And when it's all bolted together, it looks like this. The easiest way to attach the 1" diameter fan blades in place is to weld them. The last time I tied to weld aluminum with my tig I just made a horrible mess, but these parts are a lot thinner and don't need a lot of weld to keep them in place. This will move a surprising amount of air, which will be directed over the cylinder, and hopefully keep the engine cool.--particularly if the engine is a hit and miss, because all the time the engine is missing, it is pumping ambient temperature air thru the cylinder and out the exhaust.
