Tire fill: Something different in the air

[ecomodded]

I think he is expected much more then a .5 psi difference,
That .5 psi measurement shows there is little to no change.
Should be fine using a psi gauge with 0.5 psi increments as any psi change that size and smaller can be classified as no change.

[NeilBlanchard]

As has probably already been mentioned, air is ~78% nitrogen, so the remaining ~22% has to be pretty huge effect. Most of the 22% is oxygen - which is on the outside of the tire, anyway.

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

[bryn]

sure, it just seems pointless to go through the procedure and not get any data. 0.01 - 0.99 2.48% change at 40 psi. could be significant. with the cost of the gasses being used, why not buy a better gauge and have some data that is usable.

[JRMichler]

Originally Posted by oil pan 4

I thought there would be a much wider pressure swing with the R-404a mixture, because of the way refigerants act in a refrigeration system.

If you cooled a tire filled with 100% R-404a down to -20 deg F, the pressure would drop to 31 PSIA, or 16.5 PSI on the tire gauge because some of the R-404a would condense to a liquid.

If the tire is filled with 100% R-404a until the R-404a is a mixture of gas and liquid, then the pressure will be the saturation pressure listed in the refrigerant data sheet. That would be 150 PSIG at 70 deg F and 450 PSIG at 150 deg F.

I would expect gases with larger molecules, such as CO2 and R-404a, to have lower lead rates.

[oil pan 4]

[QUOTE=bryn;430109]

Originally Posted by oil pan 4

My difference between the N2 tire test and the gas mix test was about a half PSI dIfference between the 2, that difference was likely caused by even heating of the N2 tire versus the uneven heating of the gas mix tire.

you have a pressure gauge accurate to 0.5 psi and you are using a recorded difference of 0.5 psi as significant data?

so... um... well good luck with the research.

The gauge is graduated in half psi increments. The gauge is dead on other wise.
I know this because I checked it against a master gauge calibrated in 1/4 psi increments.
Unfortunately I do not have a climate controlled lab with double precision instruments, but my measuring equipment is a lot better than what most people have.

Alot of people have tire pressure indicating tools that cant even detect a pressure change in their tires after driving. This is partof the reason people believe nitrogen doesn't change pressure in a tire as it heats up.

[oil pan 4]

Originally Posted by bryn

sure, it just seems pointless to go through the procedure and not get any data. 0.01 - 0.99 2.48% change at 40 psi. could be significant. with the cost of the gasses being used, why not buy a better gauge and have some data that is usable.

I am not developing a temperature pressure chart for this gas mixture. All I need to beable to do is detect wild pressure swings and accelerated leak down for CO2 and helium.

[BrandonMods]

There's no reason any of those gases would pull any measurable heat out of your tires any more than the nitrogen would, and it also seems kind of irresponsible to test your theory on the road with no idea how those gases react with the tire material under heat & load, while pulling trailer loads of welding equipment.

Argon and Helium should not react at all with the tire material, they are both ideal gases of group 8 on the periodic table with full valencies meaning they do not react unless under extreme conditions, (I doubt the inside of a tire at a higher temperature is a concern). If the CO2 were to react the only reaction it would undergo is an oxidation reaction where it would gain another oxygen and become carbonate, again unlikely given the conditions and the carbonate would not react with the tire material as it would be a very weak base. The refrigerant might react, it depends on what its chemical make-up is.

[oil pan 4]

Originally Posted by BrandonMods

There's no reason any of those gases would pull any measurable heat out of your tires any more than the nitrogen would,

Oh really?

Originally Posted by oil pan 4

The 2 main ingredients of R-404a are kind of cool.
R-143, the main ingredient (aka canned air) has some interesting inferred absorbing properties.
R-125, HFC-125 is kind of neat too, in its other life its used for fire suppression, it pulls heat away from burning material so fast it shuts down the combustion process, in addition to suffocating the fire. Not a bad material to have inside your tire.
R-134a, (only 4% of the blend) is there to make the other 2 play nice when inside a heat pumping system.

So R-125 sounds like the best thing, but I would be willing [to bet a pure or high % mix] has already been tried by its self and not favored.

I noticed they don't use nitorgen in fire suppression systems.

Originally Posted by BrandonMods

and it also seems kind of irresponsible to test your theory on the road with no idea how those gases react with the tire material under heat & load, while pulling trailer loads of welding equipment.

Argon and Helium should not react at all with the tire material, they are both ideal gases of group 8 on the periodic table with full valencies meaning they do not react unless under extreme conditions, (I doubt the inside of a tire at a higher temperature is a concern). If the CO2 were to react the only reaction it would undergo is an oxidation reaction where it would gain another oxygen and become carbonate, again unlikely given the conditions and the carbonate would not react with the tire material as it would be a very weak base. The refrigerant might react, it depends on what its chemical make-up is.

Well I don't think there will be any on road helium tests. I am expecting helium to leak out really fast.

Did you read any of the other posts?

Originally Posted by oil pan 4

I know the gases I am going to test have been used on road [and on the race] track before.
A company called stayfill sells a fluorocarbon to fill vehicle tires, likely HFC-125 (fire suppressant), R-134a, or "canned air" aka R-143.

All the likely canidates used in stayfill are found in R-404a.
My money is on "canned air" (R-143a).
CO2 is widely used to fill tires on motor cycles, according to stayfill CO2 is the main bottled product they compete against.
Street legal off road and jeep guys often use CO2 to fill their tires after going off road before the drive home.
CO2 is very stabile.

Originally Posted by oil pan 4

An R-404a mixture was used in F1.

These numbered "R" chemicals are stabile to some where in excess of 400'F. At those temperatures the tires is likely on fire already, then at that point would you rather have a tire filled with air, or fire suppressant?

And why does everyone assume this is going to be a welding trailer. I live in the ghetto. The trailer will not fit in the garage and it wont fit in the back yard. If I left welding equipment out side on the trailer crack heads would decend on my valuables like roachs on a chinese restraunt after hours. Anything they couldn't steal, like something bolted to the trailer would have leads cut off or be broken from attempts to pry or hammer it free.
Or they would just steal the trailer, contents and all.

The heaviest load I plan to carry on this trailer is water tanks filled with water. Or stranded electric vehicles.

I weighed my mostly finished tandem axle trailer. It weighed in at 1720lb with no wood decking or tool boxes.

[CapriRacer]

Just so we are all on the same page:

The point of the test is to simulate the heat buildup in a tire and see how that impacts the pressure buildup. Oilpan4 says he doesn't expect much, but he never explained why. I suspect it is because the Ideal Gas Law is a pretty good way to predict pressure buildup.

But the one thing that jumped out at me when I reviewed the posts in this thread was that using the sun to simulate the heat buildup in a tire was somewhat non-analogous. That is, the heat in the air chamber of a tire comes from the hysteretic properties of the tire components (mostly the rubber) and that is not uniform around the perimeter of the tire. The tread will generate more heat than the sidewalls because the tread has much more material that is being moved.

And I think the point of using a different gas in a tire (ala F1) was to move that heat away from the tread area to an area where it could dissipate - like the sidewall. The net effect would be to slow the heat buildup internally to the tire, and to speed the cooling down. In F1, this would help preserve the tires, plus allow the driver to push for a longer period, then have less time to cool the tires down before having another go at fast laps.

[oil pan 4]

Yes heating the tire in the sun with the help of a sheet of aluminum was the next best thing to driving it on road.

This gas mixture in the tire at normal tire pressure and temperature will act a lot more like an ideal gas than the working fluid all by its self in a charge bottle.