Twin Engines

An alternative to two engines – one engine and a flexible drive!!

A brief overview of the twin engines drive unit for the RC Mosquito by Bob & Ron Lane.

I removed the outer part of the flexible drive and the drill chuck as it is too heavy. I am sure you can work out the method of the bearings in the clear plastic tube. The engine end of the flex drive is soldered in, other end is ground slightly flat to fit into a slot as per the sketch. This is so that the engine can be removed with the drive for lubrication and maintenance. If the outer tube is fed through holes in the wing ribs it will not be moving.

single engine twin prop schematic

We made a new conrod with a wider bigend to drive the rear crankshaft.

bench run of twin propeller and single engine

The space area left in the crankcase should be as small as possible to ensure a good pressure when the piston descends to inject fuel up the transfer port. A 2 stroke has a much better power to weight ratio than a 4 stroke given the same capacity.

From initial tests I think to drive 2 props off one I would increase the engine capacity by 50% above that recommended for a model using one engine.

I’ve found about 20 to 25 ounces a square foot wing loading always works on a model of about 72″ span, but use propellers that are slightly smaller diameter, one has to experiment to get it right.

The photos are not very clear but will give an idea. I’ve run the setup for around an hour on the bench without any overheating or problems.

These are my own theories but I think more qualified people than me could improve the system, its not a new idea just my version.

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