gearing

I've mostly been working on figuring out what parts to use in the drivetrain. I've settled on #35 chain, which I believe is commonly used in go-karts. The guys at McGuire Bearing said this chain would be appropriate for the RPMs and torque of my application.

Here's where it got tricky: the Vespa axle is 17 mm at the location where I want to attach the driven sprocket, and the axle gets wider at both ends of the shaft - this means I have to use some sort of split sprocket. Apparently 17mm is an odd size, so I would have to have something specially machined. The bearing shop estimated 90 minutes of shop time at $1 per minute to modify a standard sprocket, so I decided to look for another option.

I went to the McMaster Carr website (thanks for the link, Reikiman) and ordered a flat 30-tooth sprocket and a split collar with an 11/16" bore. The parts arrived the other day, and the collar fits nicely around the shaft and screws down tight. The hole in the sprocket will need to be increased to just over 1" to fit on the axle, then I plan to weld it to the collar. Fortunately, I have a very kind friend from my scooter club who has the requisite machining and welding equipment and skills and has offered to help me with the work.

We'll also be building a mount for the right axle bearing. Probably just 2 or 3 plates stacked up and bolted to the motor mount plate, with hole in the last plate machined out for the bearing to fit into.

I also got an 11-tooth sprocket from McMaster Carr. It comes right out of the box, slips onto the motor shaft, tightens with set screws and a 3/16" key, and Bob's your uncle. At least some parts of this project are simple.

I made a stack of the motor, the motor mounting plate, the swingarm (old engine case), and the sprockets to see how everything fits up. I discovered that the 30-tooth driven sprocket is too wide to fit in the engine case. Once I get the sprocket in the right place on the axle, I'll need to slice out a section of the case for the sprocket and chain to fit through. Hopefully this won't weaken the case too much, but I can probably get my friend to help me weld on some additional reinforcing around the slot.

Can anyone recommend how much lubrication my chain and sealed axle bearings will require?