If you want to get that technical, you want to be on endlesssphere.com

Are you thinking of a friction drive, or what?

I’m not sure why you want to re-invent the wheel. Is it for the technical challenge or to do something new? I doubt you’ll save any money over buying from a wholesaler like bmsbattery, elifebike greenbikekit or similar.

Look at the kits from BMSbattery, to give yourself a BOM (shopping list). 80-50% of the ebikes on the market use these basic parts as a building block em3ev.com has a lot of good technical data and some good kit ideas.. Go to ebike.ca calculator to design your components.