Gas in tires

[megz]

Avagadro's number 6.03*10^14 or was it 6.13*10^14 I think.

Yes but is it not pheasible to say a lighter gas would constantly be on the inside of the tyre as it has less momentum than a heavier gas the heavier gas would be thrown toward the surface of the tyre. But if the specific heat capacity of the heavier gas is less favourable than the lighter one this could create problems would it not.

For arguments sake, they're using Radon and Nitrogen

before you go saying that Radon is rare, it's found practically every low lying area just above ground level in trace amounts. ESPECIALLY in Uranium mines.

[Ciro Pabón]

Almost: 6.022*10^23, that is, 602.200.000.000.000.000.000.000

The specific heat is different, but the difference between nitrogen and air is negligible, as posted before.

Of course, if that was the reasoning behind gas use, ss_collins wouldn't have argued that "nobody has come close to the real reason" to use some gas inside the tires: we've already commented on that possibility.

In this thread we had a talk about helium and its weight and it was suggested internal friction between the gas and the rotating tire: A weighty subject

Another reason (that I'm making up on the fly) could be the lack of reaction between the compound and the gas (if inert), but I've never heard of tyres desintegrating from within.

Of course, the gas could be affected by temperature in some other way: for example, when the tire cools, the water vapour could condense (it's pressurized) and the water could "slosh" inside the tire. It's this, or the global warming, as syguy suggests, I'm out of ideas...

[checkered]

Now here's a

bunch of things to consider: Ferrari's new tyre gas; post by "jig" - link, F1 tech discussion, Speed Forums. The post deals with a range of issues such as water vapour, the significance of pressure changes, comparisons between gases, compression waves in tyres, adiabatic heating and relative heat capacities. To make use of such phenomena requires a tremendous modelling effort, at least I'd presume so. Anyone seen any CFD/heat transfer visualisations about what goes on inside a tyre lately?

[ss_collins]

No but thats very interesting and I'd not considered that - this is why I love F1T when we are trying to fathom something it leads to very interesting discussions. I know what the gas is, how it works but theres more to it which in a couple of weeks we will all be discussing here.

[megz]

Can't think of appropriate reasoning, but its not Iodine is it?

[Ciro Pabón]

I read the post checkered referred to. Allow me to play devil's advocate:

The post points to water vapor pressure: I think this is improbable, as tyres are preheated well over boiling point before being used. I don't know what's the boling point of water when pressurized in a tyre (I wait for corrections), but I guess the working temperature range of a tyre never falls enough for water to condense inside (unless in park fermé, after the race).

Besides, nitrogen is notoriously inert at standard conditions, but when mixed with water and oxygen and some heat, it produces nitric acid, a fact I don't like when putting it inside a tyre that exists in the real world, not in Formulaoneland.

About the adiabatic waves, well... I'm pretty sure heat is produced by deformation of rubber. The small volume changes that the tyre undergoes must be relatively small, unless the car is bumping on the air and falling again, like in kerbs. Even then, if the "patch" disappears because the tyre has no load, I bet the change in area is less than 10%.

I fail to see why the volume of the tyre is different in straights and curves, unless centrifugal action is taken in account: if the tyre flexes sideways, the "oval" of the tyre, that is, its section, probably does not change its area dramatically.

I do not understand if the author of the post thinks that air inside the tyre compresses and flexes the same way rubber does... gas is not rigid and does not "flex" with each revolution.

All this criticism holds unless the gas rotates with the tyre (probable) and receives a compression wave every time it "passes by" the patch. Really?

[syguy]

Here’s another thought.

My guess is that the new(ish) wheel covers that Ferarri are using are causing higher temperatures around the brake disks and wheels.

The turbulent air in and around the wheel without a cover was able to dissipate (convect) the conductive heat that accumulated in the wheel from contact with the brake disk.

What’s the betting that Ferarri found degraded brake performance with the wheel covers?

Now how to compensate for this increased heat?

You could rely on the gas inside the tire to absorb this heat. So you go looking for a gas that absorbs and dissipates heat quickly, i.e., it has a low specific heat capacity.

Here are some constant pressure specific heat capacities:

N2 - 1.03
CO2 - 0.86
Argon - 0.52

Units kJ/kg K

Find more specific heat capacity data at http://www.engineeringtoolbox.com/spesi ... d_159.html

Now which gases would you choose?

Exactly. Argon if you can get it, and if not, then CO2.

I think it’s the same reasoning that favors Argon over CO2 over N2 for welding thin metal.

[checkered]

I'd guess the

water "vapor" thing has little to nothing to do with Formula One tyres and I think even "jig" kinda seemed to recognise that much. He also speculates that most of the tyre heat is dispersed via the hub of the wheel; seems implausible unless he meant only the heat of the gas and not the structure of the tyre.

The deformation of the ply, bead and rubber of the tyre, as well as the friction do generate much of the heat. How could they not?
I wonder, though, if the differences in the specific heat capacities of the structure of the tyre and the gases within are great enough for this to have an effect of some kind? There are also issues to do with transfer of heat here that, on the surface of it, might warrant attention.

I'm not saying I've yet managed to follow the train of thought of the poster all the way through. But I was interested, since these things have to be considered in all sorts of processes (like engines) where thermodynamic efficiency is still quite poor - compared to an ideal situation.

Edit: Oh, syguy already took some of those thoughts a bit further. As I noted before, both Ferrari and Toyota use BBS wheels and -covers, so perhaps the internal wheel structure is engineered to convey as much of the braking heat into the tyre gas as possible (very thin patches with large conductive areas?) ...

[syguy]

perhaps the internal wheel structure is engineered to convey as much of the braking heat into the tyre gas as possible

Brings to mind the cooling passages through exhaust turbine blades. I wonder if it would be feasible to have passages within the wheel structure to maximize the area of gas in contact with the hot metal.

Or what if extra cooling vanes (heat sinks) were added to the wheel rim to increase the surface area - these vanes could also act as baffles disturbing the surface flow to encourage more mixing (turbulence) and leading to more efficient heat transfer within the wheel gas during acceleration and deceleration.

[Ciro Pabón]

Well, if you use the gas to refrigerate the tyre from the inside, then you want a gas with a high termal transfer rate. Any bets?

If that's the case, you'd expect fins on the inside of the hub, as Syguy mentions, to work as the heat sump in your PC chip. Hey, that could be a good idea. On the other hand, you do not want paddles inside the tyre, thus creating a second volume of air that causes drag.

[checkered]

The secret seems to

be out and about. In short, 50 per cent HFC R404 A and 50 per cent CO2. Kudos to Racecar Engineering and our resident reporter Sam Collins for braking this highly interesting story. There's a highly abridged version available online, at SpeedTV's website: SPEEDtv.com EXCLUSIVE: F1, Racecar Engineering--Secrets of the F2007.


Image linked from SpeedTV website

[megz]

Well weren't we sort of half close haha, very interesting.

[persovik]

I wouldn't be surprised if these gasses were to be outlawed in the regulations due to their global warming effect.

[kimi]

can anybody explain me how this HRA 404 A gas helps keeps the tyre cooler and also controls the wear.i read the article but still need a detail analysis of it..
thank you..

[Belatti]

I have heard about a gas containing Magnesium that has the "weird" property of not increasing its pressure when heated.

I find it hard to believe and I guess the person who told me that was not well informed at all, maybe he thinks that Gay Lussac was a famous homo writer or something.

Anyways, he also told me the gas costed 300Usd per tyre set pumped and that it was used by some top level teams in a local series here in Argentina.