3 position cylinders

[Racer26]

Interesting note: Does <R74> as written outlaw the design 1075 used in 2004 and 2007 for stopping a pneumatic cylinder mid-stroke?

By passing the exhaust ports of a valve into the P port of another valve, with a looped hose connecting A and B, plugging EA. This seems like TWO valves controlling the flow through that ONE cylinder, though only ONE valve is DIRECTLY connected to the cylinder.

[bstrong1218]

Originally Posted by 1075guy

Interesting note: Does <R74> as written outlaw the design 1075 used in 2004 and 2007 for stopping a pneumatic cylinder mid-stroke?

By passing the exhaust ports of a valve into the P port of another valve, with a looped hose connecting A and B, plugging EA. This seems like TWO valves controlling the flow through that ONE cylinder, though only ONE valve is DIRECTLY connected to the cylinder.

No clue if it's just a negative externality of the pneumatics rules this year, but position control with multiple solenoids or even a single 3 position, normally closed solenoid seems to have been outlawed.

Check the official Q&A... our team asked about what you're describing as did a few others and the answers point to a violation of <R74>.

[craigcd]

3 port center port closed solenoid valves were illegal because they trapped pressure and would not allow the full pressure to be relieved. Why can't you add addition pressure relief surge valves to the line to the cylinder and accomplish the same thing? Might be a good question to ask the GDC..

[Racer26]

Originally Posted by craigcd

3 port center port closed solenoid valves were illegal because they trapped pressure and would not allow the full pressure to be relieved. Why can't you add addition pressure relief surge valves to the line to the cylinder and accomplish the same thing? Might be a good question to ask the GDC..

Which is odd, because a center-closed valve doesn't trap any usable pressure. If you closed off a center-stop solenoid (trapping the air in the cylinder to keep the cylinder locked in one position), removed the air pressure from the P port (ie. open the dump valve) and then simultaneously open both sides to atmosphere, nothing will happen, except that gravity might take over, and actuate the cylinder. I think this is another case of the GDC being closed minded and limiting innovation they've allowed in the past, citing a rule intended to provide safety, when their rule arguably makes things less safe.

Center closed solenoid valve would keep a pneumatically actuated arm locked wherever it is, even if robot power or pneumatic pressure is removed. Any other configuration of valves results in a robot appendage that can move when solenoid power is lost (breaker, or field disabled), or when air pressure is lost (dump valve opened). I'm certain many teams can attest to needing to teach their students to be aware of robot actions that can occur when the pneumatic system gains and loses power.

[wilsonmw04]

Originally Posted by 1075guy

Which is odd, because a center-closed valve doesn't trap any usable pressure. If you closed off a center-stop solenoid (trapping the air in the cylinder to keep the cylinder locked in one position), removed the air pressure from the P port (ie. open the dump valve) and then simultaneously open both sides to atmosphere, nothing will happen, except that gravity might take over, and actuate the cylinder. I think this is another case of the GDC being closed minded and limiting innovation they've allowed in the past, citing a rule intended to provide safety, when their rule arguably makes things less safe.

Center closed solenoid valve would keep a pneumatically actuated arm locked wherever it is, even if robot power or pneumatic pressure is removed. Any other configuration of valves results in a robot appendage that can move when solenoid power is lost (breaker, or field disabled), or when air pressure is lost (dump valve opened). I'm certain many teams can attest to needing to teach their students to be aware of robot actions that can occur when the pneumatic system gains and loses power.

This was my thought process as well. I have taken the approach that I need to expend my energy working on a solution rather than railing at the lack of sense the GDC is making. Rules are rules after all. My team would have been much better off if we had read the rules better at the beginning of the year. Oh, well...

[implosionprez]

Is it legal, per rule <R74>, to use Bimba's 3 position cylinder, shown in the link below, on the robot this year? http://www.bimba.com/pdf/catalogs/FL...ne.pdf#page=67
2011FRC2484

GDC:
As long as <R74> is followed and "each commanded motion of a pneumatic cylinder is accomplished via the flow of compressed air through only one approved pneumatic valve" and these cylinders meet the requirements of <R66>, the cylinders are allowed.

So... Does that mean it' legal to use them, or not? Would a three-position valve have to be used, instead of 3 open-or-closed solenoids, to make it legal? Is there such a thing as a three-position valve? The GDC isn't cryptic on this one at all, are they?

[wilsonmw04]

Originally Posted by implosionprez

So... Does that mean it' legal to use them, or not? Would a three-position valve have to be used, instead of 3 open-or-closed solenoids, to make it legal? Is there such a thing as a three-position valve? The GDC isn't cryptic on this one at all, are they?

center blocking/locking valves have been deemed illegal.

[implosionprez]

So what does everyone think? Are the 3 position pistons legal, using only solenoids of the type supplied in the KoP?

[wilsonmw04]

Originally Posted by implosionprez

So what does everyone think? Are the 3 position pistons legal, using only solenoids of the type supplied in the KoP?

we are making our own "three position pistons" and betting the farm that they are legal.

[implosionprez]

Yeah, that would probably be legal, since they are two totally seperate cylinders, and each one is controlled by a seperate solenoid.

[craigcd]

Originally Posted by wilsonmw04

This was my thought process as well. I have taken the approach that I need to expend my energy working on a solution rather than railing at the lack of sense the GDC is making. Rules are rules after all. My team would have been much better off if we had read the rules better at the beginning of the year. Oh, well...

Reading the rules at the beginning of the season would have still lead you to the original assumption that 3 port center port closed was legal. The ruling was made 01-31-2011, 02:05 PM http://forums.usfirst.org/showthread.php?t=16642 to make them illegal in the FIRST Forum Q & A. Team 2221 designed their robot after reading the original rules and had to add additional cylinders to meet the rule change.

[wilsonmw04]

Originally Posted by craigcd

Reading the rules at the beginning of the season would have still lead you to the original assumption that 3 port center port closed was legal. The ruling was made 01-31-2011, 02:05 PM http://forums.usfirst.org/showthread.php?t=16642 to make them illegal in the FIRST Forum Q & A. Team 2221 designed their robot after reading the original rules and had to add additional cylinders to meet the rule change.

Yeah, us too. We started off with two valves in series thinking that we were ok since only one valve's worth of air was going to the cylinder. Then, center locking was banned. At least the bimba cylinders have the same ends on them regardless of stroke length making finding the right combination easier.