I am planning a second build based on a Turnigy 80-100 outrunner running a reduction drive using a generic pocket bike transmission/gearbox (ebay). I have put together a mock-up of how I'd like to see things come together. The outrunner and gearbox would be mounted to 1/4 inch thick plate aluminum and that assembly would be mounted to the underside of the downtube. The motor would drive the transmission using either a belt or chain with something like a 3:1 or 4:1 reduction. The gearbox has a ratio of 5:1. The output of the gearbox would then drive a freewheel crank with another reduction. The overall reduction could be anywhere from 15:1 to 30:1 and would hinge on what motor wind I use and what type of performance I ultimately decide I want. (I have a stock delta 130kv and a rewound wye 70kv and most of my riding would involve an average grade of about 5-7%.) I would like to maintain the function of the rear cluster/derailleur under electric drive as I have found this works a treat on my existing e-bike and the hilly terrain.
Before I proceed beyond the mock-up stage and order more parts, I have to resolve a few issues and make certain there are no show stoppers to this design.
1. The input shaft to the gearbox is somewhat thin and a bit short (that's what she said anyway). It originally had a centrifugal clutch bell attached to it and after having removed that I can see that it's roughly 8mm in diameter and threaded (see pic). Assuming it is strong enough for this application in the first place, I somehow need to extend it a bit and make it compatible with the mounting of a belt or sprocket. Any ideas here?
2. Once item 1. is resolved I think getting the output of the transmission to drive the crank with a chain should be doable. The outupt shaft is about 9mm and splined and the gearbox unit came with a T8F, 22T sprocket. My hope here is that I could somehow adapt and fit a freewheel, bicycle size sprocket on the gearbox output shaft.
3. I don't have any experience with a freewheeling crank so any help here would be appreciated. Are there any good threads that outline the process and describe a good source for these parts.
The pictures show the reduction mock-up mounted to an old Costco full suspension mountain bike. The pulley's and belt were just laying around and are used simply to get an idea as to how the bits will fit together. Also, I have not decided on the actual bike yet but I figure this thing will make for an adequate test subject. I will probably end up using a bike with a bigger triangle for more battery and controller space. Rear suspension is undecided at this point but I figure would be easy to implement with a crank driven setup. All feedback and questions are welcomed.
Martin
Before I proceed beyond the mock-up stage and order more parts, I have to resolve a few issues and make certain there are no show stoppers to this design.
1. The input shaft to the gearbox is somewhat thin and a bit short (that's what she said anyway). It originally had a centrifugal clutch bell attached to it and after having removed that I can see that it's roughly 8mm in diameter and threaded (see pic). Assuming it is strong enough for this application in the first place, I somehow need to extend it a bit and make it compatible with the mounting of a belt or sprocket. Any ideas here?
2. Once item 1. is resolved I think getting the output of the transmission to drive the crank with a chain should be doable. The outupt shaft is about 9mm and splined and the gearbox unit came with a T8F, 22T sprocket. My hope here is that I could somehow adapt and fit a freewheel, bicycle size sprocket on the gearbox output shaft.
3. I don't have any experience with a freewheeling crank so any help here would be appreciated. Are there any good threads that outline the process and describe a good source for these parts.
The pictures show the reduction mock-up mounted to an old Costco full suspension mountain bike. The pulley's and belt were just laying around and are used simply to get an idea as to how the bits will fit together. Also, I have not decided on the actual bike yet but I figure this thing will make for an adequate test subject. I will probably end up using a bike with a bigger triangle for more battery and controller space. Rear suspension is undecided at this point but I figure would be easy to implement with a crank driven setup. All feedback and questions are welcomed.
Martin