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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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    TL;DR here is my advice for folks I link here:
    Read on to learn more about why these are my recommendations. =)

    Note: This image is/was my first motion sim build, this thread is about replacing it with something much better for flight!

    iron eagle.jpg

    Shortly after I completed my first motion simulator build I learned about G-seats and immediately knew it was something I wanted to add to my setup. In order to build my 6DOF motion sim I looked around online until I found a particular set of components a couple other people had used and reported great success. This is the sim I found online and borrowed the parts list from:
    6dof.png

    I bought all the same critical parts so I could be confident the sim would work. All of the dimensions and aesthetics were my own designs, but the selection of motors, gearboxes, and electronics were tried and true. The first image in this post is my simulator after completion, the second image is the design I mostly copied:


    The same method didn't work out for me with the G-seat. I wasn't able to find a nice neat list of motors, gearboxes, and electronics guaranteed to work, and I wasn't able to find straightforward instructions that seemed simple enough I could follow to program the electronics to work with SimTools. Many of the G-seat builds on the forums had builders expressing regret in their choice of motors, and many others just didn't specify what they used. I saw quite a bit of information on what not to use, but no solid suggestion as to what I should use. As a result several years later I still haven't started working on it.

    On the other hand there is tons of information on the mechanical design of the G-seat itself readily available here. What I found to be the most educational was the thread "SeatTime's Sims" which depicted and explained many of the clever innovations he has made over the past few years. These designs vary drastically from the standard commercially available consumer level G-seats.

    It turns out there are two ways of going about generating cues with a G-seat. The common method is to have moving parts on the seat apply pressure to the driver or pilot, simulating the pressures against his body that would result from G-forces pushing him around in the seat in a real vehicle. The problem with this is that it actually moves the person in the opposite direction that they would if experiencing real G-force.

    For example:

    Let us say we have a driver sitting in a high performance car. The light turns green and he takes off with maximum acceleration. That driver will be pressed back into the cushions of his seat, the seat applying pressure to his back as it resists being compressed by his weight.

    Now consider simulating that situation with the traditional G-seat method. The cue for this would be that the seat moves the back cushion forward against the back of the driver to simulate the pressure he would have felt in a real car. Instead of the driver being pushed back by G-force, he is pushed forward by the seat. Instead of the steering wheel and pedals getting farther away from him they got closer, and instead of his eye point moving back and down, it moved up and forward. This constitutes a false cue and is something we would very much like to avoid for a more correct and realistic experience.

    The other school of thought is to move the driver in the correct direction while still applying the pressures for cues. This requires some very creative design work, which SeatTime has been doing over the past couple years.

    I intend to borrow a lot of inspiration from SeatTime, in particular his concept of three panel seat bottom heave and three panel seat back surge. The idea is that, for example, in a forward acceleration situation as described above; the center panel of the backrest moves rearward, allowing the drivers body to hopefully move back "into" the seat like he should. In doing this to correct the direction of movement we have created a problem. Now we don't have that increased pressure against the driver's back to cue the G-forces. To resolve this we design a system where the center panel moves back, but the two side panels simultaneously move forward and/or inward. This applies pressure to the sides of the driver's back to give the impression that he is being pressed back against the cushion without having the undesirable side effect of moving him forward. Genius!

    I also hope to add some innovations of my own or from other sources so I've looked at actual military flight simulator technology. I figure a whole lot of spending on R & D go into military applications so they should be using some pretty well engineered systems.

    The most interesting thing I found was the True Q DMS "Dynamic Motion Seat" system by ACME https://www.acme-worldwide.com/trueq-dynamic-motion-seat-g-suit-systems/

    They have numerous graphics and videos depicting the operation of their seats which are of particular interest to me because these seats are designed specifically for aviation. Even better for me they have models specifically for helicopter simulation which is my highest priority (followed by Aerobatics, Navy jet fighters, warbirds, and finally racing sims). These ACME G-seats have at least one novel design characteristic I've not seen anywhere else. The seat bottom cushion tilts left and right. Take a look at the video here.



    These seats also share some features with SeatTime's most recent experiments. The seat bottom and seat top being independent and able to operate either in the same or in opposite directions depending on the cue required. In particular, having the bottom move up while the back moves down and vise versa seems very useful.

    They've even got a specific model for the Huey, which is the helicopter for which I'm building a full cockpit! The one they built this seat for is a fully modernized Huey that is a HUGE performance upgrade from the Vietnam era DCS and XP11 versions of the UH-1 I fly, but the seat design is still very similar with the exception of the headrest that was added.

    ACME_UH-1Y_012_arrows (1).jpg

    I've spent hours looking at their videos trying to see how they are using the various axes to create each cue, but have had limited success. I have learned that while some of their cues adhere to the the concept of not moving the pilot in the opposite direction he should, others violate it. My current plan is to hybridize this general design concept with SeatTime's three-panel heave and surge mechanism concepts hopefully along with some of my own innovations.

    Finally, one other thing I am very, very interested in is applying the crushing pressures of high-G maneuvers to the pilot in modern combat jets. I want carrier launches and retrievals to leave me sore afterward! I want to have to ease up on my high-G turn not because my VR display is going dim, but because it hurts! The ACME system uses a g-suit with air pressure cells to push against the pilot which seems exciting, and the G-suits themselves seem to be available for somewhat reasonable prices on Ebay. Check out the video, it sure looks like this human test dummy is hurting a bit!



    The issue with this though is that the logistics of an air system may be more trouble than it is worth. Noise especially is a concern. That brings me back to one of SeatTime's experiments. He used a "G-Vest" with bowden wires applying mechanical pressure to the body in a manner similar to the air operated G-suit but a quiet and simple mechanism. I believe I only need to apply this pressure for forward accelerations, always pulling the pilot into the seat, back and down. I may also experiment with lateral forces but I expect that will be better handled by back-panel sway.

    This project will likely progress very slowly, but this gives me a place to discuss ideas and ask questions. One unfortunate thing about an advanced G-seat like this is it requires at least six axes! That gets expensive quick. =(

    After weeks of iterating on design drawings, researching, and discussing things I have arrived at the following semi-finalized design and am working on the drawing now:

    G-seat:

    Seat back nearly identical to SeatTime's current design. Heave, sway, and surge with basically the paddle arrangement he used that avoids moving the pilot in the wrong direction.

    Seat bottom with paddles like SeatTime's for heave. It will also have surge. The Sway/Roll on the bottom cushion is going to be ACME style, where the bottom tilts left and right on the roll axis. I haven't seen anyone in this community try that method yet and I see several possible advantages.

    Heave Elevator:

    2 Kilowatt Heave Elevator with at least 1000 mm (39 inches) heave travel with washout for an epic sense of flight!

    Surge/Sway table with 200 mm on each axis for G-onset cues. This will be sharing motors with the G-seat so I will not be able to use washout. <- Scrapped due to much higher than expected increases in space required, material cost, and weight added to the elevator platform.

    Features:

    G-seat
    • G-Seat back cushion Surge
    • G-Seat back cushion Sway
    • G-Seat back cushion Heave
    • G-Seat bottom cushion Heave
    • G-Seat bottom cushion Surge
    • G-Seat bottom cushion Roll
    G-Loading (Body)
    • G-Loading Chest Surge
    • G-Loading Chest Heave
    • G-Loading Thighs Heave
    • G-Loading Head Sway
    • G-Loading Head Surge
    Active Harness
    • Shoulder tensioner
    • Lap tensioner
    Motion Sim
    • Heave Tower 1000+ mm Heave
    Motor assignments

    Motor 1: Surge.
    • seat back surge (with parasitic paddles)
    • seat bottom surge
    • G-vest surge
    • head loading surge
    • Harness tensioner
    Motor 2: Sway.
    • Seat back sway
    • G-vest sway
    • Head loading sway
    Motor 3: G-Heave
    • seat bottom heave (with parastic paddles)
    • seat back heave
    • G-vest heave
    • Thigh loading heave
    • Harness tensioner
    Motor 4
    • Seat bottom roll (tilt)

    Motor 5-6
    • Heave elevator straight up and down 1000 mm or a little more powered by two linear actuators and running on four 16mm linear bearing guide rails.
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    Last edited: Feb 15, 2020
  2. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    On the topic of the G-suit implementation:

    I put in some time and managed to find some numbers. Apparently the typical max pressure for a G-suit is 10 PSI.

    It seems to me like you don't need all that bulky and noisy equipment for this application.

    You should be able to just have a sealed system with an air cylinder and piston ram, or an air bladder that you can mechanically compress. This would be connected directly to the G-suit hose with no valves or anything. I'd use an electric motor to power either.

    With an air ram you wouldn't even need to worry about slow bleed-off if the system is at atmospheric pressure when the piston is retracted. That being the case it seems like it wouldn't be out of the realm of possibility to make one basically from scrap. It would have to be pretty big, ~ ten times the volume of the G-suit bladders fully inflated I think.

    Last edited: Nov 19, 2019
  3. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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  4. MarkusB

    MarkusB Well-Known Member Gold Contributor

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    Hi Trip,

    thanks for sharing your thoughts. Yet another thread to follow. :)

    I have started to re-build my rig from scratch, and this time I am also focusing on the g-seat approach. One of my inspirations (apart from the ones you already mentioned above) is Bergison's Integrated G-Seat. In some way it is similar to the professional ACME seats, but much simpler. In fact, this seat is driven by only three motors, which are probably aligned in a 3DOF manner. All g-seat paddles are kind of secondary devices that are moved by the three motors.
    Have also a look at his introduction video. I found it quite interesting.
    I plan to use 6 motors instead for having more independent movements, but I am still in the planning phase.

    And about your thoughts about the "squeezable" air reservoir: Did you have a look at the Pneumatic G-Seat FAQ?

    Best regards,
    Markus
  5. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    Thanks Noorbeast. My air ram idea would generate vacuum when retracted about equal to the pressure when compressed if I'm not mistaken, so that option might be very good if I can figure out what to make it out of that won't cost a fortune.
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  6. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    So I rather derailed my own topic with the talk of the G-Suit ideas. Trying to accomplish that without a pneumatic system is definitely more practical so I'll be trying that first and hoping to never have to go to those lengths. I think it's a good idea though!

    Anyway back on topic, what I do currently need to focus on is how to get my g-seat built somewhat economically. Buying six or more motors and the equipment to run them all is more than I want to add to the credit card balance!

    So, I've been trying to casually brainstorm whether or not I could get really good results with just three motors, or maybe four. Hopefully tomorrow night I'll really sit down to think through the various cues I want to produce and see how detrimental to those reducing the number of independent movements would be. I'll definitely post any progress I make on that front.
  7. MarkusB

    MarkusB Well-Known Member Gold Contributor

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    Hi Trip,

    your added the question above into @SeatTime 's thread, but I prefer to answer to your thread because it actually is related to your own thoughts.

    I implemented such an up/down-movable seat back in my previous rig:
    Movable_Seat_Back_01.png Movable_Seat_Back_02.png

    See also the initial post of my build thread for some more details.

    I still like this idea, but the effect was rather weak and hardly noticeable. I will re-implement it in my new rig, but this time I plan to combine a 'down' movement of the seat back with an 'up' movement of the seat base and vice versa.

    I will try to do this without separate motors for the seat back, just by connecting the seat back via a bowden cable to the moving seat base. In this way the seat back shall remain on a globally(!) fixed position and just move relative to the seat base.
  8. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    Thanks for the reply Markus. Sounds like you and I have very similar plans.

    I'm going to try a very similar approach. For heave my bottom cushion will operate the same as SeatTime's design, but simultaneously the seat back will move the opposite way to hopefully add a bit of additional pressure or lift while helping prevent the pilot from moving the wrong direction spatially.

    I would definitely prefer this be separate motor with independent axis control, but for cost saving I think (initially at least) the bottom cushion heave and seat back heave will be driven by the same motor via bowden cables.

    For surge I'm also thinking about tilting the whole seat forward or back a little to help keep the pilot moving the correct direction but I'm not sure if I will try that yet.

    I also I don't know yet if I'm going to try the bottom cushion tilt I showed above, have to think on that a bit more yet.
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  9. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    After giving it some more thought and some very high tech experiments (like sitting in a kitchen chair with books under both left legs) I'm thinking that the main place that I think needs improvement from other designs is in negative heave. That weightless feeling, or hanging upside down from the harness in continuous inverted flight.

    The biggest thing bothering me is how to reduce the pressure on my bottom. Ideally the solution would be to lift me up off it, as I described is my hope with the rear cushion heave movement.

    So how to maximize this? First is to maximize the seat back's ability to support some of my weight and lift me a bit. A high traction surface and/or a G-vest attached to it are my best ideas there.

    I' can also lower the bottom cushion away from me a bit, but only if I am otherwise supporting my weight enough for my eye point not to move down as a result. Maybe a thick bottom cushion that doesn't get lowered can still support some of my weight but get "softer" when I lower the support structure beneath. That sounds like another little step in the right direction. I think that's probably the way to do it, combine a bunch of subtle effects and let them add up to something big.
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  10. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    Ok I've got another idea!

    Buy a super squishy seat cushion, probably a Gel type. This is underneath the (mesh probably) surface I'm sitting on. It get's raised up underneath so it takes my weight when I need that weightless feeling.

    The key to this working is the surface I'm sitting on the rest of the time has to have "slack" in it when the soft cushion raises up, and the material has to be pretty thin and pliable so it doesn't prevent the gel cushion from feeling nice and squishy.

    Think it might be viable?

    Alternate possibility, have two semi rigid panels over the top of it to do exactly what I said I need to avoid above, that can be "retracted" to the sides when the negative-G cue is required. Engineering that in a way that works in reverse will be an interesting, and potentially impossible problem though.
    Last edited: Nov 22, 2019
  11. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    I suspect anything but momentary mechanically simulated weightlessness is a tough one while upright, and may need Galvanic Vestibular Stimulation to actually fool the brain.
  12. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    Ok I've got another idea!

    Buy a super squishy seat cushion, probably a Gel type. This is underneath the (mesh probably) surface I'm sitting on. It get's raised up underneath so it takes my weight when I need that weightless feeling.

    The key to this working is the surface I'm sitting on the rest of the time has to have "slack" in it when the soft cushion raises up, and the material has to be pretty thin and pliable so it doesn't prevent the gel cu
    Tough indeed! I'm just hoping to make it a little bit better than what others have done. Try to distribute my weight across a larger surface area of my body so I feel the pressure of the seat "soften" as much as possible.

    Vestibular stimulation is something I'd love to play with. =) I suspect quite impractical though. I know Palmer Luckey was playing with it during the Oculus DK1 or DK2 days.
  13. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    The basics are really simple, a 9v battery and some wires: https://www.wired.com/2015/09/hacking-inner-ear-vrand-science/

    But we are still a long way from refined Vestibular stimulation and even further from that being useful across different people.
    • Informative Informative x 1
  14. GWiz

    GWiz Active Member

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    I think for a weightless feeling, you would need ideally more pressure on the belts over your shoulders and less under your derrière. Maybe a seat where the centre drops down leaving you sitting on the rim (Wide enough to be comfy) and belts that tighten at the same time? Perhaps the centre moving away would make the pressure on the seat feel greater though in which case the opposite way may work better like you suggest.

    It's a tricky problem to overcome, much more so than forces involved in racing sims. I look forward to seeing what madcap idea you come up with! Good luck. :thumbs
  15. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    You've got exactly the right idea!

    The solution SeatTime has come up with is what you described, except what you called "the opposite way". So getting pushed down into the seat by G-force = is putting the load/pressure on the outer edges, and "less" pressure on the bottom cushion for negative G's is the center raising you up away from the edge pressure.

    The belt pressure on the shoulders is definitely going to be in the mix. I fell in love with that concept the first time I heard about it several years ago. =)

    I am rather obsessed with coming up with my own addition to the system to really help sell the negative G's though. Another thing I learned from my experiments is that my tailbone is more sensitive to pressure than most of my bottom, so minimizing pressure there will help.

    I think the most practical ideas I've had are:

    An air or water filled cushion, part of which is not being sat upon and acts as the reservoir. To activate it you squeeze that extra part with an actuator to pressurize the part the pilot is sitting on and lift him up on a cushion of air or water.

    or

    A three panel bottom like SeatTime's except the center panel is a super soft and squishy gel cushion.
  16. Pierre Lalancette

    Pierre Lalancette Sir Lalancelot Gold Contributor

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    Hello Trip.
    I've always liked your simulator, or I should say, dislike, as it's so much better looking than mine.

    First question:
    Do you fly it with Star Citizen? If yes, I'll start to look out how it's done. If not, why the logo?

    About vestibular stimulation, I've read somewhere that people were using white noise to remove motion sickness. Maybe something to try?

    An idea I just got while reading your thread that I will throw like this without any preliminary, would be to use a simple vest with Velcro that would attach you to your seat at the back. You could then play with the heave of the seat, push on the shoulder. Maybe this could work.

    Bergison's Integrated G-Seat looks great. Definitively some good ideas to be taken from it.

    Looking forward on your next iteration.

    Edit.
    No second question.
  17. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    Thank you Pierre!

    I do not use it with Star Citizen. I asked Chris Roberts (who at the time was holding a photo of my sim in his hand) in person to verify that the stretch goal about "sim chairs" was indeed referring to official motion simulator support and he said it was. So, I hope that someday I will be able to play Star Citizen with motion and VR. I currently don't play Star Citizen at all while I wait for development to progress for years on end...... When I built the sim Star Citizen was meant to be my primary use for it, but I didn't know at the time that it was going to be many years before that would be possible.

    My interest in vestibular stimulation isn't about motion sickness, but simply about making attitude changes even more convincing. I'm half tempted to tinker with it, but the cue I'm most interested in is heave and from what I read vestibular experiments with vertical acceleration produced only subtle results. For roll it looks very promising though!

    Your idea is a good one, I can say this with certainty because it's already in the plan! After much internet shopping I decided this is something I'll have to make from scratch. One key point I had in mind is that if the "vest" goes over the shoulders it will be applying pressure there in the wrong direction, opposite the harness tension. Since this is the case the "vest" will really be more like a velcro corset. Maybe it will improve my figure!

    After exchanging emails with Bergison I am once again hopeful that I might be able to use only a G-seat with integrated pitch and roll like his and eliminate the true motion platform completely to eliminate the need for motion compensation and the sim taking up a very large space in my tiny house. I'm not terribly hopeful that I'll be able to get satisfying heave cues, but I'm going to try it before I buy any more parts for the 6DOF 2.0. Bergison says that he flies the huge level D motion sims all the time and that with his G-Seat setup he is 100% satisfied with the feeling of flying and would have no desire whatsoever to add real motion even if it took no money or effort. I'm still a bit skeptical, but I intend to find out for myself.

    Since I already bought the six servos for my new motion sim build I'm going to use those (for now at least) to power the G-seat. I think it will be the most ridiculously over-powered G-seat ever! 1kW per motor! I think it will have five motors so 5KW total. LOL, such overkill, much wow.
  18. GWiz

    GWiz Active Member

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    LOL, for extra fidelity, you could add an ejector seat with that amount of power at your disposal! :grin
  19. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    Is telemetry available for ejection? I'd love to have a big heave kick for that just for the fun of it!

    Ok I think I've more or less finalized the plan.

    I'm going to build the G-seat with just three of the motors, and with the other three I'm building the heave elevator for the entire sim. It should have 24-36 inches of heave travel (600-900 mm).

    The G-seat will by a hybrid design based on Bergison's, SeatTimes, and the Acme military models.

    From Bergison I take the concept of having the entire G-seat tilt in the pitch and roll axes in addition to the pressure paddles.

    From SeatTime I take the seat back sway concept and the three-panel design of the G-seat paddles that go down/back in the center while the sides apply pressure the opposite way. Also most of the linkage concepts for powering these things and the Bowden wires idea.

    From Acme I'm taking the seat back heave and my favorite element which is the tilting bottom cushion.

    Designing a mechanism that would allow me to have the bottom cushion independently tilt and also still have the three panel heave design, be compact, and not interfere with one another was my biggest challenge so far.

    Here's the basic design motion study, it works great!

    G-seat bottom mechanism.gif

    @MarkusB Somehow I missed your first post in this thread Markus, and didn't see it until now. I must have not refreshed the page until I made my next post. If I had seen it I would have found Bergison's G-seat sooner and maybe saved a bit of time! I wound up finding it on my own I think, though I'm not 100% sure now. Anyway, I agree with you that it's a great setup and it definitely inspired me to make some changes. I had thought about tilting the seat in pitch and yaw axes like that myself a few weeks ago and then decided it was probably not going to work really well. After I checked out his setup I went back to that idea and it's one of the things I'm excited about with this build.

    I'm still cramming to figure out as much of the parts list as possible so I can buy the stuff during these holiday sales! I'll be placing a big Aliexpress order in the next couple days for my ballscrews, linear slides, and such.
    • Like Like x 2
    Last edited: Nov 29, 2019
  20. Trip Rodriguez

    Trip Rodriguez VR Pilot

    Joined:
    May 8, 2016
    Messages:
    675
    Location:
    Lake Ariel, Pennsylvania
    Balance:
    3,920Coins
    Ratings:
    +330 / 6 / -0
    My Motion Simulator:
    6DOF
    Tonight I ordered the following to get Black Friday discounts:

    Three ballscrews 300mm for the G-seat with end supports and nuts
    Three ballscrews 1165mm for the elevator "" room for vertical expansion!
    Four SBR16 guide rails 300mm for bottom cushion heave assembly
    Four SBR16 guide rails 1500mm for the elevator
    Four 400mm aluminum extrusions for the G-seat actuators

    I sat at the computer for nine hours price shopping each component to get the best possible price.

    I'm going to have to give some thought to the construction of the elevator platform. The elevator actuator towers will be a 2"x2" welded steel frame for absolute rigidity but I don't want the platform to be super heavy.