TSDZ2B motor eventually speeds up to maximum while loosing tractive power

[hotsquirrel]

My Tongsheng 500W 48V is mounted on a trekking bike with Rohloff 14 gear. No OSF installed, but heat management from ebikestuff.eu is mounted inclusive thermal sensor LM35. I am running the motor at 8 Amperes max. and speed limit at 25km/h. A second bearing on the left side of the crank is also installed. Actually I run this setup for about 4 months and 1.600km.

Since 1.500km the problems began: Especially, when I cross some bumps in the street, suddenly there is a compete loss of traction power while the motor speeds up to its idle speed. This failure is not associated with my power of pedaling and cannot provoked by increased force.

I have found two ways as a work around until I will get rid of the real cause for the failure:

1.) I can stop pedaling for a very short time. Immediately the motor will return to an adequate rotation speed and the traction force will be back again.

2.) I have installed a small push button at my handle bar, by which I can stop the motor in cases, when I have forgotten to downshift in time and cannot do it under heavy load. If the failure occurs, I simply need to use this button for a very short stop of the motor and immediately the TSDZ2 will return to ist normal function.

There is no special noise from the gear or other mechanical components, when this failure occurs. I did compare my observations with some YouTube video, where they are reporting about a failure in the sprag clutch. But they all report about a noise as if the chain would jump over the chain wheel, similar to a chain suck. I do not have such a noise.

I would be happy, if someone here could give me a hint, how or where to find the cause for this failure!

 

[endlessolli]

There are 2 sprag clutches: One to engage the pedals (the big one integrated into the main gear) and anotherone inside the small blue gear (which engages the motor). The one failing in your setup is likely the one in the blue gear. When these fail, there is no special sound other than from the motor running at high rpms.
The blue gesr (with clutch) is around 20$ and very easy to exchange. Good luck!

 

[hotsquirrel]

Oh, I was not aware, that there are two sprag clutches in the drive!
It is strange, because I have a TSDZ2B version, which doesn't have a blue gear. The blue gears seem to not very reliable but I thought, the white ones would be.
Is it realistic, that my white gear sprag clutch did last 1.500km only?

 

[Zambam]

My Tongsheng 500W 48V is mounted on a trekking bike with Rohloff 14 gear. No OSF installed, but heat management from ebikestuff.eu is mounted inclusive thermal sensor LM35. I am running the motor at 8 Amperes max. and speed limit at 25km/h. A second bearing on the left side of the crank is also installed. Actually I run this setup for about 4 months and 1.600km.

Since 1.500km the problems began: Especially, when I cross some bumps in the street, suddenly there is a compete loss of traction power while the motor speeds up to its idle speed. This failure is not associated with my power of pedaling and cannot provoked by increased force.

I have found two ways as a work around until I will get rid of the real cause for the failure:

1.) I can stop pedaling for a very short time. Immediately the motor will return to an adequate rotation speed and the traction force will be back again.

2.) I have installed a small push button at my handle bar, by which I can stop the motor in cases, when I have forgotten to downshift in time and cannot do it under heavy load. If the failure occurs, I simply need to use this button for a very short stop of the motor and immediately the TSDZ2 will return to ist normal function.

There is no special noise from the gear or other mechanical components, when this failure occurs. I did compare my observations with some YouTube video, where they are reporting about a failure in the sprag clutch. But they all report about a noise as if the chain would jump over the chain wheel, similar to a chain suck. I do not have such a noise.

I would be happy, if someone here could give me a hint, how or where to find the cause for this failure!

"Since 1.500km the problems began: Especially, when I cross some bumps in the street, suddenly there is a compete loss of traction power while the motor speeds up to its idle speed."

By "traction power", do you mean motor assist?

I don't understand how "the motor speeds up to its idle speed"? Shouldn't Idle speed be zero when there is no assist (i.e. motor not turning)?

Are there steep hills where you are? Do you start on low gear at the start of a climb on your Rohloff? You set limit to the motor to 8 A and 25 km/h which is conservative. Is the cooling kit needed? What does the motor temp feel like after a typical ride?

 

[hotsquirrel]

By "traction power", do you mean motor assist?

Yes.
When the problem happens and the motor speeds up to idle speed (4000 rpm), there is no motor assistance and it seems, that the motor is not mechanical coupled to the gear any more.
It is already recognized, that the sprag clutch, which is combined with the white gearwheel, eventually will fail and then the effect, I have described, will happen.
Because of this fact, further discussion is not needed.

 

[endlessolli]

Oh, I was not aware, that there are two sprag clutches in the drive!
It is strange, because I have a TSDZ2B version, which doesn't have a blue gear. The blue gears seem to not very reliable but I thought, the white ones would be.
Is it realistic, that my white gear sprag clutch did last 1.500km only?

Sorry; I was thinking the non b Version. In the b version, there is no sprag clutch in the WHITE gear, so that can not be the culprit. Instead, there are 2 sprag clutches (concentric) in the massive main gear. I would guess one of them is failing.

 

[Zambam]

Yes.
When the problem happens and the motor speeds up to idle speed (4000 rpm), there is no motor assistance and it seems, that the motor is not mechanical coupled to the gear any more.
It is already recognized, that the sprag clutch, which is combined with the white gearwheel, eventually will fail and then the effect, I have described, will happen.
Because of this fact, further discussion is not needed.

Idle speed 4,000 rpm? Isn't 4,000 the maximum rpm of the motor? Does your display have a reading for motor rpm?

Whatever the problem, I think you should try replacing the sprag clutch and see if that fixes the problem.

 

[hotsquirrel]

4,000 rpm is the nominal idle value, which shows up on the label of the device.

Concerning the clutches: Yes I am wrong: There is no sprag clutch connected with the white gear. But it was unknown for me, that there are two sprag clutches in the big main gear.
There is a YouTube-Video from Tongsheng, showing how to replace the clutch:

I suppose that most people cannot do the replacement without the special tool, which is shown in the video. In the video, it looks like they replace only one of the clutches.

I could run in another problem, concerning guarantee services: When I send the TSDZ2B to service, they may refuse servicing, because I already had optimized thermal management by parts from ebikestuff.eu

 

[hotsquirrel]

I just see, that a similar problem has been discussed here already:

TSDZ2 free spinning not enganging

Hello. Was wondering if anyone could help. Quite often, my cranks spin without engaging the gearing/motor at all. They are just completely loose. This seems to happen irregularly and only for a few spins - until I stop and try pushing the pedals again or pedal harder maybe (I need to do more...

endless-sphere.com

They solved the problem, by diluting the grease in the clutches by applicating WD40 and perhaps after this, relubricating the clutches a bit.