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retrodirect/glowbike

Member since Oct 2014 • Last active Feb 2021
  • 15 conversations
  • 130 comments

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  • in Frame Builders
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    sweet clamps. group buy? were they all snapped up?

  • in Frame Builders
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    MVI_4266

    This is what the wheels do. They were adjusted way too tight in this wee video. Have been loosened off now and run well, but i don't have video of that. :) They turn the extrusion into a big linear rail.

    Click the photo for video

  • in Frame Builders
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    orange = main beam
    green = upright
    red = anchor points to upright

    The upright is anchored across the full width of the plate so that the stifness comes from the cross-section of the extrusion rather than relying on the cross-section of the plate. See how the upright goes across all of the metal plate?

    The same thing is happening with the main beam so the extrusions end up mating face to face. (with the plate acting kinda like a big washer)

  • in Frame Builders
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    The arrow was supposed to be pointing to the airgap between the two bits of extrusion where all the load will be transferred through two thin plates. I lack paint skills.

    You want the bits of extrusion to clamp to each other face to face not cantilevered up on thin plates.

    Re:price
    You don't need S355, fixtures need stiffness not strength. Better steel gets you a better yield strength but the stiffness will be the same.

    That price will go down if you add more bits. Small orders are priced WAAY higher to account for set up and office time.

  • in Frame Builders
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    re:pricing.

    • 20%tax + post
  • in Frame Builders
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    Couple of things.

    Your price sounds off...
    Have you checked your DXF sizing? DXF files are unitless, they are essentially just a set of lines that the software follows. make sure before you export them they're in mm as that's what fractory use.

    The bit which has the arrow pointing to it is where all the flex is going to come from. The extrusion is by design quite stiff (high second moment of area). this means you'll get the best results using that stiffness to your advantage. A plate has quite a low second moment of area which means it'll be flexy.

    If you can mount the upright beam across the full width of the steel plate it'll support the plate and stop it flexing and you'll get a stiffer jig.

  • in Frame Builders
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    Also did a lasercut butt-feeler. For feeling butts



  • in Frame Builders
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    These 3 plates cad'd up quickly to prove the idea worked. A proper version TBC.

    I wanted to use 3d printer wheels to ensure there was no slop in a plate which could both slide and have an angle adjust. usually with 8020 as you loosen a bolt the whole plate will become loose in the slot and weeble wobble about in all planes. the wheels limit the degree of freedom to 1. they're adjustable on eccentric nuts to take up any slop.



  • in Frame Builders
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    I've just lasercut a framejig from 5mm plate. The biggest issue you'll have is validating alignment once it is built. I did it via the long route using angle finders etc. for now. I'm currently figuring out how to make a laser aligner for this purpose.

    I used wheels from a 3d printer on eccentric mounting nuts in place of a linear rail system. It holds alignment and has no slop. I'll update with photos of it assembled when I get into the workshop tomorrow eve.

  • in Frame Builders
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    It's just rammed in there to check fit. :)

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