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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.
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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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