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Torque Washers and Torque Arms

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    Torque Washers and Torque Arms

    Click image for larger version  Name:	torquewasher.jpg Views:	0 Size:	720.8 KB ID:	154196 Click image for larger version  Name:	bafangwasherinplace.jpg Views:	0 Size:	778.7 KB ID:	154197 Click image for larger version  Name:	hubshaft1.jpg Views:	0 Size:	898.5 KB ID:	154195
    I've got a mountain bike with aluminium front forks and a 250W motor. The motor shaft has a 4mm long, 12mm diameter step with 10mm flats for Bafang-style torque washers. However I have read elsewhere that on aluminium forks the washer can force apart the dropouts so I should use a torque arm. I'm sure that would be a good idea with a more powerful motor, but I'm not sure with 250W. What is your view?

    #2
    These guys are the go to when it comes to hub motors. 250w seems kinda minimal need but it wouldn't hurt especially on aluminum.

    For every force there is an equal and opposite force, and for every torque there is an equal and opposite torque. Sadly with import hub motors this opposing torque is often born entirely by bicycle dropouts that are not up to the task, allowing the motor axle to spin out. Grin has pioneered the design of aftermarket torque arms to transfer this axle reaction torque safely up to the bicycle frame and away from the dropouts.

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      #3
      Considering that the fork might actually be Magnesium which tends to crack rather than bend, and the drastic consequences of a failure in that area I would play it safe and get the torque arm. Braking torque is never resolved at the dropout slot, always further up the fork. Electric motors make a lot of torque at low RPM.

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        #4
        Guys , what do you think. The way I installed this torque arm , does it serve any purpose? I could not fit it behind the bolt as the front fork tube is on the way. I also have torque arm on the other side and it is installed well. Front hub is peaking 1000w.Also it is so thick , even if I managed it behind the bolt, then the axis bolt would dangle were the axis opens to let the wire out…Click image for larger version  Name:	4B3FCE63-8556-4923-83E8-0131D8658B0F.jpg Views:	0 Size:	92.8 KB ID:	164596
        Last edited by ALEX222; 09-14-2023, 03:29 AM.

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        • Retrorockit
          Retrorockit commented
          Editing a comment
          I hope the hose clamp isn't going over the wires. Use a plastic zip tie for that. I would flip the clamps over so the bolt will be behind the fork so it doesn't snag on things, but still facing out. But that should get the torque load up the fork away form the dropouts slot.I would be looking for a bigger front brake rotor too.

        #5
        Thanks for advice, I will turn the clamps and look for bigger brake rotor. As bike maybe weight 45 kg and my 100 kg is surely too much…

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          #6
          I've built 3 @ 3 wheel adult trike electric front hub conversion kits and swapped out with aluminum forks (for disk brake set up) and the torque arm at the way to go.
          ​​​Saved my hub from spinning wires and tire from coming off.
          electric trikes rock

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            #7
            Solution: I stuck with the torque washers and didn't bother with a torque arm. Works fine with a 250W motor, even for mountain bike track riding.

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