BBS motor with Gates belt...

[Brik]

...has any one done this?
I'm hankering after some shiny new metal as a bit of a treat for my upcoming birthday and have spotted a new belt drive bike with hub gears, It looks like the bike uses a concentric bottom bracket to tension the belt and I'm wondering if it would be possible to at least get a Bafang mid drive in and the belt tight?
Obviously I would then need to sort out a way of mounting a Gates pulley to a Bafang spindle, and sort out the drive line.

 

[matthewslack]

No, but...

If you search images of eccentric bottom brackets there are various types, some of which accept a standard bottom bracket. If your target bike is like that, then there is a chance, however slim!

Remember that BBS01 relies on clamping force onto the BB to hold it in place. That might be the obstacle.

A bespoke eccentric insert might be a technical answer, but I think there is a high chance that it is not worth the bother.

A belt bike that uses a different method of tensioning is probably a better bet.

 

[Bikes4two]

If you look at the pic below with the RED arrow, this shows the gap between the Bafang motor body and the 'bottom bracket' axle - this dimension will be the limiting factor and it is very unlikely to be enough to allow fitting into an eccentric bottom bracket (EBB, 2nd pic). The TSDZ2's construction is similar to the BBSxx in this respect as well.

There may of course be other mid drive kit motors that could work which I'd be very interested to know about as I'd like one for my IGH fitted tandem.

As you can see from the EBB below, with the 'axle hole' in anything other than the very lowest point of adjustment, the distance to allow fitting of the motor increases, to say nothing of the EBB securing arrangement (two screws in the pic) getting in the way of the motor too.

 

[Raboa]

You could use the Veer belt system this is designed for horizontal dropouts. If you are mechanical minded you use probably adapt a chain tensioner to keep the belt in tension. The advantage of their system is it will work with standard frames

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Here's one from AliExpress I have not looked into how this one works.

Page Not Found - Aliexpress.com

 

[saneagle]

Here's one from AliExpress I have not looked into how this one works.

Page Not Found - Aliexpress.com

That one can't work with a standard frame. You'd have to cut a gap in the seatstay to get the belt on, then find some sort of clamping joiner to hold the two parts together again. If you look closely at their photo, you can see such an arrangement on the OEM installation.

The only way to get a belt on a standard frame would be either to cut a gap in it or use a belt that has a join in it, though I don't think I'd trust a joining belt.

Here's one way to do it, but don't forget that you need a perfectly straight chainline for a belt.

 

[Brik]

Thanks for the replies, I've had a think and have decided to fit a 3 speed Sturmy Archer hub to my existing bike instead, see if that can quell the desire I have for New Stuff.
I purchased a new hub already built into a 700c wheel a few months ago but when I came to fit it I realised the axle was too short for my bikes 135 m.m. drop outs, I see you can get longer axles so will strip down the Sturmy hub and fit one.

...the bike uses a concentric bottom bracket..

Eccentric, much like myself.

 

[guerney]

BBS motor

3 speed Sturmy Archer hub

Which BBS motor? Could be wrong, but I fear a Bafang HD would munch through a 3 speed Sturmy Archer hub. Perhaps a 36V BBS01B could too at 20A=720W?

 

[Brik]

Which BBS motor? Could be wrong, but I fear a Bafang HD would munch through a 3 speed Sturmy Archer hub. Perhaps a 36V BBS01B could too at 20A=720W?

I don't have a HD but the one I do have has a function whereby you can limit the amount of power being delivered so hopefully t'will be fine.

 

[Deleted member 16246]

Thanks for the replies, I've had a think and have decided to fit a 3 speed Sturmy Archer hub to my existing bike instead, see if that can quell the desire I have for New Stuff.
I purchased a new hub already built into a 700c wheel a few months ago but when I came to fit it I realised the axle was too short for my bikes 135 m.m. drop outs, I see you can get longer axles so will strip down the Sturmy hub and fit one.


Eccentric, much like myself.

I'd be interested to find out how the SA hub would stand up to the power of a 250 watt crank motor. I had one on a counterfeit Brompton I had about 15 years ago. I rode that set up 4000 miles before I retired it, but it only had to deal with my own power output, and being a 16 inch wheel, I imagine the torque force on the hub gears were lower than a large wheel. I mean by that that the wheel would move through a number of degrees of rotation with lower force than a bigger one. I like those hubs. I had mine apart every now and then to re-grease it, and then fitted it with an oiling nipple and added a few drops now and then. I'd say that old hub has loads of life left in it, but it is lying at the back of the garage now.

 

[Brik]

I'd be interested to find out how the SA hub would stand up to the power of a 250 watt crank motor.

I'm just back from an initial test ride after fitting the 3 speed and all seems good so far, there was a bit of a noise which I've just identified as the link in the single speed chain passing through the tensioner, but other than that I'm happy with the conversion from 7 speed derailleur.

 

[Brik]

A few pictures.

 

[guerney]

Because I don't trust waterproof claims made about anything, I covered the speed sensor connector with self-amalgamating rubber tape. Also the other connectors, some with 4:1 self-adhesive marine heatshrink in addition. My speed sensor has survived complete submersion for 13 seconds, as well as a lot of heavy rain.

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There have been Bafang speed sensor problems reported on the forum, caused by water ingress over the past couple of years.

 

[Brik]

I'd be interested to find out how the SA hub would stand up to the power of a 250 watt crank motor.

So, after about 4 or 5 weeks and a little over 200 miles all is still good with the 3 speed conversion, I ended up using the original narrow axle as fitted to the Sturmy 3 speed and just adjusted the o.l.d. to about 130 mm using spacers between the lock nuts, the axle thread had a good few turns sticking through the frame so I was able to use finger pressure to tighten the wheel nuts to allow the ali frame to 'spring' together the few mm needed each side. I was advised on another forum that this isn't a good idea and have been listening for strange creaks and looking for cracks to start, nothing untoward yet.
I can say definitely that a 3 speed SA hub should easily be able to handle a 250w Bafang middrive for at least around a 1000 miles or three to four months, I'll let you know if (or maybe when) mine fails.

One problem I do have though is that I may have acted a little prematurely in fitting the 3 speed, it did satisfy my craving for new stuff but that now seems to have worn off.
I ordered a new bike the other day...

 

[Brik]

...here is a picture.


Why am I fixing a puncture on a brand new, just out the box, bike?
Also no clamp to hold in the seat post included either.

 

[guerney]

I can say definitely that a 3 speed SA hub should easily be able to handle a 250w Bafang middrive for at least around a 1000 miles or three to four months, I'll let you know if (or maybe when) mine fails.

I'd be very interested to read about how you get on - have you programmed the firmware, and if so, could you say what your controller's current limit is and what changes you have made? Is your 250W Bafang mid-drive 36V or 48V?

 

[Brik]

... have you programmed the firmware...

No.

 

[Brik]

I'd be interested to find out how the SA hub would stand up to the abuse of a powerful crank motor.

I'd be very interested to read about how you get on...

Six months and 1100 miles and the Sturmy 3 speed is still performing perfectly.
I can also say that single speed chains are a lot more durable than 7 speed.

 

[guerney]

Which BBS motor?

I don't have a HD but the one I do have has a function whereby you can limit the amount of power being delivered so hopefully t'will be fine.

Six months and 1100 miles and the Sturmy 3 speed is still performing perfectly.
I can also say that single speed chains are a lot more durable than 7 speed.

Thanks for the update. So far so good! What's the chain wear measurement at this point? I've often wondered if I can get away uphill with a legal 720W BBS01B converted 16" or 20" wheeled fixie, and if it would still provide adequate speed over flat roads. An SA hub does appeal, but it would be useful to know what power your motor is using, and which specific motor. You've said your BBSXX(X) isn't a BBSHD, but could you say which one you do have, and what are it's firmware settings? Are you adjusting pedal assist levels via the display only, using stock firmware settings? Whatever those are on whichever BBSXX(X) motor you're using.