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would this concept be possible

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by Mortisedsnail36, Mar 9, 2020.

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  1. Mortisedsnail36

    Mortisedsnail36 New Member

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    ok so my thoughts are possible 4 shocks (one in each corner) with adjustable coil over. I had thought of using scooter shocks they are usually cheap and would provide the assist on supporting platform weight.[​IMG] Screenshot_20200309-104740.png
    then use a worm gear drive motor on each corner to simulate the car suspension and body movement. then have a seat mover for g forces and to finish off have loss of traction on the back with front pivot point. Don't judge this sketch too hard it's a quick scribble [​IMG] IMG_20200309_110649730.jpg
  2. Ads Master

    Ads Master

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  3. Map63Vette

    Map63Vette Member

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    I actually had pretty much the exact same idea in the past. I wasn't necessarily looking at shocks, just plain springs, but it would be the same idea. I don't see any reason this couldn't emulate a DBOX style setup. You would just have to be pretty picky with the springs if you wanted the motors to have the same response both up and down. That could take some changing of springs rates on the front vs rear and making sure the compressed heights all balance out. The travel of the springs could be the other limiting factors. It's tough to find springs with a lot of compression height depending on how much travel you want at each corner.

    For example, assume you want 2" of travel at each corner. That would mean your spring needs at least 2" of travel from free height to full compressed. Now figure what your static corner loads would be. Let's keep it easy and say it's perfectly balanced at 50 lbs a corner. That would mean you'd want 50 lb/in springs at each corner so that the springs would be halfway compressed at "neutral" with you sitting in the seat and would give you 1" up and 1" down in travel. The motors wouldn't have to support the frame at all at that point.

    It gets trickier if your rig isn't perfectly corner balanced though. If the front is only 25 lbs a corner and the rear is 75 lbs each (more likely since the seat and you are at the back), one option is 25 lb/in springs in the front and 75 lb/in in the back (same idea as before), but this now means the front motors don't have to work as hard to compress the springs further compared to the rear, so you'd likely have poor response since the front and back would be differently loaded and the front would move easier than the back. The "better" idea (at least in my head) would be to keep common lb/in springs at each corner, but go with different compression heights. So the fronts only need 2" of total travel (1" up and 1" down, neutral position would be halfway), but the rears would then 4" of compression. The first 3" would be the static loading and the last 1" would be what the motor could push down to match the front. That would make it so that if any motor exerts 25 lbs of force the respective corner would raise or drop 1".

    Hopefully that makes some sense. I'm not sure how preload could work into the equation though. You might be able to run common springs at each corner and have different preload on each, but I haven't really thought about that or done the math on it yet. I think travel is the biggest issue. When I was looking for springs to see how feasible this idea was, I was having a hard time finding springs with common spring rates, but fairly large compression height differences. Doesn't mean it's not possible, but springs typically aren't built for a whole lot of travel.
  4. Mortisedsnail36

    Mortisedsnail36 New Member

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    I know my butt can fully bottom out a stock gy6 scooter spring, lol. that's why I was thinking bout them plus I could up the preload on rear ones with coilover nut. the front ones dunno. I figured decent gear motors could compress them if needed. it's mostly the lift that would need assist. plus I would want more than an inch or two of movement or it be bouncing all over room. the seat mover would take care of g forces
  5. Map63Vette

    Map63Vette Member

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    Ah, okay. Didn't know you were going for a seat mover as well. I think it's a reasonable idea. The lever arm gets a little tricky in that the vertical movement isn't going to be linear, but I'm guessing you could tune that with a profile. I see no reason the concept wouldn't work, would just have to run the math to see if the numbers made sense. It's not all that different in theory than a 6 DOF style platform in a way.
  6. Mortisedsnail36

    Mortisedsnail36 New Member

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    short term I hope the wife and baby will allow me to build a seat move in near future but long term I have many ideas bouncing around. I just want each step to build upon the next. money is tight nowadays even when working 7 days a week
  7. Map63Vette

    Map63Vette Member

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  8. Mortisedsnail36

    Mortisedsnail36 New Member

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    I had already looked thru that one before thinking of the scooter shocks. but more pondering and thinking I thing it would have very bad clarity and very unstable with no real guide for shocks
  9. Map63Vette

    Map63Vette Member

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    Yeah, I had considered doing something like a post on the base frame with a spring around it. That would give each corner a guide it could move up and down, but it would still be kinda sloppy as you'd need to have an oversize hole for the guide rod to account for the angles the frame would go through. I guess the system is a bit unconstrained without some kind of bumper pads or something.
  10. Agosky

    Agosky New Member SimAxe Beta Tester Gold Contributor

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    If you have a seat mover on top and use bottom part only for up/down heave movement, then some sort or guides are doable. But if you want the bottom to pitch/roll also, it gets quite tricky.
    In general that’s not a bad idea, although shock absorbers in your photo have no use, only springs. In middle height when lever arm is at 90 degrees, you get the least amount of linear force from gearmotor and springs would help there. As springs expand they lose force but you start getting more from lever angle. And lever force increases also downwards to compress springs more easily.