Mid-drive motor on an enduro bike frame

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kalevvaska

100 mW
Joined
May 5, 2020
Messages
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Hi, I'm pretty new here and I'd love if someone could help. I've been working on a low power bike that is done, but isn't really satisfying, so I'm looking into getting a new one. My primary interest is using an electric enduro bike frame and then using a QS 138 70H mid-drive. My question is, is it possible to mount a mid-drive motor to this frame? I have also considered a hub motor, so I may just use a QS 205 50H hub motor if I can't figure out how to get a mid-drive on. Do any of you know if anyone's done this before? I would much rather use a mid-drive motor, and I could make mounting plates and/or weld it on, but I'm not sure if it would work. Please respond if you know anything about this. Thanks!
 
I thought about doing the same but the QS138 70H is a bit too wide (215mm) in my opinion so I ended up using hub motors - including a QS205 50H and currently a QS273 40H
 
The new version of the 138 70h looks like it has a good mounting system.

But the motor is huge. You couldn't fit it on the stock swing arm, there isn't a place for it. And it's wider than the pedals by a lot.
You might be able to use the bike as a base, but likely have to ditch pedals for motorcycle style pegs, and fabricate a new longer swing arm and a stronger pivot point. You would also need to relocate the shock, and strengthen the frame to handle the stress of the new shock location.

Lot of work, but might be worth it.
 
I have noticed it seems quite large. I am okay with using a hub motor, but I have some questions. I live in a fairly mountainous area, so do you guys have any issues with cooling? Is the acceleration good enough? I see what you mean about the 138 70H being far too big, so do you know of any smaller motors similar to it?
Thanks
 
Use a QS273 40H heavier than a 205 or 138 but runs much cooler
 
It runs cooler than a 138? How's the acceleration and hill climbing? Another thing that drew me to the mid-drive was the ability to change the gear ratio.
 
Tangent drive is a option. Superlight and 3 or 6 Kw power. Problem is your bikechain. Mines is max 350 km and then it brakes.
 
Tangent drive is certainly interesting. I see your point, bike chains aren't meant to handle that much power. But if I were to use a mid-drive on an enduro frame, I would probably remove the gears and use a fixed gear ratio with no pedals, and probably a 428 chain or a belt.
 
kalevvaska said:
Tangent drive is certainly interesting. I see your point, bike chains aren't meant to handle that much power. But if I were to use a mid-drive on an enduro frame, I would probably remove the gears and use a fixed gear ratio with no pedals, and probably a 428 chain or a belt.
Click to expand...

RC motors are loud.
 
Looks promising, my only doubt is that it uses a bike chain, which is not super strong. Do you know how they perform on steep hills?
 
I think the cyclone bikes are somewhat customizable, to order??.. belt drive option.. maybe even ask for a 219 cart chain option.. those handle high power and it's not overkill like 420 or 428 chain..
 
Yeah it seems on their website you may be able to get a belt drive, but if I could get a 219 that would be great. I agree that dirt bike chains are a little much. Thanks for the recommendation!
 
it's more of a heads up than a recommendation, since I don't personally have one.. but I find the designs interesting, and I think some ppl have them? maybe pop over there and ask;).. "how good is cyclone coaxial" thread.. something like that..
 
I'm starting to realize that a big mid-drive motor isn't realistic on an enduro frame. If I were to use an enduro frame, I would probably use a QS 205 or 273. Are any of you aware of any sturdy frames meant for electric bikes that can fit a mid-drive?
 
I think lightning rods is still offering mid drive kits for enduro, vector frame?? and with newer IPM motor should be more high power capable..
but imo for a mid drive bike these days just buy a surron, much easier and probably even cheaper than building something comparable (unless you want or need pedals)..
 
Yeah well my idea behind building a mid-drive like this was to basically build a homemade sur-ron. I think those are cool, but I like building things myself and I don't really have the budget to buy one.
 
not likely to be cheaper building one.. unless you already have most the parts laying around.. reason is you may need to pay retail for every part, that adds up fast.. especially the battery, do you have battery building experience or willing to accept the risks of large capacity and high voltage homemade battery?? even if you succeed, enduro frame is not great suspension for off-road use bc standing rider is unsprung weight due to pivot location.. how will the bike be used, why mid drive and not hub drive??
 
I don't have battery building experience, but I'm willing to do a lot of research and I know a phd electrical engineer. You might be right about building it at home costing more than a sur-ron. I'm also ok with hub drive. Are you suggesting that an enduro frame is not suitable for off-road riding? That was my primary intended use. My idea was that I would ride around on roads but also take it on my local trails.
 
I wouldn't mind using it primarily for road riding, though, if trail riding wasn't realistic.
 
you can definitely ride an enduro hub motor bike on trails.. just not the sharpest tool in the shed for that task, but much easier to build than mid drive.. also quiet:) .. but you may need to apply human power and mechanical sympathy on steep climbs to avoid overheating the hub motor..
 
Yeah, I can see how they overheat quickly. I wouldn't mind applying human power in certain sections. What's your opinion on Statorade and hubsinks? I heard they can be pretty effective at cooling the motor better. Also, would you recommend the 273 40H or the 205 50H?
 
stator aide seems to work, but may unglue your magnets over time?? and hub sinks need the ferro fluid for effective heat transfer.. forum member Emmett on the stealth thread has had good luck with oil cooled hub so have a look for that gem.. (also search "oil cooling not snake oil" something like that).. I don't have much advice on which hub motor to chose, but others likely will if you are very specific about what you want, need, use, terrain, etc.. they are all boat anchors, some more than others so prioritize your needs..
 
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