new festo valves

[kws4000]

I managed to download the document 2010FestoFIRSTvalve.pdf . In the electrical connection portion it says to attach one end of each cable to a 24vdc supply and the other to an 0VDC signal. Does it matter which cable goes where? Do both cables have to be doubled up to function as one? Do the cables have to be reversed to move as one? I understand they go to the pnuematic breakout. It also says the red cable is 24vdc and black is 0. Which one goes where?

Just for fat: Is the Red cable ALWAYS live, and black ALWAYS nuetral except when connecting intermediate devices?

Thanks

[dmlawrence]

To teams who have already used the 2009 Festo single solenoids in regionals this year:

Was the Pneuaire website (http://www.pneuaire.com/4waysova.html) accepted as valid documentation for the cv and orifice size?

Thanks,
Dave

[Dad1279]

Originally Posted by dmlawrence

To teams who have already used the 2009 Festo single solenoids in regionals this year:

Was the Pneuaire website (http://www.pneuaire.com/4waysova.html) accepted as valid documentation for the cv and orifice size?

Thanks,
Dave

Dave,
I brought that printed out along with this Q&A from first stating that the valve was legal: http://forums.usfirst.org/showthread.php?t=14677

While we were not asked for further documentation at the regionals we attended, better safe than sorry.

[Tristan Lall]

If I were inspecting your robot, I'd be inclined to reject the Pneuaire chart you linked.

The C_v of a valve depends on its internal geometry, measured at a given set of working fluid conditions. Relating the port diameter to C_v is not even remotely accurate—especially when it isn't clear whether those are actual diameters, or nominal NPT diameters. Also, despite a similar-looking valve being pictured (to the 2009-and-earlier Festo valves), there's no model number or manufacturer specified.

Now, with regard to C_v and that Festo valve, you can derive it from the flow rating in standard cubic feet per minute (SCFM), which is given on the specification sheet (as "cfm"). The conversion process is documented here (for example).

Since FIRST hasn't specified the pressure at which the 0.32 C_v rating applies, you might rightly wonder how to calculate the C_v properly. Manufacturers often provide C_v at the maximum operating pressure (usually around 120 lb/in², but varying considerably depending on the parts). By contrast, FIRST established this limit based on the flow of the 2010 KOP Festo valve at 60 lb/in²,* but never specified this in the rules.

My calculations for the 2009 KOP Festo valve (unofficially) yield C_v = 0.395 at 25°C and 60 lb/in², and C_v = 0.177 at the same temperature and 120 lb/in². To be absolutely sure, contact Festo using the phone number listed on the datasheet and get the maximum pressure rating, operating pressure rating and C_v (and the pressure and temperature at which that C_v is valid).

Of course, you can also run multiple valves in parallel, and increase the flow of the entire system.

*According to the explanation that was provided to robot inspectors by FIRST staff.

[Turbinator]

so both sets of wires off the 2010 festo valve go directly to the 24v bumper, but different terminals?

[gpetilli]

Originally Posted by Tristan Lall

Of course, you can also run multiple valves in parallel, and increase the flow of the entire system.

*According to the explanation that was provided to robot inspectors by FIRST staff.

I think there is a rule which requires every motion to be controlled by flow in exactly one valve - so two valves in parallel would not be legal. The multi-valve issue came up in a GDC response to a question from a team looking to use a three position cylinder.

Was this true in previous years?

[Mark McLeod]

This thread is from the 2010 season and does not reference current 2011 rules.

In previous year's there was no rule against feeding a cylinder from multiple valves.

In 2011 there is such a rule.