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Question A linear drive in the center can be used?

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by misoswan, May 7, 2017.

  1. misoswan

    misoswan Active Member

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    hello


    A linear drive in the center can be used? If yes how?
    thanks
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  2. SilentChill

    SilentChill Problem Maker SimTools 2.0 Beta Tester

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    I have no idea how they are doing that it must have a mix of every DOF going into it, for each of the 2 axis which it is connected to. I can picture its use for Heave but its hurting my brain trying to think how its being operated for the other DOF's
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  3. adgun

    adgun Member

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    I think it,s a pneumatic cylinder used as a gasspring
  4. SilentChill

    SilentChill Problem Maker SimTools 2.0 Beta Tester

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    Haha oh well thought it was a bit weird , maybe I should of looked closer
  5. iTek

    iTek Tek

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    I don´t see so many using this kind of support for the platform in the forum and wonder way? I have seen some builds with it though. I am thinking of using it my self with some kind of gas spring or so. In my opinion, as a novices in this hobby, I belie this would be a huge help to support the platform and alter the calculations of motor, speed and ballscrew. Or am I wrong?
  6. SeatTime

    SeatTime Well-Known Member SimTools 2.0 Beta Tester

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    My Motion Simulator:
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    I have used gas struts in a similar setup to help with the weight of my Direct Drive servo motor, just need to be careful of the Nm used as they can dampen movement if the Nm is too high and monitor them for any failure. Better to design the rig so that you do not need them.
    Last edited: Nov 28, 2018
  7. iTek

    iTek Tek

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    Thanks for the input.
    Maybe gas spring isn't the best solution, an ordinary spring maybe be better without any damping. I thinking any support must be better then none even if it is 50 kg lift it is 50 kg less to move up and 50 kg less force to break then going down. Even if designing without the support it must be easier and less wear on all moving parts if you have some sort of support. I think, as you say, designing with out is the best way to start .
    A easy way to do it could be to use springs attache to the ceiling with wires or even rope, if the ceiling can hold it that is? Of course safety must be considered and it might not be the safest solution.
  8. SeatTime

    SeatTime Well-Known Member SimTools 2.0 Beta Tester

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    My Motion Simulator:
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    I'm not a fan of using springs to support a sim frame, as they can cause oscillations/bounce - think of a car with springs and no dampeners. Lots of sim videos out there which are fitted with springs were you can see this happening.
  9. iTek

    iTek Tek

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    Ok, I have not seen this, have to google more i think. :) But compared to a car with no damper the sim has electric motors to control the whole movement (active suspension :)) and as you said earlier damping is not what you want. As far as my example with 50 kg lift above, wouldn't that be the same as put a 50 kg lighter person in the rig? Wouldn't the optimal to have support for the hole rig with driver so it wold be almost "weightless"?
  10. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator SimTools 2.0 Beta Tester

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    My Motion Simulator:
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    Weightless is the ideal and at rest my compact rig with assisted heave knee is like that.

    But there is a small amount of resistance and that increases the further the rig moves from its weightless assisted state. Fortunately in my rig the total axis movement is not huge and well within the torque capabilities of the 60:1 200W motors, which don't even get warm after hours of use.
    Last edited: Nov 29, 2018
  11. SeatTime

    SeatTime Well-Known Member SimTools 2.0 Beta Tester

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    No, I wish it was that simple - what complicates matters is inertia and the storage of energy in a spring, especially in a fast moving sim. Often the best teacher is self discovery.
    Last edited: Nov 29, 2018
  12. iTek

    iTek Tek

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    Thank you!
    Then I might not be totally out of bounds. Now I have to find right kind of spring. I belie the length can be a problem. My be I have to make them my self?

    Ok. You might be right, and definitely right about "self discovery" :) I think I'am going for it any way and learn by doing. Thank you for sharing your experience.

    Is there anyone else out there with experience in the matter?
  13. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator SimTools 2.0 Beta Tester

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    My Motion Simulator:
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    Some have made Springs, but it is not easy to get the parameters spot on.

    Personally I went the other way and recycled the adjustable spring from the high-end DX office chair I used for my sim, which means I can dial it in for different user weights, which is really what it was actually designed for.