motion cockpit

[michael]

I am in the process of designing a motion simpit, building it is the easy part (I'm a welder/fabricater by trade and do blacksmithwork as a hobby)
what I would like to have is opinions on driving the platform from orbiter I will either be using hydraulic or pneumatic both of which I have extensive experience with and you're input would be most appreciated as it will help decide which will be the most efficient
Thanks in advance

 

[Scrooge McDuck]

Hi Michael, welcome to the forum.
Building a hexapod would be nice, but overkill, I guess

I'm not sure about the hydraulic vs pneumatic question, possibly which ever can react the quickest, but you know this better than me.. Using the Orbiter SDK you can easily get the right values for pitch/roll/bank etc, to drive your platform controllers.

Anyhow, a simulator motion platform for Orbiter specifically, is a bit strange as you are most of the time in orbit instead of atmospheric flight. Of course it would still be nice for the atmospheric part of the flights.
Maybe adding one extra cylinder that enables the whole platform to tilt 90 degrees all the way up would be very nice, as you could simulate things like a space shuttle launch!

regards,
mcduck

 

[michael]

thanks for the reply
the debate that i am having with pneumatic vs. hydraulic is that with the hyd. system you have the pumps lines etc. all places for a leak which can be a terrible mess. however the air system requires a compresser and its plumbing The fabrication work that I do is on semi-trailers mostly heavy hauling rigs and I was toying with the idea of using airbags which can lift a lot of weight with low pressure, can be controlled with electric dump valves and because of the nature of what the components were designed for have a very controllable reaction time (very fast to very slow) but not being a programmer I wasn't sure how to actually get control for the valves out of orbitor
the airbags would also have the advantage of being low profile as opposed to hyd. cyl.
thanks again

 

[tomek]

There's no way to get such output directly out of orbiter. There is a way to get the vessel orientation and angular acceleration, but the software to translate that into control signals for your setup would have to be written from scratch (or nearly from scratch).

I also agree that such platforms are much better fit for ground race simulators than aerospaceflight simulator such as Orbiter. You can't simulate weightlessness with such a platform, and you can't even simulate any significant acceleration for any prolonged period of time. The way it will move will have very little to do with how actual aerospacecraft feels and handles.

 

[Scrooge McDuck]

You can't simulate weightlessness with such a platform, and you can't even simulate any significant acceleration for any prolonged period of time.

You could simulate a 1G acceleration in forward direction if you pitch the platform with the seats up to 90 degrees, but when this acceleration returns to 0, you'll have to rotate the platform back, and you can feel this rotation which would be unrealistic. So yes, it will be very hard to actually simulate anything outside of atmospheric flight.

Those airbags sound like a nice idea (I'll remember this for our own glider simulator), but I think the time it takes them to fill will probably be too long for quick turns in the plane?

Not being able to program an interface/conversion between raw Orbiter values and commands for the pump electronics is a big disadvantage indeed. Maybe you could check out if there are living any orbiter fans (developers) near you. There are even some (static) orbiter/shuttle cockpit builders here..

regards,
mcduck

 

[dougkeenan]

Vibrations during a launch would be cool.

 

[michael]

actually the airbags when outfitted with the correct dump valves and pilot valves will fill and exhaust completly in such a quick time that it has been used on thirteen foot spread-axle trailers you exhaust the front axle , as soon as it crosses the scales you fill it and exhaust the rear (way to cheat the scales unless you get caught) i have seen a loaded trailer do this axle load swap without dropping in hieghth at all but i was thinking of using something slightly more compact like the bags used for the cab (same mat and structure just more compact) as far as everything else you are absolutly right I am wanting it for aircraft as well

 

[tomek]

The airbags sound a bit risky to me (if you're talking about same airbags I'm thinking of). I'm sure they're designed to meet timing requirements, but are they designed to withstand arbitrary expansion/contraction for arbitrary periods of time under load?

On the other hand, due to lower profile, a ruptured airbag might be less of a problem than malfunctioning hydraulics...

Where do you live anyways?

 

[michael]

the airbags that i'm refering to are able to withstand pressures well above 200lbs. per square inch they bolt in a both the top and bottom on an common supension they have two 3/4 inch studs at top and anywhere from 1 to 4 half inch bolts in the bottom they support there load on approx. 120 lbs pressure (normal for most tractors) they are usually made by firestone (walls are basically the same mat as a bias ply tire) even when hyper-extended they withstand tremendous pressure in fact when a detachable gooseneck trailer of 100 ton capacity loaded goes over a set of rr tracks it clears by hyper extending the bags and still these bags will last for years they are really tuff I live in florida and have worked on anything from fl-spec dumps to 200 ton cap 4 axle 12 foot wide goosenecks meant for hauling the main body of a minning loader for about 25 years

 

[estar]

what you need to do is be able to "heave" in all 3 axises. The only thing you feel in space is the acceleration once you are at motion there is little sensation at all from within the spacecraft. (There is an exception if you are rotation really FAST).

The only useful full motion for traditional rockets is tilt and that is used during 90 degree launch. But that may be more elaborate than you want.

The heave is used for the initial jolt of acceleration and for substantial tilting (in one or all axis) when accelerating or decleratiing. By tilting you are using earth' gravity to force the user to one (or more) side giving them roughly the feeling of what continuous thrusting is like. Combined with a enclosed cockpit with a view only out the "window" it can create an effective illusion for normal operations.

 

[tomek]

Apparently I wasn't thinking about airbags you were referring to.

Well, I don't know then. I can imagine how to control a hexapod - math would be relatively straightforward actually, though I'm not sure if the real thing can be controlled as precisely as mathematical model. Airbags, on the other hand... I can't imagine an easy way to do 6 degrees of freedom with airbags. You can probably use them for tilting the platform a bit, but that's about it...

The reason I was asking where you live is that it would be nice for whoever would be writing software for this thing to have access to the actual thing, to see how the program performs live. I'm in California, so that's a bit far.

 

[michael]

first off I want to really thank everybody for their help
I was really only looking for motion ability for orbiter when in an atmosphere and for fs kind of a duel purpose cockpit but if need be I might need to abandon the idea of motion for orbiter, at least for now

 

[michael]

Hi Tomek
I have a prelimenary design for the mechanicals of the platform, these bags (if you use the correct ones there are probably close to if not more than a hundred different types)will have several inches of travel in each direction
I sometimes wonder which is more fun the sim or trying to build something new and trying to make it work
by the way i've never been to california but I know the equipment out that way is a lot different I just had to cut two trailers (57 ft, most here are 53ft) down from 14 feet tall to 13.6 feet tall ,bridges don't move:huh:

 

[Zatnikitelman]

I had thought of a gimbal ring design which would give me basically 360 degrees in any axis, but I don't have the money or space to build it so I have to shelve it for now. It'd work great as long as you avoided gimbal lock!

 

[Imagineer]

Michael,

Most professional-grade aircraft flight simulators use hydraulics with six to eight feet of travel. The use of hydraulics instead of pneumatics is the compressibility of air results in damping problems.

These simulators simulate moderate forward, backward and sideways accelerations with tilt. This mostly works because airliners tend to change acceleration slowly enough that the rotation goes unnoticed. Turbulence is simulated by rapidly moving the hydraulics a short distance. The bumps of landings are also simulated.

The performance of the delta glider would need a motion cap with exceedingly long travel and lots of power to simulate. Weightlessness is especially tricky You can get a few seconds using a KC-135A.