Tongxin motor in non-steel forks

[Pedalo]

I have a bike to which I was thinking of fitting a Tongxin motor. The forks are suspension forks and do not pass the steel test (i.e. don't stick to a magnet).

I just stumbled upon some threads cautioning the use of non-steel forks for fitting a motor but it seems it 'might' be O.K. for lower power motors.

What do you think? I could:
i) Get the forks replaced for steel non-suspension forks.
ii) Sell the bike and get another (e.g. Ebay cheapie) more appropriate for electric retro-fit.
iii) Fit a motor anyway and see how it goes.

I'm tempted to try it and possibly/probably upgrade to a generally better bike later. My company is planning on starting the cycle to work scheme next year so would be a good time to upgrade. There doesn't seem to be a lot of point changing the forks unless I could get it done really cheaply.

Advice as always appreciated!

 

[HarryB]

No need to change your forks. Most of the Cytronex use alloy or carbon forks. I used some alloy suspension forks with a tongxin and never had any problem. If you are worried then buy a torque arm but I don't think this is needed.

 

[Barnowl]

As Harry says Cytronex seem happy enough with the Tongxin and non steel forks to ride them and sell them. My 7.3FX is non steel. I believe the Trek 7300 is aluminium suspension. I thought carbon forks may have been a problem but apparently not.

 

[frank9755]

Personally I would want to have a torque arm if the forks were other than steel.

I recall how the motor started to chew up the aluminium rear drop-outs of my old Wisper after just a couple of hundred miles, before I fitted a torque arm. Instances of drop-out failure from this cause are not unknown - in early Wispers and other bikes with aluminium frames.

I'd also want to protect a carbon fibre frame. That material can be designed by a framebuilder to be very strong in certain directions where strength is needed but there is no way of knowing how it will resist a force that it wasn't designed for.

The Tongxin is not exactly a low power motor so should be treated in the same way as other motors.

 

[daniel.weck]

Drehmomentstütze - ebike-solutions.de


www.ebikes.ca Homepage of the revolution

 

[daniel.weck]

Drehmomentstütze

 

[RobinC]

For a Tongxin hub should two torque arms be used, one on each side?
I think the Tongxin axle is split in the middle so I was wondering if there could be a problem if one side is attached more firmly than the other.

 

[daniel.weck]

For a Tongxin hub should two torque arms be used, one on each side?
I think the Tongxin axle is split in the middle so I was wondering if there could be a problem if one side is attached more firmly than the other.

Well, presumably you'd have a regular torque/locking washer on either side already, so the torque arm would really be for the extra peace of mind. I'd say that the side where the cable exits out of the axle/spindle is the one to secure...but that's just from intuition, not from validated technical facts

 

[jerrysimon]

From what I have read and what I have done myself only one is required.

Its usually fitted on the non cable side (as shown in your pics daniel) otherwise you would have to dismantle the cable connector to fit it on the cable side.

Regards

Jerry

 

[daniel.weck]

otherwise you would have to dismantle the cable connector to fit it on the cable side.

Well, not on the Tongxin. The 3 crimper-type connectors fit through the M10 nut hole, washer, etc. On the Bafang, that's another story of course, because the cable connector is in the way, indeed.

 

[HarryB]

For a Tongxin hub should two torque arms be used, one on each side?.

Now we are talking about two??? Has anybody found an actual need to fit a torque arm? I can see that it would be required with the Wisper motors but the tongxin is not that powerful. Has anybody had a problem - I have run tongxins for thousands of miles and had no problems with the locking washers failing or the spindle wrecking the forks.

 

[jerrysimon]

Has anybody found an actual need to fit a torque arm?

My gut feeling for the Tongxin is no, none is required though I would want to fit torque washer(s) in aluminium forks for sure.

On my Alienocean kit I would NOT want to fit it to aluminium forks without a torque arm though. It has way more low end torque. That said my kit is fitted in steel forks and I do have a torque arm mainly for peace of mind. Their not exactly hard to fit.

My Cytronex with a Tongxin motor and in aluminium suspension forks has no torque arm fitted.

Regards

Jerry

 

[daniel.weck]

Has anybody found an actual need to fit a torque arm? I can see that it would be required with the Wisper motors but the tongxin is not that powerful. Has anybody had a problem - I have run tongxins for thousands of miles and had no problems with the locking washers failing or the spindle wrecking the forks.

I can't say from experience (yet), but here's how I am doing it in my ongoing e-Brompton project:

http://www.pedelecs.co.uk/forum/electric-bicycles/4778-diy-stage-6-fork-hub-torque-protection-photos.html#post60504