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Budget compact seat mover

Discussion in 'DIY Motion Simulator Projects' started by Micheal, Jul 11, 2020.

  1. Micheal

    Micheal New Member Gold Contributor

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    My Motion Simulator:
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    Hi all,


    After creating my first wooden fixed racing frame about 8 years ago, I decided its time for an upgrade. This time I wanted a few upgrades this time, it needed to take up less space and I wanted it to have motion.


    After doing lots of reading on this forum and talking to a friend whose also made his own simulator, I decided to go with a seat mover rather than a full frame. It would also hopefully make it easier to make compact.


    I started with looking at the control equipment needed, and I decided to go with this:


    Motors: Motion dynamics 12V 200W worm drive motors

    https://www.motiondynamics.com.au/worm-drive-motor-12v-24v-200w-180-rpm-20nm-torque.html


    Power supply: HP 12V 575W server power supply (I found the tutorial on these forums on how to modify it so decided to stick with it)


    Control boards: Pololu JRK G2 18v19 (I thought these would be easiest as programming isn't a strong suit so thought these would be easiest)

    https://www.pololu.com/product/3146

    Potentiometer: TT Electronics 180deg. sensing range hall effect pot with continuous rotations

    https://www.digikey.com.au/product-detail/en/tt-electronics-bi/6127V1A180L.5FS/987-1392-ND/2620661


    Framing Dimensions:

    I then used SimCalc to play around with different dimensions to see how it changed the forces etc. It took me a while but I ended with dimensions I thought were going to work well. I then found an aluminium profile company that had reasonable prices and also had an online CAD tool so I was able to draw everything up and then order it.

    The idea is that the front half with the pedals and wheel attached sits on top of the base and will slide back and forth to allow for different users height and also slide back to make it compact for storage. The pedals would also fold up to make it compact during storage and would also allow for different angles and heights.

    Once I had this all down the CAD spat out a BOM which made it really easy to order. So I ordered the framing and then was able to get onto something else.

    Control box:

    I needed something to house the control equipment and decided to put the equipment into a mini ITX box (stole that idea from my friend). I used this one: https://www.coolermaster.com/catalog/cases/mini-itx/elite130/

    It was long enough to fit the power supply in which was my main concern. I had to modify the internals slightly by removing the 3.5” drive bay and the USB cables which were bulky to give plenty of room inside. I then 3D printed a plate to screw the server power supply where the ATX power supply would have normally gone and a hanger to support the rear end of the power supply from a mount that used to support the 3.5” drive bay. In order to mount the JRK controllers, I printed some mounting brackets on a frame that would attach to the motherboard mounting points in the ITX case and also space for terminal blocks in for the motor power. I also printed a blank grill to cover the motherboard I/O cover on the case and cut some holes where the terminal blocks are to allow for the motor cables to enter into the case.

    After soldering everything up (took a while using my cheap soldering iron) I was able to mount it all in place. I reconnect the cases fans and bought a switch to turn the power supply on and off (the power button on the case was the typical momentary switch which wouldn’t work with the power supply).

    A few things took me a while to get right, and even then, its not perfect. When I connected the USB to the JRK it clashed with the internal fan, so I had to move it as well.

    This is about half of the progress to date. I’ve received the framing (and modified it again), mocked up the motors with the control boards and pots and also started to have some brackets fabricated to mount the motors, along with brackets to have the universal joint welded to. I’ll share in another post soon.

    Attached Files:

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  2. Ads Master

    Ads Master

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  3. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
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    Sounds like a great start, I am looking forward to following your project updates :thumbs
  4. Micheal

    Micheal New Member Gold Contributor

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    Thanks noorbeast.

    So I put the frame together which went relatively smoothly. I couldn’t put it fully together because I want to wait until I have all the brackets before I drill the profile to lock things in permanently. I put the base frame together using temporary brackets however the full front to mount the wheel and pedals could be completely finished. The folding mechanism worked well for storage but was totally useless when it actually came to using the sim. When putting any sort of decent force on the pedals the front collapsed. Should has seen it coming, was good in theory I guess lol.

    I printed some temporary posts to support the front but that means I’ll lose a lot of the adjustability I was hoping for so I bought some more profile so I can adjust the angle on the pedals again and also made some more solid supports with short pieces of profile.

    To make the front section of the profile slide against the base I printed some sliders. One would be locked at the front of the base (to the base), the other would be locked at the end of the front frame section (to the frame) but would also have a bolt that is easily accessible to lock it to the base and stop the front frame from sliding.

    So once I had it all together I tried the sliding function. Didn’t work like I hoped, it’s a bit too grainy but it’ll do for now. I also didn’t make the front section overlap enough with the base so when its fully extended there’s a bit of flex when putting force onto the pedals which had me a bit concerned. I decided to add a brace to make more rigid. I also decided to put wheels under both the base and the front frame. It’ll make it easier to manoeuvre in and out of storage and help the front section of the frame slide out (help support some of the weight, so it doesn’t bind up so easy).

    I’m also having brackets made up to mount the motor to the frame, weld the universal joint to and mount to the seat frame. In the meantime, I’ve just solid mounted the seat to the frame so I can still have some fun with it until the brackets are all finished.

    Attached Files:

  5. Micheal

    Micheal New Member Gold Contributor

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    My Motion Simulator:
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    I’ve decided to at step up as much of the control side of it as I can while the motors etc. are still off the frame. I printed up brackets for the potentiometers so it could be mounted using the all thread rod that will eventually mount the motors. I also printed some spacers to make sure it was evenly spaced all round and I wouldn’t accidently bend the pot shaft. I also printed some mock shafts just to get it all going and set up before the proper ones go in (still being made at this stage).

    I connected up the pots onto the JRKs, but I had to use a different pin configuration to what the website recommended. They said it should be connected to AUX for positive, POT- for negative and FBA for the feedback signal. I found that I had to use different pins for the positive and negative connections on the pot, I used the +5V regulated pin for positive, GND for negative (which made sense to me but I don’t know why its different to the user guide? Might just be my pots.) I found if I connected as the user manual, I did get a signal but it was static and didn’t change as the position of the pot changed.

    Once I had the pots all working I then started to play with the PID of the motor. It was interesting to play around with it and see how different values cause the motor to continuously ‘hunt’ for the position. I spent about 30mins playing around with the settings (I didn’t want to spend too much time because I’m going to have to do it all again once the motors are mounted to the frame and have load applied) but I go the motors to a reasonable response. Looks like it reaches to position pretty quickly and doesn’t have too much overshoot.

    I’d be interested to know what settings other people have used on similar set and what their response is.

    I also found the JRK utility difficult to objectively measure the variables. The graph shows it, but I can’t seem to figure out how to select a point and it tell me its position and time in relation to the graph. If I can figure that out I can really see if I’m making he response faster and see how much overshoot I’m actually having. Does anyone have experience with this?

    Attached Files:

  6. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
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    Any further updates, have you mounted the motors yet?
  7. Micheal

    Micheal New Member Gold Contributor

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    Nah no more progress since. I’m still waiting for the mounts, it’s being made for free by a family member in their metal fabrication shop so it’s a lower priority (understandably).

    Im trying to gain access to simtools via the good people on xsimulator so I can continue to progress the control side of things. Hopefully I can have it all ready to go so once the brackets are ready I can bolt it all together, sort out the connecting rods and it’ll be good to go.
  8. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
    3DOF, DC motor, JRK
    Just so you know your rig needs to be complete and ready to be tested to be eligible, which is why I was asking.
  9. Micheal

    Micheal New Member Gold Contributor

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    Ah ok thanks. I was unaware that the rig had to complete, I knew it had to be at the testing phase which I thought was the control side of things.

    I’ll see how long the brackets will take to come, if it’s still some time off I might purchase a license :thumbs
    • Like Like x 1
  10. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
    3DOF, DC motor, JRK
    Have you managed to snag the engine mount brackets yet?

    I am looking forward to your next update.
  11. Micheal

    Micheal New Member Gold Contributor

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    Nah not yet unfortunately, hoping they come soon.

    I’ve had an issue with the sliding mechanism. I’ve used M8 bolts to hold the sliders to the frame, but if the frame goes slightly on an angle the thread is digging into the aluminium. It’s just seized up so I have it apart at the moment. I need to sand down the profile to remove the burrs and remake the sliders to use M6 bolts.
  12. Micheal

    Micheal New Member Gold Contributor

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    My Motion Simulator:
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    So after some time I have some updates. I received the brackets and shafts back complete and powder coated which looks awesome.
    upload_2021-1-26_22-34-11.png
    The universal joint has two plates with nubs on them which go into either end of the universal joint and then has grubs screws that screw in to hold it. The only problem is that is could still twist when the seat is tilted to one corner (pushed from one motor and pulled from the other). So I grabbed some JBWeld and packed it in either end. I also jigged it up with some profile so I knew the two plates would be square for when it was installed into the rig.

    upload_2021-1-26_22-34-23.png upload_2021-1-26_22-35-36.png
    I also made a jig to drill a hole in the centre of the shafts but with varied results. I ended up making another centering jig which worked better. I’m using a 5mm (I think) spring pin so I had to drill out the collars on the gearboxes to suit as well. I think found that my shafts holes didn’t align with the motor collar holes (of course not, why would they?), so I had to drill new holes into the collars but used the holes in the shafts to guide it through and they lined up great. I could then put the spring pin in and hold the shafts to the gearboxes.

    I mounted everything to the main frame and could measure up exactly how long I need the connecting rods to be between the motors and the back of the seat frame.

    I bought some hex bar and put a right hand thread in one end, and a left hand thread in the other end. That way I can twist the hex bar for adjustment, just like a turnbuckle.

    I mounted everything and tested it all without power to the motors and had to make some adjustments to the pot positions and the rod end positions to make sure nothing bound up. I then re-did the pot calibrations and tested it again and it all works pretty good! I haven’t fully cranked up the acceleration yet and I may need to re-do the PID but it works for now.


    upload_2021-1-26_22-35-48.png upload_2021-1-26_22-36-22.png
    upload_2021-1-26_22-36-15.png upload_2021-1-26_22-36-37.png
    • Like Like x 4
  13. Micheal

    Micheal New Member Gold Contributor

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    My Motion Simulator:
    2DOF
    So its been a while since an update.

    I've had the sim up an running for a while and I've made a few tweaks . I've made some brackets to mount my Fanatec power supply, USB hub and also made some clips to help with the cable routing.

    I've had some annoyance of the motors though. Theres some backlash which I know is expected with the motors I have, so after the advice of my mate, I moved my pivot point forward so its not "perfectly" balanced and more weight is transferred onto the gears constantly pushing them back. I also lowered the seat closer to the actual pivot so the COG isn't so high.

    I still seem to get side to side movement though. I made the lever arm have multiple CTC lengths (which I had on the longest length) so I shortened it but the backlash is still there. One motor is actually worse than the other. There was one motor that I took apart a bit when I first got them so I dont know if could have damaged something or even if its the same motor.

    So given I need new gearboxes, and I want to make the pedals fixed mount (not on swivel arms), I'm going to change from a shoulder mount to an under seat design. Which means new gearboxes so I'm to go the 50/60:1 boxes from motion dynamics.

    I talked to them about mating them to my current motors and they seemed to think that the current motors wont last, but it'll be the same setup that you had @noorbeast on your DX racer (I read your full thread, great work by the way) and you didn't seem to have any issues?

    Also in regards to the level arms, I was considering keeping my current ones which are with the hollow gearbox shaft as Motion dynamics think it might be possible to change the solid shafts in the new ones with the hollow ones from the old. I'm thinking thats probably not a good idea considering taking apart my old ones may have damaged them and it looks like you had something similar @noorbeast so I'd be keen to get your thoughts.
  14. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

    Joined:
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    My Motion Simulator:
    3DOF, DC motor, JRK
    I had problems with one gearbox, but its replacement, the other original 60:1 gearbox and the third one I got for the upgrade to 3DOF have been doing fine for 7 odd years.

    I have done general maintenance like change the brushes in the motors, which were available via Motion Dynamics, but have never touched the wormdrives.

    The backlash is still the same today as it was when I shot this video in 2017: https://www.xsimulator.net/community/faq/wormdrive-backlash.293/

    I would go servos if I was doing it again now, but that is a personal thing in terms of where technology has moved on to, not any reflection of the durability of my rig or its hardware.

    This is my rig today, still waiting for me to build a new desk hung pedal mount, I am hosting a Bathurst V8 Supercar qualifying day on my rig for a bunch of mates on 4/12/21:

    DX.jpeg
    • Like Like x 1
  15. Micheal

    Micheal New Member Gold Contributor

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    Oh that’s great then. I’ll put in an order for those 60:1’s and then play with the level arm length to get the right speed.

    Servos hey? I might have a quick look at them, Im trying to get away with changing as little as possible though for this one. Maybe on my next one

    that looks good, so your wheel isn’t mounted to the frame anymore? And your moving your pedals off too?
  16. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
    3DOF, DC motor, JRK
    Correct, having tried both and I found I personally preferred the seat shaker design over full frame, as it provides additional motion cues at the wrists and feet, plus significantly reduces the load on the rig: https://www.xsimulator.net/community/faq/full-frame-vs-seat-shaker-designs-which-is-better.213/
  17. Micheal

    Micheal New Member Gold Contributor

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    Ah right, yeah I read a lot of threads around here before I went one way or the other. Plus my mate had a full frame and then redesigned it to be a seat mover only.

    I'll post progress on how I get along. Time to get together a parts list.