Pneumatics during teleop

In realty the small compressor won’t use that much energy from the battery but I get the idea of using as much stored energy as you can.
But remember if you stack up too many accumulators the compressor may not be able to refill them to a usable pressure.
Use that calculator and find you sweet spot.

I’m not sure I would go with the “recommended KOP Tanks” on that calculator - it’s only determination is not to fall below 20 PSI. With a 250C-IG compressor, total cylinder volume of about 1/3 of a clippard tank, and actuating the cylinders ever 1 second, it recommends… 1 tank, and the graph shows a quick drop to about 26PSI, which is a relatively stable state (which makes sense, the CFM of the compressor backs this up).

Personally, I’m of the opinion that more is better. For us, that means we ended up with 8 tanks this year - we have the space and weight for it, so why not? It means we’ll be able to complete 6 scoring cycles before dropping below 90PSI. That means 6 cycles without turning on the compressor (assuming perfect usage per cycle). That means the compressor doesn’t turn on during those 6 cycles, and we save the battery for other stuff. Much better than 1 tank, where the compressor would run the entire match and drain more battery!

I was kind of asking whether or not it’s legal. It appears to be, but I want to make sure I’m not missing something.

The problem with “more is better” in this situation is that these little bitty pumps really aren’t designed to work with duty cycles that long, and they take a long time to pressurize eight tanks. Given the restriction of one compressor on or off the robot (that’s still the case, yeah?), the poor little thing is going to get very hot and its lifetime is going to be shortened to a degree that may or may not be great for your season. (And consider if you have a slow leak and have to queue before opening ceremonies…)

Further, in a six-minute turnaround in eliminations, filling eight tanks with an FRC-legal compressor is going to eat an alarming amount of that time (while making your poor little thing rather toasty).

I do agree that I don’t trust the calculator most times. In most years, if we’re somewhat pneumatic heavy, we try to run practice matches and see how few tanks we can get away with without impacting robot performance–usually starting with two, and almost always upping it to three.

Only on the robot, no off-board compressors at all anymore.

It is worth considering duty cycle of the compressors. That’s why we chose the 250C-IG - it’s rated for 100% duty cycle at 100PSI. The 90C that many teams use is only rated for 9% duty cycle at 100PSI. There was some consideration for getting the 330C-IG, but it’s even heavier, bigger, and since we already have a 250C-IG, a lot more expensive :slight_smile:

One of the challenges for teams is to find the time to detect and fix leaks while in the relative quiet of their own shop, before getting to competition. If you can do that, then your robot can sit for 10 minutes or even an hour without loss.

Check out section 11.7.2, specifically table 11-3. The new Double Elimination playoff format guarantees a minimum of 17 minutes between matches for a typical playoff bracket.

There’s no rule that says robots need to be depressurized between matches - in a quick turnaround situations like elims, I would expect to not really need much time to refill the tanks, since they’ll already be mostly good. Even filling from empty, 8 Clippard tanks is 4296 ml in volume. At the worst, the 250C-IG fills at .39CFM at 120PSI - that’s 11 L per minute. I feel pretty confident that it’ll fill up fairly quickly!

1 Like

Do you have a link to the compressor yall use?

1 Like
1 Like