Placing a Tank after a solenoid valve

[apples000]

So our team's planning on using pneumatics to launch the ball, but as others have noted, there's not enough flow rate. So, what we do is lock down the cylinder, open the solenoid valve which fills a small tank, then unlock the cylinder. However, the team is convinced it's illegal, but I can't really find any rules saying you can't. Has anybody else done this before?

[Team 4057]

so long as you don't use multiple solenoids you look ok to me. the rule your team mates are talking about refers back to previous years that prohibits long runs of tubing to gain extra air storage.

[Wire Monkey]

It looks like R78 says you can't.

If pneumatic COMPONENTS are used, the following items are required as part of the pneumatic circuit and must be used in accordance with this section, as illustrated in Figure 4-15.

The drawing has the tank before the solenoid. IF the rule says it must be done EXACTLY like this picture then I don't think it is legal.

[Madison]

The following is a schematic of the pneumatic system we used in 2012 for our catapult. It was, of course, completely legal and did have storage tanks on the low-pressure side of the system.

http://www.chiefdelphi.com/forums/at...9&d=1330055105

We did use a valve between the storage tanks and the cylinder, so the implementation you're suggesting is a little bit different. I can't speak to the legality of impeding the motion of a cylinder mechanically, though there doesn't appear to be any rule prohibiting that at a quick glance.

[FrankJ]

Originally Posted by Wire Monkey

It looks like R78 says you can't.

If pneumatic COMPONENTS are used, the following items are required as part of the pneumatic circuit and must be used in accordance with this section, as illustrated in Figure 4-15.

The drawing has the tank before the solenoid. IF the rule says it must be done EXACTLY like this picture then I don't think it is legal.

So the picture does not show cylinders or solenoid valves?

Figure 4-17 shows a low pressure accumulator.

A little heavier, but unquestionably legal: Use a cylinder with a longer stroke than is required & don't retract it fully.

[BBray_T1296]

Lets take this by the rules:

R74: Pass, parts are legal
R75: Pass, tanks are rated for 125+PSI
R76: Pass, parts are unaltered
R77: Pass, parts are legal
R78: Pass, this rule lists the parts of a pneumatic circuit, but not in any specific order
R79: N/A not a compressor
R80: N/A not a compressor
R81: Pass, not operating above 120PSI
R82: Pass, beyond the primary regulator, and working at or below 60PSI
R83: Pass, though white-listed to be useable in 120PSI, not specifically required to be there
R84: N/A not a pressure gauge
R85: N/A always on-board
R86: Pass operating at 60PSI or less
R87: N/A not a relief valve
R88: N/A not a pressure switch
R89: N/A not a vent plug
R90: Pass, operating on a single solenoid
No blue boxes are applicable either.

So, since this passes all applicable rules related to pneumatic, I say it IS legal

[DonRotolo]

Consider alternative ways of 'assisting' your cylinder's extension with, say, latex tubing.

EDIT: If you place a storage tank after a solenoid valve, will THE one Pressure Vent Plug reliably vent all stored pneumatic pressure from the system when the release valve is opened? If not, R89 will be violated.

[MechEng83]

Originally Posted by DonRotolo

Consider alternative ways of 'assisting' your cylinder's extension with, say, latex tubing.

EDIT: If you place a storage tank after a solenoid valve, will THE one Pressure Vent Plug reliably vent all stored pneumatic pressure from the system when the release valve is opened? If not, R89 will be violated.

The pneumatic valves from FIRST Choice last year (and possibly this year, as I don't have access due to school STILL being closed... ) violate this rule. The valves have a neutral position, which means that unless the solenoid is active, the pressure from both sides is dead-headed. This is different behavior from the KoP valves from several years ago.

[KevinG]

Originally Posted by DonRotolo

Consider alternative ways of 'assisting' your cylinder's extension with, say, latex tubing.

EDIT: If you place a storage tank after a solenoid valve, will THE one Pressure Vent Plug reliably vent all stored pneumatic pressure from the system when the release valve is opened? If not, R89 will be violated.

Why would the amount of air located on one side of the solenoid valve matter? There's 60 psi of air contained within the tubing, and that has to vent just as reliably as air contained in accumulators.

[ToddF]

It's our opinion that as the rules are written, an accumulator downstream of the solenoid valve is legal. If a QA answer rules this out, it is legal to connect multiple cylinders to a single valve. Just pick one with the internal volume of the tank you want, and plug one of the ports. Viola, instant accumulator. Not as weight efficient as a tank, but performs the same function.

Or, as someone else mentioned, pick a cylinder with a large internal volume and only plan to use half (or less) of the stroke. (This is actually the most weight efficient solution of all.)

[Al Skierkiewicz]

R89
The pressure vent plug must be:
A. connected to the pneumatic circuit such that, when manually operated, it will vent to the atmosphere to relieve all stored pressure, and
B. placed on the ROBOT so that it is visible and easily accessible.
If the compressor is not used on the ROBOT, then an additional pressure vent plug must be connected to the
high-pressure portion of the pneumatic circuit off-board the ROBOT with the compressor (see R79).

Air pressure in a storage tank is "stored" in the rule above.

[FrankJ]

So using the accumulator as described is OK as long as the vent valve will release its pressure?

[Al Skierkiewicz]

I have to ask the OP to be sure...
OP, You are using a valve to charge a tank and operate a cylinder in the same circuit? Is that what I am reading?

Madison,
In looking at your drawing, I do not see how the stored pressure can be vented immediately by opening the manually operated valve. Should there be a failure in either of the regulators, opening the valve leaves high pressure air still in the tanks. While that may have passed inspection at your events in 2012, I do not think it was legal in 2012 or now.

Please ask the question of the Q&A.

[Madison]

Originally Posted by Al Skierkiewicz

I have to ask the OP to be sure...
OP, You are using a valve to charge a tank and operate a cylinder in the same circuit? Is that what I am reading?

Madison,
In looking at your drawing, I do not see how the stored pressure can be vented immediately by opening the manually operated valve. Should there be a failure in either of the regulators, opening the valve leaves high pressure air still in the tanks. While that may have passed inspection at your events in 2012, I do not think it was legal in 2012 or now.

Please ask the question of the Q&A.

Al -- Unfortunately, pneumatics isn't my area of expertise, so I can't provide a definitive answer for your concern. I do know, however, that we were able to vent all the pressure from the system with the single release valve. I'll ask the folks who were responsible for this to provide some clarification. It may be that the system was changed after this schematic was created.

-Madison

[gpetilli]

Originally Posted by Al Skierkiewicz

I have to ask the OP to be sure...
OP, You are using a valve to charge a tank and operate a cylinder in the same circuit? Is that what I am reading?

Madison,
In looking at your drawing, I do not see how the stored pressure can be vented immediately by opening the manually operated valve. Should there be a failure in either of the regulators, opening the valve leaves high pressure air still in the tanks. While that may have passed inspection at your events in 2012, I do not think it was legal in 2012 or now.

Please ask the question of the Q&A.

I too am not an expert, but I believe the standard FRC solenoids use a supply "pilot" which means that if the input air pressure goes away (think manual dump) then the solenoid opens allowing the output air to back through the output to the input. This works only if there are no check values in the system and does not depend on any electrical signals. We have had issues in the past that if the working pressure is too low, there is not enough energy to "engage the pilot" and the solenoid does not activate. If I am correct, then this would allow the low pressure storage tank to vent when the manual release is opened.