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Showroom 2 DOF Sim V3 (plus WMR VR headset)

Discussion in 'DIY Motion Simulator Projects' started by Bruceaust, Feb 6, 2019.

  1. Bruceaust

    Bruceaust Member

    Joined:
    Sep 2, 2011
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    Occupation:
    CNC Routing
    Location:
    Launceston, Tasmania, Australia
    Balance:
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    +11 / 0 / -0
    My Motion Simulator:
    2DOF
    Hi all
    l have started building my third motion Sim.
    This time around I am endevouring to place the centre of rotation at the VR headset position. (Just in front of my eyes)
    This means my head should stay revativly in one position which hopefully will negate the need for any movement compensation fudges.
    (I have discussed this idea in the VR forum also.)

    Anyway, I will post pics as the project develops.

    At this stage I have nutted out my drawings and built the seat and the seat mount with the above mentioned centre of rotation. I will be making my own linear actuators from linear bearings and DC work drives. Hopefully this will give me + - 15 deg on both axis . The actuators will be at the front of the rig and driving once again around the centre of rotation point.
    Fingers crossed it all will be well !
  2. Bruceaust

    Bruceaust Member

    Joined:
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    Occupation:
    CNC Routing
    Location:
    Launceston, Tasmania, Australia
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    Ratings:
    +11 / 0 / -0
    My Motion Simulator:
    2DOF
    IMG_20190206_205348.jpg The seat mount.
  3. Bruceaust

    Bruceaust Member

    Joined:
    Sep 2, 2011
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    Occupation:
    CNC Routing
    Location:
    Launceston, Tasmania, Australia
    Balance:
    320Coins
    Ratings:
    +11 / 0 / -0
    My Motion Simulator:
    2DOF
    The seat in position showing the centre of rotation IMG_20190206_205515.jpg
  4. Bruceaust

    Bruceaust Member

    Joined:
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    Occupation:
    CNC Routing
    Location:
    Launceston, Tasmania, Australia
    Balance:
    320Coins
    Ratings:
    +11 / 0 / -0
    My Motion Simulator:
    2DOF
    My CAD sketches - work in progress Sim v3.1.jpg
  5. Erik Middeldorp

    Erik Middeldorp New Member

    Joined:
    Sep 15, 2018
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    Occupation:
    sheet metal worker
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    Interesting design, I haven't seen one like that before. I'm hoping to build my first motion rig in the near future and I like the idea of a high point of rotation because it would mean the initial acceleration you'd feel as the rig starts to move would be in the same direction as the acceleration you're trying to simulate by tilting the rig. Has that also motivated your choice for a high pivot point as well as trying to reduce head movement? The only other rig I've seen with a high pivot point is this one https://www.xsimulator.net/community/threads/new-lighter-2dof-simulator.11118/ which is pretty similar to what I hope to build with its use of rollers and rails except i'm thinking to have the pivot at eye or head level like you are.
  6. Bruceaust

    Bruceaust Member

    Joined:
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    Occupation:
    CNC Routing
    Location:
    Launceston, Tasmania, Australia
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    Ratings:
    +11 / 0 / -0
    My Motion Simulator:
    2DOF
    Yes, my original idea for having the pivot point at the head was as you described. After building 2 Sims I realised that the physics of the motion was not emulating the g forces that was supposed to be simulated. For example, with a pivot point lower than your head, under braking the movement of the seat pushes you in the back as the seat rotates forward. In a real car situation, your body is accelerated forward relative to the de-accelerating movement of the vehicle and you feel a force of the seat belt pushing you on your chest!. Having the pivot at the head will more closely simulate what happens I the real world.
    The happy coincidence is that it should also cancel out the forward/up movement fed back into a VR headset as the rig rotates under braking.
    I hope I make sense!
    I am really looking forward to testing this idea.
    • Like Like x 1
  7. Bruceaust

    Bruceaust Member

    Joined:
    Sep 2, 2011
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    Occupation:
    CNC Routing
    Location:
    Launceston, Tasmania, Australia
    Balance:
    320Coins
    Ratings:
    +11 / 0 / -0
    My Motion Simulator:
    2DOF
    This pic shows the yoke and bearing attachment to the seat frame. IMG_20190208_201554.jpg
  8. Erik Middeldorp

    Erik Middeldorp New Member

    Joined:
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    Occupation:
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    Have you done stress calcs for the round bar? I just did some guesstimate calcs assuming the bar is 25.4mm dia, the distance from the pitch pivot to the roll pivot is 500mm and the load the yoke will have to support is 150kg using the Cantilever Beam with Point Load Calculator at amesweb.info with these values:

    INPUT PARAMETERS
    Parameter Value
    Load [P] * 1.5kN
    Beam Length [L] 0.5m
    Distance a 0
    Distance x 0
    Modulus of Elasticity [E] 200GPa
    Distance from neutral axis to extreme fibers [c] 12.7mm
    Second moment of area [I ] ** 20431.711mm^4

    RESULTS
    Parameter Value
    Reaction Force 1 [R1] 0.0
    Reaction Force 2 [R2] 1.5kN
    Transverse Shear Force @ distance x [Vx] 0.0
    Maximum Transverse Shear Force [Vmax] -1.5kN
    Reaction Moment 1 [M1] 0.0
    Reaction Moment 2 [M2] -750.0Nm
    Moment @ distance x [Mx] 0.0
    Maximum Moment [Mmax] -750.0Nm
    Slope 1 [θ1] 2.629 degrees
    Slope 2 [θ2] 0.000
    Slope @ distance x [θx] 2.629 degrees
    Maximum Slope [θmax] 2.629 degrees
    End Deflection 1 [y1] -15.295 mm
    End Deflection 2 [y2] 0.000
    Deflection @ distance x [yx] -15.295 mm
    Maximum Deflection [ymax] -15.295 mm
    Bending Stress @ distance x [σx] 0.0
    Maximum Bending Stress [σmax] 466.2 MPa
    which indicates it might not be strong enough, depending on my guesses and what type of steel the round bar is.
  9. Bruceaust

    Bruceaust Member

    Joined:
    Sep 2, 2011
    Messages:
    73
    Occupation:
    CNC Routing
    Location:
    Launceston, Tasmania, Australia
    Balance:
    320Coins
    Ratings:
    +11 / 0 / -0
    My Motion Simulator:
    2DOF
    Wow,
    Thanks for taking an interest in my protect. As you point out, I am concerned withe the cantilever being the weak point. I have used 25 X 75mm section RHS where possible. I have just finished tacking the other parts of the rig together. After manualy moving the rig, I found that some parts need to be beefed up. I am working on it! I reckon I can make it work well. ------ work in progress
    • Like Like x 1