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Linkup 2DOF Wood VR Motion Rig

Discussion in 'DIY Motion Simulator Projects' started by Linkup, Jan 22, 2016.

  1. Linkup

    Linkup Member

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    Hello all

    Thought it was about time to share my 2DOF Full frame wood rig as the advice and ideas from many here have helped me get this far. I set my budget at $300 for a full frame and choose wood as I thought I could make a lighter upper frame(it's around 17-22kg), didn't really work out, but I was able to save here and there as since this is a VR rig things like having a monitor mount were left out. I'm a bit late to add in some of the ideas to make it a better rig for VR, but there is always next time. I tried to make sure it was a stable construction though I had to re-enforce certain areas more than planned.

    Parts List

    - Converted office chair
    - Arduino and 2x MotoMonster from Aliexpress(seems to be working fine)
    - Work harness as a seat belt
    - U-joint with a brace to prevent twist
    - 2x Used Wiper motors(Denson 150W I think)
    - 2x HP server PSUs 700W 56A
    -

    Spent about $250, but I still need black paint and some other things.

    Let me say a few things about the parts list. First things, I live in Sweden so that probably makes some parts more expensive than say in the US. Second is that the U-joint was a mistake as I didn't quite understand the difference between CV and got a front wheel drive shaft when a rear one would have been cheaper with no brace needed. The office chair and wood were free so I made use of them, to be honest there is plenty more of these chairs and wood for free. I'm using M8 thread rods and connectors, but may change it all to M10.

    Last design I did in Sketchup
    1 isometricview2DOFfullframe.png

    Getting the office chair ready
    IMG_20151213_094134.jpg

    Bottom frame
    IMG_20151231_202906.jpg

    This is the re-enforcing I was talking about
    IMG_20160106_162518.jpg

    Putting in the chair
    IMG_20160113_192637.jpg

    Pedals and wheel stand measured and put in
    IMG_20160112_203921.jpg

    Shifter/HOTAS stand
    IMG_20160116_145433.jpg

    Camera mount
    IMG_20160116_145336.jpg

    Parts for chair mount and rod mounts
    IMG_20160116_163114.jpg

    Chair mount for rods
    IMG_20160116_165419.jpg

    Upper frame mounting socket for U-joint
    IMG_20160117_185149.jpg

    and finally the current state of things
    IMG_20160117_192410.jpg

    Attached Files:

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    Last edited: May 14, 2016
  2. Linkup

    Linkup Member

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    I finally started to feel better and got quite a bit done. The motors are mounted though not secure as I didn't have the proper washers with teeth to prevent slipping when it's pulling/pushing ~100kg. I mounted the motors in reverse and I did test them like this so I should be okay on that end. I finished the seat belt so the converted office chair is nearly done. I will add some foam, smooth some edges, and put a seat cover over it to finish it. I think the whole chair, harness, and safety clips setup cost me less than a $25 4 point harness and feel pretty good especially in keep the legs and shoulders glue to the seat.

    Next I need to trim the threaded rods to proper length and stop the twist. I have some struts that I'm considering to put facing out toward the front in parallel. To be honest I'm not sure if it wouldn't be better to place the near the pivot point, but then they would have to be more sturdy, these aren't super thick heavy duty struts from a car hood so that might not be a great idea.

    IMG_20160214_162208.jpg IMG_20160214_162326.jpg IMG_20160214_170556.jpg IMG_20160214_170601.jpg
    IMG_20160214_162215.jpg
  3. Linkup

    Linkup Member

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    I finished trimming the threaded rods to the proper length and used the struts to stop the twist. I could of welded the ujoint to the flanges it is sitting in but I decided that now wasn't the time, maybe once it's working. I ended up having to weld the lever and nut as I couldn't find decently priced 7mm locking nuts and couldn't find thread locking glue.

    Next step is to align the speeds of both motors in both directions, I used a phone app to figure out that the left is doing 190 rpm and the right is doing 230, not sure if the units are right, but the difference was noticable so I will be working on that fixing this next.

    My current problem is potentiometers. When I welded the nut it kind of destroyed the idea of using some tubing and clamps to connect the pot and motor to get the readings. I've looked into contactless potentiometers and hall effect sensors, but the arduino hall effect sensor had a very low resistance, maybe around 64 of which I would only use 32...just way to low. I'm still aiming to keep the budget within $300, but if I grab the recommend sensors many use on here I will be in the $370 range so that will be a last choice.
    IMG_20160226_201749.jpg IMG_20160311_161657.jpg
    IMG_20160311_161645.jpg IMG_20160311_161713.jpg
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  4. Linkup

    Linkup Member

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    Okay I found this hall sensor http://www.mouser.se/Search/Product...virtualkey57700000virtualkey858-6127V1A180L.5 it's non contact and basically the same as what is recommend except the shipping etc is better to Sweden.

    Considering the pictures of the welded nut I posted will this non-contact sensor still work? Do I have to have the shaft touch the rotating lever or does having it float right next to it with a few mm gap work?
  5. Nick Moxley

    Nick Moxley Well-Known Member

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    My Motion Simulator:
    2DOF, 3DOF, DC motor, JRK


    Lol its not a magical sensor that can some how magically sense the position of the motor No. You need to Physically hook up the Pot to the Motor. Flex coupler's come in handy for such purposes but with Wiper's your forced to find a different way, I highly suggest you surf around the forum and the FAQ section to learn a bit more on how thing's are connected and all work together.


    Little advice too, Practice welding on a piece of scrap before working on the Final pieces. Im not too sure that weld is actually holding anything.
  6. Linkup

    Linkup Member

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    Ah I get it now, it's non contact because it uses magnets on the inside of it. I thought there was a sensor that worked off Of magnetic fields to perceive directional change on a nearby objects and it output a number if hooked up to an Arduino.

    I might be able to still use the pots I have. A rotational proximity sensor sounds super useful though.

    Yeah, he doesn't weld so often, but it does seem to be holding, I did test it. The bolt was tightened before welding, but it was a last choice type of thing to stop it from coming loose over time after use.

    Anyway thanks for the advice.
  7. Linkup

    Linkup Member

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    What about a magnet and hall sensor? Angle sensing using a magnet attached to the welded bolt and replace that pot with a hall sensor to detect rotation. Are there is examples of someone using such a setup?
  8. Nick Moxley

    Nick Moxley Well-Known Member

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    My Motion Simulator:
    2DOF, 3DOF, DC motor, JRK

    No because its more hassle than its worth. Thing's move and tweek on a rig, ensuring there is ZERO movement of the motor arm for a Contactless sensor is pretty hard and in the end not worth it.

    As i said, Flex coupler's are your friend and can help big time.
  9. Linkup

    Linkup Member

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    Forgot I had them and some steel epoxy.

    You're right, I always try to keep it simple and inexpensive so I'll go with what I have.
    IMG_20160312_160339.jpg IMG_20160312_170321.jpg
  10. Nick Moxley

    Nick Moxley Well-Known Member

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    My Motion Simulator:
    2DOF, 3DOF, DC motor, JRK
    Good idea, Just Make sure there's no Radial play, Pots even with Flex couplers dont tend to like that.
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  11. Linkup

    Linkup Member

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    Tested it with the steel epoxy applied and it's working well, just a bit of flex as I raised the potentiometer to match the motor arm. Second coating is drying now.

    Going to start hooking up the electronics today I hope =)
    IMG_20160313_000441.jpg
  12. Nick Moxley

    Nick Moxley Well-Known Member

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    My Motion Simulator:
    2DOF, 3DOF, DC motor, JRK
    I would also Highly suggest a Emergency kill switch, Worst case scenario you might be able to prevent some mechanical damage if thing's try and go for a Run on you.
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  13. Linkup

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    Last edited: Mar 17, 2016
  14. Nick Moxley

    Nick Moxley Well-Known Member

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    My Motion Simulator:
    2DOF, 3DOF, DC motor, JRK
    Glad the bolt is holding....for now....lol :)
  15. Linkup

    Linkup Member

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    Yeah now I can see that, the cheap pots won't last and neither will the couplers especially with the flexing. The motor mount, motors, motor levers, screws, pots, pot mounts and distance all have to be really exact for this to last any amount of time.

    I have better pots, but I'll switch them once I have it actually working.
    Last edited: Mar 17, 2016
  16. Linkup

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    Here are the setup up pins pictures. I put a heatsink on the MM and have wired in a 12v PC case fan on the power supply 12v wire to make sure it has some cooling along with a 40A fuse between the MM and PSU on the 12v wire. Next I'll solder on power to the MM board along with the 4 wires for directional feedback, I believe the red led needs/supposed to light up. I still need to solder the pot control wire to the A0 and A1 as has been updated on the tutorial.

    If something looks off, feel free to let me know.
    IMG_20160317_183700.jpg IMG_20160317_183826.jpg IMG_20160317_183833.jpg
  17. Linkup

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    Pretty much all setup now. I gave it a quick test and it seems to be working. Not sure exactly which lights are supposed to be on but I've got one each on the Arduino and MM for power, the directional LEDs are off. One of my motors is mounted in reverse so I will change the 12+ and GND- so that it goes in the opposite direction, matching the other motor.

    I also modified the 10k pots such that their stopper is gone and they can spin a full 360, though it's just so that it doesn't break, I believe only 180 degrees is actually needed. I've got wiring in opposite directions if you are facing them toward the motor, but will change that when I change the polarity on the reversed motor. The last thing I did was brace the pot on the back side so that the little metal shield and body are nice and stiff.

    @RacingMat Why does it talk about finding the pot amplifying ratio then say to go to gearMotorRorLPotRatio on line 17 in the arduino 2dof code though it's not there, crtl+F gear or ratio and neither came up? Did it change or is it not need any longer?


    I'll add the respective pictures later today.
    IMG_20151220_114706.jpg IMG_20160318_012418.jpg IMG_20160318_012436.jpg
    Last edited: Mar 19, 2016
  18. Nick Moxley

    Nick Moxley Well-Known Member

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    My Motion Simulator:
    2DOF, 3DOF, DC motor, JRK
    You can use Thinner AWG wire on the Pots if you want. Doesn't need to be that Thick as in the picture.
  19. Linkup

    Linkup Member

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    I had some thinner stuff I was using, but it was a pain to use so I switched to the thicker wire. I hope it doesn't cause problems.

    I have tested it with the polarity fixed and now both motors rotate forward in the same direction, unfortunately they continue to rotate then pause for a second then continue on doing that for a awhile until they stop. Might be a short or maybe the boundaries set in the code is off so I'll resolder the pots and connect the other connections.

    I have to turn the pot to the middle position before connecting it to the motor right? or does it not matter?
    Last edited: Mar 19, 2016
  20. Linkup

    Linkup Member

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    I tried rewiring and resoldering the pots, but all I got was a continuous rotation from them.