Yuba Mundo BBS02/Nuvinci (3400 mile update)

[snowranger]

Fraser,

I have a 20t sprocket on the Nuvinci hub. That gives me 10 - 35t. However, my front chain ring is a single 46t. That gives me a low ratio of 46/35 or 1.31. A mountain bike would give 22/32 or .69 . To get the same gearing you would need to use a 22t chainring up front. I don't think this is possible with the bbs02.

Without power, I find it very hard to pedal up hills. That's one disadvantage of a single chainring.

 

[NFN01]

Fraser,

I have a 20t sprocket on the Nuvinci hub. That gives me 10 - 35t. However, my front chain ring is a single 46t. That gives me a low ratio of 46/35 or 1.31. A mountain bike would give 22/32 or .69 . To get the same gearing you would need to use a 22t chainring up front. I don't think this is possible with the bbs02.

Without power, I find it very hard to pedal up hills. That's one disadvantage of a single chainring.

Hey Snowranger

Your Yuba Mundo is a long tail yes?

Well your chain line is not an issue due to the long distance between crank and rear axle.
In your case with your long chain, you should be able to install a working double chain ring setup.

I have my KMX Vemon recumbent trike running with a 750W BBS02 and a working double chain ring setup 48T/38T driving a nuVinci N360 CVP hub with 18T sprocket, controlled by their Harmony intelligent shift system. (Top speed so far achieved is 36mph. Hill climb capability is 17% (1 in 5) max on the 48T chain ring, I have not tried any steeper climbs using the 38T chain ring yet).

The trick was to get a fat-bike front derailleur direct mount adapter which moves the front derailleur 15mm further out from the seat tube allowing it to reach over to reach over both chain rings. If you measure your BB+motor total BB width you'll find it is as near as damn it 100mm. (Same as a fat bike). Well mine measured about 100mm.
The chain rings are mounted on a 4 bolt 104 BCD adapter with a 3.2mm spacer ring between the adapter and BBS02 drive flange.

The smallest chain that can be fitted to the 104BCD adapter is a 30 tooth.

I hope this gives you food for thought.

 

[snowranger]

Thanks for the info on the double chain ring. Do you have a close up picture of how the chainrings are bolted together?

 

[NFN01]

Thanks for the info on the double chain ring. Do you have a close up picture of how the chainrings are bolted together?

Sent you a pm

 

[snowranger]

Even with the long tail cargo bike, I was getting persistent chain dropping on bumpy roads. I imagine many are dealing with chain ring derailment. It is nerve racking to jam the chain between the motor and chain ring at 30mph through an intersection.

After trying a few things, I used the Origin8 chainguide. It is wide enough for a 100mm bottom bracket, but I still needed to shim the guide out by 1/2 cm. Haven't dropped a chain since.