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Wheel arrangement for heaviest load on rails

Discussion in 'Concepts and Ideas' started by Jodes, Mar 7, 2016.

  1. Jodes

    Jodes New
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    Hiya,

    I'm stuck on how to get wheels arranged best to allow the maximum load for that rail.

    I want a rail that will move linearly. Let's say it's a short 20mm x 20mm profile that slides parallel on another, longer 20mm x 20mm profile. The load will be on top of the short profile. I want to optimise the wheel arrangements so they can handle the greatest force that the profiles can take.

    It makes sense that the main load bearing wheels should be in between the two profiles. And some how, both sides of the wheels' axles should be supported by the bottom rail in the strongest possible way.

    I can't seem to find any plates or brackets which would allow an arrangement like that. Am I missing something?

    (I will also need some wheels on each side of the top profile to hold the top rail in place).

    Thanks!
    Jodes
     
    #1 Jodes, Mar 7, 2016
    Last edited: Mar 7, 2016
  2. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    You need to understand that the concept of "maximum load" is somewhat of a vague target and any maximum load is also relative to the overall system, not just individual parts. If you want to put say 50 pounds on the top rail, it can be done but the bottom rail will bow downward several inches at the middle. Would that still serve your purpose?

    Wheels aren't exactly designed to "hold things in place". They roll for a reason....

    You need to give us a much better idea of what you are trying to do in order for us to be of much assistance. (A Sketchup model would be nice.) On the surface it sounds like what you are asking can be done with a couple of standard gantry plates on the sides with through bolts, spacers and high and low wheels but without more information its really hard to say.
     
  3. Jodes

    Jodes New
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    Rick, thanks for your reply. This is incredibly daunting for me, especially given the budget I'm on. I apologise for the poor question.

    Do you have a drawing handy showing the arrangement you described with the through bolts and high/low wheels? I can't visualise it. (Or, two questions, by through bolt, you mean one where both ends are supported by gantry plates? and, these high and low wheels, what orientation are they? i.e. are their axles horizontal or vertical?)

    I'm afraid I cannot use Sketchup to save my life. But I will try to be as clear as possible:

    I can deal with any bowing of the beams. (Use thicker beams).

    The scenario:
    • Two beams arranged in parallel: one beam is above another: the small top beam slides horizontally, parallel to the bottom beam.
    • The top beam carries a significant weight.
    Constraints:
    • The top beam should not be free to lift off the bottom beam. (Hence my previous description "holding the beam in place".) But relatively little forces would be encountered that might cause derailment.
    Solution part (a):
    • Implementation: have wheels that slide in the side grooves of the bottom beam. This would stop the top beam from being derailed from the bottom beam.
    • The problem: with the direction of force on the wheels: the forces on those wheels would be parallel to their axles. I don't think the wheels or bearings are meant to take great forces in that direction. Instead, I suspect they are much better at taking forces perpendicular to their axles.
    So, solution part (b):
    • Implementation: Add additional wheels, attached some how to the top beam, that allow it to roll along the top groove of the bottom beam. This certainly fits with how radial bearings are designed to take the greatest forces. And I suspect wheels as well.
    • Implementation: implementation in part (a) would still be required to stop the top beam derailing.
    • The problem is:
      • I don't know what brackets/plates could be used to attach the wheels from part (b) while maintaining the alignment of the wheels from part (a)
      • The axles for the wheels in part (b) would have to be supported on both sides, since (if my maths is correct) this would make the axles capable of handling roughly 4 times the load, even though the axle length would be doubled!
    I hugely appreciate the help.
    Jody
     
  4. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Is this along the lines of what you are looking for?

    rail on rail.jpg
     

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