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Old 05-05-2012, 01:41 PM   #1
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Default Air at the track - CO2? N2?

Just curious if anyone is using CO2 for tires and possibly air tools at the track?

I don't have the patience for electric inflators so I use a 7-gallon air tank. Problem is, every time I reach for it, its empty.

I've tried nitrogen but didn't get the results I was hoping for; pressure differentials between hot & cold were less, but not a huge improvement over air. I'm sure the results could have been better if I did a better job purging the air, but realistically I don't see myself taking the time to do more than fill and purge each tire a couple of times. So....

CO2. About as dry/stable as N2, 3x the capacity. From what I've read, a 10 pound tank of CO2 is equivalent to a 200 gallon air tank. I've seen pro teams use small 2.5 pound CO2 tanks to run impact guns for pit stops. A tank of CO2 does not drop pressure as it is emptied, the pressure remains constant (~1200psi(?)) until it is just about empty. Obviously, a regulator is required.

So, any experience? What are you using? Tank size? Regulator? Where did you get it? Would you do it again?

Thanks,

Will
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Old 05-05-2012, 02:26 PM   #2
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Dry air made my life so much easier. It's fast, light and quiet.
Filling it in the basement at work for free makes it easier.
0.85L 200bar is enough to fill four 205/50-15 from empty to 30 psi, enough for a lot of adjustments.
This year I added a 3L 300bar bottle too, since I then can share it with more friends. But the bigger bottle is not as convenient.
On the picture it's a unbalanced regulator 200 to 7bars with no manometer.
The 300bar bottle needed a 300bar regulator and I added a manometer as well (the price went up somewhat).
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Old 05-05-2012, 04:42 PM   #3
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A tank of CO2 does not drop pressure as it is emptied, the pressure remains constant (~1200psi(?)) until it is just about empty.
The ideal gas law would like to have a word with you.

I have a small bottle of nitrogen in the shop for tires, but I have been meaning to pick up a small scuba tank for track days. It's a great idea - you just have to be meticulous about removing the regulator and capping the bottle during transport.
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Old 05-05-2012, 05:17 PM   #4
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I've got scuba tank experience from my diving days and oxygen tank experience from my current medical days. Scuba's definitely a different animal, with the required yearly(?) hydrostatic(?) testing and 3000psi vs. 300. A number of instructors that owned their own tanks did have regulators with tire adapters.

If I had a tow vehicle, I'd throw my little 5 gallon compressor in there and plug it in at the track. That is if you can find power at the track.
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Old 05-05-2012, 05:41 PM   #5
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The ideal gas law would like to have a word with you.
The tricky thing is that CO2 isn't gas in the can, it's a liquid, constantly boiling off gas at the same pressure.
http://www.teamonslaught.fsnet.co.uk/co2_info.htm

Wasn't the Ferrari mix 50:50 of CO2 and some refrigerant, with the goal of improving the heat exchange between the "thread" and the wheel.

The scuba tanks have a 5 year inspection interval here, and I have free access to a scuba compressor at work (so I have not needed to get a larger tank and a decanter line). I keep my regulator in the bottle, and it's been fine for years.
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Old 05-05-2012, 09:40 PM   #6
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Now that I have a tow vehicle I'm considering hooking up a power inverter and bringing along a small air compressor. I could bring along impact tools too
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Old 05-05-2012, 10:48 PM   #7
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Originally Posted by NiklasFalk View Post
The tricky thing is that CO2 isn't gas in the can, it's a liquid, constantly boiling off gas at the same pressure.
'tis true.

CO2 behaves much like propane in this regard. Even at room temperature, CO2 remains a liquid at fairly reasonable pressure (around 800 PSI.)

This is the primary reason why more and more paintball players are switching away from CO2 to compressed air at high pressure, typically 4,500 PSI. CO2 has a nasty habit of getting into the marker in liquid form and causing all sorts of hell, whereas compressed air does not cause such problems, as it does not liquefy as readily.

At any rate, any time you have a liquefied gas in a closed container, the pressure of the gaseous portion at the top of the container will remain constant (for a given temperature) regardless of the quantity remaining in the container. As you draw gas off from the top, a portion of the liquid at the bottom will immediately vaporize to fill the space and maintain pressure equilibrium.

http://en.wikipedia.org/wiki/Vapor_pressure

This is why you can't determine how much propane is left inside a BBQ tank by measuring the pressure- you have to either weigh the tank, or get a fancy one which has a dip-tube with a float inside, like the fuel level sender in an automotive gasoline tank.
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Old 05-05-2012, 10:54 PM   #8
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As a diver, I used to bring an aluminum 72 cubic foot pony bottle with me to the track with an old first stage regulator fitted with a tire inflator. It was big enough that I didnt have to worry about how much air was in it, Id use it over and over and I could easily bleed some pressure out of one of my 120 cu foot tanks into it without making them useless for diving.

I think the scuba route is very cost feasible. You can use old crap no longer suitable for use, which can be found for next to nothing.
I think the regulator I was using was an old aqualung aquarius first stage probably from the 1960s.
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Old 05-06-2012, 09:44 PM   #9
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Another option is to get a small tank of nitrogen from a welding supply place for about $20 and buy a nitrogen regulator for about $70.
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Old 05-08-2012, 01:59 AM   #10
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Keep in mind that some sanctioning bodies (SCCA) require the top of the tank/regulator of a high pressure system to be caged at all times.
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Old 05-11-2012, 01:47 PM   #11
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Awesome responses, thanks. I just got back from a few days at Summit Point. Sure enough, within 5 minutes of having all of my gear unloaded, someone asked to borrow my air tank....and brought it back empty.

I have zero experience with SCUBA equipment. Nicklas, any special handling or transportation precautions you have to take with a setup like yours?

Joe - your hat size must be XXXXL because your brain is friggen' huge!
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Old 05-11-2012, 01:57 PM   #12
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One of my buddies is a minitrucker (don't ask) and he uses the big CO2 bottles from restaurant soft drink systems. They're usually easy to find, and he probably has 5 free ones sitting in his garage at any one time.

The only catch to using CO2 is that as the bottle heats up in the sun the CO2 boils off and will blow the bottle burst disc if you're not careful with it. You're fine if you leave them in the shade, but it's really easy to leave one sitting in front of the trailer during a race and come back to an empty bottle and pissed off paddock neighbors.
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Old 05-11-2012, 02:41 PM   #13
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I gave up on air tanks for the same reason and went back to using the small tire pumps. For power tools, I just use a half inch drive battery powered impact. Pretty sure I could drop a tranny or a diff with a single charge.

The safest and least fiddly route is probably the more expensive one, unfortunately. I'd recommend buying a cylinder and regulator and just swap it out as needed at a welding supply. Keep it fixed to the wall or station in/on the trailer and just ran an air hose to the car. Just about as low a fiddle factor as you can get.

The gas is cheap - $21 for the last big bottle of C25 I picked up and CO2 is cheaper if memory serves. The bottles likely range from $180-$300 to purchase depending on the size. There's a pretty active used market for the cylinders - might find a deal on CL or something in a pawn shop - CO2 is part of TIG and some MIG welding rigs, so the cylinders are certainly out there.
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Old 05-11-2012, 11:15 PM   #14
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Indeed- the homebrew community also uses a lot of CO2, and you can purchase cylinders in the 5-10lb range for $50-60 pretty easily.

One thing to note when buying a used cylinder (and this goes for Scuba tanks as well) is that all compressed gas cylinders must be hydrostatic tested every 5 years, wherein the tank is filled with water at 150% of rated pressure and examined for leaks or deformation. Most gas supply shops can either do this in-house or have a company that they ship cylinders to for testing, but it's an annoyance and costs a few extra bucks. So try to get a bottle that's had a recent certification.


@ wildo- honestly, this is just basic high-school physics. Gaseous fluids liquefy when you pressurize them enough, and they all follow the Clausius–Clapeyron equation. Even the gasoline in your fuel tank follows this rule, gasoline just happens to already be a liquid at the temperatures and pressures which we normally experience on the surface of the earth. If you lived on the planet Mercury, your gas tank would look a lot like a CO2 cylinder, and for the same reasons. (You'd also be more dead than Nikki Catsouras, but that's a different matter.)



I wonder how many tire fills you'd get out of standard 20oz paintball tank? They're extremely cheap and lightweight, so you could easily keep 2 or 3 of them on-hand. Just gotta find the right regulator...
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Old 05-12-2012, 06:21 AM   #15
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Originally Posted by wildo View Post
I have zero experience with SCUBA equipment. Nicklas, any special handling or transportation precautions you have to take with a setup like yours?
The small alu bottle is so light that I don't take any specific precautions, I just place it somewhere where the neck/regulator have a smaller chance of getting hit by something (in the box with all the straps and stuff). The larger bottles would probably need better fixing, but so does the fire extinguishers and all other heavier stuff.

Filling a scuba tank or exchanging Nitrogen cylinders at the gas depot is up to you. But my tiny alu bottle can be carried around with two fingers... and is big enough to fill four 205/50-15 to 2 bar from empty (i.e. enough to adjust pressures for several weekends).
If you want to run a media blasting business, you don't choose cylinders...

Different gear for different purposes.
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Old 05-12-2012, 06:24 AM   #16
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I wonder how many tire fills you'd get out of standard 20oz paintball tank? They're extremely cheap and lightweight, so you could easily keep 2 or 3 of them on-hand. Just gotta find the right regulator...
That's almost 3/4 of my 0.85L bottle. So I'd say 3 tires from empty if you can cram 200 bars in them (about 2900psi).
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Old 05-12-2012, 01:47 PM   #17
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That's almost 3/4 of my 0.85L bottle. So I'd say 3 tires from empty if you can cram 200 bars in them (about 2900psi).
I meant a CO2 paintball tank (I'm honestly not sure how to figure the expansion of LCO2 to gas at ~ 30 PSI), but one of the newer HPA paintball tanks would also work. The higher-end ones are typically filled to 4,500 PSI, and contain up to 88ci.

The only problem is filling them. You'd have to take it to a dedicated paintball shop, as they're generally the only ones with compressors capable of putting out 4,500 PSI and fittings to mate with the tank's fill port.
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Old 05-12-2012, 06:02 PM   #18
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The only problem is filling them. You'd have to take it to a dedicated paintball shop, as they're generally the only ones with compressors capable of putting out 4,500 PSI and fittings to mate with the tank's fill port.
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Old 05-12-2012, 06:18 PM   #19
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Really? I thought SCUBA tanks maxed out around 3,000 PSI.
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Old 05-12-2012, 06:42 PM   #20
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Really? I thought SCUBA tanks maxed out around 3,000 PSI.
At least here they exists as 200bar (2900psi) or 300bar (4350psi), with different depth on the thread for the regulator.
But you are not so lucky so you have to settle for max 3442 psi...
http://www.scubaboard.com/forums/tan...k-4350psi.html
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