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Unread 28-03-2006, 09:15
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Re: pneumatics or hydraulics ?

Hydraulics are the better choice if you want more precise motion control as you won't have to deal with the high compressibility that gases have. The downside to hydraulics is that you will have to run a pump for every movement as you can't store energy in compression of the fluid as you can with pneumatics.

Both systems can put out the force that you need. You can get the partial stroke movement using pneumatics with the correct valve, but you still don't have precise control of position or velocity.

My vote goes to hydraulics. Just try to find a relatively quiet pump.
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Unread 28-03-2006, 16:25
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Re: pneumatics or hydraulics ?

Thank you for your help.A lot more help than I expected.This chamber
I want to build will also hold the computer and lcd monitors(2).The chair
won't have to be so strong as to lift a person ,just side to side and
front and back movement.Also would work as flight simulation.

Thanks Rex
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Unread 28-03-2006, 16:30
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Re: pneumatics or hydraulics ?

Heres an interesting prefab motion chair I came across. Maybe it can give you some ideas? Link below...


http://shop.rightthing.nl/index.php?...products_id=17
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Unread 28-03-2006, 16:42
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Re: pneumatics or hydraulics ?

Im not sure I understand why people are saying pneumatics are rough, and hydraulics would be smoother?

Pneumatics use air, which will compress. Pneumatic cylinders act like adjustable air shocks, or air springs.

Hydraulics use oil, which is un-compressible. When you extend a hydraulic piston to a certain position it will be rock solid and will have zero give.

With hydraulic valves you can let small rates of fluid through - they are proportional valves, but you can also let large amounts of fluid at high pressure through, and send very violent jerks into the chair someone is sitting in.

Last edited by KenWittlief : 28-03-2006 at 19:36.
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Unread 28-03-2006, 19:28
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Re: pneumatics or hydraulics ?

I think that everyone means that it will be smoother(if u want it that way) with hydrolics, with air its very fast and harder to control accurately.

To me it think i would need to know more about the kind of motion you want, it you want it smooth and undeniable but still very flexible(in options) then go pneumatics,

if you want insta-action that is giving but sometimes "mushy" then go pneumatics the choice is ultimately up to you.
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Unread 28-03-2006, 21:56
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Re: pneumatics or hydraulics ?

Quote:
Originally Posted by KenWittlief
Im not sure I understand why people are saying pneumatics are rough, and hydraulics would be smoother?

Pneumatics use air, which will compress. Pneumatic cylinders act like adjustable air shocks, or air springs.

Hydraulics use oil, which is un-compressible. When you extend a hydraulic piston to a certain position it will be rock solid and will have zero give.

With hydraulic valves you can let small rates of fluid through - they are proportional valves, but you can also let large amounts of fluid at high pressure through, and send very violent jerks into the chair someone is sitting in.
I have seen that before on hydraulic hoists in big OLD auto-shops. Our school use to have an auto-shop before it became the robotics shop, and this had 2 gigantic hydraulic hoists. I remember lifting it without a load on and it would lag and jerk around, but with a load it still did it, just not as much. I think the jerking is due to a lack of oil lubricant. Now I am not sure, but I do agree now, that pneumatics are smoother. I forgot about that hydraulic experience. I know at times pneumatics time to time might have a minor lag, but that is only at low pressures (from my experience). I think mainly because people touch the shaft and leave it out extended and it collects dust.
Thanks for the reminder, I just still say hydraulics because you can regulate the stroke . I am not sure if it is the same on pneumatics, because I have never seen a device that can do that.
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Unread 29-03-2006, 13:18
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Re: pneumatics or hydraulics ?

I have a post puller or frame machine and it uses pneumatics and
hydraulics. the pump is connected to my compressor witch pumps the
fluid into the ram,slow but real strong.

If this chair is to react to video game software ,it needs to be quick
and smooth.Maybe even use an electric motor ,that would pull and
push the chair from side to side,or just push with an opposable spring
of some kind.Braking would be quicker motion forward and a slower
motion coming back to normal position and the reverse of that for
acceleration.Also the chair would have to lean and accelerate at
the same time.Any Ideas I can get get would greatly appreciated.
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