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Trip's G-seat project (primarily for flight)

Discussion in 'DIY Motion Simulator Projects' started by Trip Rodriguez, Nov 19, 2019.

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  1. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    A couple nights ago, while trying to fall asleep, I suddenly thought of a little problem I should have seen all along. Nothing too hard to solve though.

    I'm going to have two actuators driving the "elevator". If one goes and one doesn't or lags behind will it do electrical or mechanical damage? AASD based servos with 1610 ballscrews are what I'm using.

    I think these can be driven by the platform so I don't think it would be mechanical damage unless they decided to go opposite directions. Do I need to worry about the servo acting as a generator and damaging the servo drive or AMC if it backdrives? I would expect there to be some protection built in but you never know.

    Anyway, I figure I need a shear pin on each actuator, and attachment to the platform done in such a way as the platform can't drop, but it can leave one actuator behind by shearing the pin as it goes up. If for no other reason, in case somehow the two heave actuators do somehow decide to drive in opposite directions.

    Thanks! The cutting steel, drilling steel, and welding is going to be a lot of work for sure. I don't enjoy cutting and drilling steel. =(
  2. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    So my heart nearly leaped from my chest when I saw the price quote this morning for the steel stock I need. I was just about to sit down and do a redesign to use as little steel as possible.

    Fortunately I looked at the quote again and saw that... well that I'm an idiot. I told him three of each, so each line on the quote was for three, not one! $200, not $600. =)

    Now I just have to try to get my trailer pulled up and out from it's hole, with a 2 wheel drive pickup and snow on the ground.
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  3. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    Glad you sorted that and I look forward to your next build update, good luck with the trailer.
  4. MarkusB

    MarkusB Active Member Gold Contributor

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    I also once had two motors run in parallel. In my case these motors were lifting the backrest of my seat in order to increase the sensation for 'heave'. I had the same concern as you, and therefore I mounted the rods in a way that they were able to move independently from each other, at least in a range of some centimeters. Here is a picture, in which I have highlighted the relevant area with a red circle.
    2ActuatorsInParallel.png
    More details can be found in my build thread.

    Edit: I guess that even small deviations in the synchronous motor movements will cause the motors to work against each other, which in turn will cause high currents, heat, and reduced overall torque.
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    Last edited: Jan 21, 2020
  5. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    Thanks @MarkusB . Unfortunately I don't think that approach will work for my design but it was a clever solution! It would work if I put the lift actuators all the way at the back but I'm nervous about counting that heavily on the vertical slide rails for lifting a very, very heavy and large load from one edge.

    I think I'm going to attach the ballscrew nut (indirectly) to the elevator platform underneath the frame with yoke and shear pin. That should do nicely. I could even just leave it so they aren't actually attached, but then if one actuator is a little lazier than the other there would be a bump every time it catches up and re-establishes contact with the frame.

    Thank you for the well-wishes @noorbeast . I'm anxious to get started! As soon as I pick up my steel I'll essentially have all of the components and materials for the entire project. I'm sure excitement will keep me burning the midnight oil once I get started.

    My design at present is a hodgepodge of parts of several drawings I made, and the final design varies from even those in terms of dimensions and the placement of the towers etc. but I don't think it's worth spending a day or two making a new drawing at this point. Based on the CAD work I did I'm confident I've got everything figured out.

    Here is a rundown on the upcoming build:

    In the end I decided to use six towers instead of four. Each tower will be made from 3/16" x 2.5" x 2" steel angle rather than rectangle tube to simplify drilling and bolting on parts. A second piece of angle will be welded on to box the angle where additional stiffness is needed. I did this once before and it worked very well. The perimeter frames will be bolted rather than welded to the towers. This makes it possible to disassemble the sim and relocate it to another room or another building.

    There will be one tower at each corner with a 1500 mm SBR16 guide rail. Each corner of the elevator platform will have two of the linear guide bearings on it's corresponding tower rail, one at the very bottom of the platform, and one mounted a few inches higher to help prevent torsion problems. These four towers will be held in place by a 1" x 1.5" perimeter frame on the floor and another perimeter frame either at the top, or at some point lower but at least one or two feet up from the bottom one.

    Bolted to the upper and lower perimeter frames will be also be one additional tower on each side, toward the rear, with the 1500mm ballscrew actuators to move the heave elevator through it's potentially 50" (1270 mm) heave travel. (I will not be able to use the full travel due to not having a high enough ceiling, and it starts on the floor! I might later make a place for it with higher overhead clearance so I can use it all!) The ballscrew nuts will be attached to mounts at the outside edge of the "elevator frame" which is the base component of the moving platform. These towers will be located to match the forward/back CoG of the platform as measured late in the construction process. It would be measured again and the location of the lift towers adjusted if/when I made changes to the sim that would alter it's CoG dramatically. I think I'm going to put the motors at the top of the towers rather than the bottom. This is the simplest solution to my requirement that the when the elevator is at the bottom of it's travel it is basically on the floor.

    The "elevator platform" will be 9" longer and 9" wider than the "floor" of the sim to allow for surge and sway travel. From here on when I say "elevator platform" I'm referring to this specific frame and not the others atop it. It will be made of 14 gauge 1.5" x 1" steel rectangle tube laid flat rather than vertical to minimize height. This frame will be built without any cross members in the front center area so the "foot well" of the cockpit can go right down flush with the bottom edge of the elevator frame. Right on the floor.

    That frame will have another frame made with the same stock atop it with slides and rollers between to allow it to move on the surge axis. Atop that is another frame of the same stock, with slides and rollers between to allow it to move on the sway axis. The cockpit floor will be attached to this frame. The G-seat will be mounted to this frame, but it will be bolted to pieces of the angle stock so it can be removed with four bolts. Also the rear "legs" of the G-seat will be shorter, but bolted up higher normally. There will be another set of holes in the angle down lower, so the back legs can be dropped down and get bolted in a lower position to put the G-seat at a more reclined angle for the F-16 cockpit. The actuator rods for the G-seat roll and possibly sway axes may need to have a way to quickly adjust them when the seat angle is changed in this manner.

    The surge actuator ballscrew nut will be attached to an SBR16 slide rail mounted crosswise on the elevator platform as well as to a linkage/Bowdens for the G-seat surge, harness tensioners, and body G-loading system. The sway actuator nut will be attached to an SBR16 slide rail mounted lengthwise on the elevator platform, and to the G-seat and body G-loading systems via Bowden cables. The roll actuator is attached only to the bottom cushion portion of the G-seat by a direct (via bellcrank) actuator rod . The G-seat heave actuator is completely independent and is mounted to the back of the G-seat in a vertical orientation. Linkage will attach it to the seat bottom and top cushions, and to the harness tensioners.

    G-seat design will be very similar to the ACME DMS, but with a paddle design for heave and surge based on SeatTime's "parasitic" paddle system that has the center move the opposite direction of the paddles to avoid moving the pilot spatially in the wrong direction creating a false cue (see OP). I also think I'll have surge on the bottom cushion, though I'm not sure how useful it will be since I now plan to have a surge table. I might put the slides in but disable it pending testing and experiments.

    The seat bottom rolls left and right, and this will be an independent axis run by "roll rate" telemetry in the air and roll Euler Angle when on the ground. When you are picking up a helicopter and the right hand skid lifts and you tilt to the left, the bottom cushion will roll appropriately to cause you to feel the tilt. The seat back would also move to the left (same direction as roll tilt) in this situation so in effect the "whole seat" tilted as the virtual helicopter tilted. In contrast, when you yank the stick hard to the left in flight the bottom cushion will roll left with the airplane, but the seat back and G-vest will pull your torso to the right to simulate the G-force caused by the sudden acceleration (opposite direction from roll tilt).

    The body loading system will include head loading, thigh loading, and chest loading. The chest loading system will involve Bowden cables attached to a corset-like vest that is in effect attached to the seat. It would be spread out to the sides so when you sit down you'll be able to grab the two sides, pull them around in front of you, and secure them together with shear pins or a similar mechanism.

    My intention is for carrier launches and landings to be uncomfortable, and for pulling too many G's in flight to risk cracking a rib. This is not for use by guests. =D Safety features to prevent (serious) injury will include a breakaway at the front where you close it and redundant breakaways on the Bowden cables. The breakaways will likely be 3D printed so I can make them in various strengths and easily replace them when they break. I could allow some guests to use it with much weaker breakaway pins.

    The active harness will tension and relax both the lap belt and the shoulder belts for surge and heave cues.

    Now to see what goes horribly wrong!

    Trip
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    Last edited: Jan 21, 2020
  6. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    Now it really begins! I got the trailer out no problem and picked up my steel yesterday.

    I wish everything was in one place for a photo before I begin, but I don't think it's worth taking the time to move everything around twice just to take a picture. I expect to make the first cuts and welds Friday if all goes well!

    72 linear feet of 2" x 2.5" x 3/16" angle
    60 linear feet of 1" x 1.5" x 14 gauge rectangle tube

    IMG_20200122_163018.jpg IMG_20200122_171304.jpg
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  7. Pierre Lalancette

    Pierre Lalancette Sir Lalancelot Gold Contributor

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    A simulator, a G-seat, a car to rebuild.
    If there is someone with you, that someone must be quite patient.
  8. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    FYI- This post is a reply to the comment above, it's me blabbering about personal stuff and contains no significant simulator content so most of you folks will probably want to skip over it. =)


    Actually I've got two cars to rebuild Both Corvairs. Plus one Corvair engine to rebuild. And you didn't know about my beloved $700 sailboat! I have to disassemble it and turn the hulls upside down to do a little fiberglass work. I'm also hoping to refinish the hulls while I've got it apart. Oh, and my house (which is a trailer on owned land and a mortgage) is all torn apart for renovations! No carpet, half a kitchen, etc. That's just the big stuff. I don't pay anybody to do anything I can possibly do myself, so if it's broke I fix it myself. I do the same for my 93 year old Dad's home and property plus play chauffeur for him a lot, clean his house, cook, etc. and do my best to provide him at least an hour or so of conversation most days. That kind of stuff alone keeps me busy much of the time. This week I was a plumber and an auto-mechanic. Next week auto-mechanic and electrician.

    That said, you rather had the right idea @Pierre Lalancette, if there was "someone" it's highly unlikely all this would be possible! I never had kids and I fired the wife two years ago next month, following her arrest. o_O That's a good story. If anyone wants to hear it you can PM me LMAO. Honest to goodness soap opera material. Anyway I have no intention of finding a replacement female. In fact I have been making every effort to avoid temptation in that department. So far my resolve has strengthened rather than wavered. Everyone keeps telling me forty years old is too early to swear off women and I won't be able to do it, but I think I can. I hadn't been single in twenty two years, with the exception of a couple ~six month gaps. I'm loving it! :thumbs Now I only have to compromise with myself!

    70393445_485020015677614_5823755647971229696_o.jpg


    Sorry for all the nonsense. Hopefully the warning up top will more or less prevent this from annoying anyone. hug:
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  9. Pierre Lalancette

    Pierre Lalancette Sir Lalancelot Gold Contributor

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    My goodness. Even without the women, how can you find time to do all of this?
    I pay for everything, since I'm good about almost nothing. That gives me time for all the little things, and I'm broke.
    Life is all about choices I guess. Good luck with everything. :cheers
    A sailboat?
  10. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    I'm planning to make the first cuts and welds today if all goes well!

    @SeatTime @BlazinH and other G-seat buiders: I have been questioning a bit my decision to have a 4-6 inch wide flat between the paddles. This seems to me like it would better apply pressure to the correct areas without moving the human in the wrong direction, but I imagine yours are the way they are because that's what you found worked best.

    I might use the paddles that go all the way to the center first and see how easily I can make a swappable paddle assembly to try out both unless one of you folks let me know why it's better without the flat.
  11. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    I can't find time to do all this! But there is no deadline for the hobby things so I do the things that can't wait first, and the rest very slowly progresses over the years.

    I'm not good at anything either, but that doesn't stop me from doing it! =P

    I put a picture of the Sailboat in that post, did it not show up? It's a Hobie Cat 16. Best $700 I ever spent, it's crazy how cheap older used ones are. It really provides much needed stress relief and roaring along at 20 knots and flying a hull is a blast! So far my friends have failed to capture any good photos of me flying a hull but here is an example with a boat the same model as mine.

    [​IMG]
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  12. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    Alright so I didn't quite get to making the first cuts, but I'm now ready to set up the saw and get started. Hopefully Wednesday, tomorrow I probably won't have time.

    I spent my time tonight making a final drawing of the first two frames to make sure I was satisfied with the dimensions and how things fit together. I wound up making quite a lot of tweaks to the design to simplify the build and mechanicals.

    The yellow vertical you see sticking up is welded to the bottom most frame. This is what the sway actuator nut will be attached to. It will have braces to stiffen it up. The reason it sticks up so high is that same yellow post will be the actuator for the G-Seat back sway DOF.

    I almost certain I can shorten the length of the platform at least six inches due to the final sway actuator layout, so I'll be taking a look at that before I start cutting.

    This is just the platform for the elevator, and the sway table. There will be some superstructure added to the elevator platform (the lower frame here) at the points where the guide towers and actuators will be attached. Atop this will be a set of slides for surge with the cockpit floor on them directly so the total height/thickness of the floor will be 3.75 inches. The leg area will be sunken in, so it will be about 3 inches lower than that. Every inch I save in height is one more inch of my heave travel I can use without my Huey overhead panel hitting the ceiling!

    Trip Sway Table.gif
    Last edited: Jan 28, 2020
  13. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    Surge table drawn.

    Render of final sway/surge table design. Changed the upper frame to red to more easily see the separate parts. It's approximately 6 feet (183 cm) square at the outside edge. Bigger than I hoped but I wanted to leave plenty of legroom and make sure that all future cockpits would fit on it.

    surge and sway.gif
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  14. BrassEm

    BrassEm G-Seat + SFX100 Builder Gold Contributor

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    Through trial and error I have found that the operation of the centre section of the seat flaps is extremely important. Flaps to the center give wrong cues, i.e. in +g heave, the center pressure falls away on the body where the pressure should increase. The split flap works but is not ideal, possibly having a separate motor for the centre section would be the way to go but I haven't made any progress on that yet. Very impressed with your design progress.

    Also for your info the DCS carrier motion is problematic. :(
    No word on when it is to be fixed...
  15. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    Thanks for the info!

    So, what happens from carrier motion? This is a shame, I'm really really looking forward to flying the F-14 in carrier ops. =(

    Maybe we can fix it on the LUA end?
  16. BrassEm

    BrassEm G-Seat + SFX100 Builder Gold Contributor

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    Same... I say problematic. The shot and trap motion is fantastic as expected, but the motion on deck is either on or off depending on whether the aircraft is rolling in ths slightest or not. As in no motion at all.

    https://forums.eagle.ru/showthread.php?t=261323

    Cannot modify data if it is 0.0. I am informed that they did this to stop the aircraft sliding off deck. (Apologies for diverting the subject of your great work!)
  17. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    No worries about the off-topic content, do that to myself all the time anyway!

    So they've got telemetry turned off if the aircraft is stationary on the carrier, right? Hmm.. interesting.

    I'll go continue this conversation at that link, thanks!
  18. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    BrassEm, What is the 2nd image you posted there? The statement you made about boat pitch and roll being noisy makes me think that this graph is the Carrier motion.

    If so, we may be able to toggle over to that telemetry via LUA when the aircraft telemetry cuts out. This is FAR from ideal but would be better than a complete loss of motion. Assuming you move slowly on the deck I'd think that really the only thing significant that would be missing is cues for using the brakes. I imagine shakers will be offline as well but still, much better than nothing, no?
  19. BrassEm

    BrassEm G-Seat + SFX100 Builder Gold Contributor

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    Trip, I've replied on the other forum thread - new-output-possibilities-for-dcs. Looking forward to seeing more of your design and build!
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  20. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    Just cut up all the rectangle tube, then decided that I think it was a mistake to let it get so much bigger and heavier. I think I'm going to go back to the original plan and eliminate the surge and sway table. There was a good chance it wasn't going to work all that well anyway and I was worried about the added strain on the linear guide bearings from the surge and sway accelerations.

    So back to just heave, and the "advanced G-seat". Hopefully I didn't waste too much material with the cuts I made today but even if I did and have to buy a bit more tube it will cost much less than going through with the design shown above.