Influencer I
Just wanted to clear some things up here. Air, Nitrogen, Oxygen, Argon, Helium, etc are normally stored in high pressure gas form (yes, I know there are exceptions but not that equate to traveling/Overlanding). Where as CO2 is normally stored as a liquid that vaporizes in the cylinder. This is why when you look at the volume of a normal scuba tank it says something like 80 cubic foot @ 3,300 psi. When referring to a CO2 tank you will see tanks listed as 5lbs., 10lbs., and 20lbs., because you are literally weighing the liquid in the tank.
The conversion rate from liquid to gas from a CO2 tank is one pound liquid = 8.741 cubic ft of gas, so a:
5lb CO2 cylider would hold 44 cu ft. @ 850psi
10lb CO2 cylider would hold 88 cu ft. @ 850psi
20lb CO2 cylider would hold 175 cu ft. @ 850psi
Also, under normal conditions a CO2 tanks pressure will never exceed 850psi. As you use the gas vapor off the top of the liquid, the liquid remaining vaporizes as you go until all the liquid has turned to gas. I find it funny to see 2 gauges (tank pressure & line pressure) on a CO2 system because the tank side will always read 850psi until it's all gone. You can regulate the pressure on the line side via tank regulator conected to the tank valve or with a combination tank regulator and in-line regulator. For example, I have a fixed 150psi regulator on my tank so when filling tires it gets all 150psi line-pressure to the schrader valve, but when using air tools I connect an inline regulator and dial the pressure back to 80-100psi depending on the rating of the tool. I use a digital luggage scale (looks like a handle with a hook on it) to weigh my cylinders to determine how much CO2 I have remaining in each tank. I have also seen people use deep-sea fishing scales with a dial. Any kind of weight scale will work. Just remember to weigh your empty tank with regulator and anything that will normally be on the tank (tare weight) so you can subtract it from what your tank weighs after filling and determining how much you have remaining while on the trail. I always write the tare weight on the tank with a Sharpie.
I just wanted to make it very clear to all that there is a big difference in carrying a 10lb. CO2 tank @ 850psi and a 80 cu.ft. Scuba tank (with Air, Nitrogen, Nitrox, or Argon) @ 3,300psi. While both look similar, both carry about the same cubic feet of gas, and both will scare the holy crap out of you if the valve gets knocked off, the high pressure 3,300psi is more apt to seriously harm or kill you. When I was working as a high-rise welder there are tunnels in New England that you cannot drive your welding truck through because you are carrying high pressure gas cylinders. Believe me, they are no joke if that valve gets hit. Just be careful and do your homework, know what you are putting in and on your rig!! And for goodness sake, have fun.........
The advantage that CO2 has always had over a compressor is speed. You can fill your tires in a fraction of the time using a CO2 tank over a compressor. But I also use it to so much more, filling air mattresses, pressurizing my Road Shower, blowing out the tent before closing, running all my air tools, and also filling tires. But the slow compressor will always be a good backup and for those extended trips.
Ok. What is the smallest CO2 tank that can inflate four 37s from 0psi to 30psi? Space is at premium so I am asking for the smallest. Thx.
Need more data:
What is the rest of the tire size, ie. 37 x 12.5 x 15 or simular....?
I assume you want to start at zero because you will be putting a new tire on a wheel on the trail?
37/12.5/17. I'm now on 315/17 but planning ahead.
Inflate pressure from 15psi to 30psi on trail but I said from 0psi for some reserve just in case (ie. seat a bead).
I am looking at minimal space/volume, the smallest co2 tank. I do have an arb compressor under the hood for backup.
The formula for it’s volume is R squared times D times PI squared, where R is the Radius of the doughnut and D is the diameter from the center of the doughnut across the hole to the center of the doughnut on the other side.
Say your tire is a 37 - 12.5 - 17. The tire is about 12.5 inches across at the sidewall, so R is 6.25. The diameter from the center of the sidewall across the hub is about 22 inches. So the volume of the tire is 6 times 6 times 22 times 9.8696…, but 9.9 will work fine. That calculates to 7841 cubic inches. Divide by 1728, the number of cubic inches in a cubic foot, and you get a tire volume of about 4.5 cubic feet. Of course you can work entirely in cubic inches, too.
To figure out how much air it takes to inflate it, it is easiest to think in atmospheres, or multiples of atmospheric pressure of about 15 PSI. If you shove 4.5 cubic feet of air into your tire, the pressure will go up by 1 atmosphere, or 15 PSI. If you want to air up from 10 PSI to 25 PSI, put in 4.5 cubic feet. To bring it up from totally flat to 25 PSI, or increase pressure by 1.67 atmospheres (25/15), will take about 7.5 cubic feet – 4.5 times 1.67.
And how big a tank do you need? Lets say you want to air up your 4.5 cubic foot tires from 15 PSI to 30 PSI. That’s an increase of 1 atmospheres (15/15), so you need 18 cubic feet of air (1 X 4.5 X 4). If you fill your tank to 150 PSI, that’s 10 atmospheres. Air will stop going into the tire when the tank pressure equals the tire pressure of 30 PSI, or 2 atmospheres, so you have 8 atmospheres available. Subtracting one more atmosphere will leave about 15 PSI in the tank when you finish, so with a reserve you have 7 atmospheres usable. Consequently it will take a 2.57 cubic foot tank (18 / 7). ~ calculations from Jim_Lou from off-road.com and modified by me to meet your criteria.
The conversion rate from liquid to gas from a CO2 tank is one pound liquid = 8.741 cubic ft of gas, so a:
5lb CO2 cylider would hold 44 cu ft. @ 850psi
10lb CO2 cylider would hold 88 cu ft. @ 850psi
20lb CO2 cylider would hold 175 cu ft. @ 850psi
So, for every pound of CO2 you would get 3.4 fills (4 tires from 15psi to 30psi) ie (8.741 / 2.57).
Or, a 5lb CO2 cylinder would give you 17 fills (4 tires from 15psi to 30psi) ie (8.741 * 5 / 2..57).
The conversion rate from liquid to gas from a CO2 tank is one pound liquid = 8.741 cubic ft of gas, so a:
5lb CO2 cylider would hold 44 cu ft. @ 850psi
10lb CO2 cylider would hold 88 cu ft. @ 850psi
20lb CO2 cylider would hold 175 cu ft. @ 850psi
Also, under normal conditions a CO2 tanks pressure will never exceed 850psi. As you use the gas vapor off the top of the liquid, the liquid remaining vaporizes as you go until all the liquid has turned to gas. I find it funny to see 2 gauges (tank pressure & line pressure) on a CO2 system because the tank side will always read 850psi until it's all gone. You can regulate the pressure on the line side via tank regulator conected to the tank valve or with a combination tank regulator and in-line regulator. For example, I have a fixed 150psi regulator on my tank so when filling tires it gets all 150psi line-pressure to the schrader valve, but when using air tools I connect an inline regulator and dial the pressure back to 80-100psi depending on the rating of the tool. I use a digital luggage scale (looks like a handle with a hook on it) to weigh my cylinders to determine how much CO2 I have remaining in each tank. I have also seen people use deep-sea fishing scales with a dial. Any kind of weight scale will work. Just remember to weigh your empty tank with regulator and anything that will normally be on the tank (tare weight) so you can subtract it from what your tank weighs after filling and determining how much you have remaining while on the trail. I always write the tare weight on the tank with a Sharpie.
I just wanted to make it very clear to all that there is a big difference in carrying a 10lb. CO2 tank @ 850psi and a 80 cu.ft. Scuba tank (with Air, Nitrogen, Nitrox, or Argon) @ 3,300psi. While both look similar, both carry about the same cubic feet of gas, and both will scare the holy crap out of you if the valve gets knocked off, the high pressure 3,300psi is more apt to seriously harm or kill you. When I was working as a high-rise welder there are tunnels in New England that you cannot drive your welding truck through because you are carrying high pressure gas cylinders. Believe me, they are no joke if that valve gets hit. Just be careful and do your homework, know what you are putting in and on your rig!! And for goodness sake, have fun.........
The advantage that CO2 has always had over a compressor is speed. You can fill your tires in a fraction of the time using a CO2 tank over a compressor. But I also use it to so much more, filling air mattresses, pressurizing my Road Shower, blowing out the tent before closing, running all my air tools, and also filling tires. But the slow compressor will always be a good backup and for those extended trips.
Ok. What is the smallest CO2 tank that can inflate four 37s from 0psi to 30psi? Space is at premium so I am asking for the smallest. Thx.
Need more data:
What is the rest of the tire size, ie. 37 x 12.5 x 15 or simular....?
I assume you want to start at zero because you will be putting a new tire on a wheel on the trail?
37/12.5/17. I'm now on 315/17 but planning ahead.
Inflate pressure from 15psi to 30psi on trail but I said from 0psi for some reserve just in case (ie. seat a bead).
I am looking at minimal space/volume, the smallest co2 tank. I do have an arb compressor under the hood for backup.
The formula for it’s volume is R squared times D times PI squared, where R is the Radius of the doughnut and D is the diameter from the center of the doughnut across the hole to the center of the doughnut on the other side.
Say your tire is a 37 - 12.5 - 17. The tire is about 12.5 inches across at the sidewall, so R is 6.25. The diameter from the center of the sidewall across the hub is about 22 inches. So the volume of the tire is 6 times 6 times 22 times 9.8696…, but 9.9 will work fine. That calculates to 7841 cubic inches. Divide by 1728, the number of cubic inches in a cubic foot, and you get a tire volume of about 4.5 cubic feet. Of course you can work entirely in cubic inches, too.
To figure out how much air it takes to inflate it, it is easiest to think in atmospheres, or multiples of atmospheric pressure of about 15 PSI. If you shove 4.5 cubic feet of air into your tire, the pressure will go up by 1 atmosphere, or 15 PSI. If you want to air up from 10 PSI to 25 PSI, put in 4.5 cubic feet. To bring it up from totally flat to 25 PSI, or increase pressure by 1.67 atmospheres (25/15), will take about 7.5 cubic feet – 4.5 times 1.67.
And how big a tank do you need? Lets say you want to air up your 4.5 cubic foot tires from 15 PSI to 30 PSI. That’s an increase of 1 atmospheres (15/15), so you need 18 cubic feet of air (1 X 4.5 X 4). If you fill your tank to 150 PSI, that’s 10 atmospheres. Air will stop going into the tire when the tank pressure equals the tire pressure of 30 PSI, or 2 atmospheres, so you have 8 atmospheres available. Subtracting one more atmosphere will leave about 15 PSI in the tank when you finish, so with a reserve you have 7 atmospheres usable. Consequently it will take a 2.57 cubic foot tank (18 / 7). ~ calculations from Jim_Lou from off-road.com and modified by me to meet your criteria.
The conversion rate from liquid to gas from a CO2 tank is one pound liquid = 8.741 cubic ft of gas, so a:
5lb CO2 cylider would hold 44 cu ft. @ 850psi
10lb CO2 cylider would hold 88 cu ft. @ 850psi
20lb CO2 cylider would hold 175 cu ft. @ 850psi
So, for every pound of CO2 you would get 3.4 fills (4 tires from 15psi to 30psi) ie (8.741 / 2.57).
Or, a 5lb CO2 cylinder would give you 17 fills (4 tires from 15psi to 30psi) ie (8.741 * 5 / 2..57).
