BBS02 pedaling ability

[Abagrizzli]

I was wondering about how the motor would react, if I attach to it pedalable 32T chainring?

The goal is to achieve the ability to pedal the motor when the battery runs out on one hand, or maybe use the motor as an auxiliary unit, mean pedal it, and turn it on when assistance needed.

Any insights, friends?

 

[toxie]

If you just want the ability to turn off/on the assist, you can do that without any modifications. Just set PAS level 0, or turn off the motor. Then you can pedal with a dead/missing battery.

Maybe I'm not understanding your question though.

 

[Abagrizzli]

The problem is that with 42t chainring it's not really pedalable. With 38t it becomes more realistic, but still very much not optimal. Besides, the only option I found for 38t chainring for this motor is Bistark, and it costs like it was made of gold. My idea is to fit through an adaptor a regular MTB narrow-wide 32t chainring (to prevent chain drop). The questions are:

1. How the motor will handle such a small chainring?
2. Does a lot of pedaling at 0 PAS or with a turned off motor inflicts any damage at all to BBS02?

Now it's more clear.

 

[Abagrizzli]

I summon crossbreak into this thread

 

[toxie]

Ah, yes, that's much clearer

I'll try to answer your questions, perhaps others with more knowledge will also join in. I'm no expert but think I understand this enough to answer.

> 1. How the motor will handle such a small chainring?
It should handle it very well. The controller limits the max RPM so there should be no danger in damaging the motor from having too light a load. I would expect the motor would last longer with a lower gearing.

I assume you are aware already since you mention chain slip in your post, but the adaptor plus chainring will move your chainline outward a bit. If your chainline is already offset this might not be what you want.

> 2. Does a lot of pedaling at 0 PAS or with a turned off motor inflicts any damage at all to BBS02?
No, this should be fine.

 

[Abagrizzli]

Actually, there was no issues with the chainline until now. The chain drops happen because I used a cheap SRAM X9 rear derailleur. It doesn't have any tension, or moreover a clutch. If I go for 10-speed cassette with 13-42 cogs and Shimano's Dynasys clutch, combined with a narrow-wide chainring - I think it should eliminate any chain drop no matter how bad will be the chain line...

 

[tinasdude]

I think if you have a 42 cog, you don't need a 32 chain ring

 

[Abagrizzli]

42t cog will not work well on 8 speed cassette. Besides, with 42t chainring, it gives 1:1 ratio, which is not great for climbs. On steep climbs you need at least 0.8 ration, and I'm talking here about light bike with a fit rider. On heavy bike with a not so fit rider 0.76 is much more preferable. Although it doesn't sound much, but the feel...

 

[Abagrizzli]

Hi,

a smaller gear works very well on a bbs01 od bbs02. The top speed goes down but you get more torque. Our experience is that it works best with a 36 tooth sprocket. Look at this link to see how we mount this. The best is a narrow wide sprocket. Then you will never have any chain drops.

Thank you, I'm still considering the purchase of one of your adapters via eBay. But not until Alcedo Italia will answer me. They have 36T chainring as well, but inclined inside, which is almost as good as the original chainring.

Also, for those who suffer of high wearing of the narrow/wide alloy chainrings, here's what I found - stainless steel 30T chainring by Wolftooth (excellent company, I have their CR and GC on my bike):
http://www.wolftoothcomponents.com/collections/chainrings/products/104-bcd-stainless-steel-chainrings