We’re adding a pneumatic system to our robot and though we’re not happy now, but we hope it’ll make us happy later. I haven’t worked with pneumatics in years, so my knowledge is a bit rusty, but I have to have a drawing ready for our laser cutter by this evening, so I’m trying to lay out the plumbing right now.
The rules say that we have to have pressure gauges that display both working and stored pressure. Presumably, the pressure regulator displays working pressure and I need to add the second pressure gauge to the system before the regulator. The schematic in the pneumatics manual supports this.
Is that correct?
Also – there’s some chance we’ll leave the compressor offboard. How do I manage that connection such that the air doesn’t leak out of the system when the compressor is disconnected? The check valve seems to be the answer there, but it’s not mentioned in this year’s manual, so I’m not sure if we have any around.
If you look at the regulator you will see an arrow. Upstream is 120# while downstream is your regulated pressure. A pressure gage can be added to one of the other ports to provide indicated working air pressure. You are correct that another gage upstream of the regulator will provide indication of system pressure.
For off board compression, use a manual relief valve with an open tubing connector on one end (goes to compressor) and the other end connected to the accumalators (either directly or via more tubing). You may want to add a T with another valve so that you can vent pressure between the isolation valve and the compressor to disconnect the jumper tubing.
Be sure to double check the rules on this. I believe that if you leave the compressor offboard, you are still required to have the controls (spike, pressure sensor, software, etc) on board. You must plug in the compressor power and air tube, and turn the robot on to charge the air tanks. This has been a problem in years past for some teams who failed to notice this rule, and left off the software, spike & sensor.
Just out of curiosity, what does this one actuator do? What size and stroke.
The reason I ask is, there is a rule of thumb for using pneumatics. Use them if you can do two or more functions with them. ie. A shifter and a lever etc. Sometimes the weight added isn’t worth it if only one function is added.
As with all “rule of thumbs”, there are exceptions, such as, it is the best way to do what we need.
If you can leave the compressor off-board, you have fairly well handled the weight issue.
The actuator rotates our ball manipulator up against the robot to better control the ball. We had designed a built a claw-type manipulator, but weren’t happy with ball control, so we’ve switched to something a bit simpler, but more effective. For it to operate properly with motors, we’d need either a worm or screw drive to prevent stalling the motors for long periods of time.
The pneumatics allow us to quickly control the position of the manipulator and we only have to worry about managing a single pneumatic tube – since we’re planning to vent to atmosphere on the actuator, I think – along our lift’s extension.
Luckily, weight is of little concern to us right now. We’ve swapped a 17 lbs. claw mechanism for a 4 lbs. manipulator. We’re well below our weight restriction.
As long as you are using a 3/4" dia., short(ish) stroke piston, you should be just fine with the compressor off board.
As an example:
We tested a 3/4" dia. 5" stroke piston on 60 PSI working pressure in 4 Clapard storage tanks. We only lost about 1 PSI per stroke. We were able to cycle the piston 25 times w/o much of an issue. The last 5 cycles were a bit weak.
Then you have plenty of weight available to have the compressor on-board, and not have to worry about the hassle of having it off-board. (: In my experience, having it off-board is a hassle - you have one more thing to do/check between each match; you have to be extra careful about avoiding a leaky pneumatics system (I’ve never seen one that’s 100% leak-proof); if you have delays before starting the match, the leaks add up that much more. We’ve used an off-board compressor in the past (when our only pneumatics was shifting), and it worked, but if you have the weight, I would recommend against it. You could always put it on, and plan that if weight becomes an issue, it’s the first thing you take off.