Well, I went looking for information on the boiling point of CO2, and found that the boiling point is lower than I had thought (like -109). But, for purposes of airing tires using liquid CO2, the point is still the same. I found a chart which gave values for pressure at different temperatures, and the chart showed that CO2 at 31c (87.8 f) would produce 73 atmospheres (significant pressure - somewhere near 1,000 pounds I think). But, at -56c, it produces only 5.1 atmospheres (maybe 70 to 80 pounds). Minus 56 celcius is something like minus 68 degrees f, which is really cold, no doubt, but I have seen minus 55 right outside the door here, and the pressure drop from desert hot to winter cold is substantial. The point, I guess, is that there is a pressure gradient for CO2 that is driven by temperature as long as the volume remains constant, and the usable pressure of a CO2 tank decreases significantly as the outside temperature drops. If you have large tires and need to seat a bead, drive an air tool, or inflate a large tire, having only 70 psi at low volume might not get the job done. Be prepared to keep your tank warm in order to get proper performance from it.
Air or CO2???
- Thread starter OldSven
- Start date
david despain
Adventurer
^^^ thats a fine point about the temp and vapor pressure thing, however under "normal" circumstances i doubt if it would casuse too much problem. as i was reading your post i kept thinking "wow thats cold, and a huge tire. they should keep the tank inside the cab" this type of thing is the same reason that you would put a little 1 lb can of freon in a tub of warm water when servicing a system back in the olden days. its also a big concern with nitrious oxide systems on race cars for proper tuning its essential to have constant pressure i think it would be super trick to have a heater blanket on a co2 air system in really cold places such as Alaska. :Wow1: something like this http://store.summitracing.com/egnsearch.asp?Ntt=nitrous&N=115+4294858254&Ntk=KeywordSearch
SEREvince
Adventurer
Just to clarify, the tank pictured is mine. It's a standard tank used for Co2, mixed welding gases etc. I tried to paint it green to match the apearance of my Taco and ended up looking like I stole from some ederly person in a wheelchair
I have since upgraded to a polished aluminum 20lb tank with a neck guard, not for lack of volume. Pretty much just got a great deal on it. Plus it's super bling! The regulator cost about $40 and the rest was nickle and dime. If you don't count the cost of my original tank, I have less than $100 in the new system with fill. $100 doesn't buy a whole lot of air compressor IMO.
Cheers
Vince
I have since upgraded to a polished aluminum 20lb tank with a neck guard, not for lack of volume. Pretty much just got a great deal on it. Plus it's super bling! The regulator cost about $40 and the rest was nickle and dime. If you don't count the cost of my original tank, I have less than $100 in the new system with fill. $100 doesn't buy a whole lot of air compressor IMO.Cheers
Vince
david despain said:
Quite right. I mentioned it only so that someone thinking of using CO2 would also realize that temperature is very important to just how well the system will work. It would also have impact as the system is depleted. It's like taking a dead spray can and soaking it in hot water, just to get that last squirt of paint or whatever. Sometimes ideas that are perfect in warm country don't work in the cold, but we just don't see it coming until it happens. It also doesn't have to be 50 below before a CO2 tank would become equal to a bicycle pump. The decline in performance is a exponential gradient, not a linear one. Just dropping the tank down to 30 degrees would see a significant drop in performance, and thermal mass being what it is, it could take a long time, perhaps a hour or more, to warm a full tank once it is chilled.
Just provoking thought here, not running down the idea of CO2. Personally, I have two onboard air systems, and all the free air I can use. The way I look at it, the CO2 could be great, until the tank runs dry in the middle of nowhere. Then it is just a tank, and even if you could pressurize it with air, it would hold almost nothing, being only a 2 or 3 gallon tank to start with. Without a backup system, it could be a long day if the CO2 runs out. Even if someone wants to run CO2, I think they should have a backup plan.
saltamontes
Observer
moisture
my understanding is that compressed air or CO2 is wet, wet, wet and its that moisture that leads to variations in pressure when the moisture is heated in the tire.
additionally, as some have pointed out, moisture may rust the inside of the rim. That rust gets airborn when opening the valve and minute particles of rust will prevent the valve from closing completely thus leading to a very slow leak at the valve stem. i have no idea whether this is true, but i did read it somewhere.
if your source of nitrogen does not adaquately dry the gas, the entrained water vapor defeats many perceived benefits. remember, its all about dry gas, whether that be air, CO2, nitrogen, helium, etc.
what to do?
an old jeeper trick is to pour rustoleum type paint into your bumper tank and slosh it around to rustproof the inside.
additionally, get a good air dryer (prob dessicant-based for small size) and use your onboard compressor/bumper-based air tank.
my understanding is that compressed air or CO2 is wet, wet, wet and its that moisture that leads to variations in pressure when the moisture is heated in the tire.
additionally, as some have pointed out, moisture may rust the inside of the rim. That rust gets airborn when opening the valve and minute particles of rust will prevent the valve from closing completely thus leading to a very slow leak at the valve stem. i have no idea whether this is true, but i did read it somewhere.
if your source of nitrogen does not adaquately dry the gas, the entrained water vapor defeats many perceived benefits. remember, its all about dry gas, whether that be air, CO2, nitrogen, helium, etc.
what to do?
an old jeeper trick is to pour rustoleum type paint into your bumper tank and slosh it around to rustproof the inside.
additionally, get a good air dryer (prob dessicant-based for small size) and use your onboard compressor/bumper-based air tank.
Gear
Explorer, Overland Certified OC0020
Safety Concerns
Just read thru the entire thread and have a couple of questions. I want to mount my Powertank inside my Jeep Rubicon 4 door JK. It will fit nicely on the rear roll bar with there bracket and clamps. My question is regarding safety. Can I keep the powertank inside the Jeep on a day to day basis while having two kids in the back seat. The tank will be mounted very securely. I am concerned about the blow off valve and our ears should it let loose. I talked to a friend who also mentioned that if the CO2 leaks it could cause you to pass out. Any thoughts.
Thanks
Just read thru the entire thread and have a couple of questions. I want to mount my Powertank inside my Jeep Rubicon 4 door JK. It will fit nicely on the rear roll bar with there bracket and clamps. My question is regarding safety. Can I keep the powertank inside the Jeep on a day to day basis while having two kids in the back seat. The tank will be mounted very securely. I am concerned about the blow off valve and our ears should it let loose. I talked to a friend who also mentioned that if the CO2 leaks it could cause you to pass out. Any thoughts.
Thanks
spressomon
Expedition Leader
Gear said:
Have had mine in the drawer that resides inside my LC for the past 2+ years without issue. Used to get the tank filled at the dry ice shop...but after one of the idiots there overfilled it and caused the safety valve to release (when that happens you need to have it pressure tested to the tune of about $40 + another fill charge) I only have it refilled at a fire extinguisher supply house here...
Point: As long as you have someone experienced, competent & trustworthy fill the tank I don't think you have much to worry about. Not much different than checking your exhaust system now and then to prevent carbon monoxide from building up in the cabin.
Andrew Walcker
Mod Emeritus
I've had my CO2 tank in the back of the D-90 for at least 1.5 years with no problems or concerns.
Steve Curren
Explorer
I have been using Co2 for a number of years now and I find it great. I did have the safely valve blow once, I was out in the hot Arizona sun with the top off and was not paying attention. We were working on another vehicle and as I left the valve blew, I was able to get a bottle of water in the stream and I sure had a nice cold drink.
wADVr
Adventurer
I started out running CO2 and decided to convert my AC compressor to OBA. While I wont convert and lose AC again I will add a york on my next set up. For me there were 4 main reasons to convert to OBA;
1) I kept running out mid trail run or halfway through airing back up.
2) Space, I carry my family and all their things, that space is much more useful carrying the kitchen sink.
3) Reading stories about the safety valve popping and filling the cabin w/ CO2 didn't interest me much for my kids in the back seat.
4) In the event of a rollover, that plastic or even tubular valve guard isn't going to help much resulting in the above situation and making the situation that much worse.
I see you are looking at a simple solution which the CO2 tank does provide and having a pick-up does eliminate a few of those concerns. Watch how much you use and be conservative. Sometimes a single trail run can provide several times to use air which can leave you empty faster than anticipated.
1) I kept running out mid trail run or halfway through airing back up.
2) Space, I carry my family and all their things, that space is much more useful carrying the kitchen sink.
3) Reading stories about the safety valve popping and filling the cabin w/ CO2 didn't interest me much for my kids in the back seat.
4) In the event of a rollover, that plastic or even tubular valve guard isn't going to help much resulting in the above situation and making the situation that much worse.
I see you are looking at a simple solution which the CO2 tank does provide and having a pick-up does eliminate a few of those concerns. Watch how much you use and be conservative. Sometimes a single trail run can provide several times to use air which can leave you empty faster than anticipated.
devinsixtyseven
Explorer
A few more random factoids...
CO2 sinks. If the valve blows in the cab, open the door...the gas will spill out. I had the same concern keeping 15# (truck) and 20# (welder) CO2 tanks in the garage.
All the aluminum CO2 bottles are made by the same company, so I heard from the guy from whom I recently got a 20# bottle for 135$. That homebrewer supply price is great, if I'd known when I was buying a tank, I'd be running a pair of 10# tanks for redundancy and low-height storage (fit under the bed rails, ie under a rear-open RTT), and a large compressor in addition to the tiny one running the lockers.
Sounds like a lot, but I've on two occasions been unable to use the regulator mounted on the tank...the first time I had no spare reg and had to drive back to Moab on 20psi (REALLY glad I didn't drop to 10psi!), the second time I was carrying a spare and the only reason the first wasn't working was grit in the quick release. I've also had the bottle run out and needed a compressor to finish the job.
Maybe it's the AeroE education, but I always prefer backup plans for my backup plans...separated, dedicated systems with overlap for emergencies...but that translates to more weight and more money.
It's not hard to plumb a block to run your lockers (or your air source) from either the dedicated compressor, spare compressor, or CO2.
CO2 is vastly easier and cheaper to deal with than nitrogen, it is also lighter and safer to store, just keep an eye on your tire pressure as it will sink. If you're always airing up and down, nitrogen is a waste...keep it in the shop for when you're home, and for shocks.
Best solution is run both CO2 and OBA of some sort. Doesn't matter which you use as primary, so long as you have both.
-Sean
CO2 sinks. If the valve blows in the cab, open the door...the gas will spill out. I had the same concern keeping 15# (truck) and 20# (welder) CO2 tanks in the garage.
All the aluminum CO2 bottles are made by the same company, so I heard from the guy from whom I recently got a 20# bottle for 135$. That homebrewer supply price is great, if I'd known when I was buying a tank, I'd be running a pair of 10# tanks for redundancy and low-height storage (fit under the bed rails, ie under a rear-open RTT), and a large compressor in addition to the tiny one running the lockers.
Sounds like a lot, but I've on two occasions been unable to use the regulator mounted on the tank...the first time I had no spare reg and had to drive back to Moab on 20psi (REALLY glad I didn't drop to 10psi!), the second time I was carrying a spare and the only reason the first wasn't working was grit in the quick release. I've also had the bottle run out and needed a compressor to finish the job.
Maybe it's the AeroE education, but I always prefer backup plans for my backup plans...separated, dedicated systems with overlap for emergencies...but that translates to more weight and more money.
It's not hard to plumb a block to run your lockers (or your air source) from either the dedicated compressor, spare compressor, or CO2.
CO2 is vastly easier and cheaper to deal with than nitrogen, it is also lighter and safer to store, just keep an eye on your tire pressure as it will sink. If you're always airing up and down, nitrogen is a waste...keep it in the shop for when you're home, and for shocks.
Best solution is run both CO2 and OBA of some sort. Doesn't matter which you use as primary, so long as you have both.
-Sean
vengeful
Explorer
I agree with what devinsixtyseven said.
I've had a 10lb CO2 tank in the back of my Pathfinder for going on 2.5 years now. I've never had any problems with it, and it's always kept in the truck, until recently, when I decided to relocate the mount to build a new cargo drawer. I didn't have a problem with the tank when I was in Phoenix, in 118 degree heat, and I haven't had any problems with it in Rochester, with 3 Degree cold.
I had a tank let go in the garage once, several years ago. Make a pretty loud racket, and covered everything with snow. Scared the bejeezus out of me, but didn't cause any harm.
I like the simplicity of the CO2 system. You don't need a running engine, or battery power to run it. You don't have to worry about motor heat, you don't have to worry about running electric. But, that's all a trade-off for not having a renewable air source.
As Devinsixtyseven said, in order to be truly prepared, you should have both. CO2 in case the compressor fails, and the compressor in case you run out of CO2, whichever way you have the primary source set up. Currently, I only have CO2, but I am building an On-Board Air Compressor (York Based, electric...yeahhhh to replace the CO2 as primary air source. CO2 will accompany in the vehicle as a backup to the compressor in case of failure or need for a portable air source.
I've had a 10lb CO2 tank in the back of my Pathfinder for going on 2.5 years now. I've never had any problems with it, and it's always kept in the truck, until recently, when I decided to relocate the mount to build a new cargo drawer. I didn't have a problem with the tank when I was in Phoenix, in 118 degree heat, and I haven't had any problems with it in Rochester, with 3 Degree cold.
I had a tank let go in the garage once, several years ago. Make a pretty loud racket, and covered everything with snow. Scared the bejeezus out of me, but didn't cause any harm.
I like the simplicity of the CO2 system. You don't need a running engine, or battery power to run it. You don't have to worry about motor heat, you don't have to worry about running electric. But, that's all a trade-off for not having a renewable air source.
As Devinsixtyseven said, in order to be truly prepared, you should have both. CO2 in case the compressor fails, and the compressor in case you run out of CO2, whichever way you have the primary source set up. Currently, I only have CO2, but I am building an On-Board Air Compressor (York Based, electric...yeahhhh
to replace the CO2 as primary air source. CO2 will accompany in the vehicle as a backup to the compressor in case of failure or need for a portable air source.
BMAN
Adventurer
Great reading in this thread. Everyone has touched on just about every facet that I could think of so I will simply tell you that I have run CO2 in the FJ40 as long as I've owned it. I bought my entire CO2 rig from a fellow wheeler who converted to OBA. I have never had any issue with failures of seal or regulators. The tank sits exposed in the back of my topless 40 year round in Phoenix. I have however run out of air during fill up and had te rely on other means to finish filling. My ONLY complaint about CO2 is the continual cost of refills. At $15/fill and 4 air-ups per tank (35x12.50's from 8psi to 30), a season of wheeling can get expensive.
My plan for the FJ60 is to run a York OBA with aux tank for the primary system with the CO2 for redundancy. I am currently running Lockrights but plan to eventually replace them with ARB's that will be fed by the static OBA. I also have planned to keep one of the small MV50 compressors in the rig as a secondary backup, as they are cheap and have proven to be money well spent by multiple members of our club.
It seems that youve made your decision to use CO2, a good one for sure, but you might still consider a York based OBA setup for your rig. I'll have about $150 into mine when all is said and done, but I can fab my own brackets and whatnots. If you can fab or have a good friend who can fab, there's no reason you shouldn't be able to do the same.
My plan for the FJ60 is to run a York OBA with aux tank for the primary system with the CO2 for redundancy. I am currently running Lockrights but plan to eventually replace them with ARB's that will be fed by the static OBA. I also have planned to keep one of the small MV50 compressors in the rig as a secondary backup, as they are cheap and have proven to be money well spent by multiple members of our club.
It seems that youve made your decision to use CO2, a good one for sure, but you might still consider a York based OBA setup for your rig. I'll have about $150 into mine when all is said and done, but I can fab my own brackets and whatnots. If you can fab or have a good friend who can fab, there's no reason you shouldn't be able to do the same.
crawler#976
Expedition Leader
I've used three different systems for airing up tires.
2001: I bought a 20lb CO2 tank and used the Nitrogen regulator from my MIG welder. The regulator I bought was not specifically designed for CO2. It worked fine in the summer months, but froze solid in the winter. Initial cost was $110.00 for the tank, and it would refill approx 30 tire from trail pressure (4 to 6 PSI) to street pressure (22 to 25 PSI) at an average cost for the CO2 of $0.60 per tire.
What did I learn? Regulators must be rated for CO2 use.
2002: Since the regulator was made for Nitrogen, I tried Nitrogen. Worked fine, but had a very limited capacity for the cost. A tank roughly the same size as the 20Lb CO2 cylinder would only air up 8 tires. That averaged out to almost $2.00 PER TIRE!!!
What did I learn? Nitrogen is a dry compressed gas and doesn't have anywhere near the cubic feet of gas capacity that a similar sized tank of CO2 does. It does not freeze regulators. One huge advantage to Nitrogen is it's use for charging coil-over shocks or other emulsion shocks. The current trend in buggy building is the Air Shock, and Nitrogen is used to change the shock rate in those too. The extreme pressures in the tank are skeeery - it's a serious hazard in a roll...
Still in 2002: Sold the nitrogen setup and bought a CO2 regulator for the MIG and used it for my second CO2 setup. Worked great - Even tho the regulator and hose got frosty, it always worked properly. Nitrogen makes for a nicer weld, but CO2 is OK...
What did I learn? It still cost me $0.60 a tire, and over a 5 year period of using 2 or 3 tanks of CO2 a year, I spent enough to pay for a nice compressor.
2005: Bought a ViAir 400P to use in our two Tacos. At $229.00 it was kinda spendy, but provided reasonably fast air ups. It takes approx 8 minutes to do 4 tires on the Tacos.
What did I learn? That sucker gets HOT - kinda the opposite of the CO2 system!
2007: Sold the CO2 system, bought another (Q-Maxx) portable for the '05 Taco. Still using the ViAir in the '98 Taco. It's been used perhaps 30 times in the last two years, and when I'm on a trail ride, it usually does my tires plus anyone else in the group that doesn't have a air source. It's been very dependable, and has provided "free" air since it's initial purchase.
What did I learn? I like all three setups for different reasons, but for my needs at this time, the medium CFM compressor works fine. If I had to add one thing to my setup, it would be a storage tank that could provide enough volume/pressure to reseat a bead. Since I'm no longer doing the extreme wheelin' that caused bead failures, it's not been an issue I've had to overcome (yet).
Mark
2001: I bought a 20lb CO2 tank and used the Nitrogen regulator from my MIG welder. The regulator I bought was not specifically designed for CO2. It worked fine in the summer months, but froze solid in the winter. Initial cost was $110.00 for the tank, and it would refill approx 30 tire from trail pressure (4 to 6 PSI) to street pressure (22 to 25 PSI) at an average cost for the CO2 of $0.60 per tire.
What did I learn? Regulators must be rated for CO2 use.
2002: Since the regulator was made for Nitrogen, I tried Nitrogen. Worked fine, but had a very limited capacity for the cost. A tank roughly the same size as the 20Lb CO2 cylinder would only air up 8 tires. That averaged out to almost $2.00 PER TIRE!!!
What did I learn? Nitrogen is a dry compressed gas and doesn't have anywhere near the cubic feet of gas capacity that a similar sized tank of CO2 does. It does not freeze regulators. One huge advantage to Nitrogen is it's use for charging coil-over shocks or other emulsion shocks. The current trend in buggy building is the Air Shock, and Nitrogen is used to change the shock rate in those too. The extreme pressures in the tank are skeeery - it's a serious hazard in a roll...
Still in 2002: Sold the nitrogen setup and bought a CO2 regulator for the MIG and used it for my second CO2 setup. Worked great - Even tho the regulator and hose got frosty, it always worked properly. Nitrogen makes for a nicer weld, but CO2 is OK...
What did I learn? It still cost me $0.60 a tire, and over a 5 year period of using 2 or 3 tanks of CO2 a year, I spent enough to pay for a nice compressor.
2005: Bought a ViAir 400P to use in our two Tacos. At $229.00 it was kinda spendy, but provided reasonably fast air ups. It takes approx 8 minutes to do 4 tires on the Tacos.
What did I learn? That sucker gets HOT - kinda the opposite of the CO2 system!
2007: Sold the CO2 system, bought another (Q-Maxx) portable for the '05 Taco. Still using the ViAir in the '98 Taco. It's been used perhaps 30 times in the last two years, and when I'm on a trail ride, it usually does my tires plus anyone else in the group that doesn't have a air source. It's been very dependable, and has provided "free" air since it's initial purchase.
What did I learn? I like all three setups for different reasons, but for my needs at this time, the medium CFM compressor works fine. If I had to add one thing to my setup, it would be a storage tank that could provide enough volume/pressure to reseat a bead. Since I'm no longer doing the extreme wheelin' that caused bead failures, it's not been an issue I've had to overcome (yet).
Mark