Could some kindly take some measurements of a tongsheng and bafang mid drive?

[matthewslack]

This arrived today:
View attachment 45834

This is how it looks:
View attachment 45835

View attachment 45836

It would need about 6mm of spacer on the chain side, which means not enough thread on the clamp nut side. I could shave 5mm off the bottom bracket face to improve that.

I think the options are:

A. Shave a mm or two off the chainstay and a mm off the motor casing and a few mm off the bottom bracket opposite face.

B. Cut 5mm off the chainstay and weld a reenforcement on the back of it.

C. Bafang HD 1000w

I’m going to investigate what the chainline would be with A. Can you get an offset/dished chain ring for the tongsheng? 40 teeth or less.

The cardboard model from Matthews measurements was pretty accurate.

I think you are so close that A is worth a go. The nut plus the support bracket on the non-drive side is exactly 10mm total thickness, with no added washers. It looks like you might have 4 already. There is almost enough BB that end, especially if you eat into the weld a little. The drive side can spare a bit, but being aluminium, don't go too far, and keep finished surfaces smooth to reduce likelihood of fatigue cracking.

 

[mr_ed]

btw if anyone reads this thread and would find the broken tongsheng casing useful for a similar purpose get in touch and I'm sure we can sort something out.