I come from a mechanical engineering education background. Been working hands-on on various project in university, from design to fabrication. I have been working on cars, karts, engines and recently electric motors. This is my first engineering/design post to share my experience and knowledge.
Choosing the size of your wheel
The first thing that has to come in mind is “What size I want for my wheel?” Normally bicycle comes in 16”, 20”,21”,24”26” diameter wheel size. Do check with local repair shop for these sizes, and the spokes length available. You would want a hub designed and you can't put into a rim because you’ve got no suitable spokes for it. Do design a hub with minimal post machining work.
Big Wheel or Small Wheel?
Big wheel needs a bigger torque to initial the rolling but possesses larger rolling momentum once it rolls on a specific speed.
Therefore, designer needs to play around with the torque formula-Torque=Force x Radius and find the compromising values from these parameter.
Normally, when deciding the wheel size for the vehicle, driving wheel should be as close to sprocket size for minimal force required to drive the veh
icle and driven wheel should be as big as possible to be driven at ease.
Choosing the right type of bearings
What makes the wheel roll? Bearings of course. Normal bicycles use ball bearings; some wheel chairs use sealed bearings. When designing a wheel hub, it is necessary to think what type of forces will be exerted on the wheel. A steered wheel will experience radial force from reaction force from ground, lateral force when the car steers. Hence we need to choose bearing which design for these two predominant forces. Normal seal bearing will only withstand radial force and could not handle lateral axial force. In this case, angular contact bearing is recommended.
