Miscellaneous Internal-Combustion Engines.

Opened: 29 Sept 2008
Updated 12 Oct 2009
O'Donovan face-cam engine


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This gallery shows the truly bizarre engines that fit nowhere else; for example, the Polizzi flap engine, which looks like one of the great losers of all time.


Left: The Polizzi flap engine: 1929.

Originator: Paul Polizzi, USA

Quite what benefit Mr Polizzi hoped to gain from this ludicrous arrangement is unclear. There would have been the usual sealing problems at the end and sides of the flap, plus extra difficulties sealing the pivot point at 12.

Info from Patent 62251


Having been rather rude about the the engine above, it came as rather a shock to find that there is a flapper engine under serious development today. Run, don't walk, to The Pivotal Engineering website. (Thanks to Jones The Engine for bringing this to my attention)

Left: Two, three and four chamber Pivotal engines.

These engines are assembled from modules.

Info from Pivotal Engineering website

Left: Two views of the water-cooled flap piston.

Info from Pivotal Engineering website

I only know what is posted on their website, but it does look as if they know what they're doing. They claim that their engine can have its combustion space thermally controlled, with no hot-spots, and that makes it especially suitable to run on hydrogen. Trying to run a normal IC engine on hydrogen results in catastrophic pre-ignition because hydrogen has such a low ignition temperature.


Left: The Bakewell engine front view: 1939.

The Bakewell engine looks at first like an ordinary radial, but it was nothing of the kind. It consisted of four 90-degree V-twin engines, each with its own crankshaft, which was then geared to a common central propellor shaft. Propellor reduction gearing was fitted, the standard ratio being 1.57 to 1. This form of construction was claimed by the makers to give "inherent balance".

The eight cylinders had a bore of 4in and a stroke of 4.5in, giving a displacement of 452 in3. (7407 cc) Output was claimed as 165 HP at 2800 rpm. The compression ratio was 5.4 to 1.

From Aerosphere 1939.

Left: The Bakewell engine rear view: 1939.

Fear me, earthling! The Bakewell engine was built by the Shaw-Palmer-Bakewell Co of Los Angeles. Why it was called "Wingfoot" is currently obscure.

Because of the 90-degree V angle, the cylinders nestling together in fact belonged to different V-twins.

At least one of these engines has been preserved.

From Aerosphere 1939


Left: The James engine: 1963.

This engine was put forward by Richard James Cylindrical Motors Ltd. It was a two-stroke engine with two swivelling opposed pistons operating on a single crankshaft at the bottom of the housing, and employing uniflow scavenging. It was based on work started as long ago as 1929. This is believed to be a picture of the prototype, which may well have been the only one made.

An friend of Alan Lea (who has kindly provided the report on which this article is partly based) said: "he'd seen one in Vancouver in the early 70's. He said he'd seen it running on an office desk with a (exhaust ) pipe stuck out of the window. No vibration or apparent unbalance."

The James engine apparently got some support from the Canadian Federal Government, but what happened after that is currently unknown.

Info from Setright

Left: The James engine: 1963.

The internals of the James engine.

The prototype engine had a swept volume of 29.2 in3 (478.5 cc) and a compression ratio of 11:1. The pistons were 2.375 by 2.750 in, at the rectangular section, and had a 2-inch stroke. (measured at the outer radius?) The engine body was of aluminium alloy with a cast-iron cylinder liner. The water jacket was cast integrally with the main block. The connecting rods were of drop-forged H-section steel, the big end having a single-row roller bearing; the small-end bearing were of the needle-roller type.

The pistons were sealed by L-shaped piston "rings" of cast-iron, pressed against the cylinder walls by spring expanders.

From report An Evaluation Of James Hemispherical Opposed Piston Engine by John J Szendrey Dipl. Ing., 17 March 1967. (Very kindly provided by Alan Lea)

James animation
Left: The James engine animated. Click on buttons to start/stop.

The fuel/air inlet is at extreme right. The transfer port is visible behind the right piston.

Another fine animation by Bill Todd. Javascript must be enabled for buttons to work.


This single-cylinder engine was designed by the motorcycle racing rider and manager Don O'Donovan, for Raleigh, who then made motorcycles as well as bicycles.

Left: The O'Donovan face-cam engine: 1930

The induction and exhaust valves were actuated by tappets bearing on a horizontal face-cam. The vertical shaft to the face-cam was driven by bevel-gearing from the crankshaft.

A similar 350cc engine was designed earlier, in 1926, for motorcycle manufacturers Chater Lea by their development engineer Dougal Marchant, and it went into prodution. According to Bird, O'Donovan "would have had ample opportunity to study it". Enough said.
The O'Donovan engine was never actually used on a Raleigh but was sold to Dunelt who used it in one of their models.

There is unfortunately a terrible snag in this very neat and compact arrangement. Since the same cam is used for induction and exhaust valves, there is no opportunity for optimising perormance by having different event timing for the two valves. I Am Not A Motorcycle Engine Designer, but I would have thought this introduced crippling limitations. (The Chater Lea engine had a separate face-cam for each valve, and so did not suffer from this problem)

The original source of this drawing is unknown, but from its style probably Motorcycling magazine.

Info from "A Glimpse of the Vintage Years of Motorcycling at Brooklands" by Roger Bird. (self-published in 2008)

Left: The O'Donovan face-cam engine: 1930

Note the telescopic tube around the valve driveshaft, to allow for thermal expansion of the cylinder. The oil pump can be seen underneath the bevel box.

Left: Don O'Donovan contemplates valve-timings

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