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PT-Actuators 3DOF system?

Discussion in 'Commercial Simulators and Peripherie' started by LukeBrown, Jul 1, 2019.

  1. r3df0x

    r3df0x n00by Racer Gold Contributor

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    Wow, your RIG look awesome! Nice and clean. It's a good evolution.

    Looking forward to seeing all this in motion ...
  2. yobuddy

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

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    Hi Guy's
    I think both the 4 and 3 axis PT setups are just fantastic!
    But I really like 3 legged version myself, as they make more sense to me, as you have 3 motors for a 3DOF sim that way.
    (No sense paying for the 4th motor if it does not add anything?)
    And PT Actuators are strong as can be anyway.

    The other thing I really like is there is no way the sim could ever "high leg" (where one leg is a bit off the ground).
    Not that we have seen it to be a problem with 4 legged setups, but its just not possible with the 3 legged version at all.
    And the 3 actuator MDBox controller also support vibration input (which I have been told works quite well with GameVibe).

    In the end thou, what I really like, are the looks you can get from a 3 legged setup.
    Just take a look at this work in progress by @nclabs, wow is all I can say. :eek:
    sm1black.png

    sm2black.png

    sm1.png

    sm2.png

    Just wow! :thumbs
    Take care,
    yobuddy
    • Like Like x 6
  3. SeatTime

    SeatTime Well-Known Member

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    Totally agree, I would although like to see the actuator attachment points placed a bit higher (should be easy to do), so that the roll center is more realistic.
  4. yobuddy

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

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    They are hip level in the pic :thumbs
    Although the way it works, I don't think it changes much..
  5. LukeBrown

    LukeBrown New Member Gold Contributor

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    Quick video just showing everything all setup and working....

    • Like Like x 3
    • Winner Winner x 1
  6. SeatTime

    SeatTime Well-Known Member

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    Your right - it is a solid box, but that means the roll center ends up very near the floor. That's unfortunate, luckily though in practice it does not roll much.
  7. Skerper

    Skerper New Member

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    Is that with the extra cross member at the front to attach the front actuator?
  8. LukeBrown

    LukeBrown New Member Gold Contributor

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    Yes that's right, I added in an extra length of 40x160 at the front. Makes the frame into a completed rectangle shape.
    • Useful Useful x 1
  9. stashy

    stashy New Member Gold Contributor

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    hi guys just got the pt actuators , any guide for installing ?
  10. Thanos

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

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    Its pretty simple, PT-ACTUATOR can provide a wiring diagram for it. If you don't have the manual for the AMC controller email me.
  11. r3df0x

    r3df0x n00by Racer Gold Contributor

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    Or, see the pictures of LukeBrown in the previous pages ...
    • Like Like x 1
  12. misoswan

    misoswan Active Member

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    hello how mutch cost this actuator?thanks
  13. LukeBrown

    LukeBrown New Member Gold Contributor

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    Best to just message PT actuator and ask them for a quote. It depends on your country for shipping and also there are some options in terms of which actuators and controllers you want.
  14. Absomfs

    Absomfs New Member

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    Hi everyone . Yes that’s what I did . Contacted them through messenger via Facebook . Very helpful . I ordered the 4DOf set using the AMC - ASD15A. Just waiting for them to arrive :) . I’m sure I will have lots of questions
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  15. Hocky

    Hocky Member Gold Contributor

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    I agree that the 3 legged prevents the "high leg" but why does it happen? Now on 2.4 its more or less not doing that anymore?!? Problem with the 3 legged is that the one actuator in the back must take more load then the front and the rig is heavier in the back.

    I would also want to know more about how to get the MDBOX vibration feature and GameVibe. I have tried it and could not get it to make any good vibrations. Who has done it successfully?

    Thanks
  16. LukeBrown

    LukeBrown New Member Gold Contributor

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    Put the single actuator at the front and also bring the rear actuators forwards a little bit so that they are closer to the centre of gravity.

    Another benefit I've realised of having only 3 actuators is that the front single actuator only has to handle 3 DOF (Heave / Pitch / Surge) and does not need to any assignment for Roll or sway. That means you can actually assign a higher percentage of the actuator stroke to those 3 DOF. If you are running a 4 actuator setup, then the two actuators at the front would need to cover all DOF so would be assigned something like 20% each for Heave/Pitch/Surge/Roll/Sway. However, with 3 actuators then for the one at the front you still assign 20% for Heave but then can increase it to 40% for pitch and 40% surge. So you actually get more more range of motion in Pitch/Surge with a 3 actuator setup vs. 4 actuators.
  17. SeatTime

    SeatTime Well-Known Member

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    Why is a 4 leg system naturally unstable compared to a three leg?

    - A three legged platform is naturally stable like a three legged stool. Even if you change the actuators or 'stools' length it will still remain stable and not allow any wobbling - or in this case lifting of one leg.

    - what happens when you add a fourth actuator? Well, now there are multiple ways that the platform
    'stool' can 'solve' the problem of which legs to use for support as the actuator lengths change.
    Wobbling occurs when the Platform (stool) can't 'decide' which solution to use especially as the length of each leg changes.

    In effect, during the time that the Rig is actually wobbling, it's
    really a two-legged stool, with one degree of freedom - which is the
    direction of the wobble.

    As for a rear biased load, you could always have two actuators at the back and one in the front, although these types of actuators are quite powerful.
  18. Skerper

    Skerper New Member

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    I asked the PT Actuators' support guy directly whether there's any problem weight-wise with running one actuator on the back and two on the front.

    He said that there's no issue, and that you should be spacing your actuators so that they're evenly around the center of gravity anyway - meaning that if the actuators are properly configured, the rear actuator is not taking more weight than the others.
    • Agree Agree x 1
    • Informative Informative x 1
  19. LukeBrown

    LukeBrown New Member Gold Contributor

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    Yes that's right. If you have 2 at the front then they actually should actually be roughly in line with the steering column uprights and not at the very front corners.

    I think it makes more sense to just have 2 at the back and 1 at the front though. With the 2 at the back they will be either side of the seat, you will feel more in the way of bumps etc.
  20. Skerper

    Skerper New Member

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    Intuitively yes, but if the actual motions are the same, surely it shouldn't cause a difference unless you have vibration effects on those actuators...

    I guess the big limiting factor here is that the further back you mount the front actuators, the higher you'll have to mount the body to ensure the rig doesn't hit the ground at full forward pitch, which in turn means the roll center will be higher.