Part suggestions for mid drive + hub motor design

OSCookUp

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May 5, 2022
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Came up with this design for a mid drive and hub motor combo, where the motors are meant to be used separately, in order to maximise the strengths of both. The hub for silent high speed, the midrive for extreme torque/ wheelies :)

I’m gonna have two chains, one for the mid drive and one for the pedals. So I can attach a huge sprocket to the midrive and hopefully be able to wheelie easily at 1200w (hopefully be able to do power wheelie, because of the extreme torque, would like to hear your predictions) since the hub is used most of the time the slower top speed of the mid drive doesn’t matter at all.

When the hub motor is in use the middrive chain will rest on a sprocket that slips completely because it’s on bearings. When it’s time to use the midrive I’ll move the chain to the active sprocket that attaches firmly to the hub motor and you’ll be able to use it (look at the attached pic). If I don’t do that the hub will drive the mid drive all the time and it’ll be inefficient, and if I use a one way freewheel you’ll get the loud clicks. The pedals will have a regular small one way sprocket.

The parts that would be used for this must be very rare since this is an uncommon build, but would kill for some part suggestions.

It’s way easier to understand using the attached pic but I’ll summarise:
1. Big sprocket that attaches solidly to the hub motor
2. Big sprocket where the chain can rest when the mid drive is inactive (that’s slips because it’s on bearings or any low friction solution)
3. A regular one speed freewheel for the pedal chain.

Thank you
 

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Have you considered left drive using the brake rotor mounting points? That’s what I’m looking at using a motor with planetary gearbox to keep the sprocket size smaller than the brake disk. Cyclone 6000 with metal gears and freewheel on output
 
What exactly is your use case for this bike? While I've seen this done a few times it does make for a very heavy bike. If your mid drive is only 1200w then why not just run it through a derailleur and it will be just as efficient if not more so than the hub motor. You'll have to work the ratios accordingly but you also have the option to just increase the size of the motor and battery given all the weight you saved.
 
electric_nz said:
Have you considered left drive using the brake rotor mounting points? That’s what I’m looking at using a motor with planetary gearbox to keep the sprocket size smaller than the brake disk. Cyclone 6000 with metal gears and freewheel on output
Hey man thanks for the reply, the only problem would be that the hub motor would spin the mid drive, and without the rear break the bike stops slowly even though I have hydraulic brakes
 
scianiac said:
What exactly is your use case for this bike? While I've seen this done a few times it does make for a very heavy bike. If your mid drive is only 1200w then why not just run it through a derailleur and it will be just as efficient if not more so than the hub motor. You'll have to work the ratios accordingly but you also have the option to just increase the size of the motor and battery given all the weight you saved.
It’s important to me since the bike itself is like a prototype for an electric motorcycle that I’m going to build. I’ve seen mid drives that can use throttle independently without moving/assisting the pedals, but they tend to be very pricey.
I just have a simple motor, It’s not really a mid drive but I’m gonna mount it by the pedals. The throttle is very important for me since I plan to use the mid drive to wheelie. And the silence of the hub motor is very nice.

And I think you’re 100% right about the efficiency and simplicity of just using a mid drive for the bike, but when I get to making a motorcycle/dirt bike the loud mid drive sound will bother me a lot, especially at high speeds. Having the option to switch between the 2 different motors is like a nice gimmick for me, and a benefit of building the bike myself. I’ve also thought about just mounting a very large mid drive using a shaft drive so you can have it parallel to the motorcycle, I’ve seen some people do that and their noice level was not bad at all. “Higher Voltage” on YouTube did that for his electric motorcycle.

The bike is also running and working with a hub motor since way back, everything that’s needed in it is there, I just ordered the extra motor for fun.
 
OSCookUp said:
electric_nz said:
Have you considered left drive using the brake rotor mounting points? That’s what I’m looking at using a motor with planetary gearbox to keep the sprocket size smaller than the brake disk. Cyclone 6000 with metal gears and freewheel on output
Hey man thanks for the reply, the only problem would be that the hub motor would spin the mid drive, and without the rear break the bike stops slowly even though I have hydraulic brakes

My plan is to use a freewheel with ratchet on the mid drive motor output, so it can freely turn without turning the motor- check how it’s done on the cyclone motor. I will also look to use a large diameter disk brake on the same mounts as the smallish sprocket so I can still have a rear brake (or you could use regen braking if you’re using a direct drive hub)
 
electric_nz said:
OSCookUp said:
electric_nz said:
Have you considered left drive using the brake rotor mounting points? That’s what I’m looking at using a motor with planetary gearbox to keep the sprocket size smaller than the brake disk. Cyclone 6000 with metal gears and freewheel on output
Hey man thanks for the reply, the only problem would be that the hub motor would spin the mid drive, and without the rear break the bike stops slowly even though I have hydraulic brakes

My plan is to use a freewheel with ratchet on the mid drive motor output, so it can freely turn without turning the motor- check how it’s done on the cyclone motor. I will also look to use a large diameter disk brake on the same mounts as the smallish sprocket so I can still have a rear brake (or you could use regen braking if you’re using a direct drive hub)

Yes it’s a great idea and I was planning on using that design too. But won’t the freewheel have that annoying click? That’s what put me off a bit. But if it doesn’t bother you then it’s great, I think I’m the outlier here with my opinion on it
 
Too complicated and heavy. If you put all the weight of the extra motor and rest of the extra drive train towards a single motor set up you can wheelie and have straight line performance.
 
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