Hubmotor as a mid-drive

Discussions related to motors other than hub motors.
This includes R/C motors, botttom bracket, roller and geared drives.
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John in CR   100 GW

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Hubmotor as a mid-drive

Post by John in CR » Nov 07 2015 10:53pm

My friend Carlos wanted to build an ebike for use at his farm to use instead of motorcycles that get stolen or break. Cheap, durable, not too fast, not pretty, 10 mile range, and able to slowly climb crazy steep rocky muddy roads were the order of the day. I suggested he use one of the high Kv hubbies I had laying around with a gear reduction to the rear wheel. I couldn't talk him out of the V belt instead of a chain. We did a saddlebag arrangement of 12p20s well worn Konions, Sony 18650V harvested from Makita cordless tool packs that I first put into service in early 2009, and still have 16ah of their 19ah nominal. I paralleled 6 tested to be good and still balancing 2p strings, so no BMS is needed. We set the controller up with 60A battery side limit and an estimated 100A phase limit, along with regen and a 6 out of 10 on the throttle response.

He's got a bit of work to do...battery cover to weatherproof the battery, wiring cleanup and eliminate connectors to make them highly water resistant, add the rear brake cable to the motor's drum brake, and maybe put a pedal chain, but he's having a blast with it. With the motor geared down almost 2:1 with a 21" OD tire it climbs anything and still does somewhere north of 35mph. I'm surprised how well the V belt is working, but time will tell. He did rig a tensioning setup similar to motos on the rear axle.

She ain't pretty...hopefully ugly enough not to get stolen, but she's a workhorse already.
Carlos mid drive with hubbie 1.JPG
Carlos mid drive with hubbie 1.JPG (52.41 KiB) Viewed 1842 times
Carlos mid drive with hubbie 2.JPG
Carlos mid drive with hubbie 2.JPG (57.75 KiB) Viewed 1842 times
Carlos mid drive with hubbie 3.JPG
Carlos mid drive with hubbie 3.JPG (55.21 KiB) Viewed 1842 times

Harold in CR   1 MW

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Re: Hubmotor as a mid-drive

Post by Harold in CR » Nov 08 2015 8:03am

Is that one of the mid motors I want to get ? I still haven't blown the 50A main fuse you told me wasn't high enough on my bike ?? On the hill to my house, I pull the motor down pretty well. Gotta get that motor from you. Wife has a broken Clavicle, so, can't carry much over 10 pounds.

maybe Victor will visit during Navidad. :roll:
Thanks to Justin, the forum is open source and NON-commercialized.

dtx1   10 mW

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Re: Hubmotor as a mid-drive

Post by dtx1 » Nov 08 2015 8:58am

I think it's beautiul. If you gave a good clean, some paint, a little plastic here and there and some stickers you could make it look like a NASA Moon vehicle

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TheBeastie   10 MW

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Re: Hubmotor as a mid-drive

Post by TheBeastie » Nov 08 2015 10:42am

Cool.
I still haven't electriced my old China 250cc ATV and I have been thinking of doing it this summer. I have still only been eyeing standard heavy duty mid-drive motors for the job. But I do like the idea of using a hub motor as an option because there are x10 as many heavy duty hub motors for sale out there for every heavy duty mid-drive kit at least which would bring down costs.
Is it a serious process converting the motor? any details on that? I never really thought about it till now but I guess I need to attach a chain compatible cog on as well as coming up with a welding fork job that can hold the motor in place.

John in CR   100 GW

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Re: Hubmotor as a mid-drive

Post by John in CR » Nov 08 2015 11:04am

Harold in CR wrote:Is that one of the mid motors I want to get ? I still haven't blown the 50A main fuse you told me wasn't high enough on my bike ?? On the hill to my house, I pull the motor down pretty well. Gotta get that motor from you. Wife has a broken Clavicle, so, can't carry much over 10 pounds.

maybe Victor will visit during Navidad. :roll:
Sorry to hear about your wife. I hope she heals up quickly. You need to make one of those 4 wheelers with the Wesl suspension but use 4 smallish hubbies for 4wd for smooth riding on your terrain.

No, that's just one of those motors like you rode on my blue cargo bike with a 40mm x 203mm stator from the factory that holds the Chinese patent on the design so widely copied by 9C, Xlyte H35, MXUS, etc. MidMonster is wider but much smaller in diameter, and is a far superior motor of about the same weight, as well as much easier to implement in a mid-drive. Your MiniMonster is far superior too, which is what I had on the Wahoo frame before, but Carlos wanted a sealed motor instead of the vented Mini. That's the kind of implementation I've been suggesting for you though, since with it geared down you could more readily creep up the rocky muddy hill in a controlled manner with the motor switched to low (series winding) and still have a reasonable top speed in high (parallel high speed winding) for the main road. With it geared down you could hard wire it permanently in high for absolute durability and get virtually identical results and control with a controller with programmable throttle and using a 3 speed switch without controller stress.

John in CR   100 GW

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Re: Hubmotor as a mid-drive

Post by John in CR » Nov 08 2015 11:32am

dtx1 wrote:I think it's beautiul. If you gave a good clean, some paint, a little plastic here and there and some stickers you could make it look like a NASA Moon vehicle
Thanks, but I preferred it like below. It just needed a smaller fatter tire up front and move the rear shock mount to slacken the geometry for stability at higher speed. The 500wh pack behind the down tube was great for shorter rides, and I carried a backpack battery for long range. I'm working on something similar with much more battery room in that ideal location but running about 15kw geared and suspended to be an off road beast. Smallish wheels to free up more space and that kind of swingarm shape layout make some good things possible, and I want to try to avoid the pregnant guppy look and heavy feel of putting a big battery in a in-the-triangle battery compartment, but keeping the effective unsprung mass pretty low unlike my SuperV.
Wahoo with MiniMonster mid drive as tested.JPG
Wahoo with MiniMonster mid drive as tested.JPG (53.63 KiB) Viewed 1757 times

John in CR   100 GW

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Re: Hubmotor as a mid-drive

Post by John in CR » Nov 08 2015 11:50am

TheBeastie wrote:Cool.
I still haven't electriced my old China 250cc ATV and I have been thinking of doing it this summer. I have still only been eyeing standard heavy duty mid-drive motors for the job. But I do like the idea of using a hub motor as an option because there are x10 as many heavy duty hub motors for sale out there for every heavy duty mid-drive kit at least which would bring down costs.
Is it a serious process converting the motor? any details on that? I never really thought about it till now but I guess I need to attach a chain compatible cog on as well as coming up with a welding fork job that can hold the motor in place.
Motor mounts for hubbies in a mid-drive are simple. On this build the mount for Carlos' front pulley to the motor was the trickiest part, since centering is critical. Using a hubbie with a disc brake mount makes that part easy. I still have a few advanced design hubmotors stateside that are mid-drive ready and have much higher efficiency than typical high power hubbies. Give me your load and desired performance info (estimated total weight including rider and the desired top speed), and I'll analyse it for you. With a quad you might want to look at multiple hubbies running in-wheel though.

Tony01   10 W

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Re: Hubmotor as a mid-drive

Post by Tony01 » Nov 13 2015 4:57am

The v-belt drive will work well. One thing to consider is to build an enclosure for it. Vbelts are prone to slippage when wet and dirty. You can use something like brake cleaner to clean dirty pulleys. After the initial new belt stretch period, a retensioning is all that is needed and you're good to go.
I don't always listen to Pantera.... but when I do, SO DO THE NEIGHBORS :D

John in CR   100 GW

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Re: Hubmotor as a mid-drive

Post by John in CR » Nov 13 2015 12:45pm

After Carlos' results I don't recommend a V-belt at all for this kind of reduction. The rpm is too low, so the drive pulley sees a lot of torque at low rpm and it slips. It's forcing him to put a lot of tension on the belt and it's still slipping a bit, and that kind of constant tension on one side of the bicycle hub can't be good. That's all before considering the considerable efficiency loss. I warned him of these issues, but insisted on going v-belt since he had them in stock. He ended up paying as much just for the pulleys as I charged him for the motor.

When I go belt drive I'll use the Gate Poly Chain GT pulley stock that I have, and a 12mm Gate Poly Chain Carbon belt like Zero uses on its e-motos. First though will be a more forgiving chain drive fore an off-road high power ebike, since belts get clogged up and ruined in sand and mud.

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