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My build has officially started (2 DOF platform mover, eventually 3 DOF)

Discussion in 'DIY Motion Simulator Projects' started by Map63Vette, Jan 26, 2021.

  1. Map63Vette

    Map63Vette Member

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    I've been dragging my feet on doing anything with my project since getting some motor controllers about a year ago, largely due to budget constraints. However, I had an epiphany recently as I was reorganizing my basement. I had an old treadmill that I had taken apart for scrap for projects and realized that the tubing I had from it was near perfect for the rig I had been designing. With this recent development I decided to finally jump in and start cutting and welding. I broke down all the pieces of the treadmill and cut off welds to get individual tubes and brackets to play with. From that I started making the new "spine" of my system. The central spine is a piece of 1.5" x 3" x 0.120 wall tubing (at least I think that's the thickness). I also got some 1.25" square tube from the treadmill and had a piece of 1" square tube from another project sitting around that I used to make the seat and pedal mount tubes. I'm pretty much building mine to mimic the seating position of my car and to only mount the components that I have. The wheel is a Thrustmaster TX/T300 with matching T3PA Pro pedals and a T8HA shifter. The seat is out of a gen 1 Viper.

    It will probably still be a while before I finish all the fabrication as I'm trying to scavenge as much tubing as possible for the low low cost of free. For anyone else looking to save some money, a lot of exercise equipment has the perfect size tubing for stuff like this if you have the means to cut it down. Overall, based on my model I'm estimating the weight of the upper frame with controls and seat to be ~80 lbs without a driver. The frame itself is only around 30 lbs. The wheel, pedals, and shifter are another ~30 lbs. The seat is actually pretty light and I would guess is somewhere between 15-20 lbs.


    CAD rendering of completed upper frame:
    IMAG3334.jpg

    Physical progress so far:
    IMAG3333.jpg

    I need to find some more tubing to make the steering wheel hoop, but haven't had any luck finding any old broken treadmills yet to restock the supply.
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    Last edited by a moderator: Jan 26, 2021
  2. Map63Vette

    Map63Vette Member

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    Some more progress. I had originally earmarked some of my tubing to build the base as it seemed like it was going to be just enough, but the more I thought about it, the more sense it made to just finish the main spine structure so that I could test and use the setup as a static rig. The main treadmill belt section was a large U shaped 1x2 tube that was 24" wide, which was almost exactly the width I was originally planning on for my main steering wheel hoop. The bent corners also meant less welding and a bit more of a finished look. The shifter piece is just some leftover from the other cuts I've done so far. To use the setup as a static rig I built a cradle of out spare wood I could set the spine on. It can still roll side to side if you aren't careful, but I could probably fix that easily enough with another piece of wood. It's stable enough once you're sitting in it.

    IMAG3342.jpg

    I worked on isolating the ground on another motor last night (I've done one test motor so far, so this would be enough for a 2 DOF rig). I got to thinking about it and I think what I might do in the meantime is build a base frame out of wood to attach the motors to so I could do a 2 DOF setup as an interim option. I have plenty of scrap wood around the house, so that wouldn't cost me anything. I just need to come up with a pivot at some point. There used to be some scrap halfshafts and stuff around my house and my parents, but I think we finally cleaned house a while back and I can't find them. Along those lines, has anyone ever used a CV style joint from a halfshaft instead of a traditional U joint? Guessing there isn't really a practical difference, but didn't know if the CV joint might offer slightly smoother motion.
  3. darkknight

    darkknight New Member

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    My Motion Simulator:
    4DOF
    A great start!
  4. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
    3DOF, DC motor, JRK
    It depends, some CV joints allow lateral rotation and you don't want that in a motion rig.
  5. Map63Vette

    Map63Vette Member

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    Here's the latest plan for a temporary 2 DOF setup at least. I've got the rectangular portion of the base built already and the motors mounted. I just got my U joint and flanges today, so I know what size to cut the main post. My rod ends are supposed to be showing up tomorrow, so I believe I'll have everything I need to get things running as I got my power supplies as well today.. I still need to weld on the main bar that the rod ends will connect to on the spine and get the U joint mounted, but that shouldn't be too bad. Hoping I can have this thing moving this weekend. Will try to get some pictures of the actual base when I mount up the electronics.

    IMAG3349.jpg
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  6. Map63Vette

    Map63Vette Member

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    A little more progress. Got the U-joint mounted on the center post the other day and set up the electronics on one side to do a system test. It's much easier to test all this stuff bolted down to something compared to when I first got the JRKs as was trying to hook them up to a computer power supply and hold everything in place, lol.

    Seems to work okay, though I'm wondering how fast the motion is going to be. Guess I'll just have to finish it and see. It's supposed to be single digits around here for the next few days though, so a little less fun to try to cut and weld stuff in the driveway. Either way, hoping to have it mechanically assembled this weekend with some luck.

    Need to work on my JRK mount some more as well. They kind of fit, but the wire is so stiff they are hard to hold in place. The screw holes are so tiny it makes it pretty hard to find screws or print something that doesn't just want to snap. I didn't really have anything that would fit it, so it's just hanging in space right now for testing. I might look into one of the clip style JRK mounts in the FAQ section though. I'm also planning to make some fan mounts near the JRKs at some point as well, but haven't gotten that far.

    IMAG3352.jpg IMAG3351.jpg
  7. Map63Vette

    Map63Vette Member

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    Had a good day today and managed to get pretty much everything together aside from new JRK mounts and some connectors for the main AC plug I'm putting at the back to run the motors. It's not nearly as polished as I had hoped it would look, but hopefully it performs okay. I had some issues with the U-joint and I'm not super happy with it at the moment. The side to side movement binds a bit and isn't nearly as free twisting as the front to back. Hoping it might wear in a bit and seat itself with some use, but worst case scenario I'll just get another U-joint as that's cheap enough.

    IMAG3356.jpg IMAG3355.jpg IMAG3354.jpg

    Not that far off from the model, which is kind of novel to see side by side. Hoping I can get some motor tuning in this weekend and maybe get my first taste of driving. Still need to come up with a Rift camera mount at some point I suppose, but that should be easy enough to just zip tie on for testing.
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  8. Map63Vette

    Map63Vette Member

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    So I seem to have a strange anomaly I can't quite figure out. I have a box full of these wiper motors, but it seems like only one of them is "easier" to back drive. The rest are pretty stiff and will hold the weight of the rig statically okay (not when someone gets in it, but that's a different issue). The strange part about it is that the "loose" motor seems to be the most powerful. It has no problem pushing the rig up from the lowest position when using the JRK utility software. The motor on the other side that will hold up the weight okay won't drive up against the weight of the rig. It makes some noise, but no movement. I've modified one other motor to ground isolate it so far, so I figured I'd give it a try and it has the same response. Maybe it's just a backlash thing and it's just barely enough extra drag in the system that it can't push through it, but it seems really weird that only the one motor seems that way (I tugged on the lever for all the other motors I had and none felt as easy to turn), yet at the same time that one seems like it has the most power as well.

    As a side note, since I was having issues with the rig back driving further than I wanted, I thought I'd share this little idea I came up with. My goal was to give the rig something to rest on so it wouldn't drive past 45 degrees down on the lever and potentially invert the linkage and hurt something on startup. I basically just took a chunk of wood and a piece of rubber sheet and stapled the sheet on the top of the wood at the thickness I wanted. The brackets for the wiper motors have some ribs pressed into them that help lock the block in place. I took a Dremel and made some matching notches so they seat in those ribs really well. On the other side I had to drill a clearance hole for the bolt head it sits on, but that also helps keep it keyed in place. Gives it a nice solid stop, but also some compliance if it drives down on it too hard.

    IMAG3357.jpg

    The motor issue is less of one in actual practice though. With a person sitting in the seat the balance on the rig is better and there isn't as much stress on the motor, so it can drive better, though I think it's still a bit weak on the tight side. I'm going to see about modding the motors a little more to completely redo the wiring myself. The datasheets say they can pull 20 amps, but looking at the wiring I'm less confident it would want to do that for long. The motor wires look more like 16 gauge or something like that, which can carry that current, but I wouldn't want it to do that for long. There is also a thermal breaker (at least I think that's what it is, it says Klixom on it and that seems to be what they are for) that I might get rid of. It makes ground isolating the motors more difficult because it's crimped on the end of the negative motor brush and just hard to work around. May try taking it off one motor and running all new larger wires for everything to see if that makes any difference.
  9. Map63Vette

    Map63Vette Member

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    It's alive! Took a little bit to get some settings dialed in, but pretty cool to feel it in action. There is definitely room for improvement, but happy that it's functional at the least. The wooden base is interesting. The post really isn't screwed in solid enough, but it works with someone in the chair. If no one is sitting in it the motors are doing their best to try to splinter out the screws from the wood. There is also just some general slop in the system, but not bad enough that I mind for now. The JRKs are doing great temp wise after all the messing around I was doing with settings, though there was a decent amount of downtime in there while I was trying to get settings where I wanted them. The motor that back drives easily got pretty hot, but the other one was barely warm. I think the "loose" one takes a few amps to even hold position though, so I may see about swapping it out for another one to see if that makes any difference.

    I set the min/max stuff up with a really nice custom Viper model in Assetto Corsa as that's what I'm most used to driving, but for fun before I quit for the night I hopped in a Ferrari F1 car to see how it would compare. That was a blast and more what I was expecting, though I realize that's also pushing the rig pretty hard. Nice to see it would actually do it though. Next priorities are just going to be cleaning up the wiring and JRK mounting so everything is nice and tight to the frame. Maybe after that I'll see about reinforcing the main pivot post. Then I really need to see about getting my shakers back on the system somewhere. I think that would really help with stuff like rumble strips and engine vibration to get that last dimension.

    As a total side note, interestingly enough the Rift didn't really seem to care that I didn't have the camera mounted to the rig. As a temporary setup I just put it on a stand in front of everything so I could even use it and I never really noticed anything moving funny. Might be different with slower constant movement like a flight sim though, so will have to play with that. Also need to make a mount for my joystick at some point so I can give it a try as well.
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  10. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
    3DOF, DC motor, JRK
    Generally speaking on small axis movement sims you can get away without motion cancellation.
  11. Map63Vette

    Map63Vette Member

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    Some small updates. I've since welded the bar the motors attach to to the central spine. I had originally just bolted it in case I needed to move it to tune the ratios better, but it was moving around way too much as I had to oversize the holes for bolt alignment. While I was at it, I took the opportunity to drill some holes for cable routing. I had a bag of press in cable clips that were the right size to match the convolute tubing I had, and it gives it a much nicer look than the beaded chains I was using before. I also added an Aura bass shaker to the spine under the seat. Right now it's just clamped to the spine with a wood board as a backer plate as I wanted to test and see how well the vibrations came through. I'm not sure what I think just yet. I think the forces are dulled a little, but that's not a huge surprise as things aren't exactly isolated yet. I may try to find a way to attach them directly to the seat in the future as I think that would give me the best feedback. I've only got 2 of them, but didn't want to drill my seat to mount them, so still looking at ways I might be able to attach them to existing bolts.

    IMAG3385.jpg


    IMAG3384.jpg


    IMAG3383.jpg
    • Like Like x 1
  12. RacingMat

    RacingMat Well-Known Member Gold Contributor

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    My Motion Simulator:
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    good work!

    you really should insulate your wire connections (if black and red touch, you'll probably blow the board)
    upload_2021-3-10_14-38-39.png
  13. Map63Vette

    Map63Vette Member

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    Oh, yeah, I've since remade those. That was my testing setup with the wire I just happened to have around. I bought a crimper and some Dupont terminals so I could make wire that was the correct length before I used the setup for any extended period. Good eye though!
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  14. Map63Vette

    Map63Vette Member

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    Another small update. The center pivot wasn't very stable unless you were actually sitting in the chair. It had a bad habit of rocking forward and rearward so I decided to add some stiffeners to help try to clean up the motion. I guess I think of it similar to a car. The suspension can't do its job if the chassis is too flexible as the chassis basically becomes part of the suspension. Same idea here where too much of the motion was being eaten by the pivot so I don't think I was getting the full effect. Haven't tried racing with it yet, but just recalibrating the JRKs and moving it around felt less sloppy. Before it would sometime feel like it was clunking when going over center. I also coincidentally found out one of the side plates on my welded U joint setup had come loose as when I went to put the spine back on after adding the extra pivot supports the plate just fell off. Might have been another reason for the clunking, lol.

    IMAG3389.jpg
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  15. RacingMat

    RacingMat Well-Known Member Gold Contributor

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    My Motion Simulator:
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    well done
    the more rigidity you have, the more precise movements you get!
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  16. czgui

    czgui Member

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    Looking forward to your results video
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  17. Map63Vette

    Map63Vette Member

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    I think I'm debating a motor upgrade at some point though. The wiper motors work, but the gearsets don't lock that well so the system wants to move around when you get on and off of it. Also means more heat generation in the motors when they have to have more holding current to maintain a position. New ones seem like they could be cheap enough if I can find them in the right places, and I think I've got some headroom in the system to upgrade them. The JRKs are technically 24v rated ones, though I only have 12V power supplies and would prefer not to replace those. They can run up to 30A though, and my current motors stall at 20A, so I should have some room to upgrade, assuming any spikes don't shut them down.
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