Help! Bottom bracket nut loosening on Tongsheng TSDZ2

[Swizz]

I strongly suspect the poor design of the anti rotation/torque reaction mount is the root cause of the M33 nut coming loose.

One bicycle frame is different to another and coming up with a one fits all solution is a quite the task. I wouldn't be happy with having to tighten the M33 regularly at all. Better trying to solve the root cause x

 

[peter.c]

The problem is the tsdz2 bracket is flat and unless you put a few cuts or scores on the frame side it is just an odd flat washer slipping on a painted frame .The bafang has embossed dimples and grips or bites into the frame if tightened sufficiently
The tsdz2 with its multi point fix should be the better design if the rear mount is tight and fitted onto the chain stays it just does not work in practice , one rivnut has got to be better than the motor twisting /flexing under load all the time

 

[Swizz]

The problem is the tsdz2 bracket is flat and unless you put a few cuts or scores on the frame side it is just an odd flat washer slipping on a painted frame .The bafang has embossed dimples and grips or bites into the frame if tightened sufficiently
The tsdz2 with its multi point fix should be the better design if the rear mount is tight and fitted onto the chain stays it just does not work in practice , one rivnut has got to be better than the motor twisting /flexing under load all the time

Peter, it's the rear mount I am referring to. That is the one that done properly can take all the rotational stress away from the M33 nut as it is furthest away from the centre of rotation, providing of course it is a rigid frame with chainstays.

 

[peter.c]

Have to agree the rear mount and 2 pieces of flat bar do solve the problem but surprised how thick it needed to be before it stopped the flex and how awkward is was to get both side flat and in full contact
Seen a few conversions with it not fitted or just hanging

 

[Gavin]

Have to agree the rear mount and 2 pieces of flat bar do solve the problem but surprised how thick it needed to be before it stopped the flex and how awkward is was to get both side flat and in full contact
Seen a few conversions with it not fitted or just hanging

I welded a tab to the underside of my chainstay and used an 8mm rose-jointed tie rod to bolt the motor torque-reaction lug to it. The tie rod works in tension to resist the motor's torque reaction.

This means the M33 nut is only there to resist lateral and twisting forces. The sodding thing still vibrates undone though!

 

[MontyPAS]

I welded a tab to the underside of my chainstay and used an 8mm rose-jointed tie rod to bolt the motor torque-reaction lug to it. The tie rod works in tension to resist the motor's torque reaction.

This means the M33 nut is only there to resist lateral and twisting forces. The sodding thing still vibrates undone though!

Every bike is different, you just have to find what works for your scenario and engineering skills!
Been running mine like this for the last 200 miles or so without any loosening issues.
Mounted homemade AR bracket in front of TS, and dumped the the Chinese cheese metal bolt / clamp

 

[Swizz]

Every bike is different, you just have to find what works for your scenario and engineering skills!
Been running mine like this for the last 200 miles or so without any loosening issues.
Mounted homemade AR bracket in front of TS, and dumped the the Chinese cheese metal bolt / clamp

Must admit that does look really tidy too

 

[u1v1w1]

BBS style locknut comes in 7.5mm thickness, which means that there will be not enough room for two. Will have to resort to nord lock washer which is 5.8mm in thickness according to data sheet. This will make the locknut flush with the outer part of the axle hausing while not leaving any exposed threads (reduced possibility of damage and contamination).

Looks like using nord lock washers for this application might be unsuitable due to lack of information about the performance in relatively low tightening torque applications and due to prolonged un-tightening time caused by stretching of the bolt according to video found below.

Choice between Loctite or double nut method might be the best "common sense" solution in this case.

 

[u1v1w1]

Turns out Bafang type M33 nut internal diameter is 31.94mm. The original one is 32.24mm.

 

[MontyPAS]

Turns out Bafang type M33 nut internal diameter is 31.94mm. The original one is 32.24mm.

0.3mm or 12 thousands of an inch in old money.
The width of maybe 3 human hairs. Not worth worrying about?

 

[u1v1w1]

0.3mm or 12 thousands of an inch in old money.
The width of maybe 3 human hairs. Not worth worrying about?

Well, I'm unable to screw it on.

 

[peter.c]

Just tried the nut goes on the reverse way so the thread is the same . a bafang lock nut wil go on if you file the back off just leave the thread but it would end up very thin [ not worth all the aggro]
Changed both main nut and lock nut from a new bafang build. Fits ok on a tsdz2 fat bike motor with the longer shaft

 

[u1v1w1]

0.3mm or 12 thousands of an inch in old money.
The width of maybe 3 human hairs. Not worth worrying about?

In TSDZ2 installation video it says that the nut is actually M33.5 mm, not 33mm.
Anyone tried to use spacer between the chainstay clamping plates to prevent them from bending. The spacer should be slightly longer in length than a chainstay thickness (also prevents rubber pads from collapsing).

 

[MontyPAS]

In TSDZ2 installation video it says that the nut is actually M33.5 mm, not 33mm.
Anyone tried to use spacer between the chainstay clamping plates prevent them from bending. The spacer should be slightly longer in length than a chains tail thickness (also prevents the collapsing of rubber pads).

M33.5 must be a Chinese version