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Minimum RPM needed for a 2dof?

Discussion in 'Motor actuators and drivers' started by mariano68, Jun 18, 2015.

  1. mariano68

    mariano68 Active Member

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    Hi!
    I was searching the forum as I know that it was posted somewhere but I can't find it :(
    Could anyone tell me what are minimum needed motor RPM for a decent 2dof ride?

    Thanks anyway!
  2. mariano68

    mariano68 Active Member

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    Auto answer, but I think I'd read something about a lot slower motors working fine anyway (winches maybe), so if there is more info, please post it!

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  3. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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  4. mariano68

    mariano68 Active Member

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    Thanks very much! Reading...
    BTW, here is really difficult/expensive to get decent motors, but I found that the motors on the electric car jacks are about 12watts and has a double gear already mounted, and I can get them for about U$S60 locally, I mean using only the motor and gear and cutting the rest.
    http://www.ebay.com/itm/ELECTRIC-CA...601?pt=LH_DefaultDomain_3&hash=item2ee2b264a1
    This one is rated 12v 15Amp, so about 180watts... confusing as it also says "POWERFUL 100 WATT 12 VOLT MOTOR"
  5. bsft

    bsft

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    The unofficial linear speed recommended is 150mm per second.
    So RPM of motors does come into this
    SCN5 are considered the benchmark, and at 400mm per second unloaded, thats quick, but under load, they are more like 150-200m per second
    Now with different motors, lever lengths and even motor control options, it can vary.
    People start with wiper motors because they are cheap and can give that 150mm per second linear speed when they are pushed hard enough. They run 50-60 rpm
    Next step is faster motors and yes, Rob gets about 500mm-700mm linear speed out of the 150 rpm with a 65mm CTC lever using the JRKS. Loaded. Those motors 150-180 rpm shaft speed
    But remember, his ride is a shoulder mount seat mover, so he is moving using the least amount of force needed.
    My desk racer uses 40mm CTC levers, so I get about 200-270mm linear speed per second, loaded.
    It is going to vary from ride to ride and you need to consider the design on the sim, the motors used, the CTC lever ,the settings for the motors as well,
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  6. eaorobbie

    eaorobbie Well-Known Member Staff Member SimTools Developer Gold Contributor

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    Mine is design on the concept of being a scn5 killer (found to be a back killer too.)

    My personal opinion is that we are trying to simulate what's actually happening to the body while being seated in a car travelling at 200kph down lets say a gravel track on a world class rally event. Now if your bouncing around at 100mm/s which most wiper system fail to reach your only really feeling 30% of the actual motion as the motor movement is to slow to really feel any of the high speed motions and vibrations. This is where the scn5 has been supreme for years as most motor controllers couldn't keep up. So an scn5 for example can move a body(100kg) on a balanced seatmover to a recorded and tested max speed of about 200-220mm/s about 1/2 of what it can do with no load.

    So 200mm/s was my target.

    Looking at motors I settled with the 200W 25:1 units , bit of backlash(not happy jane) but 150rpm at 13.8v's ok that's the speed and the force Im looking for,
    now under testing in Jrk software its about 0.15sec to go from bottom to top so the test involves lifting the the 100kg. So when the maths are worked out the motors punch way higher and more accurate than expected on Jrks, sorry did 3 weeks testing MM and Ard, wouldn't come close actually cooked the MM on last try, smoked it. So Im getting 0.15sec to travel 80mm on a lift stroke. And the resulting motion can be mind bending to a point , oh hell this is gunna hurt as I slam into a rock wall at 100kph+ , sorry ya wont come close at slow speeds, ya result is very arcadey but have to say still a world of fun.

    So speed is a key in a sim that performs to a top level, but a sim moving under motion , no mater what speed beats any sim that has no motion at all.

    So don't be too concerned , tricks with profiles and limiting movements to a smaller range not 180 deg , more like 50deg>80deg you can achieve high enough speed to make any sim effective and a world of fun.
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  7. mariano68

    mariano68 Active Member

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    Thank you very much for your reply @eaorobbie
    None of my possibilities are over the 150mm/sec range...
    My unit will be a foot mount motors, full sim without monitors (Oculus rift here) and about 125kg pilot and platform.
    Problem is that I can't get any really good motor locally or importing it for less than U$S350 each, my options here for around U$s100 each:
    1-12v 50NM 65RPM, about 80watts (I'm almost sure that 50NM are stall torque and no real torque, more like 20NM top) U$S120
    12v 50NM.jpg
    2-1500kg Electric jack, about 100watts 60RPM, the idea is to use just the motor and gearbox, not the jack. U$S60
    criquet-para-autocamioneta.jpg


    A 2Tn 12v Winch for U$S180, but noisy and I can't do that noise at nights.

    Please Advice me guys!!! :sos

    PD Also I can get 100 or 400 watts 12/24v skate/scooter motors, but without gearbox.
  8. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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  9. mariano68

    mariano68 Active Member

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    Thanks, already read that thread, but I usually play at night and as much I can minimize the noise from winches, it wont be enough :(
    And about the gearboxes alone, yes, but they costs here about U$S200 each.
    I tried to avoid at all costs to use the rear mount model as I really don't like it(aesthetically speaking), but looks like it will be my only choice with this kind of motors.
  10. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    A foot mount design also has good leverage, so you have choices there.

    You could plan on a future upgrade to more powerful wormgear motors. Or just bite the bullet and get them at the onset where it may be a significant cost, but as @eaorobbie has pointed out is still a bargain price compared to alternatives like Dbox and SNN5-6s.
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  11. mariano68

    mariano68 Active Member

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    Yes I was thinking about that, get something to keep getting experience (and fun) and upgrade later to that great 200watts worm drives.
    I'm intrigued on the electric jack motor, I think I will buy one to test it.:)
  12. bsft

    bsft

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    Put on wipers to start with, but mount them up high above your feet to help leverage
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  13. Malik10

    Malik10 Member

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    sir...can you give some calculation about actuator support for weight?
  14. steveh2112

    steveh2112 Member

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    i've read through this thread and all the discussion is about linear speed, but i'm wondering what is the ideal rotational speed (in degrees/sec) for a 2DOF tiling chair, for flight and racing sims?

    thx
  15. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    Have a play with this handy calculator: http://www.calctool.org/CALC/eng/mechanics/linear_angular
  16. steveh2112

    steveh2112 Member

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    thanks, i get the math, its a cosine function, but my question is more about when people talk about 150mm/sec, at what radius from the pivot is that measured?
  17. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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