This is part of a series of posts called Drinking From The Firehose on getting Dr Joe back up to speed on All Things FIRST.
Today’s topic:
Brave Pneumatic World…
From what I hear, this pneumatic world of FIRST has expanded enormously since I’ve been in the thick of things.
I can read the rules easily enough but taking advantage of the new freedoms? That is another thing entirely.
So… …what do I need to know?
Some thought starters:
Care and feeding of the New Pump
Valves? Assuming that I want to take advantage of the new rules, what valves should I pick? Is there a manifold/valve pack set up that is the favorite of all the cool kids?
Tanks for the Memories. Is it true that Thunder Chickens had so many light weight tanks under the new rules that they almost needed to call time out during the elims in order to recharge them between matches? Where do I get these huge, light tanks?
Cylinder sourcing? Anything special to keep in mind or just call the local distributor (or order from McMaster)?
Tips and Traps with regard to interfacing with the cRIO
Tubing, fittings, regulators, dials, etc. Please share your best
Anything that is clever or unusual that you’ve figured out that you like to share (if you only use X in combination with Y, you can do Z)
Please share any secret sauce that a noobie needs to know to gain the edge.
Thanks,
Joe J.
My favorite valve setup for FRC is an SMC SY3000 series stack on a manifold. They have a 20+ page ordering guide that shows how the part numbers are broken down. It’s rather complex. I don’t have a link, but it shouldn’t be too hard to find that document on their site.
The only real tip or trick I have is that you can do some neat things with some really tiny cylinders.
Not sure this is the exact model they use, but 399 just received a relatively large batch of these tanks: http://www.pneuaire.com/reca28cuin.html
They are super-duper light compared to the metal tanks from the KOPs of the last few years. One caveat is that the Pneuaire tanks are 4 cubic inches smaller in capacity than the Clippard KOP tanks. 32 in^3 vs 28 in^3 I haven’t gotten around to weighing the two tanks in comparison, but in the hand, it is clear that the Pneuaires are lighter.
A few tips that you may or may not know…
-With the fittings available to us, the most optimal seal will be when the tube is cut perfectly square. We’ve had issues with air leaks in our 3 regionals and we had some trouble trying to find that one tube that was not perfectly cut.
-As with the tanks, plastic fittings and joints are the way to go for super weight savings. The brass fittings and joints are awfully heavy, and I prefer not to use them if they are not necessary.
-Tubing. The less tubing you run to any actuators, the less volume of air between the valve and the actuator. As a result, less air is consumed by actuating it. If you can help it, keep air runs as short as possible.
I know many people stick with the old compressor. The new one has some issues with heat.
Bimba has been offering teams 3 free cylinders per year. An order form will be on their website following kickoff, from which you can order just about any standard size cylinder you want.
Plastic air tanks were quite big last year…I know 217, 148, 1114, 125, and others used them to great effect. This thread has some good information.
The cRIO is a big improvement for pneumatics on the electrical side. Just plug 2 wire connectors directly into the pneumatics breakout; no more spikes for solenoids. Additionally, pneumatics breakouts can be wired for either 12 or 24 volts, allowing you to use more common 24 volt solenoids.
It is not designed for continuous operation and we managed to cook one during the elims at WPI week 2 this in Final 2.3. They piston ring (seals) failed from over heating and vented our pnumatics 30-45 seconds into the match disabling our robot. Unless you have a very large storage capacity the new compressor is so small it will run continuously and over heat.
Also the plastic accumulators that many of us used this year are amazing and worth the effort. I believe we have at least a 3 to 1 exchange with the old tanks.
Also remember for the devious side of things vacuum is not pnuematics and therefore exempt from all pnuematic rules.
If it’s not too much of a hassle, can you share the P/N for these? We’ve run into a few instances where we’ve needed a valve and can’t afford to wait more than a day for them - which makes McMaster the perfect supplier.
Joe,
The new pump has similar specs to the old pump and it is considerably lighter. However, it does struggle a little near the cutoff pressure. Heat is a really big issue. A team in Chicago last year was diagnosing a leak and had the pump running continuous for about 20 minutes when the tubing near the pump had reached a sufficient temperature and failed. The noise was like a gunshot and scared everyone within about 15 feet.
The relief valve that you may remember no longer comes pre-set for 130 PSI. Depending on how it was assembled it may not operate at all. So be sure to calibrate it the first time you use it. For the old pump, the piston seals leak at about 150 PSI, I don’t remember if the new pump can even get up that high.
The temptation for some teams is to use a secondary regulator set for something less that 60 PSI. Many valves have a minimum pressure spec and therefore do not seal at or below that pressure. Typically 20-25 PSI. If you chose this design, just be sure to meet the minimum specs.
The PVC tanks were in for the first time last year. They do need to be used with caution. OSHA issued a warning and recommendation about PVC used with pressure. If the vessel is struck while pressurized the failure produces significant splinters. Keep tanks away from the outside of the robot and away from moving robot structures. The pneumatic rules were relaxed last year, paving the way for any storage vessel including 80/20. I can’t tell you what the 2012 rules will hold at this point.
We actually didn’t use the plastic tanks this year…we used one big tank
You can see it below, underneath our minibot deployment. We used this one tank with the new compressor and had no issues through the entire season. The compressor hardly ever had to turn on with the size of the tank, even with a pneumatically actuated wrist and shifting drive train.
We also used a pneumatic manifold block that I’m trying to find the part number of. It was made by SMC. This type of manifold simplified our lives so much that we will never use pneumatics without one again. It allowed for clean plumbing of the system, and even allowed for additional ports at the ready if we ever needed to add something later on. I will report back when I have the exact part number because it really is the smartest thing you can do for your pneumatic system.
The rules have really only opened up in the past 2 years, so you are not that far behind the 8 ball on that front. I’ve heard rave reviews about the plastic tanks mentioned above. I will also chip in our rave review for one large tank if you can find a place to put it. The new pump can have it’s issues with duty cycle and overheating, but we personally did not encounter those issues.
Just so we’re all clear, storage tank size will not change the duty cycle of your compressor, compressed air use determines the duty cycle of the compressor. It is a simple energy balance.
Increasing pneumatic storage volume only increases the time between the compressor shutting off and turning back on again. The length of time the compressor runs for to bring the storage system back up to full pressure is proportionally longer. IMO the smallest effective storage system is best.
In fact, if you’re completely venting the pneumatic system storage after a match (as one should for safety reasons) a larger storage volume will take longer to recharge from 0. A larger storage tank will wear the compressor more because all of the stored energy is wasted.
In 2011 we used pneumatic shifters, a pneumatic telescoping arm, and a pneumatic wrist joint. Four KOP tanks were more than adequate. We probably could have used just 2 or 3.
All of what you are saying is true. For us however, the compressor only needed to turn on in the last 30 seconds of the match (if at all). Sure it took a while to pre-fill the tanks, but that was all apart of the pre-match routine. We were actually quite confident we didn’t even need a compressor with the volume of tank we had. However, we had the weight and decided to add it in towards the end of our build as a safety. We encountered no issues with compressor life.
Here’s a list of the SMC SY-3000 series single/double solenoid valves, manifold blocks (4 and 5-station), lead wire connectors, blocking plates, and standalone valve blocks (if you want to mount a single valve by itself, old school) - that I ordered for several local teams last year.
I used a local distributor, who gave us a nice discount. I’ve not compared the prices we got with other sources!
So far, seems everything’s been answered except for:
The cRio: Nothing special, the pneumatic ‘bumper’ on the relay module drives your solenoid valves (8 of them, which is 4 double-acting) and it does this very well. You can also drive them the old way with Spikes if need be. You get these 2-pin cable assemblies (similar to PWMs) that interface nicely at both ends with the KoP.
Tubing & fittings etc.: All the same as many years ago, nothing has changed. Except the brass bag doesn’t automatically come with the KoP any more. You can get it via First Choice if you need it.
Speaking of pneumatics, one area that you need to watch is the flow resistance of solenoid valves, specifically the Cv. Many of the new solenoid valves are more efficient than the FIRST specification and are thus not legal for FRC use, at least by the 2011 rules.
on that note, I will add that multiple soleniods per pneumatic actuator is no longer lega as of the 2011 rules. prior, one could use multiple solenoids to ither increase flow (dymaically when they are independently controlled) or to allow variable positions (separate intake and exhaust solenoids).
