h a l f b a k e r yQuis custodiet the custard?
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when running F1 racing cars air in the tyres heats up with the ever increasing tyre temp. High the temp of the tyre higher the temp of the air in the tyre and the pressure changes affecting handling. why not use nitrogen in the tyres as this is not affected by temperature as much a air.
I think..............
I
know air is 78% nitrogen anyway but it does make a difference.
physlink.com
http://www.physlink...skExperts/ae192.cfm
Nitrogen is used in airplane tires. [carsten, Nov 14 2004]
Nascar© Winston Cup TRUE TIRE HISTORY
http://www.raceline...om/tirehistory.html
Wheel and tire characteristics for NASCAR Winston Cup racing. [ed, Jun 28 2005]
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You didn't take physics in school yet, huh? |
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DrCurry: Heh, great minds think alike. There are certainly substances whose d(PV/T)/dT is greater than that of air (which I think is pretty nearly zero), but I can't think of any which are less in the operating ranges for typical racing tires. |
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A more interesting concept might be to have a relief valve to regulate tire pressure. Unfortunately, while the temperature of the air in a tire should normally increase during a race and not decrease until the tire is being removed and replaced, a red flag/restart may necessitate having a means of re-inflating tires if they cool down while the red-flag condition is being cleared. |
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¯supercat: I believe that it is not advisable to release air from a hot tire. Common sense is that lowering the pressure in the tire will cause in to run cooler, but what happens is that the hot tire is compressed more with less buoyant air within, and tread separation risks increase with the heat of the tire. Just wanting to defuse any speculation about that practice. :-) |
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<humor>
The US used to produce the world's best tires because they were filled with the most oxygen-depleted air on the planet. With the clean air that abounds since the decline of the American Rust Belt, and the advancement to tubeless tires, all tires are the same. |
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Fill em with CO like when they were conceived.
</humor> |
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In F1 years ago, our tire pressure controllers bled air off as necessary to maintain pressure while preheating. It would not be advisable to do this while on the circuit due to changes in vehicle dynamics. |
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Typical straight away temps ran 180 deg F, cornering temps peaked around 250 deg F. Pressure was only measured statically, but I would expect dynamic variation. That was 10 years ago, and I'm sure a lot has changed. |
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The "ideal gas law" demonstrates to us the fact that the volume of a gas at a constant pressure is directly proportional to the temperature of the gas within its gaseous range. This would mean that any element which attains a gaseous state at a temperature below that of oxygen would gain less pressure as a result of a given increase in temperature (for the sake of example, we'll consider a temperature increase from 80deg F to 180deg F, or equally, an increase from 299.81K to 355.37K). Oxygen becomes a gas at 90.2K (Kelvin), increasing in volume (or increasing in pressure within a fixed volume) by a factor of .209, Nitrogen becomes a gas at 77.36K, increasing by a factor of .199, Helium becomes a gas at 4.22K (the lowest temperature for gaseous form in known elements), increasing by a factor of .158. Relating to the proposed situation at hand, logic would dictate that Nitrogen is superior to common air. Helium would be superior to either of the two. |
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huh? how does boiling point have anything to do with volume as a gas? |
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True, volume at constant pressure varies directly with temperature. This is NOT dependent on when the gas will turn to liquid. The v/t plot just becomes invalid at the boiling point. For whatever gas you use, the function is nearly identical. (yes, there are -small- differences that begin to matter in very high temperature and pressure environments, but a car tire, F1 or otherwise, does not fall into that range.) |
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All this "nitrogen in your tires will improve your mileage" advertising is pure baloney. |
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Now, an N2 molecule is larger than some of the molecules in air, and therefore will not leak as quickly through microscopic perforations. Also, using straight compressed shop air is likely to introduce liquid water and some other contaminants that may be harmful to the tire or wheel. If you live in cold climates, you may wind up with liquid water condensed and frozen inside your tires in the morning, which could result in an imbalance. Growing up in the Northwest US, I have noticed unbalanced tires in the morning. |
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Using one gas over another because you think that there will be less thermal pressure variance is just ignorance. |
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Helium would be good because it would have less inertia :)
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[Freefall], hmm, I never thought about ice within tires before but I can remember what seemed to out of balance tire on cold mornings. I recall being told that it was a temporary out-of-round condition stemming from the flattening of cold-stiffened tire belts. |
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Sounds safer than filling them with
hydrogen I guess. |
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Hydrogen and helium are the worst: they change in pressure most when heated. Air/nitrogen/oxygen are pretty good I think (and similar), but I doubt any of them are optimum.
Croissant for the great idea, especially as I suspect that using a gas that has lower pressure-temperature relations would heat tyres less in use. |
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Baked. Nitrogen has been used in some racing circuits, including NASCAR, for quite some time. Linky. |
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Nitrogen is used in Formula 1 tyres for pretty much this reason. It has a more predictable response to temperature changes. |
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