Using large amounts of pneumatic tubing as additional reservoir space

Hello! One of my team members had an interesting idea and I’m making this post to refine the idea and see if anyone has used this before.

A few weeks ago, my school ran a camp for early season practice. My team used pneumatics for indexing discs into a flywheel. Because this was a very poorly optimized robot, we didn’t get many actuations out of the cylinder. (See below for data) In summary, the conversation turned to how to increase pneumatic air capacity.
One of my teammates suggested using a large amount of pneumatic tubing connected to the air reservoirs to increase the total air capacity. We tested this using the robot we already had and simply counted the number of times the cylinder could push forward and back, completing the motion against gravity in the timing specified in our code before it automatically retracts. We used an unused 100 foot spool of cable with one end capped joined with our reservoirs with a T fitting. The other end of the spool was plugged.

Pictures of the test Here are some pictures of the testing setup:

With two air reservoirs pumped to 105.5 psi, the cylinder completely actuated 57 times in each direction.
With the same reservoirs and 100 feet of tubing pumped to 104 psi, the cylinder completely actuated 78 times in each direction.

With the added air space of the tubing we had a 37% increase in the effective use of the cylinders.

From that we can find that 100 feet of cable has more than 2/3 the air storage capacity of an air reservoir. Interestingly, it we calculate the internal volume of 100 feet of tubing (2.5mm internal diameter) we find that it is almost identical to that of the air reservoir at 149.61 cubic centimeters.

Does anyone use this already? It seems like it could be significantly beneficial in the game. Putting a few hundred feet of tubing on your robot could be unwieldy but it is very flexible in how it is positioned. As you can see in the above pictures, the robot we tested this on used X-drive. If we had rewound the pneumatic tubing slightly smaller it would have easily fit inside the Drivetrain in the unused space behind the intakes and above the ground. If you really want to fit a lot in you could stuff lots of tubing in various dead spaces in the robot.

From a rules standpoint, I don’t see why this would be illegal but I easily could have missed something. I’m not aware of any rules that specify how you have to use pneumatic components that would forbid this.

Unfortunately, this isn’t significantly cheaper than buying reservoirs directly. 100 feet of cable from Robosource costs $40 at the time of writing and a reservoir costs around $50 from SMC.

Lastly, I should note some caveats of this test: This was by no means a scientific trial, just a proof of concept. We only did one trial and the condition at which we ended the test was somewhat poorly defined.


You may not use pneumatic tubing to provide increased reservoir capacity.

I suggest you re-read what is permissible in the Game Manual.


This would not be allowed by R17


You should let them re-read the rules and state where this permissible …

You know engineering design process - research :slight_smile:


Wow I don’t know how I missed that. Thanks for the help. I was hunting for the rule as you sent that. I might delete the post because it’s clearly useless.

No worries - this is well established, and hard to use search bar for past seasons.

[edit - do keep post as it will help other teams with similar questions]



I forgot to mention it in the original post. I brought up seeing this and that started the conversation in the first place.

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While you can’t use 100 ft of extra tubing for more air capacity you can still choose the best path for the tubing in order to maximize the length for additional air. Down side is that there are more places for issues to happen.

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If you choose this path, be sure to use red pneumatic tubing so the inspector knows you are doing this intentionally to circumvent a robot rule :slight_smile:


… or use a single pressure regulator tuned down to 30psi to get 100 actuations …

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You can only use black tubing, for safety (duh!).

Maybe you could use several cylinders to power a non-functional decoration, and then only use it once… seems like that would be legal and add much more additional space. My team once discussed making a reservoir out of acrylic. Teflon tape has a lower melting point, so you could use it to seal the edges without illegally melting the acrylic. Of course, this would a) be impractical and lead to more loss than gain, and b) is a borderline illegal use of Teflon tape. Technically, it could be legal, but it wasn’t practical, like many of our loophole ideas.

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Not a chance! R4-d violation upfront (safety hazard), then R9-d violation (Acrylic is an illegal plastic), R10 violation for the teflon tape, and R17 violation (2 legal VEX pneumatic air reservoirs)…there is no provision in R17 to use illegal air reservoirs.

You might get away with the air cylinders on a non-functional decoration. But that’s alot of $20 air cylinders to make up for bad design. Better to buy extra regulators so that each air cylinder received only the minimum-needed pressure to function to maximize the available actuations of your air cylinders.


You’re right, it is obviously better to just get more regulators and plan air expenditure better. But hey, get a bunch of nerds in a room and limit them, and suddenly the real task seems to be not working around the limits but rather breaking them. And hey, it’s fun to plan dumb ideas. so long as we’re in this forum, I should comment that it is possible to turn v5 smart motors into pumps. Maybe not practical this year, but we’re working on getting higher efficiency that way.

also illegal, see <r17>

Teams may not use other elements for the purposes of storing or
generating air pressure.

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Just because it’s illegal doesn’t mean we don’t mess with it in the lab. Someday the rules may change and we will have an advantage. And again, it’s fun. For many of us, that’s the point.

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Yea, but that banned by R17, and specifically by VUR12-b. I don’t thing the GDC event thinks that a VRC team would try to build a compressor, but it would be impossible since there is no legal check valve for VRC to make it work.

You raise the actual real-world situation of engineering: it’s pretty important for engineers to work in groups, to get things done. Often, one engineer will raise up an idea during brainstorming, and another will (not maliciously) tell them why it won’t work, or find some problem, and then together the group can work out the problems if the idea is actually feasible. Leave a single engineer on a problem, and you may have some time-wasting problems occurring after the process had gone on too long.

The soft-skills you guys learn during robotics definitely have real-world application, with long-lasting implications way beyond winning robotics competitions…


Regardless of the legality of it how awesome would it be to have a drive train that also does some air compression stuff?

I think building that would be a cool fun challenge where you can really learn something.


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