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Help Needed With 2DOF Motion Platform Build

Discussion in 'DIY Motion Simulator Projects' started by Joshua Rarrick, Mar 3, 2018.

  1. Joshua Rarrick

    Joshua Rarrick New Member

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    Hi guys, I am new to the forums here and am looking for a little bit of help in designing and programming a 2DOF motion platform flight SIM. It will be used in a non-profit youth outreach that is based in Memphis, TN at the moment, but we hope to build these for churches and organizations all over the country.

    The budget is $3000 total and I think we can reach the goal.

    About the build:

    I am going to build a fully enclosed cockpit that is mounted on a motion base. The frame will be wood, as will the platform base. I am going with a driveshaft/u-joint pedestal design as I think it will offer the smallest footprint and easiest build design. The first picture shows the basic type of pedestal I am planning to build.

    I am not planning to use pneumatic cylinders for this build, but rather 50:1 50RPM crab pot motors connected to arms and pushrods on ball and socket joints for hydraulic pushrods - the type used in the rear hatch of an suv.

    For the actuator controls I am thinking the Polulu JRK12v12 looks to be the simplest choice. However, I know NOTHING about computer programming or how to wire the boards etc. So, I will need help there.

    The power supply unit I think I will be using is a 12V 50 AMP 600W psu. I think one for each motor should do the trick. However, I do not understand for certain if these convert 120v to 12vDC directly or do I need a car battery in line with them...a little help there would be appreciated.

    Ok, so some of my questions about the platform build itself... the guy who built the pedestal in the picture used pneumatic cylinders and set the pedestal slightly behind and to the right of the rider in order to keep a constant load on the cylinders. Do I need to do this using electric motors as well, or should it be centered on the center of balance? Will the ball joints be strong enough to be used for this or is there a stronger option available? Also, I notice some people mentioned that 50:1 ratio might be slow for a flight sim on the DC motors...is this true?

    The last picture is a preliminary setup with monitors and seat. This will be mounted to the platform, pending a little lightening up on weight. The seat base has a homemade bass shaker under the seat.

    Any and all help appreciated! Thanks guys! NV_0414_Noon_Figure06.jpg 28058702_506678916393345_4659229511000294121_n.jpg
  2. Ads Master

    Ads Master

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  3. Joshua Rarrick

    Joshua Rarrick New Member

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    I can link anyone curious about the components, once I get to 3 posts lol.
  4. RandomCoder

    RandomCoder Active Member Gold Contributor

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    That is a very unique way of doing positional feedback. Is it just the weight of the arm on the pot that causes it to turn when the platform lowers?
  5. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    With any compact style build it helps to maximise the inherent design leverage and minimise the weight of the top frame and all it supports. SimCalc can help you get your head around some of the design related physics affects involved: https://www.xsimulator.net/communit...e-linear-speed-and-forces-of-your-design.270/

    For simplicity I would suggest using Hall sensors rather than pots: https://www.xsimulator.net/community/faq/how-to-choose-potentiometer.238/

    Hall Sensors are very accurate, you can directly connect them to the motor using a flexible coupling, they have a long life span and won't break if over rotated: https://www.xsimulator.net/community/faq/how-to-connect-protect-a-potentiometer.13/

    Don't panic about the JRKs, just ensure you double check you have not crossed a wire and that you have a heat sink and fan for cooling: https://www.xsimulator.net/community/faq/attaching-heatsinks-to-jrk.146/

    The actual setup using the JRK utility is pretty straight forward: https://www.xsimulator.net/community/faq/jrk-setup-guide-eaorobbie.14/
  6. bruce stephen

    bruce stephen Hammer doesnt fix it, must be electrical

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    thats a big poject for jrk's. maybe go with sabertooths.
  7. Joshua Rarrick

    Joshua Rarrick New Member

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    He has a spring attached to each axis to help pull it back against the pneumatics.
  8. Joshua Rarrick

    Joshua Rarrick New Member

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    LOL There is obviously a LOT more involved in this than meets the eye. Somehow I was thinking just mount the platform on the shaft, find out how far it will tilt either direction, then mount motors and build a lever system that will not allow them to over extend. I am completely stupid with electronics, so I will most likely be coming back with "what is this..." "how does this work..." etc.
  9. Joshua Rarrick

    Joshua Rarrick New Member

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    Ok maybe I can post links now, so I will show you guys the actual parts I am looking at and you can help me determine if they are strong enough to do the job.

    DC Motors - do these need to be reversible motors? And if so, how do I wire them to reverse current on command? https://www.ebay.com/itm/371596157992

    PSU - Will 2 of these be strong enough and do I need a 12v car battery as well, or will these provide what I am looking for?
    https://www.ebay.com/itm/112793230937



    And this is a link to our website, so you can see what it is that we actually do. www.impactministries360.com
  10. Joshua Rarrick

    Joshua Rarrick New Member

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  11. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    The motors you linked have been used by many members, you don't need to do anything other than wire them up.

    The PSUs selected would be fine.

    Hall sensors come in many forms but these are the easiest to connect and are available from a variety of suppliers worldwide: http://au.element14.com/bi-technolo...fs/sensor-hall-0-2v-20v-to-10v-pin/dp/2319662

    You just need to select the correct size flexible coupling to connect the Hall sensor to the motor shaft and mount with a light bracket: https://www.ebay.com/sch/i.html?_fr...coupling.TRS0&_nkw=flexible+coupling&_sacat=0
  12. Joshua Rarrick

    Joshua Rarrick New Member

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    My Motion Simulator:
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    So I am thinking I could use these at each end of a lift rod to provide a sturdy connection to the SIM base. My thought is to put a short (6-8") lever on the motor and connect a lightweight steel rod to the lever and then to the SIM base, thus the motor action would lift and lower the lever to move the SIM.

    However, I am curious as to the range of travel these joints have...Will the pitch axis lock over extend the joint on the roll axis? Anyone ever used something similar to this before?

    Attached Files:

  13. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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  14. Nick Moxley

    Nick Moxley Well-Known Member

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    PS if your looking at PGsaw motor's, PM me, i can get you a better deal. ;)
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  15. Joshua Rarrick

    Joshua Rarrick New Member

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    Ok, so the high misalignment heim connectors look like the best choice as far as something that will last for the linkage rods. However, I have looked through e-bay and cannot find exactly what I am looking for. I am thinking like a 5/8 to 3/4 size would be sufficient for the pins that will pass through the heim connector...but I cannot seem to find a ready made linkage rod with that type of size connectors. What are you guys using to connect the motors to the motion base? Keep in mind that rider and seat and controls plus monitors will all be moving so probably somewhere in the range of 350-400 pounds in the top end of the weight category. I need strength and durability.
  16. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    A suitable sized steel rod with a nut welded either end would do the job.
  17. Donerb

    Donerb Old Racer

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    Honestly aerospace quality 3/8 high angularity rods are more then capable of handling the load if you don’t use high angularity you can go up a size and make up or buy stepped bushing to step down the pin size And make high angularity. Best ones have Teflon lining w/0 that they will start to rattle at some point. This is from McMaster as an example 4586FAC7-D32E-4EF5-ACAC-038DD8C847D9.png
  18. Joshua Rarrick

    Joshua Rarrick New Member

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    I have looked at the different tie rod ends with Heim joints and had already decided that stepping down via a high angularity bushing would be the most cost effective method. However, I am having trouble finding rods that are threaded on the inside to accept the male connectors. I guess I just haven't figured out how to search for it. LOL
  19. Nick Moxley

    Nick Moxley Well-Known Member

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    Most cost effective is these By FAR, and last a really long time with legit lube in the joint, These also have more than enough angle to play with.

    https://www.aliexpress.com/item/Fre...857f274&transAbTest=ae803_5&priceBeautifyAB=0
  20. Donerb

    Donerb Old Racer

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    Ah now those I like! That was what I was think of for my seat end. I’m on the road but let me look up the ends for the tubes so you can weld together. To be honest I don’t recall ever seeing pre built ones. Have you tried speedway motors? Or some of the sprint car suppliers?
  21. Donerb

    Donerb Old Racer

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    Try these they also have weld bungs for your own tubes. image.jpg