There may be packaging and, in the case of air-cooled engines, cooling advantages in a motorcycle with a vertical crankshaft. What is normally the top of the engine becomes the front of the engine. That places what is often the widest part of the engine far forward, leaving the rest rather narrower. In the case of air-cooled engines all cylinders are oriented to the flow of air.

Drive would be taken from a bevel gear on the crankshaft to a short transverse primary shaft, and thence conventionally via chain to a clutch, gearbox, etc. Alternatively the bevel gear could drive a longitudinal shaft, clutch, gearbox, and shaft drive.

The principle is applicable to all configurations of engine, and would produce very narrow in-line twins, triples, and fours. V-engines from twins to V-8's would have their cylinder heads ahead of the rider's shins. Only flat-twins would gain nothing, being the same shape as usual.
-- Ned_Ludd, Jan 29 2007

Torque steer would be a bitch. If you really want the cylinder heads facing forwards, why not leave the crankshaft arranged transversely, and just rotate the engine on that axis?
-- angel, Jan 29 2007


just wondering: wouldn't using this lawnmower-motor mounting arrangement lower the efficiency of the drivetrain, and introduce unnecessary gyroscopic forces?

you'd need to redirect the engine's power back to the same plane as the rear wheel at some point, which would mean another large power-robbing set of gears somewhere along the way.

since the engine has most of its heavy spinning parts down low, tipping the thing vertical may be akin to creating a spinning top when running at high speeds, with a great deal of rotational inertia a good distance from the ground. maybe the bike would have some handling difficulties?

also, most primitive ICEs would need a new type of oil distribution system that doesn't rely on gravity.

i like the idea of a narrow-profile 4-banger though.

maybe two twins mounted one behind the other could also work?
-- TIB, Jan 29 2007


I'm not sure what the gyroscopic effects would be. I got the idea not from a lawnmower but from an outboard motor, which does not seem to induce gyroscopic problems, but I don't know what the effect would be on a bike.

The lubrication thing shouldn't be a problem, as there is already pressure feed to all the important bearings. Oil return is simply down the crankcase and head(s) to a small sump at the bottom end of the crank.

Nor is the drive train more complex than on a shaft-drive/transverse four arrangement. Even in the case of chain drive I see the gearbox mounted in the conventional position and orientation.
-- Ned_Ludd, Jan 29 2007



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