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Seat Harness Tensioner Questions

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by Zed, Jun 15, 2017.

  1. RacingMat

    RacingMat Well-Known Member Gold Contributor

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    upload_2017-7-25_15-44-16.jpeg we cross fingers for you! it's really difficult to create and be innovative

    soon a video hopefully :popcorn
  2. Zed

    Zed VR Simming w/Index Gold Contributor

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    Will do, Matt! Cheers!
  3. Zed

    Zed VR Simming w/Index Gold Contributor

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    Got an update on the belt tensioner design. The all-plastic printed guides work OK but I was concerned about the drag of the belts in them creating too much friction and sapping away some of the belt tension. The friction would get worse the more pull there was too. In thinking about the problem, I came up with this.

    I looked into some round bar and needle bearings to just make a wide pulley for the belts to roll over. I'm using 10 mm nominal diameter, 80 mm long metal shafting and 10 mm ID, 14 mm OD needle bearings in a printed housing to hang the bar a bit over the side of the mounting to give a more free path. The bearings and bars snap in and the strap holds the belt captive. I'm modding the design just slightly from what is shown here to give a small ridge to positively hold the bearings in the pockets and making the rod clearance slightly longer because in the test it came out with basically zero clearance and the rod is rubbing at the ends. With those changes it should be good to go and reduce the friction in the belt turns to negligible amounts.

    RollerBar.jpg Roller.jpg
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  4. Zed

    Zed VR Simming w/Index Gold Contributor

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    IMG_3063.JPG IMG_3066.JPG IMG_3065.JPG
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  5. Zed

    Zed VR Simming w/Index Gold Contributor

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    Got the final design now and will post the .stl files this evening if anyone is interested. I added a raised section to create pockets for the bearings to lock them in place. The rods I used were 10 mm dia and 80 mm long from PDTech (http://a.co/gu7TEAV) at $6 each cut to length. The bearings are Koyo HK1010, 10 mm ID, 10 mm long, and 14 mm OD (http://a.co/2sf6ITj) at $4.20 each. I'm using three assemblies since the shoulder harnesses get doubled up so parts cost is less than $50 besides the plastic. Friction is way down over pulling the belts 90 degrees around the frame through 3D printed guides. Haven't tested the whole thing out yet but I'm pretty sure it's going to work well. With the ball bearings in all the turning pulleys just about all of the pull from the motor should now end up in the seat belts. At about 12 pounds of pull on each belt, it won't squeeze the breath out, but it should provide the sensation and the spring will provide some give.

    Edited to add the .stl files for the mount in a zip archive and a Fusion 360 image of the final version where the bearing retainer bit is showing. Got one mounted now on the shoulder harness side with the double belts (still printing the other two) and it makes a huge difference in the friction! Looking forward to being able to try it out. :thumbs

    Roller.jpg

    Attached Files:

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    Last edited: Aug 3, 2017
  6. Zed

    Zed VR Simming w/Index Gold Contributor

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    Hey @RacingMat - these kind of show the layout. It's pretty tight in there but if you trace the cord, you'll see the setup as implemented. I have to say those rollers do really help out. Now that top is mated to bottom, the cord runs free and I think the seat belt tensioning will work fine. Still not tested and the final knot not even made, but as is, everything is running low friction.

    FullSizeRender 6.jpg FullSizeRender 2.jpg FullSizeRender 7.jpg FullSizeRender.jpg IMG_3081.JPG IMG_3082.JPG
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    Last edited: Aug 19, 2017
  7. RacingMat

    RacingMat Well-Known Member Gold Contributor

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    from idea, to sketch, to realisation!
    that's great :)

    eager to see forward the test
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  8. daneracer

    daneracer New Member

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    Can I order harness kit? what is pricing. Cn it interface with Sim Commander?

    Thanks
  9. RacingMat

    RacingMat Well-Known Member Gold Contributor

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    what's is your feedback after these period of time @Zed?
    still the same design?
    yours :)
  10. Zed

    Zed VR Simming w/Index Gold Contributor

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    Hey Mat, the system works but the motor and arm I used doesn't have the stroke or the force to be especially effective. I haven’t had the chance to do anything to fix it. The wide ball bearing strap rollers and ball bearings in the pulleys are all important, though. Also thinner rope than in those photos.

    In hindsight, I think bike brake pull cables would be a better solution, but for my setup I’d still need a location for the actuator. The base of the chair is very crowded so the harness has been relegated to when I get around to it. :popcorn

    Cheers!
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