Bike Tubes for Air Storage?

Our team is making a custom 2x1 frame for swerve drive this year. Last year our air tanks were bulky and got in the way. Because of our experience last year I was wondering if we could store air inside the 2x1 tubing. We were planning on drilling holes in the top of the frame and doing some side cutout patterns to reduce weight, so we would not be able to weld caps to them. I then thought about the possibility of putting a bike tube inside the 2x1. I was a little confused with the game manual’s language for air tanks, so would it be legal if the bike tube were 125 PSI rated?

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The pneumatic storage device can not be modified either, which means you would have to work with the Schrader valve on the bike tube. Is the bike tube rated to 125 and can be integrated into the pneumatic system without modification?

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You wouldn’t be able to do that anyways.

Storing air in your frame is NOT a COTS pneumatic device.

On to using a bike tube… I would say that you’re probably on thin ice at best. Pneumatic wheels are specifically excluded from being pneumatic devices (R77, Blue Box 3, item B)–but that doesn’t mean much here because presumably you’re connecting this to your pneumatic system. @Jon_Stratis, your opinion requested please.

You will need to get very creative to satisfy R86A with a bike tire. Those are usually set up to not let air out–so you’d have to defeat that setup. If you do that by removing the valve stem (the easy way), you just ran into R75 again–the tube is no longer COTS. CAN it be done, probably. Is it going to be a good idea? No, for a variety of reasons. (Being in a frame tube with holes means it’s first in line for any damage–you guys didn’t make it to the field last year so you might not realize just how much pain can be inflicted on the robots.)

On top of which… How much air are you really going to be able to store in a bike tube, compared to one of the standard FRC plastic air tanks?

I have other concerns with your plans for the year but that’s for another thread.

What I would propose would be to look for other tank options, and additionally to pay attention to how the tanks are mounted. We’ve been able to hide tanks in a lot of oddball places over the years, it’s just a matter of paying attention.

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How much are air you using that placing the air tanks is enough of an issue to go to that length? We’ve used more than 2 maybe twice? in 20+ years. Even got away with cutting down to 1 in 2019 at IRI.

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It is pretty easy to get around this hurdle, because the bike valve is a standard tire valve and there are many adaptors, which would be able to get to the standard tubing, without modifying the bike valve.

Volume wise we would be able to store around 140 cubic inches of air in the base, and that is also considering that we are using a swerve drive so there are no axles going through the 2x1. The lack of axles would also make maintenance pretty easy too.

My biggest concern still is the rigor of play that is created in actual game play, and even though replacing tanks would be easy, a tank failure would be devastating in a match.

Buddy your biggest concern is having this robot surrounded by 5+ yellow hats and someone on the phone to HQ/Big Al, laugh-crying, even if it is technically legal somehow.

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We are currently using two 12 inch pistons on out intake and a 3 inch piston for our control panel mechanism, both are 3/4inch bore. We were using two tank last year and ran into some delays when the compressor would have to refill the tanks. That never slowed us down, but we are looking at using pneumatics on our climber so we are looking at ways to increase capacity.

I cannot speak much for the legality but I think you already have some good advice there. I can however speak about bike tubes (I work at a bike shop). 125PSI is a very high pressure for a bike tube and would only be ran in very low volume, skinny tires. To store any reasonable amount of air you would need very large volume tubes (think fat-bike tubes) that are only meant to hold 15PSI at the very most. The other issue is in the plan to put the tubes in the rails of your frame. Probably 50% of the flats that I have encountered (I’ve encountered a lot of flats) are on the rim side of the wheel where the tube got pinched, poked, or rubbed on the metal of the wheel. You would need to line the whole interior of your frame tubes with a protective tape to prevent the tubes from breaking. The corners of your frame would also need to be rounded with a decent size radius to prevent the tube from going flat on one of the corners. You would also need a way to link multiple tubes as the frame perimeter of your robot is bigger than the circumference of a bike wheel. Basically this idea is creative, but not at all practical and probably not legal.

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And they would also depress the stem, I presume.

Your 140 in^3 is about the same as 4 AM tanks. I can probably find a place on your robot for 6 AM tanks that isn’t in the way of anything and is still somewhat protected. OR we can talk to some of the teams who use a Very Large Tank and see if they can recommend a mounting method.

Not necessarily. If you were to fold up a tube into one side of frame (which raises its own issues, namely kinked tubes) you’d just need one output per side to get to the pneumatics system.

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That could work but would increase the risk of a punctured tube by a lot. It would also mean you are not utilizing the full volume of your frame which is already probably not enough.

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Yes, there would probably need to be some sort of tape on the backing of the holes in the tube so it would not get a puncture. I was also thinking of using 4 road bike tubes, one for each beam. I found that a thicker road bike tube can be rated for 125 psi, which would make it a better option.

Yes but you will run into two problems with road bike tubes.

  1. there is not enough volume in those tubes to support a robots air usage
  2. They are not meant to expand to fill a 2in x 1in space and they will pop if they are not contained to a small space, like the space between a skinny road bike tire and the rim

not probably. And not only on the holes in the frame tube, any exposed metal, even if it is smooth, will cause the inner tube to pop
also see the problem that both EricH and I said will come with putting one inner tube in one frame rail, the tube will be highly likely to pop when it is folded/kinked the way it would need to be to fit in a frame rail

Points for the crazy/creative idea. But don’t build a robot around it! We’ve had a few yellow hat congregations around our machines. Even when you are confident it is a time consuming distraction.

T.Wolter

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Well, you could produce your air tank frame rail, get it pressure tested and certified, launch your own company with proper tax ID number, business license, etc, stock enough of them to be available to any team who wants one in a reasonable amount of time, and then sell yourself one. Then I think it would be legal, but don’t hold me to that.

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I’ve already bought the domain for sketchyairtankframerails . com. Working on the certification right now.

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I think this very much depends on what you’re doing with your pneumatic system. If you’re just actuating your 2 speed gearboxes and maybe a couple toggle latches or a single-use deployment mechanism, sure, slap one tank on there and forget about it. But let’s say you’re using larger bore cylinders to help with the climbing tasks in 2019 (as many teams did), your air budget goes way up.

Schraeder valves are designed to be one-way valves (until the stem is depressed by an external force).

Do you have a link to adapters that also depress that pin?

Everyone,
As pointed out above,
R75. All pneumatic items must be COTS pneumatic devices and either:
A. rated by their manufacturers for pressure of at least 125psi (~862 kPa), or
B. installed downstream of the primary relieving regulator (see R82), and rated for pressure of at least 70psi (~483 kPa)
Thank you, Charlie.
As to the use of inner tubes in a metal framing member, a team would need to show a specification sheet that would allow that implementation to meet R75, A above.

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The TIRE is rated for 125psi NOT the tube. Don’t believe it, put a tube on the table and see if you can get to 125psi.

Thus the frame would have to be rated for 125psi.

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This is not what a robot performing well under pressure usually means.

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Do you need to be using such a large bore for your pistons, especially for intakes and control panel mechanisms? Some quik maf says that:
(3/8 in) ^ 2 * 3.14 * 60 psi = 26 lbf.
If you’re using two for just the intake, that’s well over 50 pounds of force. You’ll use a lot less air by using a smaller bore. You’ll use 9 times less air if you switch to a 1/4 in bore. You’ll still have ~6 lbf using two of those instead. And if that is not enough, you can use springs or other methods to assist actuation.

EDIT: @MrForbes thanks for pointing out my mistake. It has been corrected. That’s what I get for doing quik mafs.

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