This engine was made in the summer of 1987. It has the cylinder liners, pistons and conrods from two OS 25FSR glow engines.
The crankshaft was made in parts and the crankcase machined from a solid billet of aluminium.
Although, the engine ran smoothly and managed to turn an 11″x7″ propeller at 8000rpm whilst still being run-in it had some not inconsiderable design flaws.
As can be seen from the photographs the exhaust ports are on one side and the inlet port on the other side of the engine. The original OS single cylinder engine had the cylinder liners slightly rotated.
In the photograph the carburettor is omitted, in practice I used the carburettor from the OS 25FSR and this worked like a dream.
The inlet port sits in the middle of the crankcase between the two cylinders. The drawing shows the internals of the engine and from this it can be seen that the crankcase has been split into two.
I entered this engine into the 1988 Model Engineer Exhibition and received a Highly Commended – a fantastic result.