BBS01 with 30 teeth

[Keldin]

I'm looking at converting a bike with using BBS01 or similar crank drive but the problem is the bike has a Sturmey Archer 8 speed hub gear which necessitates a front sprocket that is only 30 teeth.
Is there any way to accomplish this with the BBS01 or is there a crank drive kit out there with this option?
Thanks

 

[flecc]

The Sturmey Archer 8 speed having the first gear as direct drive is a real problem with crank units.

One company announced a spider for this hub gear on which chainrings could be fitted, enabling a much larger rear sprocket to solve the problem. It was announced in either A to B magazine or VeloVision, but I can't find a link to it.

Maybe Sturmey Archer will know of it, here's their contact page link
.

 

[Keldin]

Unfortunately the bike is limited to hub gears and the sturmey is the only make that will fit :-(
If I had known then what I know now I would have done it differently. I could do a front wheel conversion but the crank motors seem so much neater.
I've sent Sturmey (well Sunrace) a query.
Thanks

 

[mechaniker]

I don´t know the sturmey so well but with a adapter you can fit 32teeth to the bbs-motor
with 104mm. Is it not good enough for your hub-gear? from my feeling it should work
the cheapest adapter I found in australia:

http://ballaratebikes.com/collections/all

need some fine finish because it is just laser cutted but for only 12 GBP it is a good quality I would say

regards
frank

 

[mfj197]

I think Frank knows that, and he has suggested a 32t chainring via an adaptor (close to the 30t one the OP requested). Is it close enough?

 

[flecc]

I think Frank knows that, and he has suggested a 32t chainring via an adaptor (close to the 30t one the OP requested). Is it close enough?

Thanks mfj197, I misunderstood the post. I'll delete my post.
.

 

[mechaniker]

Hi flecc,
sorry for my poor english and yes mfj197 is right, thats what I meant

Another idea I describe with a photo, how about that solution by using one part of the bbs adapter to fix a 30tooth sprocket in the front? then it would be exactly the requested sproket

 

[flecc]

Your 32 tooth one might be ok Frank, the top gear with a 26" wheel would be 105 inches, with a 700c wheel 110 inches, a little on the high side.

With the adapted 30 tooth one, 99 inches and 103 inches respectively.

Top gear ratio in that hub is x 3.05.
.

 

[mechaniker]

I took a look on the original 46t Bafang sprocket and it is five arm, so it would not be necassary to buy the adapter you can cut the original sprocket and drill five whole´s into the rest and then you can fix the shimano 30t five arm sprocket to the original rest.
I think this is good, cheap, easy to build and exactly what you need

regards
frank

 

[mfj197]

I have a feeling that the issue with small front chainrings on the BBS01 is that they push the chainline even further out. The provided chainring curves in over the power transmission gear, but small chainrings can't do that.

Michael

 

[mechaniker]

I´m not sure that I understood what you mean
but the 30t sprocket I mentioned is a sprocket from the shimano ultegra front chaindrive so it should work. the chainline is a different issue but even there I guess it´ll work because it´s a long way to the rear dropout

 

[Keldin]

The 30 tooth ultegra could be a possibility. The rear 25 tooth on the hub is the largest that Sturmey do but I believe the standard one is dished (and may be reversible) and there is a flat option. This may alleviate the chain alignment problems. I suppose without actually trying it out we'll never know. I was looking at getting one to take over to the US for a temporary conversion for a bike at burning man so may be worth getting it and seeing if it works.
Thanks this all helps.