How do you make your compressorless system work, when all valves "bleed" air slowly?

[Joe Ross]

What rate do you lose air at? This year, we're losing 1-2 psi per minute when fully topped off. Is your rate similar?

[kmcclary]

Originally Posted by Joe Ross

What rate do you lose air at? This year, we're losing 1-2 psi per minute when fully topped off. Is your rate similar?

Maybe that or a bit higher with the SMC dual coil, significantly higher (up to twice that) with the single coil valves.

The grey Festo was definitely the worst case (Rexroth a close second), and the grey Festo WAS the one we wanted to use.

Things work great the second we pull of the compressor. But if the round start takes more than a few minutes from compressor disconnect, we're starting to get marginal on air. That delay happens often enough at regionals that it concerns me. That's why I'm seeking either non-leaking valves, or some kind of a "digital cork" stop-gap solution. I'm not comfortable with any "quick, let's start or we're toast" design.

(At least it's good to know that we're not the only ones that see this problem.)

- Keith McClary
Chief Engineer, Team 1502 "Technical Difficulties"

[imax48236]

The part number of the solenoid we used last year was made by Rexroth, with part # 5728400410

http://www.boschrexroth.com/pneumati...o= 5728400410

This was in last year's KOP, and is available for purchase this year. We have an extra if you want to trade/buy it.

Let me know if I can help any more.

[WeldedHarlequin]

I am on the same team as Imax, and I'm the pneumatics captain.
I encountered this problem with the new SMC dual coil solenoids this year, and if you want to go that route I discovered that the problem significantly lessens (if not dissappears) when you remove the small gasket (there are two, one more flat, one smaller and more rounded). Having only the flatter gasket seemed to help.

I remember last year trying to use the Festo valve and having a lot of problems. I really just don't like it. I ended up going with the Rexroth, and not having any port problems.

My situation may be different, but I was using the Rexroth after the SMC (In Series, to slowly adjust the throw of the actuator). Here's what I did (a little bassackwards):

I had the SMC valve as usual, but EA and EB were ported into P on the Rexroth, and the A from the Rexroth was plugged (Actually achieved by running a piece of tube out of it into a plugged piece of brass T). That's the best way I could manage to control the exhaust.

Hope it helps, but if you have any more questions, just ask.

[WeldedHarlequin]

Two years ago I also did a compressorless system with just one SMC valve, and honestly, it just came down to making sure there were absolutely no leaks, and I simply had to keep putting the valve back together to make sure all seals were tight. So it's possible. (I was using like a 1 1/2 inch throw, and got well into the 90 on two tanks).

[kmcclary]

Originally Posted by WeldedHarlequin

I am [our team's] pneumatics captain.
I encountered this problem with the new SMC dual coil solenoids this year, and if you want to go that route I discovered that the problem significantly lessens (if not dissappears) when you remove the small gasket (there are two, one more flat, one smaller and more rounded). Having only the flatter gasket seemed to help.
[...]
My situation may be different, but I was using the Rexroth after the SMC (In Series, to slowly adjust the throw of the actuator). Here's what I did (a little bassackwards): [used the Rexroth to plug the SMC's exhaust ports].

An excellent suggestion! I'll try a series valve string. (That's an easy test.) Who knows? It may at least SLOW the leak enough to work for this year.

Originally Posted by imax48236

The part number of the solenoid we used last year was made by Rexroth, with part # 5728400410

http://www.boschrexroth.com/pneumati...o= 5728400410

This was in last year's KOP, and is available for purchase this year. We have an extra if you want to trade/buy it.

Thanks for the offer, but that's the one I tried already (see above). It too slowly bleeds out its exhaust port. It was better than the Festo, but worse than the SMC dual coil. (It's also too late for mail swaps before ship, but we appreciate the thought!)

We're definitely overweight right now, so I *have* to solve this one so I can delete the compressor. (That's over four pounds!)

No more overnight shipping now (no mail on Monday), so unless someone else has some really slick trick we can try in the next two days with whatever we have on hand (or can get from a hardware store), I may have to resort to whipping up another "digital cork" servo-valve again.

Any other suggestions, anyone?

- Keith McClary
Chief Engineer, Team 1502 "Technical Difficulties"