Five Cylinder Rotary

This 5 Cylinder Rotary engine took some years from start to finish, a number of those years were down to us moving house and me not locating it after the move.

The engine is approximately 85mm in diameter with the cylinder heads attached. As this is a rotary engine, the crankshaft is fixed and the whole engine rotates around it. This did cause some issues with machining and I had to very carefully finish the propeller boss whilst it was attached to the crankcase. Also, I managed to break a tap whilst tapping the crankcase, this set me back.

The cylinders are aluminium with a mild steel liner. The pistons are just 9mm in diameter. The master conrod worried me for some time about how I was going to machine something this small.

All of the parts were machined on the Unimat 3 and HobbyMat MD65.

The air enters the engine through the centre of the crankshaft and goes just a short way down the crankshaft before exiting through the side of the crankshaft main bearing.

The air then enters one of the cylinder heads via the copper tube – each cylinder getting fed with compressed air just after the piston gets to top dead centre.

The engine rotates further and the compressed air flow is cut off, the piston is forced down the cylinder until the piston passes the exhaust ports in the side of the cylinder.

The compressed air exits the engine and the whole engine continues rotating.

With 5 cylinders the engine happily self starts as their is rarely a time when one of the cylinders is not in the correct position.

The engine runs very smoothly, but as you can see, quite a lot of oil is blown out of the exhaust ports and gets splattered over the outside of the engine.

I had to make the propeller for this engine as it rotates clockwise as you are looking at it, the opposite direction to most model aero engines.

More of my engines are in my gallery page.


plans for the five cylinder rotary engine

Five Cylinder Rotary Engine Plans

The pdf download is a 15 page document of technical drawings, images and lots of notes on the engine design.

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