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Unread 19-03-2014, 01:39
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FRC #1197 (Torbots)
Team Role: Engineer
 
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Re: Basic pneumatics questions

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Originally Posted by TheHolyHades1 View Post
1) At competition, I was talking to teams and they said they had both a high pressure and a low pressure circuit going, at 120 and 60 psi respectively. How is this possible, if there is a pressure regulator at 60 psi that's required before all pistons? Furthermore, how can the tanks get up to 120 psi if there is a 60 psi regulator in the circuit? The way it appears in the FIRST setup (http://frc-manual.usfirst.org/upload...Figure4-15.jpg) it doesn't look like there's a break between the tanks and the regulator ...
The high pressure is storage, regulated down to 60 psi for working pressure. Often it's easier to refer to the two sided separately. Tanks can be on the high-pressure side; cylinders cannot.

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2) Is there a limit to the number of tanks that we are allowed to have? Also, are we allowed to place tanks after the regulator? I haven't found anything specifically mentioning either in the rules.
No, and yes. I believe both were asked in Q&A. I will comment that the more tanks you have, the more time your one compressor will take to fill them. If you can't refill after a match in 5 minutes or less, you'll be at a disadvantage in eliminations.

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3)For a team new to pneumatics, and given the time constraints, I think a latch system to store energy, or any tampering with the pistons (removing fittings to make flow faster, etc), is out of the question. Furthermore, since a 2-3 stage setup would be needed to make a successful ram, would our only option become a trebuchet?
I think you may want to consider the application of leverage. If you have the piston fairly low on a linkage, near the pivot, and the piston fires quickly, imagine how fast the OTHER end of that link is going....

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4) I found tanks from our old seasons which are only open on one end (threaded opening). All other tanks (metal or plastic) have threaded/push to connect openings on both sides. Are the one sided containers tanks, and, if they are, would they just be connected to other tanks at the one end, using a t-connector?
Based on the description, yes (given no moving parts), and yes (though connector is up to you).

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We have about 30 pounds free to work with on the robot right now. Would this be enough for a full pneumatic system? If I'm not mistaken, we would be looking at something like 2x 10" stroke 1" bore cylinders (I think that's how one specifies cylinders?), along with the older, more heavy-duty compressor, a few tanks, likely metal (we have new black plastic Clippard tanks but are hesitant to use them due to stories of the white ones fracturing), and a little bit of tubing, brass connectors, and a few electronics. I can't imagine this getting up beyond 30 pounds; that being said, is there anything blatantly obvious I'm forgetting?
I don't think you're forgetting much, as long as the "electronics" includes solenoid valves. You'll also want the Solenoid Module for the cRIO, or a Spike per solenoid valve. You've spec'd the cylinders correctly, near as I can tell. But 30 lbs with the older compressor and metal tanks could get a little bit tight, particularly with the material of the launcher itself to factor in. Also verify that you have all the stuff that is required: relief valve for the compressor, manual vent valve, gauges, the regulator, and the pressure sensor.


A couple of other tips: Set up a test system first, to validate that your knowledge of pneumatics works. Leak check with soapy water, sprayed onto the tubing near the valves at the suspected leak point. Go with an onboard compressor--I suspect you'll have lots of leaks; you want to be able to counter them. Cut your tubing at 90 degree angles; that'll help with reducing leaks at fittings.
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2003-2007: FRC0330 BeachBots
2008: FRC1135 Shmoebotics
2012: FRC4046 Schroedinger's Dragons

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