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Converting SFX100 to 3 actuator and using 4th motor for surge?

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by Roller2525, May 31, 2020.

  1. Roller2525

    Roller2525 New Member

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    Has anybody changed their SFX100 config from a 4 actuator to a 3 actuator and using the 4th motor for surge? I am thinking of doing this to mine..
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    Ads Master

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  3. wannabeaflyer2

    wannabeaflyer2 Well-Known Member

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    Hi Im in the process of doing this right now and have to say tha 3DOF setup Throws me around with ease 1 up front and 2 at rear is working a treat so far with my testing ,,,Would have liked to have used my 4th Actuator for Traction Loss But The safety Opinion is that the 3 DOF is not As Safe as 4DOF ( Potential Tipping Issues) ..not given up on that thought yet as im still learning to Use the Excellent @pmvcda FlyPT Mover software. and having great fun doing so :)

    Forgot to add My SFX actauors are modified so i have 150mm travel range and they are capable of hnadling Push Pull Operation , Something that the standard SFX tpe actuator dont do well unless modified Cheers
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  4. cfischer

    cfischer Active Member Gold Contributor

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    I've moved my rig from 4 to 3 actuators. I recommend it as long as you watch the tip. I've had to catch myself on a desk while the rig was going over (belted in and blind to the world in vr!). I have really long actuators though so I'm probably a worst case. I run very little sway/roll right now.

    Haven't tried surge or traction loss yet. You will have to make the actuator push pull for that.
  5. Roller2525

    Roller2525 New Member

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    I was thinking fixing the actuator legs to a frame at ground level which is slightly wider than the main sim structure may help with stability..

    Using the 4th motor on a lead screw design may serve me well for a push/pull surge function..?
  6. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    A traditional 3DOF is fixed to a bottom frame, any stability issues like below are specific to the peg leg design.
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  7. Roller2525

    Roller2525 New Member

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    So attaching the SFX100 actuators to a frame is doable and should resolve instability issues?
  8. cfischer

    cfischer Active Member Gold Contributor

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    Instability can be solved a lot of ways. I currently solved mine by lowering the intensity of motion in the sway/roll direction. You could make your frame wider than mine, or your actuators shorter than mine, etc.

    My future idea is to flip the actuators upside down and attach them to a bottom frame. This not only takes the actuators weight off the moving part of the rig but it also allows me to attach the actuator high up on my rig so the center of ration is closer to the center of mass.

    I think this is a win because right now with the center of rotation below the rig, any pitch or roll feels like surge or sway. I want to make a g-seat for my rig so I'd rather feel pitch and roll vs surge and sway from the motion platform. This would definitely solve the instability, but I need to change the actuator to a folded design because it would all be way too tall otherwise.



    You might have trouble attaching the actuators directly to a bottom frame. The legs move quite a bit during rotations.
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  9. Roller2525

    Roller2525 New Member

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    I was thinking using a rod end bearing on the ends of the actuator to deal with movement.
  10. cfischer

    cfischer Active Member Gold Contributor

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    Sure but its not just the angle of the actuator that changes. The distance between the actuators change too, so there will some amount of bind in the actuators.
    1.jpg

    Maybe not enough to matter, especially for small angles. Perhaps not a deal killer. It will be an experiment.

    You also need to deal with the sfx design not being a push pull actuator. Because if the rig wants to tip over it can just pull the steel rod right out of the actuator on its way over.

    Be sure to post up when you do it. As I said, I hope to something similar, but with the actuators upside down on a floor frame.
  11. Roller2525

    Roller2525 New Member

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    I see what you mean with the distance variation between actuators through movement. That hadn't occurred to me...

    Will take some creative thinking and experimenting for sure.
  12. Roller2525

    Roller2525 New Member

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    @cfischer is your rig configured with 2 actuators at the rear, or at the front?

    I'm thinking of using 1 on the rear and 2 up front so that I can keep all 3 actuators closer to forming an equilateral triangle with my main body mass as close to the centre of the triangle as possible.
  13. cfischer

    cfischer Active Member Gold Contributor

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    I have one in the rear. It was more convenient for me.

    I feel like I should reiterate that my rig is probably the worst case on the internet for instability due to the long actuators (230mm travel). I'm sure your efforts to balance the rig and using more typical actuators will result in you never noticing any tippy driving moments.
  14. Trigen

    Trigen Active Member

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    I got 150mm to and I'll be taking on the same thing so I look forward to seeing what you do. I'm going to look into securing the internal parts for a push pull or at least a safety system. As long as its printed on the side and not bottom up fks petg can take a lot of force. I can also be filled with epoxy. It needs a bit of experimenting on print settings for dimensions which I'll do in a wee or so. My profiles just shipped today.

    Just for testing I'll use a frame with some ropes to the floor to stop any tip over. I really don't use much angle on sway as I find it very unrealistic in fast switching high G turns and I got my g seat for it anyway. I got a 60mm 2x setup right now
  15. Trigen

    Trigen Active Member

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    Mind sharing or for a part on what you have done to make them push pull?
  16. wannabeaflyer2

    wannabeaflyer2 Well-Known Member

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    Hi @Trigen ive attached a pdf of my design if you check item "rod adapter " on sheet 5 i think , you see a Machined Part ( round aluminium which acts a clamp for 30mm steel rod .. this can be either drill& tapped through the side and the 30mm steel rod will have mating hole which allows the screw to lock onto the shaft at typically 3 point 120 degrees apart , or the shaft can be bonded to the aluminium adapter . .

    this should secure the shaft to the Ballnut and ensure operation in both push and pull mode .. as always the design lends itself to being adapted to users preference .. Hope this info helps

    Attached Files:

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  17. Trigen

    Trigen Active Member

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    Thanks appreciate it! Amazing work on the diagrams!

    I had roughly the same internal idea/design in my head but there's no need to reinvent the wheel. I can get this done at a machine shop i used to work.
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