TSDZ2 120mm Axle Broke for the 2nd time on my Fatbike
- Thread starter MaartenL
- Start date
As you have read the main problem, besides the weak steel, are the circlip grooves.akkepira said:
You can improve this a bit by adding extra bearings at the outer side of the spindle.
In that case the spindle is supported on both sides of each groove.
One bearing must be pressed or glued inside the spider instead of the rubber seal.
The other bearing(s) can be easy inserted after removing the seal.
biphaeboh
100 W
The best solution might be to not buy a TSDZ2.
Why the builders don't design and spec a better spindle when the problems are well described, who knows?
Does anybody know what the cost would be to have a machine shop make a custom spindle according to proper specs?
It must be awfully frustrating for those who love that motor to see a problem like this that could be easily fixed by the manufacturer.
Why the builders don't design and spec a better spindle when the problems are well described, who knows?
Does anybody know what the cost would be to have a machine shop make a custom spindle according to proper specs?
It must be awfully frustrating for those who love that motor to see a problem like this that could be easily fixed by the manufacturer.
machanic
1 W
Has anyone tried cryogenic treatment of the shaft? This solved a similar problem on a race car axle I was involved with.
I don't know anything about cryogenic treatments of metals, so I can't answer that.
But this shaft still has mechanical design issues creating stress risers. If you actually put a load on the cranks by really pedalling, and not just using it as a pedal-controlled moped, the stress increases and may cause the failure.
It's not a universal problem, meaning not every unit fails, so it isn't *just* the design causing the problem--it's something in the manufacturing process, too, possibly variation in the way the metal is created in the first place, or tempered (if it is) or other treatment, or just machining issues (possibly even just damaged tooling passing on the damage to the shaft).
But this shaft still has mechanical design issues creating stress risers. If you actually put a load on the cranks by really pedalling, and not just using it as a pedal-controlled moped, the stress increases and may cause the failure.
It's not a universal problem, meaning not every unit fails, so it isn't *just* the design causing the problem--it's something in the manufacturing process, too, possibly variation in the way the metal is created in the first place, or tempered (if it is) or other treatment, or just machining issues (possibly even just damaged tooling passing on the damage to the shaft).
machanic
1 W
Like I said similar problem, circlip groove in a axle tried a heavy duty replacement lasted longer but it eventually broke, tried the cryogenic treatment on a stock axle and never had another failure.
Chalo
100 TW
Guwa said:
Bafang BBS02 is one solution. Homebrew Stokemonkey is another.
Throwing good money after bad isn't a solution.
endlessolli
100 W
Guwa said:
I can not speak for the non oem extended axles, but the std oem axles have since quite some time much shallower grooves for the circlip. If that is due to varying process tolerances at Tongsheng and their suppliers or an actual process change I don‘t know, but all axeles I saw in the last year had this shallower gooves. Also reports of broken axels are down since a while.
My statement only refers to std oem axle.
Chalo
100 TW
machanic said:
Using the smallest diameter bottom bracket spindle in the entire bicycle industry, and then notching it at the point of highest stress, isn't something that cryo treatment is going to fix. I expect they used low grade material for the trifecta.
ornias
100 W
- Joined
- Jul 18, 2021
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I'm currently working on getting the axles remade with hardened steel, without circlip grooves and with H7 tolerances.
Sadly enough, it will only be the normal-size axle for now.
If it works out, I will throw out a kickstart/buying-action for it and if that's populair enough I'll look into also making longer axles with same specs.
However:
The problem with the longer axles, is that the longer the axle, the more it highlights inherent designflaws (well, not really flaws, it was never designed for boost spacing anyway) mostly regarding the fact the spindle is not very-well supported in the frame (one side has bearings, other side need to transfer loads via the clutch bearing which as limited sideways/tordial load capacity.
So my advice would be not to sue the TSDZ2 on 120mm-axle bikes
Sadly enough, it will only be the normal-size axle for now.
If it works out, I will throw out a kickstart/buying-action for it and if that's populair enough I'll look into also making longer axles with same specs.
However:
The problem with the longer axles, is that the longer the axle, the more it highlights inherent designflaws (well, not really flaws, it was never designed for boost spacing anyway) mostly regarding the fact the spindle is not very-well supported in the frame (one side has bearings, other side need to transfer loads via the clutch bearing which as limited sideways/tordial load capacity.
So my advice would be not to sue the TSDZ2 on 120mm-axle bikes
Great ideas and fantastic info here. Thanks to everyone for sharing. I've the same issue with 100mm original spindle broken on the drive side circlip groove. It failed after a minor soft jump and 3,500 miles of mixed use including steep mountainous trails. I'm 63kg and like to spin rather than stand on the pedals. The fracture had clearly been there some time with rust evident on the fracture line. I do feel that the cause of the fracture building up, was less to do with jumping, more likely the pedal crank catching on passing rocks and causing the bike to jump quite violently on occasions. Full suspension catches me out like this sometimes.
I'm thinking of having a spindle machined out of stainless because it's stronger. Also, to have no circlip grooves, and adding the extra bearings in place of dust seals.
I plan to then put shims on each end of the spindle up against the pedal crank arms to control sideways float. Does anyone have a view on this plan?
I'm thinking of having a spindle machined out of stainless because it's stronger. Also, to have no circlip grooves, and adding the extra bearings in place of dust seals.
I plan to then put shims on each end of the spindle up against the pedal crank arms to control sideways float. Does anyone have a view on this plan?
VTAllen
1 mW
Well, I now know that I have company. Attached are pics of my left sided crankshaft breakage, at about 5600 miles of normal on-road riding. Fortunately I wasn't standing or in a traffic/terrain situation where this could have been bad. The pedal just disappeared from under my foot....
Attachments
Again the circlip groove, which is the weakest point of the shaft.
Did you had an extra bearing behind that rubber seal, for supporting the shaft on the other side of that groove?
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VTAllen
1 mW
No, just the stock motor/assembly.
That is a pity, because then there was a chance that this would not have happened. It is a very easy addition.
Sidux
1 µW
Just wanted to share my latest experience. I use a 36V 500W TSDZ2 on a full suspension bike for commuting to work and mixed terrain rides.
The crankshaft of my TSDZ2 broke on the left hand side but just inside of the bearing (see pictures). To me it seems like a material imperfection.
Was kinda weird to cross a street with a stronger push on the left pedal and it just fell off ... the cars were patient.
I must admit though that I have used the motor for 6200km over a few years and just replaced the nylon gear once for a nylon gear and then for a brass one.
The crankshaft of my TSDZ2 broke on the left hand side but just inside of the bearing (see pictures). To me it seems like a material imperfection.
Was kinda weird to cross a street with a stronger push on the left pedal and it just fell off ... the cars were patient.
I must admit though that I have used the motor for 6200km over a few years and just replaced the nylon gear once for a nylon gear and then for a brass one.
Attachments
![IMG_20230626_120118[1].jpg](/sphere/data/attachments/196/196658-a97582683ed21093f61bf61078ba2c95.jpg)
![IMG_20230626_120212[1].jpg](/sphere/data/attachments/196/196659-77be39ff6abb99fd391b1967524d37c6.jpg)
Does it have the circlip groove to keep the shaft/bearing from moving sideways? If so, that's why it broke there--stress riser making it easy to snap off after fatigue cracking goes deep enough.
If it had another bearing outside the groove to support the shaft it probably would not have failed, but simply not using a groove on a shaft like that in the first place is a better solution.
If it had another bearing outside the groove to support the shaft it probably would not have failed, but simply not using a groove on a shaft like that in the first place is a better solution.
Mongo
1 kW
I guess @ornias and his replacement axle effort shifted, or maybe moved elsewhere?
I just installed a 36v TSDZ2 on a full suspension bike. My problem is how to keep the motor from rotating forward. There is a clamp between the motor and the chain stays. As the chain stay moves in a FS bike I don't it's a viable place to use to lock the motor from rotation. Just curious as to what you did to prevent motor rotation?
beemac
10 kW
Last edited:
Imho there isn't.
It looks all longer third party axles are weaker than the shorter stock.
Mostly these longer ones will be used with eMTB use, which, imho, mostly means too heavier use than commuting.
Best option is to insert extra bearings on the other side of the circlip grooves.
These grooves are imho the weakest point of the already weak axis.
With extra bearings the axis is supported on both sides of these grooves.
The bearing in the spider comes instead of the dustseal, on the non spider side behind the dustseal.
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Thanks, but where can I buy these bearing ?
Do you know where I can buy a new 100mm axis ? (I don't want Ebird)
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