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Showroom Motorcycle 4 DoF Motion sim

Discussion in 'DIY Motion Simulator Projects' started by Chris_Beeves, Sep 10, 2021.

Page 5 of 12
  1. Gadget999

    Gadget999 Well-Known Member

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    My Motion Simulator:
    2DOF, DC motor, Arduino, 6DOF
    what ratio are the gearboxes ?

    how many amps / watts are the motors ?
    Gadget999, Aug 20, 2022
    #81
  2. Chris_Beeves

    Chris_Beeves Active Member Gold Contributor

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    My Motion Simulator:
    DC motor, Arduino, Motion platform, 4DOF
    1:60, 440W@24V
    Two 40A PSU’s, one front one rear,

    It does lift me in the end but very slowly.
    Chris_Beeves, Aug 21, 2022
    #82
  3. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
    3DOF, DC motor, JRK
    Perhaps you can try turning the front motors around 180 degrees and move the upper connection bar forward, to increase the inherent design leverage:

    Mod ideas.jpg
    • Useful Useful x 1
    noorbeast, Aug 21, 2022
    #83
  4. Chris_Beeves

    Chris_Beeves Active Member Gold Contributor

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    My Motion Simulator:
    DC motor, Arduino, Motion platform, 4DOF
    When the front motors work together, like pitch or heave it works perfect.
    When the rider leans left the rig leans right to simulate g-forces somewhat. The leaning is done by the front motors only, since the rear motor connections are free to rotate in that axis. This means one motor will bear all the lean load by itself, and moving it forward will reduce pitch and not affect the roll at all. The front motors would have to be moved further apart, but I don’t want to reduce range. I’d rather put a spring to unload and keep range.
    Chris_Beeves, Aug 21, 2022
    #84
  5. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
    3DOF, DC motor, JRK
    When leaning both motors are still involved, but the load is unequal .

    While moving the motors around and relocating the mount point forward will reduce pitch a little, it may not be as much as you may think, you could use SimCalc to work out exactly how much: https://www.xsimulator.net/communit...e-linear-speed-and-forces-of-your-design.270/

    Spring assist can help in one respect, counteracting a given load, it can also work against the motion fidelity of a rig. I use an adjustable spring on my rig for heave, made from an inverted DX office chair tilt mechanism, the benefit is that it can be dialed in to suit a specific mass, which may be radically different for different users.
    noorbeast, Aug 21, 2022
    #85
  6. Chris_Beeves

    Chris_Beeves Active Member Gold Contributor

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    @noorbeast, One goes down and one goes up. The one going up needs to accelerate the upper platform and the added blob (me). The one going down just needs to roll with it pretty much. When stationary again the load is more equal.

    How would the spring work against the motion fidelity?
    I understand that a gas spring would, but a normal compression spring?
    Chris_Beeves, Aug 21, 2022
    #86
  7. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
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    Even under normal compression spring fights against the compression force exerted by the motor and introduce a bias in motor responsiveness, the motors work harder when compressing the spring, but work less when reversed and are aided by the spring.

    The challenge with springs, as I mentioned referencing my own rig, is ensuring they are finely calibrated to the mass they are offsetting. Easier said than done, unless like mine where they are adjustable.

    Yes one goes down and one goes up, say in a turn, one pushing and one pulling, when returning that is reverses, the load is unequal but both motors are active.
    • Agree Agree x 1
    noorbeast, Aug 21, 2022
    #87
  8. adgun

    adgun Active Member

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    Maybe silly from my. But isnt it possible to not use the spring the whole time ,i mean when you get to far of balance the actuator arm whil be low isnt it possible to fit a spring there under and when the arm goes up the spring comes lose
    adgun, Aug 21, 2022
    #88
  9. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
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    Yes it is possible, but nonetheless it also introduces unequal load/unloading of motors, depending on the movement parameters.
    noorbeast, Aug 21, 2022
    #89
  10. Chris_Beeves

    Chris_Beeves Active Member Gold Contributor

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    My Motion Simulator:
    DC motor, Arduino, Motion platform, 4DOF
    The load of both the rider and upper platform is on the motor, I have a 4dof = no universal joint to help the motors carry the platform weight. So a spring will not mess up the bias, it will even it out. Unless I put a spring there that will lift about 150 kg. I won’t do that ;)
    No need to finely tune, just take some load off the motors.
    Chris_Beeves, Aug 21, 2022
    #90
  11. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
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    I would suggest it is not that simple, irrespective of design, as mentioned the key challenge is finely tuning a spring rate to mass, and even then one direction has greater resistance than the other, I say that as someone who uses spring assist, I am not against the idea, just pointing what needs to be be considered.
    noorbeast, Aug 21, 2022
    #91
  12. Chris_Beeves

    Chris_Beeves Active Member Gold Contributor

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    My Motion Simulator:
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    Ok, say the spring has a compression factor of 5N/mm. That would mean it would be loaded with 700N when fully compressed (roughly, I have a theoretical max travel of 140mm) with 0 preload = no load on the motors = the motors work just as quick in both directions = ideal?

    So say I put half that = the motors still work harder when lifting the platform than when dropping it = unloading the motors.

    Say I put a 10N/mm spring = the current ratio of motor load would be reversed, harder to compress than to lift.

    => a spring between 0-4N/mm preloaded would keep the motors having to work harder when lifting, just not as much.

    It doesn’t feel like I’m way off, but I won’t know until I try obviously :)
    Chris_Beeves, Aug 21, 2022
    #92
  13. Gadget999

    Gadget999 Well-Known Member

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    My Motion Simulator:
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    There should be plenty of force with the motors and gearboxes you have.

    Use a battery instead of a power supply, see if it helps.
    Gadget999, Aug 21, 2022
    #93
  14. Chris_Beeves

    Chris_Beeves Active Member Gold Contributor

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    My Motion Simulator:
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    The motors themselves have something like 1Nm of torque (stall, maybe a bit more). Geared 1:60 that would be 60Nm not counting losses, which in a cheap Chinese worm gear at the very best is around 30%, lever length 70mm => 850N x 0,7 = 600N ~ 60kg per motor..
    I’ll be pushing it without spring aid I think..
    Chris_Beeves, Aug 21, 2022
    #94
  15. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
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    The lever CTC at 70mm seems ambitious, given physics. Of course reducing it, like rotating the motors and moving the upper mount, will reduce the likes of pitch, but that is the reality of physics.
    noorbeast, Aug 21, 2022
    #95
  16. Chris_Beeves

    Chris_Beeves Active Member Gold Contributor

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    Yeah, that’s the problem. And since I don’t want to reduce the travel I have to help the reality of physics with some reality of physics! :D
    Chris_Beeves, Aug 21, 2022
    #96
  17. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
    3DOF, DC motor, JRK
    I will follow your progress with interest!
    • Like Like x 1
    noorbeast, Aug 21, 2022
    #97
  18. Chris_Beeves

    Chris_Beeves Active Member Gold Contributor

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    My Motion Simulator:
    DC motor, Arduino, Motion platform, 4DOF
    So after designing a few solutions and scrapping them for lack of suiting springs, I just took the plunge and ordered two "M-struts". Something like a gas spring without the damping and an actual spring inside. So nothing like a gas spring.. ;)

    upload_2022-8-31_21-39-43.png

    If two is too much, I'll just put a single one in the center. This will be interesting!
    Chris_Beeves, Aug 31, 2022
    #98
  19. Chris_Beeves

    Chris_Beeves Active Member Gold Contributor

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    My Motion Simulator:
    DC motor, Arduino, Motion platform, 4DOF
    That was quick shipping!
    upload_2022-9-1_14-11-42.jpeg
    I’ll try to get some testing done this evening!!
    • Like Like x 3
    • Useful Useful x 1
    Chris_Beeves, Sep 1, 2022
    #99
  20. Chris_Beeves

    Chris_Beeves Active Member Gold Contributor

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    My Motion Simulator:
    DC motor, Arduino, Motion platform, 4DOF
    The added reality of physics really did the trick!
    Now I can finally start tweaking without worrying about burning stuff up! :D
    • Like Like x 1
    Chris_Beeves, Sep 1, 2022
    #100
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