive and rotary valves. The small tube (no. 14 on the 1913 engine and no. 40 on the 1914 engine) in the stationary crankshaft extension provided oil to the crankshaft and connecting rod.

Most rotary engines had a fixed crankshaft and a crankcase that rotated. This arrangement created much stress on the crankshaft and crankcase and also imposed severe gyroscopic effects on the aircraft. The Tips engine employed several unique characteristics to resolve the drawbacks of traditional rotary engines. The crankshaft of the Tips engine rotated and was geared to the propeller shaft. The propeller shaft was geared to the crankcase, which allowed it to rotate in the opposite direction from the crankshaft and propeller. The end result was that when the crankshaft was turning at 1,800 rpm, the propeller would turn at 1,080 rpm, and the crankcase would rotate at 60 rpm in the opposite direction. Rotary engines in which the crankshaft and crankcase rotate in opposite directions and at different speeds are often called bi-directional or differential rotary engines.

The propeller shaft of the Tips 18-cylinder engine was geared to the crankshaft at a .600 reduction; the crankshaft gear had 18 teeth, and the propeller shaft’s internal gear had 30 teeth. For crankcase rotation, the 17 teeth on the propeller shaft gear engaged 51 teeth on one side of a countershaft to give a .333 gear reduction. The other side of the countershaft had 11 teeth that meshed with a 66-tooth internal gear attached to the crankcase and resulted in a further .167 reduction. Having the propeller and crankshaft rotating in opposite directions not only eliminated the gyroscopic effect inherent to conventional rotary engines, but it also neutralized the gyroscopic effect created by the propeller attached to a fixed engine.

tips-1917-18-cylinder-rotary-engine

The 18-cylinder Tips engine of 1917 was far more complex than the earlier engines. Note the paired cylinders separated by the rotary valve (24). The propeller shaft (10) was geared to the crankshaft (7) via reduction gears (8 and 9). The crankcase was geared to the propeller shaft via a countershaft (16).

On the exterior of the cylinder castings were numerous cooling fins. In addition, internal passageways for water cooling were in the cylinder castings. Between each pair of cylinders were a series of air passageways to further augment cooling. The engine did not have a water pump; rather, thermosyphoning and the relatively slow rotation of the crankcase enabled the circulation of cooling water from the internal hot areas of the cylinders out toward the cooling fins on the exterior of the cylinders. The engine’s rotation also aided oil lubrication from the pressure-fed crankshaft to the rest of the engine. The oil pump and carburetor were located on the stationary frame at the rear of the engine.

A flange was positioned on the crankshaft, between the connecting rods of the cylinder pair. Mounted on the flange via ball bearings was an eccentric gear with 124 teeth on its outer edge. Attached (but not fixed) to the crankcase was a master valve gear that had 128 teeth on its inner edge. The gears meshing with an eccentric action resulted in the master valve gear turning four teeth per revolution of the crankshaft. On the outer edge of the master valve gear was a bevel gear with 128 teeth. These teeth engaged a 16-tooth pinion attached to a rotary valve positioned between each cylinder pair. The four teeth per revolution of the master valve gear acting on the 16-tooth rotary valve resulted in the rotary valve turning at a quarter engine speed. Each hollow rotary valve had two intake ports and two exhaust ports.

Air was drawn in through a carburetor at the rear of the engine. The air/fuel mixture flowed through a manifold bolted to the cylinder casting and into a passageway that led to a chamber around the lower part of the rotary valve. Holes in the valve allowed the air to flow up through its hollow middle and into the cylinder when the intake ports aligned. As the valve rotated, the exhaust ports would align with the cylinder, allowing the gases to escape out the top of the valve head and into the atmosphere. Passageways in the lower part of the rotary valve head brought in cooling water from the cylinder’s water jacket. Water flowed up through the rotary valve and back into the cylinder’s water jacket. The rotary valve was lubricated by graphite pads and held in place by a spiral spring and retaining cap around its upper surface.

tips-1917-18-cylinder-valves-and-gear

On the left is the rotary valve shown with the intake ports aligned (Fig 3). The air/fuel mixture entered the valve through ports in its lower end (27a). On the right is the valve with the exhaust ports aligned (Fig 5). Fig 4 shows a cross section of the rotary valve with intake ports (28), exhaust ports (29), and passageways for the flow of cooling water (30). Fig 8 shows the valve gear drive. The crankshaft (7) turned an eccentric gear (44) that meshed (42 and 41) with a gear mounted to the crankcase. The result is that a bevel gear (27) engaged a gear screwed to the bottom of the rotary valve (26 on Fig 3) and turned the valve once for every four revolutions of the crankshaft.

The 18-cylinder Tips engine had a 4.5 in (114 mm) bore and a 6.0 in (152 mm) stroke. The engine displaced 1,718 cu in (28.1 L) and produced 480 hp (358 kW) at 1,800 rpm. The Tips engine weighed 850 lb (386 kg). At speed, the engine consumed 22 gallons (83 L) of fuel and 3 gallons (11 L) of oil per hour. The oil consumption was particularly high, even for a rotary engine, but the Tips engine was larger and more powerful than other rotary engines.

In 1919, the engine was mentioned in a few publications. In 1920, Leo G. Benoit, Technical Manager at Tips Aero Motors, passed away. Benoit was said to be in charge of the engine’s design and construction. No further information regarding the engine and no images of the engine have been found. This lack of information could mean that the 480 hp (358 kW) Tips engine was never built. However, given the detailed description of the engine and that it was worked on from 1917 to at least 1920, the possibility certainly exists that the engine was built and tested.

Sometime before World War II, Maurice Tips returned to Belgium. He continued to design engines and applied for a patent on a rotary piston engine in 1938. This engine was not designed for aircraft use and bore no similarities to his early aircraft engines.

tips-1917-18-cylinder-rear

Rear view of the 480 hp (358 kW) Tips engine shows the extensive fining (22) that covered the engine. The fining and air passages (23) combined to turn the whole engine into a radiator to cool the water that flowed through the engine via thermosyphoning and centrifugal force.

Sources:
“Valveless Rotary Combustion Engine” US Patent 1,051,290 by Maurice Tips (granted 21 January 1913)
“Improvements in Rotary Combustion Engines” GB Patent 191307778 by Maurice Tips (application 15 April 1913)
“Improvements in or relating to Rotary Combustion Engines” GB Patent 191506821 by Maurice Tips (application 8 May 1914)
“Rotary Valve” US Patent 1,286,149 by Maurice A. Tips (granted 26 November 1918)
“Internal Combustion Engine” US Patent 1,306,035 by Maurice A. Tips (granted 10 June 1919)
“Valve-Operating Mechanism” US Patent 1,306,036 by Maurice A. Tips (granted 10 June 1919)
“Internal Combustion Engine” US Patent 2,203,449 by Maurice Tips (granted 4 June 1940)
“The Tips 480 H.P. Aero Motor” Aerial Age Weekly (17 March 1919)
Airplane Engine Encyclopedia by Glenn Angle (1921)
http://www.vieillestiges.be/fr/rememberbook/contents/42

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