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Question 25:1 vs 50:1 from PGSAW

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by Ian Pace, Nov 1, 2019.

  1. Ian Pace

    Ian Pace New Member

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    Hi All,

    Im gonna bite the bullet and buy the motors from Canada and ship to europe.... since its quite expensive to do so, i want to be 100% sure that im getting the correct motors.

    I'm planning on building a 2dof seat mover (with shoulder mount control) including traction loss.

    I was planning to get x3 of the below 180W motors:

    x3 GEAR MOTOR 12 VOLT GREAT FOR SAWMILL/CRAB POT PULL/FEED 150/160 rpm 25:1 ratio

    I know that for shoulder controls its recommended to get the 25:1, but i would like to know WHY? Basically it would be great that if eventually i decide to go ahead and upgrade or change it to a full platform i can re-use the same motors - am i asking too much?

    What are the drawback of using 50:1 on a shoulder mount and/or using a 25:1 for a full platform?

    I have already searched the forum but i couldn't find anything that explains why one not the other or vice versa. What i found it the standard recommendations.

    Are the above 25:1 motors also good for traction loss?

    Thanks :)
  2. MarkusB

    MarkusB Active Member Gold Contributor

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    Hi Jan,

    simply spoken, the 25:1 motors rotate faster, but have less torque.

    For a full frame simulator they are too weak. I know this because I made this experience by myself.
    So if you think about changing from shoulder mount to full frame, you should buy the 50:1 motors right away.

    A cheaper alternative would be second hand wheel chair motors from ebay, which have plenty of torque. At least in Germany you can find them for 60-80€ per motor.
    But they require 24V instead of 12V.
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  3. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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  4. Ian Pace

    Ian Pace New Member

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    How noticeable is the speed between the two in reality?
  5. Ian Pace

    Ian Pace New Member

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  6. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    SimCalc will tell you that, for a given design ;)
  7. Ian Pace

    Ian Pace New Member

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    will check it out and try to understand it :)
    thanks
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  8. yellofella

    yellofella Member

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    Hi Ian
    I purchased 3 of those motors from pgsaw on ebay 2 years ago. I went for the 50:1 gearboxes on my shoulder mount rig and can confirm that on my rig they are plenty fast enough. As @noorbeast has recommended sim calc is a must when designing a rig and choosing motors as getting the balance point of yr seat, rod angles and motor lever length will determine the motor gearboxes that will be best for you.
    My seat is well balanced just biased to the rear slightly as the motors do have a very small amount of play in the gearboxes that some members have mentioned but isn't a problem for me. 40 degree rod angles, 80 mm c/c levers using 90 degrees of rotation and sim calc gave me near 700mm sec linear travel. I can tell you it feels like that much when i crash into something even though im pressing against the seat with my foot on a 100kg loadcell brake.
    Cant really help on the 25:1 motors as I haven't tried them but I can say this. an un balanced sim with steep rod angles and 25:1 motors would have hardly any holding force to centre when not powered and would not get the benefit of the extra speed if it hasn't got the torque to move the sim. However very well balanced sim with 45 degree rod angles and short levers wouldn't need so much torque so could use the extra speed that the 25:1 gearboxes can offer.
    I would study sim calc and play about with the measurements of everything till you feel satisfied that u have a good design and then choose the motors u need.
    hope this helps
    Matt
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  9. Ian Pace

    Ian Pace New Member

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    thanks @yellofella for the in depth reply!

    I gave SimCalc a go but i still need to work out the exact angles and lengths of my eventual build. My concern is that i weigh 97Kg and with that the motors will have to also move the weight of the seat.
  10. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    My Motion Simulator:
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    Even a compact design can handle way more mass than that if properly designed and balanced, with the correct motors, I use 200W motors with 60:1 on my compact 3DOF rig: https://www.xsimulator.net/community/threads/dx-compact-simulator.5866/page-21#post-107352

    So spend plenty of time with SimCalc in the design phase, and allow a margin for error, because the more the worm gearbox ratio the less mechanically efficient they are.
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