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Simple Servo Seatbelt tension system

Discussion in 'DIY Motion Simulator Projects' started by PMK, Feb 9, 2020.

  1. PMK

    PMK New Member Gold Contributor

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    Hi All,

    Here's my first motion simulator project. I've been playing around with using RC servo's as a cheap way to add more tactile feedback to my simulator.

    I was able to get my hands on some MG996R servo's which have around 10kg of torque. I figured that I might be able to double up the servo's so 2 are used on each seatbelt for around 20kg of total torque on each belt.

    I'm using an old PC PSU to power the servo's with 5V and an Arduino Nano to send the control signals from SimTools.

    Here's my inital prototype mount for test fitting. (Janky but it works)
    [​IMG]
    [​IMG]
    And here's a video of the first prototype in action.
    https://drive.google.com/open?id=1eEhfkRde5Tnr1WSGAI2UOf_S9FXXtur3

    So far the feeling of the belts is great however they're pretty weak. I'll attempt a dual servo setup after I make this post however I think I may have some issues getting them lined up and synced perfectly.

    My favorite thing about this setup is that when the belts are tight, the servo's actually vibrate and move the chair slightly.

    Attached Files:

  2. Ads Master

    Ads Master

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  3. PMK

    PMK New Member Gold Contributor

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    Managed to get the servo's aligned on both sides of the belt. Feels even better now!
    [​IMG]

    My next step is to develop a 6v regulator circuit. Currently I'm running these off the 5V rails on my PSU but I can get about an extra 1.5kg/cm of torque by using 6V. Any suggestions on the best way to go about this?

    I'm also planning to 3D print some proper mounting/alignment brackets for the servos so I can screw them in directly to the wooden beam they're currently clamped to.

    Obviously the servo's stall during heavy braking, should I worry about constantly putting the servo's into stall? Or does it not matter because it's only for short periods of time?

    Attached Files:

  4. Historiker

    Historiker Dramamine Adict Staff Member Moderator Gold Contributor

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    Do you have pictures of the entire rig?

    Cool idea, hope it works out for you.
  5. wannabeaflyer2

    wannabeaflyer2 Well-Known Member

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    Hi @PMK really like the simplicity of this option but have to say i have doubts about the tension those Servos will be able provide ,, i think this method has great promise but you'll def need stronger geared motors if the system is to last more than a few minutes of heavy breaking ... windscreen wiper motors with feedback encoder / Hall sensor Pot or standard 10k Pot may be the way to go... your option has piqued my interest and you've now got me thinking about changing the fixed Bungees im using to your active tensioning method :)

    Did you just use brake pressure sensor / Switch to activate your servos , what range are you using in terms of servo angular rotation..
  6. Moe Colontonio

    Moe Colontonio Member Gold Contributor

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    So for systems using wiper motors, or other motors, what do you do to account for motor stall?
  7. Historiker

    Historiker Dramamine Adict Staff Member Moderator Gold Contributor

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    Springs?
    • Agree Agree x 1
  8. Den1922

    Den1922 New Member

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    Springs it's a good idea, sometimes passive system will be efficace too ;)
  9. PMK

    PMK New Member Gold Contributor

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    Here's some pics of the full DIY rig. It's literally just been developed by bolting on parts as I got more and more into sim racing. I designed it so I could adjust everything independently. (wheel height, angle, seat position, pedal position, etc)

    86180369_530861331120573_8972838614429859840_n.jpg 86174044_1250532005146321_5726431719108640768_n.jpg
  10. PMK

    PMK New Member Gold Contributor

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    I'm actually quite surprised by the amount of tension these little things are able to provide. It's nothing amazing and won't punch the air out of your lungs but you can feel bumps in the road and braking forces through them. I drove around in LFS for about an hour yesterday and the servos never shut down or backed off from over heating.

    I fully agree that the wiper motors are probably the best way to go, however I got 5 of those servo's for $30 and had everything else to get this setup in a few hours.
    I've been playing with the idea of some stronger 50kg/cm servos.
    (http://www.kingmaxhobby.com/pd.jsp?id=22&nSL=[1,2,4,12,8,9,10,5,6,7]#skeyword=DCS16942&_pp=0_35)
    I think at this point it's probably better to go down the wiper motor route as they'll be faster, quieter, and more powerful.
    I'm planning to build a 2DoF seat mover anyway so I need to learn the wiper motor setup at some point.


    I set them to a 'zero' position in SimTools and attatched them to the servo's at a slightly above horizontal angle. That way deceleration forces result in the belt loosening. I'm using the the heave and sway degrees of freedom to actuate them. The servo's are honestly only moving a couple of degree's once the belts are tight on me (because they're stalling...) but it's enough to give an effect.


    Yup! I've also been thinking about this. As long as I find a spring that's the right stiffness I can limit the total force that the servo's need to exert.
    Another idea is to just soft mount the servo's and let the body/chair/belt/softmount system act as a sort of spring once I have stronger motors/servos.
    • Informative Informative x 1
  11. PMK

    PMK New Member Gold Contributor

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    I meant heave and surge*
    Is there no edit functions for our own posts?
  12. Historiker

    Historiker Dramamine Adict Staff Member Moderator Gold Contributor

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    I believe that has to do with the number of posts that you have. You get those options after a few posts. Not sure, but it should say in the FAQ section.
  13. wannabeaflyer2

    wannabeaflyer2 Well-Known Member

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    Hi @PMK thanks for the info , sketching some ideas now so thanks for this idea .. gonna hit nutty makeonothihose mode :)
    • Like Like x 1
  14. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    • Informative Informative x 1
  15. PMK

    PMK New Member Gold Contributor

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    Can anyone suggest what sort of spec motors I'd want to be looking at for a project like this?

    I can get 2 50kg/cm servo's for around $80(AUD) total.
    https://www.aliexpress.com/item/329...hweb0_0,searchweb201602_10,searchweb201603_55

    I'm very tempted to just continue down the servo's route as the setup is much more simple (and cheaper?) compared to configuring the whole wiper-motor setup with pots, motor shields, PID tuning, etc
  16. adgun

    adgun Active Member

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    Hi
    Youre motors give 5NM stall torque, a normal wippermotor is 5-6NM at rated torque.
    With a fuw it can be done , a GS4 seat is build the same way.
    Regards Ad
  17. Moe Colontonio

    Moe Colontonio Member Gold Contributor

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    Forgive my ignorance, but what's an fuw?