I know they made 11 Cylinder Aircraft Rotary engines, and I have seen large 11 cylinder industrial Radial engines. But I have never heard of a 13 cylinder single row radial engine. Happy to learn if there was such an engine built.
I would think the crowding together of 13 cylinders in a single row would be problematic. At some point there just isn't enough room between the cylinders. Unless you use really long connecting rods and increase the overall diameter of the engine.
The air powered lego engine is like a double acting steam engine. Each stroke is a power stroke so an even number of cylinders works just fine. It isn't even a two stroke, it is really a one stroke...
I was thinking that myself. It reminded me of the diagrams of steam engines showing the way steam moves through both sides of a cylinder to operate. I went through a brief railfan period.
The air powered lego engine is like a double acting steam engine. Each stroke is a power stroke so an even number of cylinders works just fine. It isn't even a two stroke, it is really a one stroke...
A conventional engine converts one form of energy into another, so does the Lego engine. If you attached a propellor to the Lego engine, it would be generating thrust. I'm not seeing much difference...