Volume of tank + tube

[blindguyinanorg]

we have our 2 tanks and about 3/4 of the tube on the 120psi side. i was wondering if anyone else who did the same thing knows aproxamatly how much the volume is or if it will easiy power the 1.5bore 8" piston in and out twice.

[ngreen]

I would think so...But at what pressure? Does it need to keep a certain pressure and force like it is for lifting? I thought the tanks were like 16 cu. in. I not sure if that is together or by themselves. And 3/4 of the 20 feet of tubing??!!

[Kevin Sevcik]

By my calculations, you can get just one cycle in and out at 60psi. The next one will be at greatly reduced pressure.
The Clippard tanks are 16 cu in each. That piston should take at most 14.1 cu in for an extend, and slightly less for a retract. thus, after one cycle, the air in the volume tanks will be at 60 psi, thanks to one of those nitfy gas laws whose name I can't remember. P1*V1=P2*V2. And I'm ignoring the volume of the tubes, as it is relatively negligible at this scale.

If you want to get all those shifts out of the 2 tanks, turn your regulator down to 40-45 psi. That should get you exactly that many shifts out of your piston.

[Joe Ross]

Originally Posted by Kevin Sevcik

P1*V1=P2*V2. And I'm ignoring the volume of the tubes, as it is relatively negligible at this scale.

The equation is right, but you forgot the accumulators are at 120psi. I'm also not sure about your volume calculations. I thought the accumulators are 2" bore x 6" long, which gives 18.8 in^3. I could be wrong, but the answer won't be terribly different if they are 16 in^3

You use 14.1 in^3 (at 60 PSI) when you actuate the cylinder. The accumulators hold 37.6 in^3 (at 120 PSI). Since you are only using the air at 60 PSI, you effectively have 75.2 in^3 of air, and when you get down to 37.6 in^3, you will only have 60 PSI. Thus, you have 37.6 in^3 of air to work and can actuate the cylinder twice. If you can regulate the cylinder to 50 PSI, you could get 3 shots.

[ngreen]

It is 16 cu in for each tank..I read that in the manual kit of parts. As for acuation. The easiest answer is not to rely on equations and just test it.

[Kevin Sevcik]

Yes, I was going by what was said in the manual as well. And the 16 figure is on Clippard's website as well, so I can only assume it's closer to being correct. So I went with the 16 figure and didn't bother with a calculator. I just estimated it out. Yes, figuring that 32in^3 at 120 PSI is effectively 64in^3 at 60 PSI minus the 32 that must be left in the tanks. so 1 cycle of extend retract. or 2 shots by your counting method. I whipped out a calculator later and 45psi seemed about right for 4 shots.

[Mr. Van]

Why not simply try it?

BTW, if you mean 3/4 of the tubing in the kit is on the 120 PSI side of your regulator, then you are clearly using the tubing as a storage device, and this is not allowed.

The rules state that only the tanks may be used as storage devices, and one of the Q & A answers stated that excess tubing was not allowed for compressed air storage.

Yes, we would like larger tanks as well...

-Mr. Van
Coach, 599

[blindguyinanorg]

oh no why would they make that rule. last year we were aloud to do it.


sometimes i get the feeling that the guys at FIRST like to just make up rules.
i.e. the sound rule

[ngreen]

You can just leave lots of slack. If you have a cyclinder on an arm put an air tank up there and connect with loose tubing.