Thoughts on custom dropout design- Mtbr.com
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  1. #1
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    Thoughts on custom dropout design

    Hoping to get some opinions on this dropout design. It's on a custom built, fillet brazed steel hardtail I had a local builder make for me (one of his first frames), with a geo for some rowdy riding. It also has to handle the occasional trials move (back wheel hops and those kind of things).

    The little front brace of the brake side dropout you see in the pic broke after 600 km of riding. It's water jet cut from a 4 mm thick steel plate, with an extra 3 mm stainless steel strip behind around the brake mount. Seat and chain stays are 4130 steel.

    Although I think it looks really nice, I also always thought the back end looked perhaps a bit too delicately built with the thin stays and big cutaways in the dropouts, but I'm no engineer and no frame builder. I'd love to hear your thoughts on the design. Could removing the 3 mm stainless strip at the brake mount, and adding a new strip with an additional brace (basically reinforcing the little brace that broke) be a long term solution, or would it be a better idea to change the whole dropout, for heavy duty riding?



  2. #2
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    I'm not an engineer nor frame builder but yeah, that looks very delicate.
    This post is a natural product. Variances in spelling & grammar should be appreciated as part of its character & beauty.

  3. #3
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    I would ask the builder who made it what he thinks, since it was his project to begin with. But I think cutting the existing brace (the little one) out and putting a bigger one in seems like a decent solution. It's probably only going to be an issue on the brake side because of all the forces/vibration involved in braking.
    Myth Cycles handbuilt bike frames
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    http://www.mythcycles.com

  4. #4
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    For me the C shaped bridge in that dropout is all wrong. It adds no structural strength, and by its very nature will flex like a hinge. I think this flexing is what has caused the failure. Nice as it may look, I donít think itís a good design feature. Also the strip thatís been added is not really doing anything to take away from the loads that will pass through the ďCĒ.

  5. #5
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    Thanks for the input guys. Removing the current strip behind te brake mount and adding a new strip with an extra bridge built in, around where the little broken C sits, is the builder's idea. I agree with you Cord that the C adds no strength, just flexes. Would it be much different if it were straight instead of curved? Trying to think along with the builder here, as this'll be his first repair of this nature, and I want to get it as right as we can.

  6. #6
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    Straight would defo be an improvement.

  7. #7
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    I would just cut out those tiny arcs, they don't do anything except add a huge stress riser.

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