6 DOF with 360 Roll and Pitch

Hi guys,

Well I have been working on this for a year now ever since the Oculus came out but the whole sim thing for about 5 years. I have built 190 degree projection screens with three projectos and blending software, had some seat time in a Jet and I fly normal aircraft as well. I have a small fabrication business in Australia and I know what I wanted to build from when I had first tried on the military VR head sets so here goes.

Now that I have the HTC Vive development kit I am ready to produce the simulator motion platform that I have been planning.

It is a Flight Gimbal with 360 in the pitch and roll ring with the 6 DOF table in the middle of it.

I have made a video to demonstrate (rendering of which is not that great sorry)

I can make a lot of thing and have some decent equipment but really the difficulty will be all in the software... bring on SimLab 2.0

will be watching this. good luck mate. will be awsome

noorbeast, Yes checked out all those guys. I will be using gas struts because the weight of the seat is relevant.

Weight
At current calculations for heaviest person at 100kgs with 6 motors with spur gear boxes as well as all control elements and PC....wait for it.... 160Kgs

That doesn't include the rings, so the outer rings are even heavier. So I have added some head real in weight bearing.

Outer ring Motors
As far as out rings, I am not sure. I was thinking 500W DC with a gear box but that may not be enough torque. If worst comes to worst it will be steppers with a leadshine driver and a 10:1 gear box. There will be massive torque in that set up but it will make the stepper whine and who wants that.
Speed
So I believe that the fastest an aircraft can rotate is in an aileron roll. Of which either the Sbach and the extra 300 is the most.
SBach roll rate is 450 degree per second = 75 rpm
Extra 300 roll rate is 400 degree per second = 67 rpm.
(I have heard that the FA-18 has a roll rate of 760 dps but I am calling bullshit on that)

So as you can see the fastest rolling aircraft in the world is not exactly quick compared to a motors ability to turn.

Safety
Now, do I want to roll that quick? Not unless I want to burst the blood vessels in my eyes, but the point is the motors can do it. I will probably be testing it and limiting it on comfort. You know, like full left stick and whoa...whoa... whoa.... Ok thats too fast... I think I am going to chuck.

To get a good roll from the ring wouldn't you have to have the center ring balanced out? In essence doubling the payload? Sorry if this seems like a silly question, just trying to get my head around it. Have you considered A/C motors with gearboxes for them?

Awesome project, I too look forward to your progress.

Not Double but yes adds more. That has been factored in to load calculation in the bearings. Not a stupid question just an obvious one to ask. Yes AC is better but ALOT more expensive and I have told myself to keep it affordable where I can.

very interesting design. @Historiker has a flight cockpit worth looking at.

in my opinion, 6DOF inside is unnecessarily costly, complicated and heavy... it's overkill
but great project! I hope you will achieve it

I disagree @RacingMat (but I am not going to be rude and give you a red X, lol); with a flight sim Heave and Sway (side slip) are a huge part of immersion. Those are the two most common feelings in normal flight (imo). The best way to get that would be the stewart platform in the center. The outer rings would give a visceral feel of pitch and roll (COMBAT!!!! ). I think this is an awesome setup and I am very envious.

This is a seriously ambitious project! I could ask a million questions about things like how are you going to make those carbon fiber rings, but hopefully you will post the progress as this comes together. If you can pull this off, it would be a definite hall-of-fame DIY project. Looking forward to it!

I'll be following this project. Good luck!

never give up on your ambitions

hi, @GusBiz,
an interesting project for sure.

I would like to ask a question.
This rig is going to be a dedicated flight sim? Or multipurpose?(eg driving).

If it is a dedicated flight sim, is it fighter jet oriented?

@Historiker sorry but I agree with you! Heave and Sway are welcome within the full roll and pitch

but this requires only a 2DOF inside
not a 6DOF!

But you still want yaw and serge, and to get those you will still need a stewart platform

See GusBiz? We really are interested in this build!

It is useable as a driving cockpit of course but the intent is to be able to use it as a jet fighter cock pit.

Like a ferarri that you drive to the supermarket to do the weekly groceries in. It can do the 747 x -plane airport to airport mission, but its capable of doing a cuban 8 if you want it to.

Yeah, when I told my wife I was going to do this she said..."oh you're not are you..".

Then again she is building a kit car with me (yes its in the garage right now) and she has been doing the grinding on the welds so she is no stranger to my manufacturing ambitions.

The carbon fibre is not that tricky it just requires coming back to the fundamentals of the materials, understanding the base properties of each element. Epoxy resin is not the same as epoxy glue for example. I will be using foam or honeycomb core and internal ribbing like an aircraft wing. The hard part is adding the ribbing and maybe the foam. Depends on how its done but again like anything, once you really do know the variables in strength and directional fibre alignment etc then its not that hard. Working out the loads on it is actually harder than the manufacturing.

A Note on carbon fibre.
WARNING: do not be impressed by carbon fibre.

It is just a reinforcement to normal polymer plastics. Fibre glass and carbon fibre is not that different. Its properties are pretty cool but working with it is no different to fibre glass. The main reason it costs more is because its not like using Chopped Strand Matt (CSM) which most people think is what all fibre glass is about CSM is your chipboard and good quality Fibre glass is like a good quality hardwood. CF is more like mahogany. It looks nice, its strong as hell but so is alot of hardwood.

With CSM you just Gel coat, lay down the mat, get your polyester into it and roll it down. Chipboard or MDF done!

With carbon fibre you have to get CF cloth and make sure the weave pattern flows, then you need peel ply, then you need breather material, then you need breather tubes or lines, then the vacuum bag material, then you need special double sided tape to seal it all up, then your vacuum pump, your catch pot, your line ties, then your expensive epoxy high flow resign that expires in 3 months so you can't do a project with some and keep it for later.

That is just for one side. If you have multiple layers in sandwiched honeycomb layers then you need to do that three times. This doesn't include the design which has to be done properly to exploit the CF properties which is why you're using it in the first place.... see, lots of time and materials. In the end, an effective, well done fibre glass application, with decent fibre glass cloth is pretty much the same.

When ever someone asks me, can I do it in carbon fibre its less about its properties and more about its appearance. Good quality fibre glass cloth will do pretty much the same thing as CF, properties wise, in most applications.

Have a guess why I am using CF.... because I want it to look cool! ( a little on lightness and challenging myself on design principals but I could be doing the same with Fibre Glass.)

Is anyone wants to really learn about composites, this link is a great place to get alot of information in the one place.

http://www.homebuiltairplanes.com/forums/composites/8888-read-first-composites-faq.html

So this question is one I asked myself and continue to ask myself because it is not a small investment to do this. financially, time wise and even mentally and effort wise. I don't want to look back and think why did I do this that way.

The story behind the build
(This is long, grab your popcorn and choc top)
Here is the answer. About 4 years ago after trying the military VR head sets I realised "hang on I could do this..." I was Palmer lucky, about the same time he was doing his work. I researched it and came up with the same conclusions that the optics don't work unless you correct for them in the software. I was in the software industry at the time and knew how much that would cost. about $1 mill. No joke. The military head sets cost AUD$85k and its mainly in the software costs not the glass and screens.

I had experimented with full immersion 2.2m high screens and knew what immersion was really about. It was about removing false positives when you test reality. Anything that didn't belong there. Let me say that again, ANYTHING that you could detect that does not match what you know as real.

Thats right people. When you are staring at your three screens, have you noticed that if you play it at night, with the lights out and you can't see anything other than the screen, it feels 10x more real.

Why? Because there is no additional information in your line of sight that indicates you are not in a car. That is what a VR head set does. Head tracking added to your ability to test that your actually there. Motion adds even more and at about 95% your brain fills in the rest and you have what they call presence. You feel like you are actually there.

The 6 DOF stewart platform in the middle has pitch and roll and doubles up on what the outer rings do. However, this allows you to do large amplitude vibrational effects without shaking the whole gimbal. It also offers you all the elements of motion, like the aircraft nose diving on the runway when you hit the brakes, the parachute launch to slow it down, the heavy vibration you get when you side slip. I could actually do without heave more than the movement "effects" that tell you "Hey this thing is really real".

When I fire the rockets on the left I get yaw, which happens at the same time as the sound of them firing, and I turn my neck and look right over my shoulder to look at them because that is where they should be if they were real. All of that TOGETHER, makes up the 95% needed for presence. Your brain does not fill in the rest unless you are at that level. That is where the magic happens. Its stead of just heave from turbulence, I am more looking forward to the Ba-Dumf, Ba-Dumf, Ba-Dumf, of the taxiway cement joins you get when taxiing because that is what you feel in a real jet! THAT is what makes you go, oh man this bitch is real.

There will be more on this later but figuring all this out is key.

This is why the greatest bit of work will be on the software and why I appreciate this forum as much as I do.

Building the stuff is the easy bit in my opinion.

If disagreeing is being “rude” @Historiker then why do we have the option? Is it to encourage rudeness to other members then? I don’t look at it that way myself.

I agree this is an ambitious project @GusBiz. I wish you the best with it. But may I ask why you feel you need the 360 pitch and roll rings for immersion? I haven’t had the experience of flying in jet fighter aircraft but I am under the impression that when you can’t see the horizon it can be hard to decipher what is up and what is down anyway. From my perspective, being upside down or facing towards the ground would be simulating the opposite of the actually forces that would be put on your body. I think it would still be a lot of fun though.

Btw, I think one of your biggest software (firmware) challenges will be driving a stewart platform inside of rings. If my logic is correct, when you are upside down for example, your PID settings will need to be the reverse of what they are when you are upright.