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Question New 6DOF + G-Seat Project Planning Questions

Discussion in 'New users start here - FAQ' started by thefost, Jan 7, 2020.

  1. thefost

    thefost New Member

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    Hi all. I'm a noob planning out my first motion simulator project - a 6DOF hexapod with some sort of G-seat eventually added. After a whole lot of reading and changing my mind a million times, I'm starting to finalize some of my build choices. To help me wrap the planning stage up I was hoping I could get some assistance from the experts :grin

    First off, here's a loose current plan:

    - 6DOF hexapod primarily for racing but also flying
    - VR Only with Valve Index and Motion Cancellation
    - 6x 80ST-M02430 AC Servo Motors
    - Thanos AMC-AASD15A Controller
    - Slightly beefier FlyPT actuator knockoff design using 20x80mm extrusions (larger profile will fit 80mmx80mm motor better, also I can pick up Misumi profiles locally)
    - 700mm SFU2010 Ballscrews ( Enabling roughly 550mm stroke and 500mm/s max actuator speed)
    - Build frame with Trip's G-seat project in mind to add later
    - Minimize frame footprint
    - Try to keep build , not including g-seat and VR, under $2k (edit: make that $2.5k) Will stretch as needed

    And here are a few questions:

    1) Is there anything you need to look out for when ordering ballscrews? Are all the chinese ballscrews basically the same quality or is there something I need to look for to reduce backlash and noise?

    2) I'm considering making the upper part of the frame out of aluminum profile extrusions. Yes, more expensive, but having modular options would be great. Has anyone done this? If not, is there any recommended software for modelling forces on the aluminum that wouldn't be too hard to learn? I'm curious to see if I could make a nice rigid frame while minimizing costs.

    3) I've gone back and forth on using a belt driven actuator like this to reduce rig height. I've read belts may be bad for racing as they can can't transmit high frequency movements. Is this really the case?

    4) I'm extremely curious about designing some kind of passive g-seat, or at least utilize the main actuators in some way to exert g-forces on the seat. It seems to me that if I already have actuators delivering 6DOF movement, it must be possible to use the motion that is already there to deliver gforces to the seat in some clever way without adding tons of motors. For example, here's someone who had some success with a passive seatbelt tensioner. I'm brainstorming similar ideas for a hexapod, likely using bowden cables, and am hoping someone else has thought about it.

    So has tried or considered anything like this?

    5) Any glaring issues with my current plan?

    Thanks in advance for any help you are able to provide!!!!!
    Last edited: Jan 8, 2020
  2. Ads Master

    Ads Master

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  3. adgun

    adgun Active Member

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    Ballscrew backlash is given in his precicion class, a c7 class ballscrew got 0.05mm backlash, ac5 and lower got none backlash, ac10 and higher got more backlash, c7 are mostly sold.
    About the noice ,normal ballbearings make noice if they have a raw ballcontact area
    A ballscrew is a bearing he only turns in a spiral in place of a cicle with a normal bearing.
    Ask if they are polished
    sorry for the bad english Ad
    • Informative Informative x 2
  4. BlazinH

    BlazinH Well-Known Member

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    Your planned budget stood out to me but time will tell. It sounds more like a starting point to me though :(.
    • Agree Agree x 3
  5. thefost

    thefost New Member

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    So, adding it up, it looks like just the servos, thanos controller, extrusions, and ballscrews already add up to $1829.... yeah I'm definitely going to end up over budget :D

    Thanks for checking out my build plan!
    • Like Like x 1
    Last edited: Jan 7, 2020
  6. thefost

    thefost New Member

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    Thanks, that was really informative and helpful. I contacted my sfu2010 supplier and they are indeed C7 and polished. Thanks so much!

    I have to admit, I'm having second thoughts about going sfu2010 and am debating going back to sfu1610. I'm a little concerned the additional angular momentum requirements of the thicker, heavier ballscrews might noticeably reduce actuator performance, but I'm not sure.
    • Like Like x 1
    Last edited: Jan 9, 2020
  7. Thanos

    Thanos Building the Future one AC Servo at a time... or 6

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    My Motion Simulator:
    AC motor, Motion platform, 4DOF, 6DOF
    Still way less expensive than SFX100 simfeedback 4DOF actuators... you got six actuators there!
    • Agree Agree x 1
  8. Thanos

    Thanos Building the Future one AC Servo at a time... or 6

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    My Motion Simulator:
    AC motor, Motion platform, 4DOF, 6DOF
    Look up the specs on this:
    http://motionsim.blogspot.com/2019/10/6dof-platform-from-pt-actuator.html

    This sold as complete platform package cost above 18000usd...

    Any way you make it, it will be a still a lot cheaper DIY.
    • Like Like x 1
  9. RacingMat

    RacingMat Well-Known Member Gold Contributor

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    My Motion Simulator:
    2DOF, DC motor, Arduino
    if you want to lift a >100kg plateform, I woudl say that the added inertia of 2010 vs 1610 is clearly not significant... but strength under stress is not the same.
    All this thinking should be calculated :)
    • Agree Agree x 1
  10. thefost

    thefost New Member

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    Thanks, you are right, and I definitely need to calculate everything :)
  11. thefost

    thefost New Member

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    Thanks Thanos, I was curious so contacted PT to see how much it would be just for the actuators and they quoted me around 7k for the set. Way of out of my DIY budget, but reasonable for a commercial product.