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Replacing Dofreality motors

Discussion in 'Commercial Simulators and Peripherie' started by niterida, Aug 4, 2021.

  1. niterida

    niterida Member

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    I have a Dofreality H3 with a broken motor. One of these :
    https://www.alibaba.com/product-det...03.html?spm=a2700.13765215.0.0.73b53c5f7bQFVD
    Dofreality want $250USD plus $50USD post for a replacement.
    The OEM manufacturer sell them for $80USD but will not supply them direct
    So I have been thinking of replacing both motors with one of these :
    https://www.motiondynamics.com.au/worm-drive-motor-12v-24v-200w-180-rpm-20nm-torque.html
    Fitting it to the Dofreality frame is not an issue but I am unsure about the sensor and arm fitment. Is it easy enough to swap the shaft over or would I have to buy a new shaft or get a custom made shaft ?
    Also because these motors have more torque I assume I would be able to fit longer lever arms to give me more movement - is that a good idea or best to stay with Dofreality arms ?
    Thanks
    niterida, Aug 4, 2021
    #1
  2. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
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    I would suggest uncoupling the motor from the wormdrive and carefully measure the bolt pattern and shaft specs, because you can then get a motor that matches those (perhaps the motion dynamics one) leave the existing wormdrrve in place and just swap out the motor.

    What are the existing lever CTC length? More torque would allow a bit more, but don't expect to go crazy, better to have a reliable setup than one where the motors are under stress, particularly if you have already fried a motor.

    As an aside, what is wrong with the existing motor? Often the most common point of failure is brushes and they are pretty easy to swap out for a new set.
    noorbeast, Aug 4, 2021
    #2
  3. niterida

    niterida Member

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    Motor has lots of free play and has zero holding torque :(
    Existing motor has 6.5 -> 13nm (6.5 on Dofreality and 13 on Longway website - I guess 13 is peak and 6.5 is holding ?) Motion dynamics motor has 12.5nm optimal and 20nm rated - so 50%-100% more. There isn't much room to do much longer on the arm - I was hoping to go from 50mm to 100mm but thinking about it now that probably more than doubles the load doesn't it ?
    niterida, Aug 4, 2021
    #3
  4. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
    3DOF, DC motor, JRK
    noorbeast, Aug 4, 2021
    #4
  5. niterida

    niterida Member

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    Sweet - I downloaded SimCalc and when I put everything in, with the only changes being 6.5nm to 13nm and lever arm from 50 to 100mm, the only thing that changed was the linear speed, Pitch and roll rotation, and pitch and roll travel, which all doubled. None of the force readings changed. so I guess thats all good :)
    Doesn't help me physically make the better motors fit yet though :(
    niterida, Aug 4, 2021
    #5
  6. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
    3DOF, DC motor, JRK
    Lots of free play is often an issue with a wormdrive, rather than motor.
    noorbeast, Aug 4, 2021
    #6
  7. niterida

    niterida Member

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    OK - I will pull it out and apart and see whats up before I buy any replacements.
    What about the fact it won't hold in position when switched off - is that an issue ? Only the one motor does this.
    niterida, Aug 4, 2021
    #7
  8. niterida

    niterida Member

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    Off topic but I just realised we both had a One Night Stand :)
    niterida, Aug 4, 2021
    #8
  9. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    +10,880 / 54 / -2
    My Motion Simulator:
    3DOF, DC motor, JRK
    A motor that moves when unpowered is called being back driven. The main thing affecting a motor being back driven or not is the wormdrive gear ratio. For example, in my experience a 25:1 with 200W Motion Dynamics motor can be back driven, a 50:1 with the same motor can't be back driven when new, but can under load once it has been used for a while, a 60:1 can't be back driven, even after years of use.

    I don't know the specs of your motor and wormdrive, but it sounds like one motor has been under more strain than the other.
    noorbeast, Aug 4, 2021
    #9