- #1
some bloke
- 278
- 97
- TL;DR Summary
- a central motor, inside the wheel, fixed to the frame. the wheel goes around the outside, but can also move up and down for suspension purposes. how best to transfer the drive?
I'm brainstorming how to make an electric motorbike, making as much use of the available space as possible to allow for as many batteries to be fitted as possible.
Batteries aren't relevant right now; my focus is on the final drive at the back of the bike.
To maximise space, I want to fit the motor inside the rear wheel - this seemed the sensible place for it, it's already round and it's where the drive needs to go. it also means one less chain / transmission to worry about, and can help make the overall look of the bike a lot cleaner.
My initial thought was simply to have the motor in the wheel, on a swingarm, but I have since learned the values of minimising unsprung weight, and the issues with having such a gyroscope on a bike - if the motor spins as fast as the wheel, it will make handling suck.
So my next step is to house the motor on the back of the frame, where the wheel will be mounted. It would then have sliders, with the suspension, mounted around it, and the wheel mounted around that.
The result would be that (taking the frame as stationary), the motor will be stationary, and the wheel will slide up and down on the suspension, with its centre of rotation passing through the motors axis of rotation at the midpoint of the suspension travel. The dimensions of the motor and wheel will be the limiting factors in the distance of the travel of the suspension, but that is another hurdle for later on.
How best can I transfer the drive from the motor to the wheel? essentially, I need a motor with the drive coming out on one side of it, which can move along a slot across its own diameter, without changing pace as it does so - suspension movement should not impact drive speed.
My initial thought was a differential, with one side connected to a rack & pinion (forming a non-turning side) and the other side connected to a vertical worm gear. The worm gear provided the drive, and if the suspension moved, both sides of the differential would roll up their respective tracks - one up the rack, the other up the worm gear - and the difference between the 2 would be nil, meaning it would not change speeds as it moved. I think that this system may be unnecessarily complicated, though.
If I can I will scan in a drawing of this to try and make it clearer. I'm sure there must be a simpler method to achieve what I'm looking for, with less moving parts to potentially fail!
Cheers,
Batteries aren't relevant right now; my focus is on the final drive at the back of the bike.
To maximise space, I want to fit the motor inside the rear wheel - this seemed the sensible place for it, it's already round and it's where the drive needs to go. it also means one less chain / transmission to worry about, and can help make the overall look of the bike a lot cleaner.
My initial thought was simply to have the motor in the wheel, on a swingarm, but I have since learned the values of minimising unsprung weight, and the issues with having such a gyroscope on a bike - if the motor spins as fast as the wheel, it will make handling suck.
So my next step is to house the motor on the back of the frame, where the wheel will be mounted. It would then have sliders, with the suspension, mounted around it, and the wheel mounted around that.
The result would be that (taking the frame as stationary), the motor will be stationary, and the wheel will slide up and down on the suspension, with its centre of rotation passing through the motors axis of rotation at the midpoint of the suspension travel. The dimensions of the motor and wheel will be the limiting factors in the distance of the travel of the suspension, but that is another hurdle for later on.
How best can I transfer the drive from the motor to the wheel? essentially, I need a motor with the drive coming out on one side of it, which can move along a slot across its own diameter, without changing pace as it does so - suspension movement should not impact drive speed.
My initial thought was a differential, with one side connected to a rack & pinion (forming a non-turning side) and the other side connected to a vertical worm gear. The worm gear provided the drive, and if the suspension moved, both sides of the differential would roll up their respective tracks - one up the rack, the other up the worm gear - and the difference between the 2 would be nil, meaning it would not change speeds as it moved. I think that this system may be unnecessarily complicated, though.
If I can I will scan in a drawing of this to try and make it clearer. I'm sure there must be a simpler method to achieve what I'm looking for, with less moving parts to potentially fail!
Cheers,