TSDZ2 120mm Axle Broke for the 2nd time on my Fatbike

[famichiki]

Has there been any improvement to the design of the these axles? For example, are they machined with rounded bottom circlip grooves to reduce stress concentration there, or do they copy the factory design with squared internal corners?

 

[HrKlev]

It looks like they have reduced the depth of the bolt hole. This is from a 100mm unit bought in May. Didnt keep it from breaking, though.... I will receive a new spindle in a few days, will post some photos then.

 

[Balmorhea]

It looks like they have reduced the depth of the bolt hole. This is from a 100mm unit bought in May. Didnt keep it from breaking, though.... I will receive a new spindle in a few days, will post some photos then.

It’s not the hole that predisposes it to break. It’s the snap ring groove. Stresses concentrate on the outside skin of a structural part, not the center. They use a smaller diameter spindle than anyone else in the business, and then they cut a groove at the point of highest stress. Of course it breaks.

 

[HrKlev]

Yes, I am aware. The depth of the hole was discussed earlier in the thread, as it was drilled past the groove. Somewhere on the way, the design has changed, as shown in the picture. However, it still breaks in the groove, of obvious reasons ... I will check the groove on my new spindle if they have at least rounded the edges. The seller told me the new spindles were improved. IDK. Personally I'm loosing trust in this motor because of this. Too bad, I really liked it.

 

[famichiki]

Perhaps the best place to make reliable axles would be a performance camshaft workshop, those guys know their stuff but you are going to pay for it. Kickstarter anyone?

 

[HrKlev]

So I got the new spindle yesterday. Cant see any difference to the old one. The edges in the grooves are still sharp (in one of the grooves looks like the tool has been damaged, so the bottom is not straight. Dont think it is intentional).



The grooves measuers 13.4mm and 13.5mm. Now, I happen to have a spare spindle for my 68mm tsdz2 around also, which was pretty interesting. This may explain why my other bike with the 68mm BB holds up to so much more abuse.



The groove measuers 14.1mm on the 68mm BB version!

Im tempted to weld the grooves, machine it down to spec again and glue the bearings inner race with loctite 638. It will probably not be easy to get it apart again, but its better than not using it. The spindles doesnt seem hardened at all (file catches), so Im thinking the welding should be OK. Im not a metal wizard, though.... Thoughts?

 

[famichiki]

So I got the new spindle yesterday. Cant see any difference to the old one.

Great info, there's certainly a few worrying things going on there.

I measured my standard 68mm spindle here and the grooves are 14.1mm deep the same as yours. It looks like your fatbike ones are wider too, did they supply wider circlips or are they loose in the groove? The standard spindles take 1.2mm thick circlips which are a little hard to find here as 1.5mm seems to be more common.

Out of curiosity I examined the reduction shaft and the stress appears to be relieved at the steps in diameter, however the bottom of the circlip groove is also squared off.

 

[HrKlev]

I measured my standard 68mm spindle here and the grooves are 14.1mm deep the same as yours. It looks like your fatbike ones are wider too, did they supply wider circlips or are they loose in the groove? The standard spindles take 1.2mm thick circlips which are a little hard to find here as 1.5mm seems to be more common.

Yes, the groove on the 100mm spindle measured 1.55mm. The circlip that was installed was a 1.0mm... So quite loose, yes

Anyway, I will not install the spindle as it is, as it will probably just break again. I'd rather try to something and fail, than just install a new part I know will fail sooner or later. So here it goes. As stated, Im no metal wizzard, so I have no idea how this will turn out....

Not sure if it makes a difference, but I machined the sharp edges. The stock spindle was soft like butter in my old lathe, btw.


Added some weld


And no more circlip groove


I measured about 0.05-0.10 clearance for bearings and the torque sensor, and if I remember correctly (there's a high probability that I dont), that is within the tolerances for Loctite 638. That is some serious stuff when the tolerances are within spec. So I glued the inner bearing races and inner part of the torque sensor with the stuff. It is curing now, so if it seems OK tomorrow, I will install it later this weekend and see how it turns out.

 

[Balmorhea]

The stock spindle was soft like butter in my old lathe, btw.

It would be a good idea to have the spindle heat treated while it’s out.

 

[famichiki]

The stock spindle was soft like butter in my old lathe, btw.

That's not good to hear at all, I can't believe it's not hardened. But please keep us updated how things hold up.

Did you give any regard to centering the spindle when you glued it? I was going to suggest Loctite 641 as an easier to remove alternative however it will only seal up to 0.1mm.
https://www.henkel-adhesives.com/au/en/product/retaining-compounds/loctite_641.html

Is there any way to install a bearing at the factory position against the splines and hold it in place using the fatbike adapter perhaps with some kind of spacer? To help support the axle along its whole length.

Also Enduro 6902 LLU MAX-E bearings have an extended inner race to 10mm but are otherwise equivalent to 6902RS. This may provide some extra support when fitted over the top of where the old circlip groove was. They are specifically designed for external use on MTBs (LLU designation = full contact dual lip seals, 90% grease fill) so you don't need to use the separate dust seal with these and could even be fitted right at the end of the spindle.
http://www.wychbearings.co.uk/6902-llu-max-e_enduro_bearing.html
https://www.bike-components.de/en/Enduro-Bearings/Deep-Groove-Ball-Bearings-6902-15-mm-x-28-mm-x-7-mm-p57556/

 

[HrKlev]

It would be a good idea to have the spindle heat treated while it’s out.

Yes, probably I have no way to heat it enough and no idea how much, so I didnt do it.

That's not good to hear at all, I can't believe it's not hardened. But please keep us updated how things hold up.

Did you give any regard to centering the spindle when you glued it? I was going to suggest Loctite 641 as an easier to remove alternative however it will only seal up to 0.1mm.
https://www.henkel-adhesives.com/au/en/product/retaining-compounds/loctite_641.html

I just let the spindle rest in the bottom of the splines inside the torque sensor and pushed the bearings to the bottom on the non driven side, and made sure the torque sensor was "compressed" on the driven side. Not easy to put down in words, so not sure if that was understandable . It is installed on the bike now. I had actually decided not to use this motor any more, but its always fun with a challenge. So far I have only checked that the motor operates normally and jumped with my 95kg on the pedals, etc. So far so good. I'll see if I can find some gnarly tracks next week and put some miles on it.

 

[famichiki]

I just let the spindle rest in the bottom of the splines inside the torque sensor and pushed the bearings to the bottom on the non driven side, and made sure the torque sensor was "compressed" on the driven side. Not easy to put down in words, so not sure if that was understandable . It is installed on the bike now. I had actually decided not to use this motor any more, but its always fun with a challenge. So far I have only checked that the motor operates normally and jumped with my 95kg on the pedals, etc. So far so good. I'll see if I can find some gnarly tracks next week and put some miles on it.

Very good, I thought you may have made up some fancy alignment tool with your lathe.

I'm looking at fitting those Enduro bearings to each end of the spindle (or at least the non-extended race versions) in place of the dust seals. Because the fitment is so loose and could let in water and dust I'm tossing up between Loctite or perhaps just silicone. While silicone won't firm up the play, with the second bearing fitted it might be all that is needed to prevent ingress, keep the bearing in place and stop the spindle spinning inside the bearing race.

 

[HrKlev]

I think the endurace bearings are a good idea. I think it would be quite easy to fix the axle with just using spacers between the pedal and the outter spacers. Silicone or even just some all weather grease should keep the water out from between the inner race and the spindle. You might actually have to grind off a little on the pedal on the driven side, as it seems likenit compresses the sealing a little.

Then you could just let a machine shop weld and machine the snap ring. Im not sure if what I have done with the spindle makes it much stronger, but if you let someone who actually knows what they are doing do it, with heat treatment, etc, I would imagine it would be a lot stronger than stock spindle, at least.

I kind of regret not being patient enough to order bearings now, instead of glueing. Oh well

 

[famichiki]

I kind of regret not being patient enough to order bearings now, instead of glueing. Oh well

I take it you mean the crank arms, not the pedals? Anyway yes marine grease would probably be sufficient. But I've stuffed around with this motor too much now as well, and would happily throw money at someone who could provide me with a properly engineered spindle that I didn't need worry about.

 

[HrKlev]

Ah, yes, crank arms of course

Did 30km with rocks and roots today. Did try to test it by landing jumps with all the weight on the pedals, until a spoke in the rear wheel gave up and I had to baby it home. I never treated the old spindle that hard, it just broke while I was loading up the front fork to find the right pressure. So hopefully this ghetto fix isnt worse than a stock spindle at least. Time will tell. Now I have to fix my rear wheel.

 

[E-bike lover]

Hi guys. I have just bought and test my motor. I have been reading from different forums that there are many problems in this motor. If i didn't mistaken, there should be 7 bearings inside it. From what i have read, replace the orginal one(s) to a "Tighter" one could prevent broken of the shaft. But is it nessary to replace all the bearings? Or only the critical one(s) have to be replaced? Adding enough and good grease to bearings could do the job too.
Is these two are the only one that we could do to prevent the shaft from broken? :? Even though there are chances that the shaft is not straight..

 

[Elinx]

.... there should be 7 bearings inside it. .....But is it nessary to replace all the bearings? ....
Is these two are the only one that we could do to prevent the shaft from broken? .......

There are 4 bearings (1x 6902, 2x 2214 and 1x CSK30P) inside and it is possible to add 2 extra 6902 bearings (or one wider 3902 type) on the nondrive side and one 6902 into the spider with removed dustcaps. So 3 extra bearings made 7 in total.

On the non drive side you can add these bearings easely, by removing the dustcap.
For the drive side, you must remove the spider and insert the bearing instead of the dustcap.
Because the dustcaps are removed it is advisable to use endurance bearings, thas has an improved water resistance.

These extra bearings are only for minimizing cq preventing the play of the axle.
The main reason for breaking the spindle are the circlip grooves and the low quality of the used steel.

 

[E-bike lover]

.... there should be 7 bearings inside it. .....But is it nessary to replace all the bearings? ....
Is these two are the only one that we could do to prevent the shaft from broken? .......

There are 4 bearings (1x 6902, 2x 2214 and 1x CSK30P) inside and it is possible to add 2 extra 6902 bearings (or one wider 3902 type) on the nondrive side and one 6902 into the spider with removed dustcaps. So 3 extra bearings made 7 in total.

On the non drive side you can add these bearings easely, by removing the dustcap.
For the drive side, you must remove the spider and insert the bearing instead of the dustcap.
Because the dustcaps are removed it is advisable to use endurance bearings, thas has an improved water resistance.

These extra bearings are only for minimizing cq preventing the play of the axle.
The main reason for breaking the spindle are the circlip grooves and the low quality of the used steel.

Thanks u have satisfy my curiosity
May I ask what makes you think that the main reason of breaking the spindle is beacause of the circlip grooves are too tight(If i didn't mistaken)? All the pressure was put into that point at the spindle?
I thought the bearings play a role too. If the axle keep playing then it will keep spining under pressure from pedeling while it spins upside down.
Then what's the solution of the circlip grooves? They have to be removed and we need to hardened the axle?

 

[famichiki]

Thanks u have satisfy my curiosity
May I ask what makes you think that the main reason of breaking the spindle is beacause of the circlip grooves are too tight(If i didn't mistaken)? All the pressure was put into that point at the spindle?
I thought the bearings play a role too. If the axle keep playing then it will keep spining under pressure from pedeling while it spins upside down.
Then what's the solution of the circlip grooves? They have to be removed and we need to hardened the axle?

There are a few factors but the most obvious is that the machining of the circlip grooves causes internal stresses in the metal. The sharp internal corners are stress concentration points. It's not the circlips themselves. The only way to fix it properly is to redesign the spindle and motor case so that circlips are not needed to retain the spindle. Better quality material and hardening will help too. However the most minimal revision would be to machine the circlip grooves with a rounded bottom, which will reduce the internal stress. The most we can really do ourselves is to add some bearings for support outboard of the circlip grooves to take pressure and stress away from the grooves.

 

[petebligh]

Having just ordered a 100mm BB TSDZ2, I am concerned by the number of failures!!
I have emailed Ebird, the company who are supplying the motor with my concerns, and received the following reply....

do not worry, the axles is easy to replace it ,we can send you the free axle for the changing is ok, and we have improved the axles, do not worry

So, on the one hand they say they have improved the axles, but don't say how, on the other hand they say they will supply one for free....can't say I'm particularly confident.

I'm not an aggressive rider by any stretch of the imagination, but don't like the idea of a failure that could be potentially dangerous.
I was hovering between the TSDZ2 and the 'Lightest ebike' motor, which sounds promising, but is not yet available, and there are no reviews. Let's hope the TSDZ2 doesn't disappoint.

Anyone who has successfully managed to source a qualuty replacement, keep us in the loop.....I would be interested!!

 

[eraue]

Hello,

Just wanted to inform you that I got my 120mm TDSZ from Ebird store 6 months ago.
Used it on my bike about 10hours on normal roads commuting to office and today it broke on the right side.

 

[eraue]

About this problem. I measured that wall thickness at the point of failure is 3.1mm..... that is because of seger ring groove and hole (7mm) inside is not exactly at the centerline of shaft. Propably tip of the drill has been bending slightly during drilling. So, solid shaft at that point may not fix that for good but would be better than 3.1mm wall.
I have found (almost) local shop who has rather modern machinery and could make shaft for me. Material would be e.g. Moc 410 (42CrMo4) and solid at seger ring area. Would there be any interest for BB100 shafts for price around 65...70€ + shipping?
I’m asking as machining one only is not possible due to high initial costs. Warranty would be just as good as with chinese supplier .... nothing

Alternatively.... has someone already tried ”self made” improved shafts ....

YES, I would be interested in 120mm shaft

 

[RyanF]

Hello. I’m looking to buy tongsheng 120mm for fat bike. Has there been any improvement on the shaft? I will be using the bikes on paved trails and rail trails mostly. No jumps etc.

 

[asterduc]

............. Sorry for the long messages, but I see this in an issue for the community, and I would like to fix it, and also clear up any misconceptions at the same time!

I am looking for a spindle, approx 20mm (3/4") longer than the stock version. Delivery in Belgium (Europe). Can you tell me where I can buy one. Thanks.

 

[Fabio]

Hi, bad news for axle 120mm TSDZ2. My 3rd axle just broke, always on the right side. I bought the 500w TSDZ2 motor via ebird (Aliexpress) already assembled with 120mm axle a couple of Years ago. The original axle worked for about 1500 km, the 2nd and the 3rd about 1000 km each. I weight 76kg and I use the fat bike mainly for commuting, never for jumping. Each time I contacted ebird (bit difficult) they kindly provided the first time the axle for 25 usd with free shipping, and the 2nd time axle and shipping free. Also for the last axle, they let me waited a while (couple of months) for having an 'improved axle'. When received it looked exactly as the previous ones, same grooves size and same weight (with a precision balance...) In addition, as someone did a test on this forum, I welded both grooves (10 usd), hoping it will last bit longer... but no way. The only difference in those 3 axles is the deep of the hole, in the first axle it was deeper, the last 2 axle have less deep hole, but as mentioned ,did not change the overall life of them.
I also understand that those axle 100 and 120 mm are third party, so that we should not blame Tongsheng, but it will be good if Tongsheng could produce those longer axles, as their regular axle do not seems to have this big issue.
I was thinking to replace the TSDZ2 with the Bafang 1000w 120mm HD, but having installed it on a fat bike of a friend and having tested hard for 80 km, I must say that I still prefer the feeling of TSDZ2. The Bafang is a beast and much more strong, but I miss the torque sensor too much. Will write to ebird for having another axle now... althought I doubt it will last longer...