Team Update #11

[Al Skierkiewicz]

Please note the updated software links for Labview and Driver's station as well as the link to NI's known issues list.

Please also note the reference to the pressure relief valve. Teams have reported that the relief valve as shipped is not set to trip at 125 psi.

"<R77> The relief valve must be attached directly to the compressor. If the relief valve is already set to 125psi, teams are not allowed to adjust it. If the relief valve is not set to 125psi, teams are required to adjust to release air at 125psi. The valve may or may not have been calibrated prior to being supplied to teams."

If you are using pneumatics on your robot this year, be prepared to check the operation of this component.

[Arefin Bari]

Cool. I will just keep the whole chassis back. =)

[Jim E]

Hi Arefin,

How many snow days did BCS have this build season? I know it was cold, but...

Jim Ehle

[Arefin Bari]

Originally Posted by Jim E

Hi Arefin,

How many snow days did BCS have this build season? I know it was cold, but...

Jim Ehle

We had 4 weeks of snow... (well snowish for a floridian). =)

[rsisk]

What is the best way to test the pressure relief valve is calibrated correctly for 125psi?

[Daniel_LaFleur]

Originally Posted by rsisk

What is the best way to test the pressure relief valve is calibrated correctly for 125psi?

Hook up the pneumatic system with just the compressor hooked to the pressure relief valve, a dump valve (manual) and a pressure gage.

power the compressor from a battery (use a fused line for safety). Bring the pressure to ~130 PSI. The relief valve should release pressure when it hits ~125 PSI.

If it doesn't then adjust the valve to release and then retry (poppit valves are notorious for not being very stable nor re-seating very well).

[Peter Matteson]

Originally Posted by Daniel_LaFleur

Hook up the pneumatic system with just the compressor hooked to the pressure relief valve, a dump valve (manual) and a pressure gage.

power the compressor from a battery (use a fused line for safety). Bring the pressure to ~130 PSI. The relief valve should release pressure when it hits ~125 PSI.

If it doesn't then adjust the valve to release and then retry (poppit valves are notorious for not being very stable nor re-seating very well).

An FYI for everyone who tests this way. The reseating pressure of the valve is usually 10-20% below the release pressure. After you make your adjustments vent the sytem, then represurize for the next test to verify you actually are at the set point and not significantly below it.

Also hysterisis on the spring will mean your valve could pop +/- a few psi and still completely meet the manufacturers spec. I suggest looking at this value to see what it is so you don't chase your tail on the variation.

[Gary Dillard]

Here's how I plan to do it:

We'll pressurize the system to cutoff with the pressure switch (around 115-120 psi), then back off the jam nut and turn the valve until it relieves. We'll go back the other way a little (1/4 turn?), jumper across the pressure switch, and watch the gauge to see where it relieves. We'll iterate from there.

... We used this method and it worked OK. You could hear the valve venting and see the pressure slow down at ~125, it went up to ~135 or less and held there until we released the pressure switch jumper; then it vented back to ~125 and stayed there. With the hysteresis on the valve I think that's about the best you can expect.

[Gary Dillard]

Originally Posted by Al Skierkiewicz

If you are using pneumatics on your robot this year, be prepared to check the operation of this component.

We've got code to manually bypass the pressure switch, but do you think it is OK just to jump across the pressure switch (run a wire or a piece of metal between the terminals) for this test?

[Al Skierkiewicz]

Gary,
We are discussing a procedure for performing this function that should be available soon. A simple alligator clip should suffice.