xxxxx - 13-5-2008 at 09:02
usually motors for bicycles use friction drive on the front wheel or a secondary chain and sprocket on the left side of the rear wheel. i wanted to
bolt a small motor inside the triangle of the frame and have the power transfered to the left side of the bottom bracket crank where it would turn the
conventional 3 front sprockets and the 7 rear sprockets with a conventional chain and conventional deraillier, with the pedals removed and new pedals
bolted to the frame somewhere. i was wondering about how much power could be transfered with an unmodifided bicycle drive chain without excesive wear,
maybe twice or three times human power, and what type of clutch might be best and what ratio of gearing would be be best between the crankshaft of the
engine and the bottom bracket.
Mr. Wizard - 13-5-2008 at 15:43
Usually we use normal punctuation and capitalization, as it conveys a spirit of respect for the other users. I think two or three times the amount of
power delivered at the very slow turning large pedal gear would not wear excessively, if well lubricated and kept in alignment. Maintaining an
'impedance match' or correct gearing for your 'small motor' would depend on what RPM your motor delivered it's power. If it was a steam engine, and
delivered maximum torque at stall it would be easier to match than a chain saw engine; for example. Another question is if you plan to pedal to start
or use the motor to start. Perhaps you should investigate electric bicycles, as they have already done much development on these. No sense in
'reinventing the wheel'.
chemrox - 13-5-2008 at 20:52
Indeed I immedfiately thought of electric bicycles I've seen because the motors were mounted the way you desire; in the triangle of the frame. I want
to add one thing here: I believe the clutch you want is a centrifugal clutch of the type made for "go-carts." I like the European Velo-cycles with
front mounted friction motors. They're pretty if not the most efficient. For efficiency I'd go electric.