9C RH205 dented rear axle

[dara]

I joined the forum in September and learnt a lof from you guys.
After that I felt confident to start my first real built, a rh205 7x9 (French 9c 2809) at 60V@28Ah on a Orbea Satellite.

I enjoyed it while it lasted, I mean a total of about 15 miles. Yesterday during inspection, I found a big dent in the axle at the dropout level, not at the torque arms. How can a dropout chew an axle, be it alloy or steel? I would thing the axle would break or deform the original dropout?

The bike has a torque arm on each side (the strongest is a ebike.ca v3).
Axle nut was fitted at 70nm then the rotation blocked with the torque arm.
I used the original controller that came with the kit (sensored, 60V/28Ah and 16s1p HobbyKing Multistar lipos)

I would like your view on the cause of denting and if you have see it before on E.S.? I used the search function but found only cases of bend axles, not dented. The freewheel side appears clean but I have yet to remove the wheel for a complete inspection.

The problem is I cannot use the bike anymore because an axle failure while riding would be catastrophic.
The engine is 6month old but 15 miles only, it was sleeping and being built during winter. The supplier cannot take it under warranty, I have to pay to get exchanged. At that time I may as weel consider another hub. Can you recommend an alternative at the same power level? I read crystallite 35xx also had their axle problem, I don't know if it is better now?

 

[dogman dan]

It's not the frame, it's the torque arms.

The torque arms are stronger than the axle, so the axle is starting to twist off. Axles are fairly soft metal. The twist is happening right where the TA holds the Axle, not in the dropout.

It should not have happened this quick, and likely not at all. But lucky you, you got a motor with a defect in the axle.

 

[dara]

Thank for your reply.
I see a bit more clearly now. Either their controller is too much for the motor they sell, or my shaft was defect. In all case it is a bad design or bad manufacturing.

I wonder why you say I m lucky? I have no tool to replace a shaft and the reseller don't take it under warranty, even though I bought it in Europe and not in China.
It is a nice door stop at present.

 

[2old]

I can't imagine the seller not offering some relief since it's his ultimate responsibility. I'd make sure he and the manufacturer know that you're going to publicize this (any forums in Belgium?) and report it (any safety organizations?). You were fortunate to catch it the way you did and not sliding down the road on your butt.

 

[Brentis]

?..

I wonder why you say I m lucky? ...

I think it was lost in translation.
He was being sarcastic, joking with you. You weren't lucky :wink:

It will probably cost near as much as a new motor, but you could have a local machine shop press out your old axle from the stator, then have a copy made in a stronger steel, then pressed back in.

That said, I'd be going after a warranty from the seller as it has so few kilometres on it.

 

[gogo]

You could use the motor in a mid drive or windmill?

 

[greg_p]

Sellers have a legal warranty of 1 year at least in France. Where did you get the motor from? Is it power-ebike?
The 28amp controller make me thing it is the case.
I have it since 1.5 years on a 8x8 rh205 that now is taking roughly 40 amp without problem, it's a real axle defect.
I am really surprised they can't take it in warranty.

Btw 70nm may be too much for a m14, it should be less I think. I have 80nm on my motorbike which has a larger axle.

 

[dara]

Thanks all,

The motor was bought in early november but slept in the garage and was built during the dark winter, I used it first time in april for a total of maybe 15 miles / 20km till today.
After several mails, I have to pay a low fee for an exchange against a refurbished motor and he will pay for the labor (relacing the hub to the rim, something I can do myself but time consuming). Both transport will be at my charge, so around 100 euro or 120usd total.

I didn't want to disclose the seller and make bad press until I found a solution with him.
I prefer to reach an agreement first. Under warranty I should maybe pay the transport in one side. What do you think of his proposal?

There must be belgian forum but I don't know them. I know only The Sphere or cyclurba.fr. I know he/they used to visit that last one in the past.

This is sad because I liked much the 9c / Rh motor. Now if accept their proposal, I will use with a 48v/17amp controller.


Voila

 

[dara]

You could use the motor in a mid drive or windmill?

The mid drive is a great idea If I cannot reach agreement, I will sell it cheap for that purpose.

 

[dogman dan]

I really see no problem with using your new motor with the same controller. I've whomped 9c motors with much more power than that, with no problems with the axle.

You just got "lucky" and got one with a weak spot on the axle, a micro crack or something like that.

Twisting off an axle does happen easier, if the torque arm is not very tight though. so if yours has a lot of slack, hand fabricate a tighter one.