I posted a new thread yesterday with a animated 2 stroke motor drawing. The site has several forms of motors illustrated with animated drawings.
But the one that gets closest to this "In wheel" concept is the "Gnome" cycle engine. Like the WW1 biplane fighters used.
Animated Engines, Gnome
As I sit thinking about it, I'm seeing a 3 cyl radial engine of 25cc per cylinder.
The crankshaft would have to be the axle too with the crank case carrying the
wheel bearings and serving as the hub for the spokes. No doubt the axle
would have to be secured to the frame to keep the motor indexed.
What I'm wondering about is whether the lacing of the spokes would require the ommision of spokes in three regions fo the wheel to provide clearance for the cylinders. This could be a challenge for those of us here who specialize in wheels.
I figure the carb would have to vent into the crankcase thru the axle on one side, while the ignition system KILL switch circut would have to come out of the other side axle. ( the unitized magnito/hall effect switch units would be on the side of the crankcase with the spark plug wires traveling to the top of each cylinder head ) So a 50cc set up would have 3, 16cc displacement cylinders, and a 3, 23cc cylinders could net a 70cc set up.
There is no provision for advancing the timing, but I wonder about an electronic dwell extender circut build into the ignition to compensate for an advance mechanism.
I could imagine the mufflers extending between the head and the rim
with a short piece of tubing leaving at an angle to vent the exhaust
close to the road during the exhaust cycle.
Any bicycle could be used with such a wheel but the dropouts on the back would have to be retro-fitted with special fastening plates that the wheel bolts into. Otherwise the carb & cable are on the outboard side of the bike and the fuel tank could mount under the seat with a fuel line to the carb.
........but since I found that animation of engines web site, I can understand this concept better now.