Hey guys, I’m wondering if the pneumatics tank could explode? Is that possible? Also how does pneumatics get infinite air? Is pneumatics expensive? Sorry for all these questions! I am an absolute beginner haha
Yes, pneumatic tanks can explode, but it is very uncommon to see in FRC. If you over pressurize them or damage them they are likely to blow up. Different pneumatic parts can be expensive such as cylinders, compressors, and solenoids. In the expensive game that is FRC these types of prices aren’t uncommon though.
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Oh okay thanks!
Not under regular operation. I believe there was a few incidents with a certain type of tank exploding several years ago, but generally if you protect your tanks from direct impact they should be okay.
Pneumatics distinctly don’t get infinite air. You have a compressor within the robot which fills air tanks which then release air to move pneumatic cylinders (commonly called pistons.) You can have your air tanks start full so in general you calibrate the number of tanks you have to the amount of air you’ll need to be using. Using a lot of pneumatics on a robot can lead to running out of air which means you won’t be able to keep using the mechanisms until the compressor gets more air in the tanks.
Pneumatics aren’t necessarily cheap, but I believe there’s ways to use some of the virtual kit of parts coupons for pneumatics components/order some off first choice. These components are also largely reusable so you may have a stock of cylinders that can be applied for a given scenario.
Given you’re programming I will note that pneumatics (from the understanding of someone who has never touched a line of robot code) are relatively easy to program as you pretty much tell them to be in or out. As far as the electrical set up of the system you’ll have air running from the high pressure tanks (120 psi) through a regulator (60 psi max) and to a solenoid which can be electrically controlled to change which way air flows into the cylinder which moves it in or out.
One important design consideration with pneumatics is in the weight. If you only have one small cylinder on the robot you still need a compressor and tank and all the other required components which is going to be significantly heavier than a similar solution using a motor. In general you want to have at least a couple uses for pneumatics if you’re putting them on the robot.
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Thank you so much again!
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Correct on both counts. It’s the only component specifically banned by part number (“with the exception of white Clippard tanks P/N AVT-PP-41),”–that’s from R804, incidents were during the 2012 season IIRC). There’s been a few cases since where a tank shattered under a direct hit.
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Here’s an excellent CD thread on blowing up these tanks with a BB gun or something.
Destructive Air Tank Testing
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I may or may not have murdered like 4 tanks on the 2019 cargoship.
Designed the tank mounts, and ran them right into a field hardpoint. Surprisingly, not very violent.
There’s also this thread from IRI 2022: 1023 Clippard Tank Explosion at IRI
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They can explode on a sharp impact, but with the correct high side pressure release (connects directly between your tanks and compressor) it should vent air before you get anywhere near the tanks normal limits and prevent over filling.
There are other versions with an adjustable thread to tune the release point but I don’t trust those. They can fail and adjust over long term usage. The spring style ones seem much better and pass inspection without fail at 125psi.
Your digital or analog pressure switch will send a digital signal at ~ 120psi, to stop the compressor. If that fails that’s when the safety release goes off at 125psi dumping any extra air.
There is also the concern of overtightened fittings in air tanks causing fractures in the plastic. Not sure if this has been a explosive root cause, but is worth consideration as fitting torque is a small detail that is easy to control.
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This will be our second year with Bimba stainless steel air tanks…
You can get a size that matches our favorite 2" high extrusion and will fit neatly into the base 
Don’t suppose you have a link or part numbers handy, do you?
Bimba D-2485-A-8 is an 8" long air tank. D-2485-A-6 is a 6" one. The key thing to remember is that most of the weight is in the Aluminum end caps, so the longer you get the lighter it is per cubic inch. Check FleaBay; that’s what I do!
Bimba aluminum end stainless tube reservoirs, all calculated for the same 35 cubic inches capacity. Going longer gets you a lot more cubic inches per pound!
1.5" OD 0.97 pounds
2" OD 1.07 pounds
2.5" OD 1.22 pounds
Vs polypropylene at 0.64 pounds per AndyMark
Also fun:
2.5" OD at 70 cubic inches comes in at 1.79 pounds.
SAME diameter and length as the polypro tank gets you a LOT more capacity:
$133 list price
2.5" OD, 53 cubic inches, 1.52 pounds
NuclearNerd did a nice comparison chart:
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Note that you aren’t required to have a pneumatic system, it’s a design choice.
At every competition, all our ‘bots are inspected by designated Robot Inspectors, including the pneumatic system if any. As mentioned above, a pressure relief valve is a required part of every pneumatic system, and teams are required to show, at the inspection, that their pressure relief valve works, and discharges air if the air pressure goes too high.
Please see robot rule “R811” of the Robot Construction Rules, off of https://www.firstinspires.org/resource-library/frc/competition-manual-qa-system
Teams should check this the first time the pneumatic system is operated. In addition, before going to any competition teams should practice adjusting the pressure relief valve rather than fumbling through it at competitions.
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What are some alternatives to pneumatics?
Motors.
That said I’m going to pull from a slightly different set than we were talking about last night. Still in R501, there’s a few lines at the end.
Electrical solenoid actuators, no greater than 1 in. (nominal) stroke and rated electrical input power no greater than 10 watts (W) continuous duty at 12 volts (VDC) (if qualifying actuator is then used at 24V, it must be approved by the manufacturer for use at 24V)
PWMPulse Width Modulation COTSCommercial, off-the-shelf servos with a retail cost < $75.
Linear actuators rated for 12V and wired downstream of a breaker 20A or less
Any one of the three will work, in the right application. It’s not totally unheard of to use servos to shift a drivetrain’s gears, for example; servos and solenoid actuators are relatively frequently used as releases for things that are gravity-powered and only need to work once per match (I have many comments about that application).
The most direct replacement for pneumatics in there is the linear actuator. The catch? They’re slow, and they can’t provide post-match movement easily like properly-set-up pneumatics can.
I’llLimelight, an integrated vision coprocessor again note that pneumatics are optional. It’s perfectly viable to build a robot without any, though many robots build with pneumatics.
In your team’s case, pneumatics can solve a number of possible control system issues. If you’d like a “pneumatics vs motors” post… I’llLimelight, an integrated vision coprocessor just start typing offline.
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ohhh awesome thank you so much again!
I figured we’d need this. So here is a list of the pros/cons (though I will say, I rather intentionally didn’t distinguish them–seems that sometimes a pro is a con and a con is a pro when you’re doing engineering).
Pneumatics
- Weight penalty: compressor, required fittings, PCM, Air tank(s)
- Only 2 positions per actuator*
- Simple (on/off means extend/retract, or vice versa)
- “easy” to expand system—add extra fitting, solenoid, cylinder and add a couple lines of code
- Has options for very creative solutions
- Fast, or strong—depends on cylinder sizing (larger diameter is stronger, smaller diameter is faster, in general)
- Able to move after match end
- Mostly used for linear motion, but rotary pneumatics exist.
- Can run into issues with leaks
- If force applied > force of internal air, will be forced backwards
- CAN be manually operated with the robot disabled (whether this is a pro or a con is up to the user…)
- *There ARE ways to monkey with this. But, in general, 2 positions is as many as you’llLimelight, an integrated vision coprocessor get.
Motors (general)
- Used for near-infinite motion, within the bounds of physics
- Rotary motion only, conversion to linear motion requires special gearing (see Linear Actuators) or linkages
- Require speed controllers to function
Linear Actuators
- Require motors to operate
- Can custom-build, requires legal motor
- Can purchase off-the-shelf, motor is legal by default if it fits the rules
- Tend to be slow
- Can stop in multiple positions
- Requires the robot to be enabled to use
- Tend to be very difficult to force backwards (backdrive)
- Two general types:
- Leadscrew
- Rack-and-pinion
- Research on these is left for the reader, or a later post
- Leadscrew is vastly more common
Servos and Electric Solenoid Actuators
- Weak
- Short throw
- Generally used as latches.
- Occasionally used as shifters
One of the generalized tradeoffs is the teams with good programmers tend to like to use fancy algorithms, the teams with not-so-good programmers get creative with their uses of pneumatics. I alluded to the creativity–but if we were to go down that rabbit hole, we’d be here all night. Suffice it to say, not much surprises me when it comes to pneumatics usage. (coughcough4907 in 2022coughcough)
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