Hub motors suitable for SM or mid drive?

SM = Stoke Monkey. Hubmotor drives chainset drives wheel
Mid = Chainset drives hubmotor drives wheel.

In both cases the hubmotor is supported by its axle and its body spins.

Either allows the motor to work through gears so that it operates at maximum efficiency over a wide range of speeds. This is most desirable for velomobiles and cargo bikes. Since it is driving through bicycle parts, the motor should not be too powerful, nor need it be. The Stokemonkey motor is EU-legal (so long as it is not used to assist above 15). It uses a direct drive rear hubmotor driving a left hand side chainwheel. The motor is mounted with the freewheel on the left hand side, and so it needs to be modified electrically to spin anticlockwise, the opposite direction to normal. The freewheel, spun onto the hub in the normal manner, ensures that the motor does not rotate with the cranks when power is off.

At first sight it would seem possible for an unmodified motor to power the right hand side, simply by flipping the freewheel before screwing it on - but in that case power applied would tend to unscrew the freewheel on its clockwise thread. A suitable hub motor therefore needs to be about 250 watts continuous rating and either run anticlockwise or allow a sprocket or freewheel to be attached without unscrewing.

Which motors are most suitable?

A question: Are you specifically excluding the possibility of a third option, that of merging the pedals and motor at some point prior to the rear wheel (or at the rear wheel)? I ask as neither description you give matches what my CrazyBike2 drivetrain does, nor what I will have on the new cargo bike.

Also, any motor with disk brake mounting holes could have a freewheel added via an adapter with whichever threading is necessary for the side of the bike it is on vs power delivery to/from the motor.

Additionally, if a jackshaft were being used (as in CB2 or the new bike), the freewheel could be on that, rather than the motor, allowing the sprocket on the motor to be bolted directly to it's casing (even if it does not have a threaded mount or a disc brake mount)


Are you specifically limiting this to motors at or below the EU limits?


If none of the above are limiting factors, then there should be a lot of motors that could be used.


To reverse a motor, almost all of them that I am aware of (other than freewheeling geared motors) simply need the correct pair of halls and phases swapped. No electrical modifications necessary, other than the order you plug the wires in.

It may be possible to file a keyway into a freewheel and its thread-on flange (so it won't unscrew). A dab of loctite would keep the key from sliding out, and yet remain removable when needed. One key should be strong enough, but two wouldn't hurt.

The keyway doesn't have to be deep to have significant holding power, but if you're restricted to shallow keyways, definitely add 2 or 3.

Like Amberwolf said, a disk brake mount can be used for a freewheel. The motor I used actually had a cover on the left side with the same threads a freewheel requires. So with the motor flipped over and a freewheel screwed on, there are no reverse running issues or freewheel unscrewing issues. I think many motors have identical side plates, so the left and right sides could be exchanged to get a threaded adapter on the "brake" side.

Here's my build thread:
http://www.endless-sphere.com/forums/viewtopic.php?f=28&t=18606

For a stokemonkeyish setup I used a front cute 85 motor and put an old style bottom bracket cup on the 6-hole disc brake mount and then threaded on a freewheel. Mine is on a recumbent so it hangs off the front end and then attaches to the tandem crank.

Thanks for the response, guys!

Amberwolf: I have an 8fun front that I might Stokemonkey with, but I thought it worth seeing what other possibilities there were (two options seemed enough for one thread). EU-legal because I don't see the need for more power, which might cause other problems.

spinningmagnets: I wish I had thought of a keyway in the days that I was riding a fixed gear with no lockring!

Rassy: Your solution is interesting, but it only works when the hub is pulling the main drive chain, so you can't use multiple chainrings. I think we really need a STRONG and wide ratio three-speed hub, say the equivalent of 60-36-21 chainwheels, with a long threaded driver to take multiple freewheels.

evblazer: That hub looks really small and - cute! It's the same sort of internal mechanism as the Tongxin isn't it? How much does the freewheel improve on using a track cog and relying on the internal freewheel?

Yeah the cute 85 (aka 108?) has an internal freewheel but i'm not sure if it all is identical to the Tongxin or not. When I bench tested the motor and first had it hooked up to just the tandem chain it seemed to be harder to start turning the motor freewheel than the cog freewheel. Might not be noticable on the road though since you would have it constantly spinning. I'm going to try and test it though because I think I'm going to blow that shimano freewheel eventually and a track cog would be cheaper and last alot longer. If only I had a fish scale to do a pull test or something :|

Hi Jenny
I'm in the process of upgrading my bottom bracket drive with a Cute 128 motor, which I think is similar to the Bafang motor. I originally used a MY1018 motor with freewheel mounted underneath the downtube, which worked very well but was noisy. I'm now trying to find a quieter solution while keeping weight down. I was tempted by the Cute 108, but it has a double set of planetary gears that make it a little noisier than the 128. The 128 is heavier than I would really like, at just over 3kg – the aluminium casing alone is 5mm thick and weighs 950g. I reckon half that weight could be safely pared away as the stresses on the casing are obviously much reduced in this application.

Being a geared hub, the Cute 128 has a built-in freewheel, so I've simply bolted a standard 22t chainring to the right-hand side of the casing. This means there'll be a slight increase in drag when the motor is unpowered since I'll be spinning the entire casing. I'll try it this way and if I don't like it I can always add an external freewheel – probably using the same approach as evblazer. I'd like to stick with the front motor if possible as it makes it easier to maintain reasonable chain line.

I'm using a Nexus 8-speed at the rear. I currently have a single chainring at the front, but want to fit a triple set just to see if it can be done without increasing the pedal spacing. The SRAM Cargo 5-speed seems like a good bet for strong, wide ratio hub.

I'm watching your build closely to see how this Cute little guy works out Malcom. I currently have a similar MY1018 set up that needs an upgrade. More power for the steep Seattle hills would be nice. Rather than try to align the sprocket by moving the motor around I think I'll probably set up a jackshaft on my seat post and run the gear from the disc mount side of the motor. Aligning the pedal side will be easier from a shaft as will adding a freewheel or fine tuning the gearing. Good luck and keep us posted on your progress.

Hm I'd need about a 56 tool chainring to replicate my gearing with a 22 driving it. I have never seen them before but today I found the TomiCOG which are bmx cogs 16-20 tooth that bolt right onto 6 disk mounts. Been around a few years and lots of people seem to have great things to say about them.
Sure would make things simple to setup although I'm wondering if there would need to be a couple washers to space it away from the hub but that is alot easier then getting an old bb, welding the lock ring onto the cup and then notching 3-6 bolt holes and getting them lined up perfectly. Swappable face covers would be ideal but I don't know if it would work with this motor.

@malcolm
What is what motor mount made from? I have to build a permanent one soon.

Sturdly
Yes, chain alignment can be fiddly, but I reckon I can manage it by making the stoker dropout spacing about half an inch wider than necessary and swapping axle spacers from one side to the other. There's lots of different ways of skinning this cat though

evblazer
Yes, the 22t ring is about the upper limit for efficient gearing with my 50t motor chainring. Another alternative that gives plenty of lower tooth options is to use a standard Sturmey Archer hub cog. You just have to file a fraction off the three little locating lugs to get a neat fit over the shoulder on the Cute motor. You would have to drill holes at the required bolt circle though. I chose to use a 22t chain ring partly because I want to use standard components as much as possible and partly to minimise chain noise and wear – I may be getting a bit obsessive about this noise thing

The removable face cover is on the left side on this motor. The rest of the casing is a single machined casting.

The motor mount shown is just knocked up out of a piece of 3mm aluminium for testing. I'm waiting for some 2mm 316 stainless sheet to arrive for the new motor mount.

Any progress on this, Malcom?

I really like the efficiency and torque of going through the bike gears, but my MY1018 is underpowered and noisy as you know.

Was it John in CR who was thinking of using a big DD motor in this way?

SM seems pretty good, but just too expensive for me.

I think there are several of us considering it.

http://endless-sphere.com/forums/viewtopic.php?p=291768#p291768

veloman said:

Any progress

Click to expand...

No, sorry. I've been concentrating on getting my motorbike back on the road, so this has been shelved for a while. I'm a little reluctant to pull my pedal bike apart just now as it runs so well with the MY1018, apart from the noise. The power is ample for my needs at 36V and I'll be very pleased if the Cute motor performs as well. I will get round to it eventually, but probably not until winter.

Amberwolf: I love those repurposed forks and the handlebar spring, but could you please just try painting one of your machines a single colour...

Was it John in CR who was thinking of using a big DD motor in this way?

Click to expand...

I have about 10 projects I want to do, but yes, I would also like a hub-motor as a mid-drive of some type someday...BTW, the skillet shown is 10-inches in diameter.

http://endless-sphere.com/forums/viewtopic.php?f=28&t=18606

veloman said:

...Was it John in CR who was thinking of using a big DD motor in this way?...

Click to expand...

Planning yes. Before I try the big hubbie as a mid drive I want to try with a ventilated 9c or my 500W Grubie torque hubbie. The kicker will be running at high voltage, probably 133V nominal, but gearing it back down to a max speed of 35-40mph. I'm pretty sure the Lyen 18fet high voltage controller will be good for 60A, maybe even 75A with such a low geared motor, so that will give me a light weight motor with simple implementation that is good for 8-10kw.

If it works out, then I think I can go left side drive without a freewheel, so I retain regen braking, and have a lightweight, high power bike that can handle 25% grades. Best of all is the simple implementation with the only specialty work being to mount a sprocket to the motor and another to the disc brake mount at the wheel, relatively easy stuff.

I want to use chainrings for my sprockets, road bike rear and mountain bike front, with one inverted. If I can match tooth count for the 3 different speeds, then I can have a pretty wide gearing range with 3 speeds that have perfectly aligned chains that is a quick stop and change. Why? I can't have a derailleur or chain tensioner with regen. Perfectly aligned chain is extremely efficient, and I believe chainring size sprockets will permit me to use bike chain even at pretty high power.

This is the drive I've settled on for initial testing for the Caribbean-Pacific without a recharge ride. Yeah, I know I've been talking about it for over a year and a half and talk is cheap, but it will happen within the next 6 months. I have enough batteries, so I could have done it at any time by strapping lots of batteries onto almost any ebike, but the past year of delay has enabled me to learn enough to make a solid effort at what I believe will be a unique and truly useful ebike that would be a valid replacement of the 2nd car in many 2 car households. For families here that don't own a car this bike would approach the freedom of transportation of a car (better when it comes to traffic), for the cost of a scooter, but far more utility, and lower operating costs than a pedal bike. Plus it would pay for itself quickly thru savings on bus and taxi fare. 8)

John

What's the smallest sized DD motor one can get? It seems the 10" diameter 9c would be too big for this setup on a typical bike.

I'm thinking of DD for long term reliability and least noise.

I bought the 16T cog that bolts onto the disc mount from Grin Tech www.ebikes.ca
http://www.ebikes.ca/shop/electric-bicycle-parts/stokemonkey-parts/cog16t.html

Google some more and found Tomicog because what if I want a different tooth count.
https://tomicog.blogspot.com/2007/12/testing1-2-3.html

Searched Tomicog on here and there were a handful of posts.

16-21T bolt-on Disc Cog
http://www.velosolo.co.uk/shopdisc.html
Want more then on cog on your disc mount?
Twin Disc Cog Package With Bolts Included - same link as above
They sell spacers as well, better then using washers :wink: :lol: 8)

https://www.amazon.com/Origin8-Ultim8-Single-Speed-Cassette/dp/B00TG3BOUW

I should take a picture of my setup. Basically what I did was take 1/4" steel plate and a 22 or 24T gear off a crank. Used some paper to get pencil shade of bolt holes and the width of the raised mount. Cut the steel - Hole for the middle, same for the disc mount. Drilled holes and bolted. Now the kicker, if your still reading this is the steel plate was only about 70% of the circular disc mount, its basically a C shape. The gear is complete. :lol: 8) Been working just fine since finished mid drive with d.d. motor a handful of days ago. I'd say 50km so far. Not a full baby riding situation, just average cruising, still do long hills at 25kph whether 8% or 2%. Gear is not centered, it wobbles not majorly so. It will suffice until Justins 16T cog comes

Take a pic!!!
Why share w/o sharing