Re: Pneumatics holding their position
 

If you use the double solenoid valve it will hold the cylinders position when power is turned off.

Re: Pneumatics holding their position
 

a double solonoid valve will hold its position.

A single solonoid will shift to its rest position -- so it either will hold its position if it starts in rest position or it will shift(and the cylinder its attached to will also shift) if you have it in activated position when the match ends.

Re: Pneumatics holding their position
 

*BE CAREFUL WHEN TIGTENING*
we had a bit of a snafu lat year with the port where the 125 psi presure release valve was connected leaking last year, so my associate wipped out the 12" long wrench and tightened it, cracking the port on the compressor, and breaking the valve. that compressor is now irriparible...

Re: Pneumatics holding their position
 

The easiest way to have a pneumatic cylinder stay in position after your robot has it's power turned off, is to use the double selenoid valve. If you notice that you have a leak in your system, the easiest way i found to find a leak, is to take a cup of soapy water with a painting brush and go over all the connectors in the system. Turn the system on, if you see a bubble appear, you have a leak in that particular valve. Take the connection off, put some more teflon tape, tighten the connection enough, and re-check. We had this problem last year and this solution solved everything.

Re: Pneumatics holding their position
 

I guess a mechanical solution would be the chinese finger trap idea, that maybe after the cylender extends, it extends passed a spring loaded switch. like how classroom doors are locked, so you cant turn the knob on the outside, but the latch can retract when you close the door. that would be the faisafe, but if you were off, you might bend the cylender, or it might get stuck. I'd stick with the double solenoid and leak prevention though.

Re: Pneumatics holding their position
 

I keep reading about the 60 psi with a 2 inch bore, yada yada and people multiplying area by pressure to get force. I have yet to see someone account for the fact that in pressurizing the 2 inch bore cylinder, the overall pressure goes WAY down to less than 60 psi and i know my compressor can't recover that quickly. The tanks are small..... Am I doing something wrong, or does this make sense? That is, that you need to account for the overall pressure drop in figuring theoretical force exerted by piston. :confused:

Re: Pneumatics holding their position
 

Brian,

If you've set up your system correctly, your tanks will be pressurized to 120 psi, and the line is then regulated down to 60 psi. This allows your cylinder to fill with 60 psi air, and the line to very quickly (I'm tempted to say almost instantaneously) recover to 60 psi.

Re: Pneumatics holding their position
 

True, but continued operation will draw down your air supply. So you need to balance cylinder size with the storage capacity of the system. In general use the smallest cylinder possible to do the job. This will greatly reduce the amount of air you consume. The volume used by one of the largest cylinders is roughly equivalent to the volume in one of the storage tanks. Since we can store at twice the operating pressure that means your first shot will be at 60 psi. But if you vent and immediately cycle the cylinder again two or three times then you will see a drastic reduction in air pressure and thus force from the cylinder.

Just another of the limitations we have to live within...