TSDZ2 problem - pedals spin freely, not engaging with gear

[jeffieh]

Greetings from the South Pacific! I write today with a minor-ish but annoying problem that's happening with my TSDZ2 mid-drive. Sometimes (and it's usually just after changing up) the cranks spin freely instead of engaging with the motor gear. It's a completely 'clean' spin - no hint of the shaft partly engaging or rubbing or anything like that. I wondered if it could be the sprag clutch but I can't see how this would totally fail occasionally and yet work perfectly most of the time. Has anyone had this experience, and if so did you get to the bottom of it?
Any feedback will be gratefully received.
Many thanks, Jeff

TSDZ2 48v, 500w with 6100km on the clock.

 

[jeffieh]

 

[Elinx]

...Sometimes (and it's usually just after changing up) the cranks spin freely instead of engaging with the motor gear. It's a completely 'clean' spin ....

There could be different reasons like.
Sprag clutch, Blue gear slipping, Fail PAS

 

[beemac]

Greetings from the South Pacific! I write today with a minor-ish but annoying problem that's happening with my TSDZ2 mid-drive. Sometimes (and it's usually just after changing up) the cranks spin freely instead of engaging with the motor gear. It's a completely 'clean' spin - no hint of the shaft partly engaging or rubbing or anything like that. I wondered if it could be the sprag clutch but I can't see how this would totally fail occasionally and yet work perfectly most of the time. Has anyone had this experience, and if so did you get to the bottom of it?
Any feedback will be gratefully received.
Many thanks, Jeff

TSDZ2 48v, 500w with 6100km on the clock.

One of my bikes has what sounds like the same issue. If I change gear under load (particularly when the motor is cold) the clutch doesn't seem to engage and it sounds like the motor is speeding up/slowing down very quickly. If I stop pedalling it will reengage and all is well again. If I ease off the power before changing gear (good practice anyway) - i can generally avoid the issue.

I've not looked into it in any detail yet as all my dev/test tsdz2 stuff is still in storage whilst seemingly endless work is being done on my house - i'm running casainho's OSF probably a few commits off the latest on that bike - out of interest what firmware is on your motor?

 

[ilu]

The problem is in the sprag clutch. For some mechanical reason it can fail in this manner. When first one broke for me it started like you describe and gradually went worse, and when I opened it up the plastic parts of the clutch were disintegrating. I've used a cheap chinese spare part for some time and it works quite well, even though an occasional slip happens every now and then when temperatures are below freezing.

 

[jeffieh]

Thank you for your replies! It seems to be getting worse, slipping a lot on my ride to the shops this morning, so I'll have to tear it down and have a look today of time permits (pics to follow).
Elinx, I looked at that github page and it all makes a lot more sense now.
I reckon there'll be a rack in the bearing housing when I open it up.
Beemac, I'm running a v20.1C.3 controller & 860C display from eco cycles, bought back in Jan this year.
Thanks again, people!

 

[jeffieh]

This is a pic from Github, not my actual bearing.

 

[Elinx]

This is a pic from Github, not my actual bearing.

Yes that is the maingear with the spragclutch inside.
You can replace the complete maingear or only the spragclutch.

The maingear could have straight teeth and helical teeth.
I think you have helical teeth. So be alert with buying options..

The spragclutch is CSK30P

After replacement you can add two extra bearings that support the spindle on more points for less wobble.

On youtube you can find Tsdz2 spragclutch replacement video's.

 

[jeffieh]

Progress report:
Took the big gear off the bike & removed the clutch housing from the bearing (turns out it's serviceable, I didn't know that!). It was an easy operation: the gear came off freely and all the innards looked clean and in pretty good shape
With the sprag clutch there didn't appear to be much wrong with all its bits & pieces, although there was a little bit of damage to part of the plastic housing (if you look carefully at the bottom pic). I cleaned everything, greased it and reassembled it. From riding up and up and down the drive I can tell you it's a lot smoother, quieter & no slippage so maybe it just needed a good clean (after all, it's done 6000km). To be on the safe side I've ordered a new bearing from aliexpress.
Result: pretty damn happy, subject to it passing a road test.
Thank you endless sphere!

 

[endlessolli]

@jeffieh
That sounds great - hope it will hold up.
I did not know either that this spragclutch is servicable.
Could you explain in more detail how you disassembled the spragclutch to extract the plastc clutch housing etc?

 

[jeffieh]

I'll try :?
There's a plastic cage that fits either side of the bearings. One part of the cage has the sprung pawls - I think that's what they're called - 13 of them (you can see a couple of them on the final pic), and places for the bearings (those little cutout semicircles). This all clips out except for the bearings. I used the blade of a tajima knife to ease it out.
The other side of the plastic cage it just a face plate really, and clips together with the other side to hold everything in place.
It's a bit of fun trying to keep the pawls & springs together when you're reassembling. So rather than remove them to clean, I just inspected everything and reassembled, then cleaned the whole sprag clutch with solvent, then repacked with grease. Not sure if that's cheating...it's not going to be on the bike for long as it'll be replaced with the new one when it arrives.
Really wish I'd taken pics along the way, though given the state of my hands my phone would have suffered.

 

[Elinx]

... So rather than remove them to clean, I just inspected everything and reassembled, then cleaned the whole sprag clutch with solvent, then repacked with grease. ...

Thanks for your illustraded "howto"
When I read your description I remember that Wapous did this service too a while back.
But he clearly indicated, after cleaning, not to use grease

"If the main gear's sprag clutch no longer drives the chainring and no "crunch crunch" is heard then it is sufficient to clean its mechanism. This mechanism must be clean and without lubricant."

 

[jeffieh]

Yes I did see the 'no grease' bit.
Oh well...it only has to last a few weeks until the new sprag clutch arrives.

 

[endlessolli]

Thanks for the explanation!
Even if it will not last forever, I really like the idea of extending its life, as for replacing the complete sprag-clutch we need some sort of press (which I don‘t have).
Therefore still a clarification question how you did it:
How did you ‚pop out‘ the entire plastic cage - and to which side? Towards the side of the ball bearings or towards the side of the sprung pawls? And did you have to remove the balls and / or the sprung pawls first to remove the cage? (All / some?)
Thanks again.

 

[jeffieh]

It came down to luck really. I have no idea what was under the plastic cover. So I just got a tajima knife blade and tried to gently prise it up. The side I chose happened to be the flat piece of cover and it clipped off as I worked around it with the blade. Once that was off I pushed the other side of the plastic cage out. It came quite freely. The bearings remained in place. But a couple of the springs and pawls fell out. To get it back in I just did it in reverse. I had to space the bearings around so that they roughly matched the indentations in the cage.
If I was doing it again I think I could still pack it with grease, because that keeps all the moving bits together and stops them falling out. Then I would just rinse it once it was fully assembled.