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3dof seat mover

Discussion in 'DIY Motion Simulator Projects' started by digitalmonk, Oct 31, 2017.

  1. digitalmonk

    digitalmonk New Member Gold Contributor

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    Well, finally got all the parts I need for my 3DOF seat mover. (roll, pitch, heave)

    4 JRK controllers
    pgsaw ebay motors (25:1 and 50:1) can't decide, and need some input
    Server power supplies (I assume i need 4)
    [​IMG]
    https://www.ebay.com/itm/Lot-of-2-D...0BB/222409818423?_trksid=p2485497.m4902.l9144


    I'm starting of with a Sim-Lab GT1 rig.
    [​IMG]

    My approach is to use a similar setup as the Simukit (4 motor) 3dof, but using wormgear motors.
    [​IMG]
    [​IMG]


    Actually already bought 2 sets of pgsaw ebay motors
    4 25:1 and 4 50:1.

    First question:
    What do you think would be better the 25:1 or 50:1 motors?

    As mentioned i will be using JRKs.
    Already started mocking things up with a 3d printed axle to test. (will be replaced with threaded rod)
    [​IMG]

    [​IMG]

    Also did a 3d print for the pot holder. Seems to work well.
    I'll upload the stl file and link it here in case anyone else wants to use it.

    I did a test config on one of the motors with the JRK utility.
    Not sure if this is normal, but when testing the movement with a max acceleration setting (600), and aggressive direction changes via the target slider on the input tab, the power supply would crap out. And I kept getting a Max Current Exceeded fault. The PS is rated at around 69A, so I'm not sure what the issue is.
    Is 600 acceleration not to be used, or do i need a more powerful PS.

    Thanks for any input and suggestions.
  2. Ads Master

    Ads Master

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  3. Lol4

    Lol4 Member

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    My Motion Simulator:
    3DOF, DC motor, JRK
    Great idea to 3d print the pot holders. Do you have the .stl files to share? Thanks.
  4. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    My Motion Simulator:
    3DOF, DC motor, JRK
    In a compact design 50:1 are better as torque really matters. Personally I use 60:1s, but they are not available via your provider.

    Use 1 PSU per motor, particularly with servers PSUs, as it helps manage the large spikes when an axis reverses. LED PSUs are more fault tolerant than server PSUs.
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  5. digitalmonk

    digitalmonk New Member Gold Contributor

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    Thanks noorbeast.

    So would you suggest I just get some LED power supplies to make sure I don't run into any issues? And would two 30A units be enough for 4 motors?

    Also one other concern I had with the 50:1 motors is their speed. 75rpm vs 150rpm for the 25:1. Is 75 enough?
  6. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    My Motion Simulator:
    3DOF, DC motor, JRK
    Sim motors may draw up to their stall current, which is far greater than their rated current, multiple motors could be handled by a single PSU but it needs to be powerful enough to supply the spike loads and honestly I consider it pays to go with one PSU per motor to avoid any possible issues.

    With respect to motor and lever linear speed keep in mind that design also affects the actual motion and speed of the seat. In a compact design moving the base requires more torque but the speed and movement range of the seat is amplified by the seat back height.
  7. digitalmonk

    digitalmonk New Member Gold Contributor

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    Here you go

    [​IMG]
    [​IMG]

    Attached Files:

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    Last edited: Nov 2, 2017
  8. Lol4

    Lol4 Member

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    My Motion Simulator:
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    Thank you
  9. digitalmonk

    digitalmonk New Member Gold Contributor

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    Slight progress...





    Managed to bench test two of the motors one 25:1 (on left) and 50:1 (right)
    The 25:1 definitely reacts a lot faster. It might be down to tuning though...

    Quite happy that things are actually working in LFS.
    Still have to read quite a bit on how to set everything up properly and then start building the actual rig to add to my Sim-lab cockpit.
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  10. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    My Motion Simulator:
    3DOF, DC motor, JRK
    What you observe has to do with physics not settings, the ratio of the wormdrives means that the 25:1 is going to react twice as fast, but have less torque than the 50:1, notwithstanding mechanical loss, which is a bit higher for the 50:1.
  11. digitalmonk

    digitalmonk New Member Gold Contributor

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    Question:
    Although initially I was going to use 4 JRK's for the project, I'm now seriously thinking about an Arduino board and 2 Sabertooth 2x32 drivers. (already have these)

    I think I have all the info in terms of setting things up (Flashing Arduino code as well as setting up the Sabertooth and wiring). the only thing I'm confused about is how do you set the Max, Min and center for the levers and pots?

    With the JRK's you set things through the utility, (pot center, Max min lever angles) and you can test the motion. I have no idea how to do this with the Arduino/Sabertooth combo, and I can't find this step in any of the tutorials.

    Thanks
  12. digitalmonk

    digitalmonk New Member Gold Contributor

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    Made the move to Arduino and Sabertooth.

    [​IMG]
    [​IMG]

    hooked everything up today, and she's alive!!

    Now I just have to clean up the wiring and get the rest set up (seat platform, and all connecting rods and support springs).

    Next will be tuning..
    Speaking of which are there any good guides to setting up a 3dof in Simtools?
    I'm getting confused as to how each of the levers are supposed to be positioned based on the DOF effect (pitch, surge..)
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  13. digitalmonk

    digitalmonk New Member Gold Contributor

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    Ok so I hit a bit of a snag. Everything has been put together. Everything works however when I test Heave in simtools the chair platform does not move straight up. It looks like it's shifting to the right on upward motion and to the left on downward motion. When the levers are centered the support springs are perfectly straight. When it goes up or down the platform shifts to either side. And the springs are no longer at a 90degree angle.

    This is what it looks like unpowered. Once powered it levels out. The springs are straight. I made sure all the threaded rods have same measurements side to side etc..

    Can't figure out what the issue is. If I pitch the front or back tilt straight down without a shift. But heave shifts the platform.

    What is the most common issue for this?

    Attached Files:

  14. RandomCoder

    RandomCoder Active Member Gold Contributor

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    Could it be the torsion link you have going from the base between the motors to the platform? The pictures don't show how it's mounted but I'm guessing it could be your problem. Due to being fixed length and if bolted to the base it will cause the platform to travel in an arc.
  15. SeatTime

    SeatTime Well-Known Member

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    My Motion Simulator:
    DC motor, Motion platform, 6DOF
    Nice build :thumbs. Don't have a comment on the geometry issues that you seem to have for heave, but IMO - I'm not a fan of using springs to help support the load, they can be OK for aircraft sims were things are moving relatively slow, but once you start moving your rig fast with you sitting on it, they will store all that inertia and release it as unwanted oscillations. If you must use something, from my own experiments I found low N gas struts (only use as much as you have to - I used three x 100N on my rig) to be better for our use case. The only issue with the gas struts is that they can fail over time - so you have to keep an eye on them. Struts will of course try to dampen movement, but if you don't go too high Newtons wise, they should not cause you any real issues. Ideally you would use nothing. Anyway something to think about :think.
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  16. yobuddy

    yobuddy Well-Known Member Staff Member Moderator SimAxe Beta Tester SimTools Developer Gold Contributor

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    Here is the problem...
    This bar pushes it to one side or the other when it goes up or down.
    20180122_225206.jpg
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  17. yobuddy

    yobuddy Well-Known Member Staff Member Moderator SimAxe Beta Tester SimTools Developer Gold Contributor

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    I think with this kind of build, you need 4? hinge connections like the one on the front of this sim.
    3-270x176.png
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  18. digitalmonk

    digitalmonk New Member Gold Contributor

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    Thanks for the reply guys. Randomcoder you zeroed in on the problem. Yobuddy the bar is supposed to be there but I had it at a too much of an angle. Base vs seat platform. It's supposed to be more like in this image.

    The design does work well. I just totally messed up the angle. I didn't think it was supposed to be almost straight.

    SeatTime do you have a link to the gas struts?

    Related question. Do I even need the springs if I'm using 4x 50:1 motors? I tried to duplicate the simukit design and that uses springs but the motors on that don't have as much torque.

    Thanks again for all your help.

    Attached Files:

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    Last edited: Jan 24, 2018
  19. digitalmonk

    digitalmonk New Member Gold Contributor

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    Finally Done!
    I fixed the angle of the middle rod and it's all good.

    Now the fun part starts with tuning the motion..

    Here are some pics of the final setup.

    One thing I noticed.
    If I turn on Output testing the platform settles to the middle position and is even. However when I start Assetto Corsa and sit in the car the seat is tilted slightly to the left. Not sure why. Is this normal? You can feel it while driving as well. As if the car has a constant roll force applied to it.

    Attached Files:

  20. prodigy

    prodigy Burning revs

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    My Motion Simulator:
    2DOF, SCN5
    Have you found min/max values in the Tuning Center?
    Reset all values in Tuning Center and run 1-2 clean laps to find min/max values.

    Maybe the sway or roll values are not even and the seat is tilted.
  21. digitalmonk

    digitalmonk New Member Gold Contributor

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    Finaly! First test in Dirt Rally.
    I think I'll have to tweak the settings a bit more, but so far so good!

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