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  • Bike frame enforcement

    Is there anything that can be used to enforce the bike frame so it will not break under the tourge of the electric motor?

  • #2
    What material frame? Mid drive or hub motor? How many Watts?

    Others have used gussets https://www.reddit.com/r/metalworkin...t_at_a_tubing/, torque arms or torque plates. Excerpt from the link: "A more effective gusset is a plate between the top tube and down tube."

    More than likely, however, you are inquiring about the axle of a hub motor cracking the dropouts, which I have done. I used 1/4" 303 Stainless Steel to make custom torque plates which have proven bombproof. Designing, fitting and installing the torque plates was one of the most fun parts of my project!
    Last edited by commuter ebikes; 4 weeks ago.

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    • #3
      Aluminum frame. It broke on the frame beside the drop out on the back

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      • #4
        It is an aluminum frame. It broke the frame on the back beside the chain stay

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        • #5
          It is a bhsd mid drive set up at 750

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          • #6
            My understanding is that once an aluminum frame is cracked then you have to replace the frame. My source of information is the instructor at United Bicycle Institute in Portland, OR.

            I use 4130 Chromoly steel frames. I would like to say that I have never cracked a frame, but I have done so running a Cromotor (with regenerative braking) with no torque plates. I later added 1/4" 303 SS torque plates which solved the problem.

            I'll bet that if you get a steel frame, then every single one of your bike parts will fit perfectly on the new frame. Mind the headset size and type, bottom bracket width, type and diameter, seat tube diameter and dropout width and type.

            When I cracked my frame, I had to completely strip it down, repair the frame (TIG with a stainless rod), make it pretty with JB Weld, powder coat it again ($200, 4 weeks) and then rebuild it. It was a pain in the neck. I posted the story of my cracked frame (with pictures) here: http://www.commuterebikes.com/torque...me-damage.html.

            Click image for larger version

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            Last edited by commuter ebikes; 2 weeks ago.

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            • Giant Rider
              Giant Rider commented
              Editing a comment
              I don't know what type of weld used to repair your crack but when dealing with aluminum and quality repair work you want to have it heliarc (TIG) welded using aluminum rod of the same type aluminum your frame is made from. Done by someone who knows what they're doing. This will be as strong or stronger than your original piece.

            • commuter ebikes
              commuter ebikes commented
              Editing a comment
              My frames are 4130 chromoly steel. The frame repair in the photos was TIG stainless (stainless rod). The guy that did it was a frame builder at the end of his 40 year career. He had had a stroke, so he was paralyzed on one side of his body. He had an assistant helping him; it was interesting to see two people welding. I think he charged $160 for the 90 minute repair. In all, this cracked dropout cost me $600, including the new powder coat. I definitely learned not to ride the bike without torque plates!

          • #7
            This is after the repair:

            Click image for larger version

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            Last edited by commuter ebikes; 2 weeks ago.

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            • #8
              If you replace your aluminum frame with steel, then you can repair it if this ever happens again.

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              • #9
                I might try something like this if your frame should fail again. I would recommend fabricating a gusset to back up and reinforce the entire bracket using aluminum material a little thinner than the existing bracket this will allow for a good welding area in the V-shaped corner created by the thinner gusset material and the existing bracket. Here's a sketch for a visual, if you're worried about your existing bolt holes you can omit conforming the gusset around them and weld only the top and bottom portion. Food for thought.

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                • #10
                  Originally posted by Giant Rider View Post
                  I might try something like this if your frame should fail again. I would recommend fabricating a gusset to back up and reinforce the entire bracket using aluminum material a little thinner than the existing bracket this will allow for a good welding area in the V-shaped corner created by the thinner gusset material and the existing bracket. Here's a sketch for a visual, if you're worried about your existing bolt holes you can omit conforming the gusset around them and weld only the top and bottom portion. Food for thought.
                  This is a steel frame. It has 1/4" steel torque plates on each side now. The torque plates are completely bombproof. The damage in the photo happened while I was riding without the torque plates.

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