Torque arm suggestion for horizontal dropouts?

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Enewb   10 µW

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Torque arm suggestion for horizontal dropouts?

Post by Enewb » Nov 30 2019 3:40pm

Hello, I want to put a geared up motor on my bike, motor 36v 350w. What would be the best torque arm setup for me? If needed at all?

Thanks
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E-HP   100 kW

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Re: Torque arm suggestion for horizontal dropouts?

Post by E-HP » Nov 30 2019 4:52pm

I don't think you'll need one with that power level, especially since you won't have regen. If you want one, it would need to be custom made to fit within the inset part of your dropout, not too difficult to make out of 1/4"steel, if you have a grinder and file.

aroundqube   1 kW

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Re: Torque arm suggestion for horizontal dropouts?

Post by aroundqube » Nov 30 2019 9:20pm

The axle in the picture is round. The common 350W geared hub motor has a flatted axle and comes with anti-rotation washers. Position the tabs of these washers inside the frame slot for the axle.

Enewb   10 µW

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Re: Torque arm suggestion for horizontal dropouts?

Post by Enewb » Dec 01 2019 12:09am

aroundqube wrote:
Nov 30 2019 9:20pm
The axle in the picture is round. The common 350W geared hub motor has a flatted axle and comes with anti-rotation washers. Position the tabs of these washers inside the frame slot for the axle.
Cool, maybe it will be enough as I understand the dropout is already quite beefy. Thanks!
E-HP wrote:
Nov 30 2019 4:52pm
I don't think you'll need one with that power level, especially since you won't have regen. If you want one, it would need to be custom made to fit within the inset part of your dropout, not too difficult to make out of 1/4"steel, if you have a grinder and file.
Yeah I was thinking a steel insert sort of U shaped that could just slot in.

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dogman dan   100 GW

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Re: Torque arm suggestion for horizontal dropouts?

Post by dogman dan » Dec 02 2019 8:26am

Yes, make a steel plate that fits inside that recess, then drill a flat sided hole in it for the axle. Drill small holes, then finish with a hand file. The hole needs to be closed, not u shaped.

Or, modify a regular front torque arm, giving it the exact shape of the big recess in the dropout. Line up the hole, and cut to fit on the outside.

A good tabbed washer will work good too, but some have a tab that is too short, or whatever, and really do nothing.

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E-HP   100 kW

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Re: Torque arm suggestion for horizontal dropouts?

Post by E-HP » Dec 02 2019 9:54am

dogman dan wrote:
Dec 02 2019 8:26am
Or, modify a regular front torque arm, giving it the exact shape of the big recess in the dropout. Line up the hole, and cut to fit on the outside.
Brilliant. Mock up using Grin's front TA:
ta mod.jpg
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Longer edge on bottom to combat the axle torque.

Enewb   10 µW

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Re: Torque arm suggestion for horizontal dropouts?

Post by Enewb » Dec 02 2019 2:27pm

Great suggestions thank you for your time! I will post my build when my parts arrive and see what I can make

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dogman dan   100 GW

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Re: Torque arm suggestion for horizontal dropouts?

Post by dogman dan » Dec 04 2019 7:38am

looks good, as the wheel turns rolling forward, the axle will try to rotate the other way, so your picture has the modified TA pointing the right direction.

If the nut won't fit in that slot when you assemble it, file the frame down just a bit, till its flush with the torque washer, or stack additional washers if the axle is long enough.

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