Gaggebees, a rotary mower engine operates like a 2 or 4 stroke engine. The prop or blade must be attached to the crankshaft before running the engine. I am not mixing apples and orange here, but let me say none of the model engines that I know of to not have a clutch and flywheel on airplane engines.. If they did, the you can discuss PTO's, that's the oranges. A designed rotary engine has to have a load on it, just like a 2 stoke model airplane engine. If you run it without a prop(airplane engine) or a rotary lawnmower, you will destroy the engine period. If you have a rotary mower, or a freind that doe's, take the blade off and try to start it.Have your wallet handy, because you will be going to the repair shop.
Usuallyl the engine will not start, but persitence, in cranking it over, it will fire up. Then the damage occurs. Read the posts earlier on this same thread, run an engine without a prop, you will be buying a new engine!. I am not argueing this point any longer, go ahead and run a 2 stroke airplane engine without a prop or a rotary designed lawnmower engine without a blade, you'll get the picture. They both work on the same principle. They rotate directly on the crankshaft ,What ever floats your boat........