Bentley BR-2 Engine Specifications


What is a rotary ? 

A rotary engine is characterized by a fixed crankshaft and cylinders that rotate. The propeller is attached to the spinning crankcase. 

A fuel metering carburetor is attached to the hollow fixed crankshaft.  Air, fuel and castor oil ( for lubrication ), are drawn into the crankcase then pass through the intake pipes to the cylinders. The exhaust is timed to exit at the bottom of the engine to minimize interference with the pilot. 

 This arrangement was common in World War I, when modern high-strength, heat resistant, steels were not commonly available. Cooling was accomplished by having the cylinders spin. 

This is completely different from the Wankel Rotary car engine developed in the 1970's.


16.5 inch diameter

16.75  inch length ( without carburetor )

1.733 inch bore x 2.362 inch stroke

50.14  cubic inch displacement

Compression ratio  5.63  :  1

Approx. Weight :  37.0 lb. without carburetor, oil tank or club

Fuel - 89 Octane unleaded

Oil  -  Caster oil ( Wont burn during combustion )

Pressure oil pump 

Fully Pressurized main bearings 

Constant loss lubrication system

There is no casting necessary, all parts are made from bar stock ! 

Direct drive

4 Cycle  -  Air-cooled
Naturally aspirated - No supercharger
Rotation:  Clockwise viewed from rear 

Spark ignition - 2 plugs per cylinder :

Ford Mechanical points with ignition coil.

Gears are available from the Boston Gear Works. 

Machine tool requirements  :

      1.  Lathe with 9'' diameter swing with 3 & 4 jaw chucks

      2.  Bridgeport milling machine or equivalent

      3.  Rotary Table 


Return to HOME page