Hi guys, new user here.
My wife and I are building a new type of vehicle, but to start with we are going to test out some drive systems by modifying one of our 27 speed tadpole bents into electric assist/drive. For various reasons I would like to keep the existing gearing and have a smaller motor (starting with the Kollmorgen 400 watt brushless) operating through the 9 gears on the rear drive wheel. Initial plans are to gear the Kollmorgen down about 5:1 via a timing belt/pulley system and have this ~600rpm shaft connected to both the rear 9 speed cassette and the 3 gear pedal cassette. I would like to freewheel both the motor and the pedals, so either can operate without forcing the other to turn. If you are with me so far, what I would have is a jackshaft turning at about 600 rpm from the Kollmorgen to which everything is connected. So this jackshaft will need a fixed single speed 16 tooth 3/32 sprocket going back to the rear 9 speed cassette/derailer and also a freewheeling 16 tooth 3/32 sprocket going foward to the 3 gears on the pedal crank/derailer. Also either the smaller timing gear pulley on the Kollmorgen motor or the larger timing gear pulley on the jackshaft would need a freewheeling hub so pedaling does not drive the motor when you strictly want human power. (later we may investigate using the motor as a generator, in which case we would want to remove that freewheel).
My background is electrical engineering. I have never done a lot with bikes but I do have a small 7000 pound cnc milling machine and an old manual hardinge lathe in my garage. Obviously I would rather buy as many of the harder to make parts like sprockets and freewheels off the shelf instead of trying to machine those parts from scratch. It would take considerable effort to make a freewheel as small and lightweight as the ones they use in bikes.
Am I missing something easy to use because of my newb status with bike mechanics? I can find 16 tooth 3/32 single speed freewheel sprockets which have a large threaded hole and I can find 16 tooth 3/32 fixed sprockets which also have a large threaded hole. If all I have to machine is various threads on the jackshaft for these that doesn't sound too bad. Is there a type of freewheel that has a smaller hole than the standard? 1.37" x 24 TPI (that makes for an awfully large diameter jackshaft)
Thanks for any advice.