Quote:
Originally Posted by M. Krass
If you can vary the gear ratio provided in the Kit of Parts by replacing either of the sprockets. To go faster, use a smaller sprocket on your wheel and leave that on the Toughbox output unchanged -- or similarly, use a larger output sprocket on the Toughbox.
Keep in mind when sourcing sprockets that the Toughbox output is a 1/2" diameter, keyed shaft. It's very difficult to find COTS sprockets that have a 1/2" bore and keyway. You may have better luck buying #35 sprockets from www.andymark.biz or www.ifirobotics.com, as those contain a bolt pattern that will mate directly with the Kit of Parts wheels.
Idlers can be made in a variety of ways. Search these forums for "idlers" or "chain idlers" or similar and you'll find lots of information.
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Another option that we considered was to buy the wheel hub from AndyMark and a larger sprocket (I think the KOP wheel sprockets are 22 tooth - you could use a larger one on the output shaftO)- use this as the output gear of the toughbox instead of actually attaching it to the wheel.
for the chain tensioner question, we designed a custom spring loaded idler with bearings pressed into the 22 tooth sprockets. we are not concerned about the chain wrap issue, however - just tensioning.
I agree that a little serpentine alignment of the idler and output sprocket will work fine like the ones used in cycling (for a bike, the sprockets are directly above each other and spaced about 2" apart). they are usually 11-12 tooth sprockets so the serpentine path engages ~1/2 of the teeth. they are spring loaded derailures, however, so a stagnant idler like your design will take a lot of force. Your arrangement will not likely slip (which is why you have it in the first place) but will cause a lot of stress on the frame, idler, and gearbox. to get around this much stress just make sure that the chain is not too tight - you want to just barely take up the slack. On a fixed gear bike (no derailure and no coasting) the chain can move about 1/4" when the wheel is locked in place - this relieves all of the drag on the chain.
I hope this helps.