My version of BBSHD Torque Arm (2018.08) CAD file added 2022.08

After standard installation of BBSHD to my bike 2018.06 or so (from Youtube method) and running it about 300km+ during the past few months, the BBSHD came loose and dropped down to its lowest position most know about. There must be a way to solve that ... then I remove the two lock nuts at the BB, to find ...

Pic1 damaged soft aluminum BB

View attachment 8


My soft aluminum BB (68-mm) was eaten up quite a bit into pieces by the notches of the triangle bracket aimed to hold BBSHD motor in place by friction ...

Pic2 : triangle bracket with notches




Now, I don't think a normal friction tightening, even with thread locker solution, will do the job. Since the motor is quite powerful and the way it operates, keep breaking the mount loose all the time even I didn't ride that hard. So after searching internet for a while, I was inspired by some of the correction method to fix this - don't remember which one but similar to what I decided to do...


Pic 3 : torque arm + dwg + installation




Here is how I do my work, unless it is unavoidable, this torque arm is aimed to be an add-on retrofitting mount to BBSHD installation without modifying any part of the BBSHD itself. If do not like it later, it can be removed without any effect to the original system.

After drafting a solidwork 3d file, I had the model printed on paper and cut to size to try fitting with the BBSHD, adjusted here and there, until looked OK. Then I had some leftover SUS304 laser cut to size, thinkness=5mm, a bit too thick but only that was available at that time. They charged me $10.- each to cut including material - not bad. I then bent it with shop vise and hammer manually to fit the shape of the chainstay. See picture, notice the curve of this arm that nicely fit with the frame. That's how one should do it. Sanded sharp laser-cut edges out, 'cos we will live with it for a long time. Then, with the help of 2 SUS hose clamps + some scrap inner tube to prevent scratches, installation was completed fairly easy. Though not so pretty like factory built but purpose served, rather permanently.

Pic 4 torque arm in place with BBSHD










Been running it for another 500+km without any issue so far. It is pretty sturdy. The BBSHD becomes the same rigid part of the bike, even when I stand on the motor.

The particular shape and dimensions of this torque arm fits my bike, MTB Bianchi Kuma 27.1 and it's 27.5 hardtail. Should anyone wanna try this, some modifications might be needed to fit ones bikes. I think 3-mm thick SUS should be OK for BBSHD because of the rigid geometry of the arm. This piece will last the lifetime of the bike and BBSHD, whichever come first, later or even combined. :lol:


Pic 5 : final assy

I hold no responsibility for anyone who wanna try this. Use at your own risks. Just another idea I think useful to the similar interests. Hope this might help some new installers encountering the same problem.

I still am learning to use this forum, any error happens please excuse my fault.

************************ 2022.08 ****************************

A user in this forum pmd me asking for CAD file. Here it is....(should be old SW2012 format)
Still using it until today (23,xxx km). Super strong.
You can use it at your own risk. I only provide info here for academic purposes.

Very nice solution to your problem.

Just a few comments for others doing an initial installation or having movement issues with their BBSxx:

LUNA sells a very similar torque arm that they designed to solve the same problem. It's made from stainless steel. I used one on my tadpole trike because I wanted to keep the BBS02 under the boom.

Since the rotational torque applied by the motor tries to turn the unit clockwise you can often position the unit such that it is against the down tube (or other frame member) so it can not turn and you will avoid the damage shown above, even without a torque arm. The problem in the installation above is that there are brake and/or shift cables running through the area where the Bafang would contact the down tube. Sometimes it is possible to position a spacer, such as a hard rubber strip with adhesive, between the cables to provide a "resting" spot for the Bafang and a stand off to protect the cables.

Rassy said:

Very nice solution to your problem.

Just a few comments for others doing an initial installation or having movement issues with their BBSxx:

LUNA sells a very similar torque arm that they designed to solve the same problem. It's made from stainless steel. I used one on my tadpole trike because I wanted to keep the BBS02 under the boom.

Since the rotational torque applied by the motor tries to turn the unit clockwise you can often position the unit such that it is against the down tube (or other frame member) so it can not turn and you will avoid the damage shown above, even without a torque arm. The problem in the installation above is that there are brake and/or shift cables running through the area where the Bafang would contact the down tube. Sometimes it is possible to position a spacer, such as a hard rubber strip with adhesive, between the cables to provide a "resting" spot for the Bafang and a stand off to protect the cables.

Click to expand...

Thank you Rassy. It is exactly as you explained. You have made it clear. And yes, I did put a 1/4-in thick rubber spacer (cut from old slipper :lol: ) between the motor and downtube exactly like you said to solve that crushed cable problem. It is circled in red in the picture...

Pic 1 :




I don't even know that Luna has this torque arm, but even if I did, buying from them and the shipping cost will be prohibitive. Couple of months ago, I ordered a tube of MobilGrease28 to lube my new BBSHD from a store in the US, the tube cost less than US$20.- but the shipping is around US$60.- :? So I better do the things I can locally - cheaper, faster, better (for me).

This e-bike thing is such a rare hobby in this area, people've heard of it but hardly in touch with one - not to mention serious "mid-drive / hub-drive, etc" things. Not counting those front hub with 200-300 watts ones for buying family groceries and running errands nearby, that have been around for a while and most people have a perception about ebikes that way. When I talk to people about this BBSHD ebike conversion with old laptop lithium batteries I made, most are surprise but quite interested with reluctant that it can really be used for daily commuting. Told them that I rode 70-km one day and still have some juice left in the 14s7p crappy batt pack of mine (sometime with 0.7V+ sagging and Luna charger finished charging with some rows still at 3.8V ) I know that I can have 50+km with moderate peddling from this ancient 18650 cells.

So when I have problems with my ebike, there is hardly anyone around to ask. Bike mechanics are scared when I mentioned ebikes !! ES is a good place I have learned a lot since I came across the forum after starting the BBSHD project. It is a place that I found people with similar interests like mine, have fun playing around trying to hack things with positive attitude. Intend to stay here a long while though :wink:

Thanks a lot to everyone sharing, contributing, researching, answering, asking or simply reading.

All the best.

In future if you're looking for MobilGrease28, check your local aviation supply. I found it at the nearest general aviation airport.

dustNbone said:

In future if you're looking for MobilGrease28, check your local aviation supply. I found it at the nearest general aviation airport.

Click to expand...

Thanks you for your advice dustNbone. The 14-oz tube I bought will last me another while but heard, after 800+km of riding, that BBSHD (especially that nylon gear) loves to bathe in fresh red grease more often than I expect. Some say every 700-800km ? That's too often, I expect several thousand (4,000-5,000 +) kms. C'mon it's a bike load with 1 passenger - not the whole airplane. Some advise, please.

However, it is kind of hard. The only MobilGrease28 I can find local is in bulk 20-kg pail cost around US$600.- from supplier who sell to airlines for their maintenance tech. I cannot find it in 14-oz tube digging everywhere locally. I live in the area where Gucci, Versace, Hermes, Patek Philippe, Lamborghini and all "that" can be found easier than MobilGrease28 in 14-oz tube. Trying not to be (too) sarcastic :lol:

Torque arms were developed by Doug Snyder California eBike and copied without attribution by others.