Seems too good to be true.


New Member
Jan 27, 2009
Toronto, Ontario
So here's what happened: The snowthrower also had a centrifugal clutch system and a chain drive. To my delight, and ignorance of gear ratios, the chain fit the sprocket on the rear wheel of the bicycle perfectly. It was the right length to go from the PTO of the engine to the wheel sprocket (by chance). When you're working on something like this, you find happy little coincidences, like matching parts. It functioned perfectly on the workbench. Start the engine, the rear wheel didn't move. Increase the engine speed and the centrifugal clutch put power to the chain and the rear wheel started to spin. Decrease the engine speed and the rear wheel stopped. The engine kept running. A perfect design, yes? No!
There I was sitting in the parking lot on my motorbicycle. Nervously I pulled the cord and the engine came to life. Thumb on the throttle lever, one foot up on the pedal, push off with my other foot as I increase the engine rpm and . . . nuts . . . slowly come to a stop with the engine working very hard for nothing. The bike wouldn't move. Back off the throttle, try again. The bike was a push toy. Like a lightning bolt, the words: 'gear ratio dummy!' flashed through my mind. I shut off the motor and returned the motorbicycle to the sanctity of my dining room. I was angry, annoyed, then despondent. I was a dummy, no question. I remembered the phrase: 'if something seems too good to be true, it usually is'. The design configuration was flawless except for one important engineering rule: a small engine providing power to a larger wheel must turn at least ten times to the wheel turning once. I had the wheel turning once to the engine turning once. Off came the chain. I had no method of fashioning a larger wheel sprocket or finding a longer chain to fit such a configuration: a 10:1 gear ratio. For me, the chain drive was out.