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Linear Actuator Designs ...

Discussion in 'Motor actuators and drivers' started by speedy, Dec 27, 2013.

  1. SeatTime

    SeatTime Well-Known Member

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    Don't get me wrong as I love DIY stuff, but for our application, purchasing ball screws from China, is still allot easier, would likely have a more consistent output from actuator to actuator (especially for a 6DOF) and not really be that more if at all expensive then purchasing bearings, hardened rods etc.
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  2. Alexey

    Alexey Well-Known Member

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    Wouldn't a threadless ball screw slip in high torque applications? Actually looks like a great idea for a router table though! Ponders...... (need a thinking emoticon)
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  3. SeatTime

    SeatTime Well-Known Member

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    Agree, some of these CNC centric solutions may not be ideal for managing the high inertia/weight as required in a sim.
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    Last edited: Apr 23, 2015
  4. BlazinH

    BlazinH Well-Known Member

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    Technically speaking, the threadless ball screw pictured above is not actually a ball screw at all (unless maybe you count the balls in the bearings). Threadless means the only thing holding the rod and bearings together is friction. The friction between the smooth pieces of metal would need to be very high to keep them from slipping the way we use them.
  5. speedy

    speedy Well-Known Member

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    Like these 3DOF tables :) ...

    3DOF :


    3DOF ...


    6DOF ... This one by VI-drive has additional 20cm heave roll and pitch small levers ... which could be replaced by using a three car scissors jack with the same bearing nut system ... that would give a full 6DOF ...

    and many others ...:thumbs

    And I wonder if any one still have doubt about bearing slipping over smooth surfaces after all these videos ? ... then you have to use rubber bearing or grooved bearing and machining such sleeve inserts is not a high tech thing to do ...
    Plus that would spare many of us from the expensive shipping cost and taxes and give a chance to free our minds a little ...
    1images.jpg images.jpg
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    Last edited: Apr 23, 2015
  6. Alexey

    Alexey Well-Known Member

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    Is it just me and my limited knowledge in sims but do those 3 sims look like they lack sustain in roll? I understand that the lateral movement simulates roll but imagine a medium-tight u turn that lasts over three seconds. Would it just hit the limits and then have you sitting there with no motion? Our seat movers would have you sitting there to the side but gravity itself is sustaining that motion queue. Would be awesome if they incorporated actual roll with that motion table.
  7. speedy

    speedy Well-Known Member

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    This one is on our home page ...


    @Alexey ... sorry if the third video is not clear but it has all 6DOF motion forces .
    they try to hide it but this long video has only 3 seconds that worth to share it . starts from 0:55 - 0:058
  8. DanielDk

    DanielDk Member

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    I'm not quite sure i follow - are you saying your examples are not ballscrews? :confused:

    upload_2015-4-23_18-35-44.png

    this one seem to be a combination of ballscrews (ground not rolled screws). V-track rollers to guide it. And rack+pinion...

    anyhow :)
    :popcorn
  9. Alexey

    Alexey Well-Known Member

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    Even rubber lined bearings will slip on a smooth surface when you try to move over 100kg of mass. What you would have to do is rough up the linear shafts (like 0.5mm groves seen on metallic hand grips) but by doing so you then have wear on the rubber lining. Then the cost of setting all that up you might as well by threaded rod. Don't get us wrong, threadless linear actuators are great but they don't have the gripping power required by rapid oscillation and high inertia.
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  10. SeatTime

    SeatTime Well-Known Member

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    Just for information, I actually tried rubber wheels on a steel rubber layered track for my traction loss and surge table and on high inertia changes in direction they just slipped (basically burnt rubber as the feedback pot was on a separate wheel :p). Ended up changing to a chain drive system. I had some high tension springs on them as well.

    Rubber wheel drives.jpg
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    Last edited: Apr 24, 2015
  11. speedy

    speedy Well-Known Member

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    I agree with all of your concerns guys ... I just have a different point of view and thanks for your valuable patience and support ...
    @Alexey ... If you do the same design as the above for the thread-less videos for the nut so [ what you see is what you get ] ... my need is to activate your Criticism as they have some disadvantages that can be improved more to fit our needs .
    • I see that they use plastic housing nut for the bearings which I guess is not suitable to providing the enough pressure required to withstand higher load .
    • I see that some of the nuts have three bearings and others have 6 bearings although they can have 4 and 8 or even more .
    • I see that a high pitch bearings path could cause more slip in the spiral motion which might be lowered to get more grip to the shaft .

    I'm not recommending using stainless steel smooth surface rod as presented earlier for any simulation lifting or moving 100kg ... we have to work things out first ...

    @SeatTime that rubber wheel usage as presented above may not be the ultimate solution ... as you may use more pressure force to increase friction ... or may be larger diameter wheels to increase contact surfaces or more wheels on the other side of the steel base to balance the motor force to the center ...

    Guys ... it's a good idea and I still believe we can benefit from it many ways and I guess that leads me to dig more with your help and suggestions as this needs more dynamic forces analysis to get the best out of it ...
    Last edited: Apr 24, 2015
  12. SeatTime

    SeatTime Well-Known Member

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    @speedy , Never thought of it as the ultimate solution, just related information on something that I actually tried in my first Sim. Maybe it can save someone some time/money? As you know I've already made a decision on what I am using in my next sim :).
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  13. speedy

    speedy Well-Known Member

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    Last edited: May 9, 2015
  14. vell

    vell New Member

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    nteresting design of the chair, on hydraulics?
  15. vell

    vell New Member

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  16. Edwardo

    Edwardo New Member

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    Hows that Actuator coming along. Not too much longer and it will be a year..:D
  17. Gabriel Vuelma Romanzini

    Gabriel Vuelma Romanzini Member

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  18. speedy

    speedy Well-Known Member

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  19. RacingMat

    RacingMat Well-Known Member Gold Contributor

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    yes, expensive and noisy and dirty... :-/
  20. Gabriel Vuelma Romanzini

    Gabriel Vuelma Romanzini Member

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    But why they are so expensive ? pressure controls and pneumatic bomb ?
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