3 position cylinders

[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.

[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.

[Chris Fultz]

<R74> Each commanded motion of a pneumatic cylinder or rotary actuator must be accomplished via the flow of compressed air through only one approved pneumatic valve. Plumbing the outputs from multiple valves together into the same input on a pneumatic cylinder is prohibited.

I posted the question.

My interpretation is that the three position cylinders are legal, as long as you only have one solenoid connected to each input. The rule does not say one solenoid connected to each cylinder.

I will post the response from the GDC when I see it.