Hub motor BB drive

When is a hub motor not a hub motor? When it's used to drive a chain ring of course...
Here's one I made earlier:
and there are a few others (much neater) near the bottom of this page: http://endless-sphere.com/forums/viewtopic.php?f=2&t=16535&start=45

Mine uses a cheap MY1018 motor, but has worked very well for the last couple of years. It's a real pleasure zipping up through the gears with it. The drawback is that it sounds a like a very large mosquito, so I want to try using a hub motor instead. I was all set to do this a year or so ago using one of the little nano motors, but then there was a string of reports of reliability problems so I shelved the idea. I'm not up to date with the what's come on the market since then, so I'm hoping you can help me with some recommendations. I'm looking for a small, geared hub motor, with a weight no more than 3.5 kg and nominal power of 250W upwards. The main priorities are reliability and quiet operation. I've read various comments on the merits of steel gears versus nylon and I'm still not decided, but it would be great if the motor was available with both. The Bafang motors seem to get good reviews, but are there any others? I'm looking for a rear motor to take a threaded freewheel and will be running a 36V pack.

Hi Malcolm,

Malcolm said:

When is a hub motor not a hub motor? When it's used to drive a chain ring of course...

I'm looking for a small, geared hub motor, with a weight no more than 3.5 kg and nominal power of 250W upwards. The main priorities are reliability and quiet operation. I've read various comments on the merits of steel gears versus nylon and I'm still not decided, but it would be great if the motor was available with both. The Bafang motors seem to get good reviews, but are there any others? I'm looking for a rear motor to take a threaded freewheel and will be running a 36V pack.

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I'm not sure if its still in production but the SRAM Sparc is very quiet (it uses belts):
http://endless-sphere.com/forums/viewtopic.php?f=28&t=4625&p=78344

SRam Sparc

there are two version:
# the old one with gears (i have)
# and a newer version with belts (quieter)and higher voltage (i think still the same motors)

pictures of my version:
at lot more pictures: http://www.kraeuterbutter.at/Bilder2/SRam Sparc/

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I don't think steel gears are important in the ~ 500w-1kw range.

Will you be modifying the hub or using it as is? If you will be using an unmodified hub reliability might be less important as you can easily swap motors for any standard geared hub motor if there are any problems.

If you can easily configure your build with the hub between the crank and the rear hub there are some advantages to a mid motor configuration, something like this:

Add a FW for the pedals to the hub and you can drive the chain directly with the hub, no reduction required. You can also use multiple chainrings when pedaling for some independent pedal gearing.

the pictures you refered (i have linked some hours ago, in another thread were you saw them)

they show bikes with use the Tongxin motor (= the nano)...
Swin had reliable problems with controller and motor...
the motor is good for 8A continouse, max. 10A for not too long

when used with an 15A controller the motor can overheat and burn...
when used with an 15A controller the "Roller-tranny" can slip under heavy loads

BUT: when used with a controller with limit set to 7-8A you will not see any of this problems
10A for not too long is also ok

ok: for "the ami-style" that sounds like very little power.. (36V * 8A = 288W * motor-eff = 200W-230W)
on the other hand: with such low currents need also only small batteries...
result: when using a light bike as basis you can build a bike including battery with under 15kg weight -> the bike is still a bike, drives still like a bike
electric bikes weighting 25kg and more are - hands down - too heavy to have fun with them driving without motorpower

AND: 200W outputpower -> that is more than the average biker can put out on the pedals continously

for your bike you already have: look here:
http://www.bike-elektro-antrieb.ch/


of course: the tonxin (Nano) is A LOT quieter
and hey: if you need more power you can take for example a Bafang with plastic gears.. not as quieter but for sure quieter than the drive you have in the moment

for the Sparc: its not usable for this kind of usage.. it has a internal 5-gear-hub, but the motor does not power through the gears
the gears are only for the pedaler
the motor drives the can where the spokes are mounted, so fixed gearing
in the motor are 2 550-sized "Mabuchi"-kind-cheap motors...
not realy worth thinking about

Thanks Mitch
The Sparc looks overly complex and fragile for my taste. Yes, I intend to trim the flanges off the motor and shorten the shaft, just to tidy things up. The mid-motor layout looks good, but there's just no room on my bike. I've been reading some more about the Bafang motors and they sound like the best bet right now. I'm tempted to try a sensorless version to eliminate another weak point. I know that e-crazyman has sold these in the past, but are there any other reliable sources? Has anyone got any longer term experience with sensorless Bafang?

Another reasonably light and fairly quiet geared hubmotor is the Fusin, at least the 36V one I have is. Nylon gears; it survived around 800 miles with Dogman before I got it, and it's survived another 103 miles with me so far, on DayGlo Avenger MkII. Most of that has been just commuting to work, hauling my 150 pounds plus the bike's total 55-ish pounds.

But at least 30 miles of it has been hauling groceries/cargo, either with the trailer or just in the pod/rack. Several of those trips were hauling dog food up to three bags at a time (120 pounds plus the trailer's 35-ish), having to accelerate pretty quickly to get across short traffic openings (with pedalling, too). I think the gears are tough enough, so far.

Hi Malcolm,

I don't know if this is a light weight hub motor how quiet they are but this looks like a good deal:
http://endless-sphere.com/forums/viewtopic.php?f=31&t=17029

Puma 500W Motors 160USD plus shipping

I have both the 500W and 350W at 36V Puma (Mac) motors ready to ship. The 500W motor is available for both front and rear wheel installation, but the front can only be used with rim brakes. Rear is disk brake compatible and can accept a 7 speed freewheel with 135mm dropout. The 350W front is disk brake compatible, as is the 350W rear.…

By the way weights are as follows:
rear 500W - 4.3kg
front 350W - 3.7kg.

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I'm told the Fusin has wider gears than the Bafang. Probably the same nylon-ish plastic material, but more beef makes the Fusin a little more abuse-tolerant?

Thanks for the suggestions! The Fusin motor looks good, although there doesn't seem to be much information available, even on Fusin motors' own site. The Puma has a strong reputation but is too heavy for my needs. I'm not too concerned about sticking to the 200W limit here, but I do want to keep the weight down. I've been reading through the long thread on Cute motors and they look very promising, with a good range, low weight and compact dimensions. People seem to be having to wait a long time for Cute motors from ecitypower, so I'll PM Lynchy and see if he has any available, as he was talking about exporting to the UK. I'd like to use a 24V motor for a 28" wheel, and run it on 36V for the extra power.

One thing I'm not sure about now is whether to go for a front motor or rear motor. I know these motors have freewheels built in, but how easily do they freewheel? I often pedal without the motor, so it has to offer minimal resistance. I'd prefer to use a front motor if possible, as it would save a little weight and space, as well as the cost of an additional freewheel, but if it means noticeable resistance when pedalling unassisted I'd rather use a rear motor and add a screw-on freewheel.

I can't find any definitive answer on whether sensorless will work well in this application. It seems to depend a lot on the specific motor/controller combination, so the best bet for now appears to be to go sensored and wait for a good sensorless controller to turn up, probably the day after I place an order

Malcolm said:

Thanks for the suggestions! The Fusin motor looks good, although there doesn't seem to be much information available, even on Fusin motors' own site.

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Ask Louispower here on ES; he's from Fusin and responds fairly quickly. Only thing I've asked about so far was getting the non-freewheeling gearset to use regen on mine (turns out it is available relatively cheaply but I have yet to have spare money for it; too many other more important things first).

I'm not too concerned about sticking to the 200W limit here,

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If you use a CA you can limit current that way and thus limit max power too.

One thing I'm not sure about now is whether to go for a front motor or rear motor. I know these motors have freewheels built in, but how easily do they freewheel? I often pedal without the motor, so it has to offer minimal resistance. I'd prefer to use a front motor if possible, as it would save a little weight and space, as well as the cost of an additional freewheel, but if it means noticeable resistance when pedalling unassisted I'd rather use a rear motor and add a screw-on freewheel.

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The fusin has no resistance in freewheeling. Due to it's much better bearings than my regular front wheel had, it actually spins *easier* than my plain old wheel. Plus their freewheel is silent--no clicking! Just make sure that if you get one you ask for the freewheeling version vs the regen version (which doesn't freewheel).

I can't find any definitive answer on whether sensorless will work well in this application. It seems to depend a lot on the specific motor/controller combination, so the best bet for now appears to be to go sensored and wait for a good sensorless controller to turn up, probably the day after I place an order

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Biggest problem with any sensorless application is that they generally don't start up fast enough with a load on them. They work great in prop-driven RC planes/helis because relative to motor power, they have very little load even from a complete stop, so they start spinning fast enough for Back EMF detection to work as position detection very quickly. In our application they have to overcome what is probably hundreds or even thousands of times the inertia that they would have in their original application, so they can't get to speed fast enough for BEMF to build up to a level that can be reliably used as position detection, confusing the controller. Keeping it moving they do very well, but *getting* it moving is harder.

Thanks again Amberwolf, that helps me a lot, especially the stuff about sensorless control. It sounds as if sensorless could actually work better in this application. The motor will have greater freedom to move on start up, since it has some additional slack to take up in the drive chain before it actually starts driving the wheel. It's worth a try.

I'll take another look at the Fusin motor as well.

Malcolm

Also, since the Fusin is already sensored, you can use it with a regular controller until you find a sensorless controller you like better.

I see you are using almost the same motor in a similar fashion as my build (link in signature).

I too dislike the noise the most. It's fine when I'm in heavy traffic and it's windy, too loud out to hear it. But most of the time on quiet side streets, and fresh batteries, it does whine a lot.

My solution is to build a reduction unit for this basic scooter motor. Allelectronics.com has a bunch to choose from.

Have you had any problems with the chains being too close and jamming? I got a wider BB from Sickbikeparts to solve that.

It took a while to get the alignment right and I did fit a wider BB. I only use one front chain ring for drive to the wheels, which makes things simpler. A 9-speed cassette is ample for my needs, especially with motor assist. The front derailleur is just there as a chain guide and for added security. The only problem I had was that the motor chain kept coming off, but that was easily fixed by raising the motor. Since then it's been trouble-free

I've found a European supplier of the "Cute" motors and will be ordering one shortly to try out: http://www.e-bicycles.eu/en/user_order_comp.php

Malcolm said:

I've found a European supplier of the "Cute" motors and will be ordering one shortly to try out: http://www.e-bicycles.eu/en/user_order_comp.php

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Any news on the Cute? Post some pics on the install when you get a chance.

Thanks.

Yes, we want some cute pics

Sorry, no cute pics yet but I promise to post them as soon as I have something to show.

It only took a year or so, which is quick work for me, but I finally have a few photos of my bottom bracket drive. I ended up getting a Cute 128 motor with Ananda controller from cell_man. These were old samples that Paul had. The motor looks very similar to a Bafang 350W and the controller is marked 36V/17A, though it's rated at 25A on the Ananda website. I really like the controller as it's fully potted, so there's no worry about getting it wet.

I've been trying to build a mounting system that is adaptable to as many bikes as possible and fairly easy to fabricate in a home workshop. This is the first version that's robust enough to handle the modest 700 or so watts that I'm putting through it. It should be able to handle a lot more when I add some gussets to stiffen the motor mount. The mount section around the bottom bracket is made from 2mm stainless, and the motor support is made from 3mm stainless. These could just as well be made from mild steel, CroMo, aluminium or even carbon fibre depending on your skills and tools available, though the material thickness would obviously have to be adjusted.

This is so much quieter than original MY1018 motor I used. There's a gentle growl from the motor under heavy load, but otherwise it's barely noticeable above the ticking of the White Bros freewheel. The motor freewheels very well without any noticeable resistance to pedalling. Improvements I'd like to make include removing the excess metal from the motor case (since it no longer has to support a wheel) and moving the motor further back so it's less obtrusive. All suggestions are welcome

how is the speed and climbing ability? 700 watts through the gears is really not bad for power from my experience, but how much do you think the little motor will take??

700W is just an estimated peak based on controller rating and voltage, as I don't have a watt meter. It's currently geared for comfortable pedalling up to around 28 mph. I've not really tested the hillclimbing ability yet but it's not balked at any of the relatively modest hills I've tried so far and has never got more than lukewarm. I'll try to do a proper hill test soon. The present power level is ample for me, but it would be fun to push it a bit just to see how the mounting holds up. I have a 6-fet controller from Lyen that I'm planning to try out at 50V, so we'll see...

Ok I would be interested to see how it takes the 50v as I run 44.4v nominal or basically 50v hot off the charger.

Malcolm said:

I finally have a few photos of my bottom bracket drive.

I've been trying to build a mounting system that is adaptable to as many bikes as possible and fairly easy to fabricate in a home workshop. This is the first version that's robust enough to handle the modest 700 or so watts that I'm putting through it. It should be able to handle a lot more when I add some gussets to stiffen the motor mount. The mount section around the bottom bracket is made from 2mm stainless, and the motor support is made from 3mm stainless. These could just as well be made from mild steel, CroMo, aluminium or even carbon fibre depending on your skills and tools available, though the material thickness would obviously have to be adjusted.

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Very nice mounting set-up. Motor size seems like a good fit. Let us know how the 50v works.

Any updates? Maybe a video? Please

No updates, sorry, I've been busy with another project. The drive is proving very reliable so far. What would you like to see in a video?

Ok, great that it holds up!

How is the hill climbing ability?

A video of acceleration and sound would be very nice

Nice work Malcolm.
The use as a BB drive with the extra gearing should be less stessful on the Bafang nylon gears than when they are over powered as a hub motor drive.