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Showroom 6DOF Motion Platform á la Knaufinator

Discussion in 'DIY Motion Simulator Projects' started by DirkGently, Nov 26, 2020.

  1. DirkGently

    DirkGently Tweaking, always tweaking.

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    My Motion Simulator:
    Motion platform, 6DOF
    Hello Folks, I've been so inspired by all of the cool designs and extraordinary talented people here that I feel that I have to build a platform for myself! It will use the excellent looking control system devised by Knaufinator:
    https://www.xsimulator.net/community/threads/compact-ac-servo-6dof-rotary-stewart-platform.14769/

    My focus will be on the mechanical design to make an aluminium version that can be bolted together. Also for use with VR (HTC Vive) Please feel free to make suggestions or point out mistakes :grin I will aim to keep you updated with the evolution of the design and my calculations as I go :nerd

    Also a big thank you to all of the people that very generously share their knowledge on here!
    • Like Like x 1
  2. DirkGently

    DirkGently Tweaking, always tweaking.

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    My Motion Simulator:
    Motion platform, 6DOF
    Capture.PNG
    This is my design so far. My intention is to use the plate at the top for mounting the seat and aluminium profiles beams for the wheel and pedals. Wiring to pass through the central hole.
    • Like Like x 3
  3. DirkGently

    DirkGently Tweaking, always tweaking.

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    My Motion Simulator:
    Motion platform, 6DOF
    Photo showing one of my kids helping with my analogue method to calculate my CoG for seat positioning :)

    Meanwhile, in spreadsheet world, it sounds like I need to be able to get some good speed (250mm/s) for this to work well with VR having found this useful reddit contribution from @noorbeast :
    https://old.reddit.com/r/virtualrea...otion_systemsplatforms_vr_latency_and_nausea/
    Does anyone have any experience with speeds and washout acceleration or jerk? This seems to be the biggest contribution to the amount of movement needed. If I use 250mm/s and washout of -0.12m/s² then the platform needs something like 250mm of movement. Acceleration doesn't seem to be such a big deal.

    Attached Files:

    • Like Like x 1
  4. DirkGently

    DirkGently Tweaking, always tweaking.

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    My Motion Simulator:
    Motion platform, 6DOF
    It's been a busy few months so I have some build photos to update the project. Starting with the servo driver Housing. The frame is made from 20mm box section steel with steel strips with threaded holes to mount the servo drivers and power distribution.

    Attached Files:

  5. DirkGently

    DirkGently Tweaking, always tweaking.

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    My Motion Simulator:
    Motion platform, 6DOF
    So after a few screwups, I managed to figure a way to get the ribbon cables nice and tidy, even though they're round the back you never see them!
    The controller housing is complete now and includes cooling, an emergency stop and a glass front.
    IMG_4970.jpg

    Attached Files:

    • Like Like x 2
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  6. DirkGently

    DirkGently Tweaking, always tweaking.

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    My Motion Simulator:
    Motion platform, 6DOF
    And the platform has progressed:
    IMG_4955.jpg

    You can see that some of my welds are getting quite good...
    IMG_4958.jpg
    and some are not!
    IMG_4956.jpg

    For every good weld, I probably ground out and rewelded about 6 but it's coming together nicely now.
    IMG_4966.jpg
    • Like Like x 4
  7. DirkGently

    DirkGently Tweaking, always tweaking.

    Joined:
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    My Motion Simulator:
    Motion platform, 6DOF
    Also, I realise that the design has changed a lot since my first ideas. Machining parts costs about 2-3x fabricated (welded) frames and they're heavier. So I had to change my plans.
  8. DirkGently

    DirkGently Tweaking, always tweaking.

    Joined:
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    My Motion Simulator:
    Motion platform, 6DOF
    These are the rods that support the platform after I welded them up (it's improving but I moved them all to only show the good sides ;) )
    IMG_4983.jpg
    And with the rod-ends fitted. These are QA1 PCY rod-ends, which have a HUGE angularity - when the platform is running, I'll post a review on the durability.
    IMG_4984.jpg

    I've been painting them tonight so I have some time to post these updates while they are drying and my garage stinks of paint fumes...
  9. DirkGently

    DirkGently Tweaking, always tweaking.

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    My Motion Simulator:
    Motion platform, 6DOF
    Seatbelts were from EBay - these were brand new but had expired their use by date so were super cheap :grin
    IMG_4981.jpg

    The frame is complete and ready to prepare for painting:
    IMG_5009.JPG

    Some details showing the cones that connect to the tops of the rods and the seatbelt mountings.
    IMG_5011.JPG

    This is the mounting plate for a vive tracker. I wanted it to be attached to a rigid part of the structure so I added this 'sting' up the back. I think it can be useful for running all of the wires to controllers and headset.
    IMG_5012.JPG
  10. DirkGently

    DirkGently Tweaking, always tweaking.

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    My Motion Simulator:
    Motion platform, 6DOF
    Rod-end attachment detail. These are 1/2" bolts.
    IMG_4990.jpg
    • Like Like x 2
  11. DirkGently

    DirkGently Tweaking, always tweaking.

    Joined:
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    My Motion Simulator:
    Motion platform, 6DOF
    It's taking me a long time to build the platform but I wanted to test the motors and all of my wiring so I built a lightweight wooden version. This is the first time I had it working correctly, it was an exciting stage to get to!


    And then with the help of my children I tested it with Simtools and PCars2


    Also a big thank you to everyone who posts on here and keeps my inspiration going when the project gets on top of me :cheers
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  12. DirkGently

    DirkGently Tweaking, always tweaking.

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    My Motion Simulator:
    Motion platform, 6DOF
    I've made some good progress lately. The base is fabricated from laser-cut steel parts that are welded together to make the motor mount pairs:
    IMG_5059.jpg

    Then these are welded onto the base plate, which is ½" steel:
    IMG_5061.jpg IMG_5079.jpg IMG_5080.jpg

    Some of the welds are even good enough to show :grin:
    IMG_5064.jpg

    And the base plate sits on the base frame, which has wheels so I can move it around:
    IMG_5105.jpg
    • Like Like x 2
  13. DirkGently

    DirkGently Tweaking, always tweaking.

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    My Motion Simulator:
    Motion platform, 6DOF
    Emergency stop circuit is now wired up. It uses XLR instrument cables so can be easily extended.
    IMG_5131.jpg
  14. DirkGently

    DirkGently Tweaking, always tweaking.

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    My Motion Simulator:
    Motion platform, 6DOF
    Seat/platform is now complete for now. I'd like to add pedals and steering wheel but that's going to have to wait until I can afford them. Priority is to get the system working and tested.
    IMG_5070.jpg IMG_5071.jpg
    • Like Like x 1
  15. DirkGently

    DirkGently Tweaking, always tweaking.

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    My Motion Simulator:
    Motion platform, 6DOF
    I also started the assembly of the base:
    IMG_5110.jpg IMG_5130.jpg

    Hall Effect sensor brackets are made from stainless steel:
    IMG_5123.jpg
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  16. DirkGently

    DirkGently Tweaking, always tweaking.

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    My Motion Simulator:
    Motion platform, 6DOF
    One of the fiddliest bits was fastening the gearboxes into the base. I need to keep the fastener heads low to clear the lever arms so I wanted the 'nut' to be on the inside. I tried a few different types of nut but there was no access to hold the nut while tightening it - I blame the designer ;)
    In the end I used corner anchor nuts:
    IMG_5128.jpg
    These were superglued in place, which was just enough to hold them while the thread engaged, then after the bond broke the shape meant they were prevented from rotating while I did the nuts up. The anti-rotation worked in both directions so they can be undone easily as well. I was happy with this solution after a lot of head scratching!

    I used ½"UNF screws in the Ø6.5mm holes, which allowed a bit of wiggle room.

    These are the gearboxes: https://www.aliexpress.com/item/32967571001.html
    These type of anchor nuts: https://www.ebay.co.uk/itm/NOS-1-4-...Nut-MK3001-B4-qty-10-N-1-MS21074/184034726659

    Attached Files:

    • Like Like x 1
  17. Ian Pace

    Ian Pace Member

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    well done on the fabrication work! looking forward to seeing this ready!
    • Agree Agree x 1
  18. DirkGently

    DirkGently Tweaking, always tweaking.

    Joined:
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    My Motion Simulator:
    Motion platform, 6DOF
    Thanks Ian - it's been a very steep learning curve. I can't wait either!
  19. DirkGently

    DirkGently Tweaking, always tweaking.

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    My Motion Simulator:
    Motion platform, 6DOF
    Lever arms were the bit I found most difficult in terms of having a cheap, reliable design that was accurate enough for what I wanted. I was quoted £300 to machine a single aluminium arm that would have a close fit on the gearbox shaft and also clamped to the key. I'll post separately about that design because it might spark some ideas but for me it was too expensive.
    After a lot of thinking, I came up with a relatively cheap solution that I think satisfies the requirements, using a keyless locking bush:

    https://www.transdev.co.uk/hardware...es/translock-standard-keyless-locking-bushes/

    There were two main parts to mounting the lever arms:
    - modifying the gearbox output shaft
    - making the arms
  20. DirkGently

    DirkGently Tweaking, always tweaking.

    Joined:
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    Design Engineer
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    +65 / 0 / -0
    My Motion Simulator:
    Motion platform, 6DOF
    The locking bushes use a double cone arrangement to clamp onto the shaft. I thought the loads might be high enough to deform the keyway if it didn't have a key in it:
    Capture.PNG
    Standard key size is 6x6mm so I ground the keys to 3.5mm thickness with this setup so that the slot would be supported but the key wouldn't stick out too far and stop the locking bush going on:
    grinder setup.jpg
    It was a bit sketchy but it worked!
    0187b8f6c5b60c686223dd9c25da037200515904a1.jpg
    I also drilled an tapped an M3 hole through the key to help me remove it:
    01c898613dcf4de2ae71e487563f57819905d13e79_00001.jpg
    • Like Like x 1