A weighty subject.

Ciro Pabón · Post 18 May 2006, 02:42

Tomba wrote:First of all, I don't think the rotational mass reduction is important since we are talking about gases here...
...
- Another reason for using N is that O is that there is 3 times less leakage. I'm not sure how Helium might do here though

Well, the surface of the wheel is rotating at 350 kph, same speed as the car. Drag works inside the wheel as well as outside. Any difference in rotational speed between the tire and the gas inside is expressed as drag. Given the big surface of an F1 tire, the small volume of gas inside and the drag coefficient, I am pretty sure that the gas acquires the rotational speed of the tire really fast. Even while the air is rotating slower than the tire, it produces drag, so it is acting all the time. You could do the math, I am sure, or you could simulate it. Hey! New idea: do the aero design of the interior of the wheel...

Seriously, I am also pretty sure that the "inside drag" effect is probably worse than to have the air rotating at the same speed of the tire, because drag effects are proportional to the cube of the velocity, while mass effects are proportional to the square of the velocity, so I do not know if some kind of "inner paddles" could help here, or maybe some kind of really light chambers.

The permeation rates of hydrogen, oxygen and nitrogen in rubber on a vacuum (you really can find anything on the Web) are 2.2, 2.0 and 0.53 (all expressed in 10^-8 square cm/sec). This means than on a rubber container, oxygen is 4 times more prone to diffusion than nytrogen and helium is just marginally (10%) harder to contain than oxygen. This is an approximation, as I understand that this is measured with vacuum at the other "side" of the rubber being tested.

Tom wrote:If an element lighter than air is added to an object of a certain mass (say 5kgs) surely that mass decreases?

No, Tom. It increases its mass in the same amount as the mass of the lighter than air element. You get buoyancy because of Archimedes effect (eureka!), but this is a different thing: it is because you are replacing air with something lighter and the air "around" pushes it with the same force as if this lighter element were air.

This reminds me of an old "joke": what weights more, a pound of lead or a pound of feathers? A lot of people, instinctively, answers that a pound of lead...

Sknguy- · Post 18 May 2006, 03:14

I thought Helium was used in tyres to limit thermal expansion/tyre expansion?

Ciro Pabón · Post 23 May 2006, 10:39

Reca pointed out in a different thread that air density is 0.0012 g/cm3, a tenth of what I used. Thus, the weight of air in all the tires is a mere 840 grams. This gaves you very little mass advantage and a really small lift if you substitute for helium, then.

mcdenife · Post 23 May 2006, 11:15

ciro! ciro!! ciro!!!
Keep 'em coming..just love ur posts.....muahahaha ....ad infinitum

Spencifer_Murphy · Post 24 May 2006, 12:04

Its probably illegal to do but it would be a good idea to fill the tyres with some helium (not all helium, the tyres would produce lift!) but lets say enough helium to make their apparent weight be near to zero. Thereby decreasing the unsprung mass of the car.

Would this work or am mistaken on this matter? I think it would work, except that the rules make this sort of practice illegal (I think).

DaveKillens · Post 24 May 2006, 15:07

If you replace the nitrogen inside the tires with helium, or hydrogen, the weight gain would be neglibable. You would be lucky if you could get one gram.

Ciro Pabón · Post 24 May 2006, 15:54

DaveKillens wrote:If you replace the nitrogen inside the tires with helium, or hydrogen, the weight gain would be neglibable. You would be lucky if you could get one gram.

The nice thing about these forums is that you can write anything you want. Anyway, nobody is going to read it!

Spencifer_Murphy · Post 25 May 2006, 11:55

JPM hasn´t delivered anything to any team, he did nothing for Williams, he hasn´t done anything for McLaren, and he won´t.

Oooops! lol, THAT might be why they dont bother. Then again....say they get one gram in each tyre...thats 4grams in total. And even tho its a tiny tiny tiny margin (yup THAT tiny lol) isnt it still worth it? I mean its not like its hard to do.

Tom · Post 06 Jun 2006, 11:40

Found this on wikipedia and obviously has huge advanatages, a piece the size of a man can support a car yet weighs just 1Kg! despite this it sounds fragile, I was wondering if F1 uses this material and if not, why not? surely even is it shatters if you hit it hard it could be used. Also it is increadably conductive with heat.

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

Jersey Tom · Post 06 Jun 2006, 17:14

Not worth it. Would be a pain to try to make things airtight. The greatest weight reduction and bouyancy gain would be to vacuum components, and even then, you'd get maybe a pound of lift from a large vacuumed volume (rho*g*volume, and rho is damn small).

Aerogel is slick stuff. It has a high compressive strength, yes. Other than that, not very structural. Would be cool to use as an insulator though. Might have to keep that in mind..

Jersey Tom · Post 06 Jun 2006, 17:32

Oh and I might add.. that wikipedia article makes it sound impressive by saying aerogels can support 2 000 times their own weight. And that's cool, especially for the light ghostly thing that it is, but an inch cube of the right aluminum alloy will support 930 000 times its own weight.

Tom · Post 06 Jun 2006, 20:21

Still seems like fantastic stuff this aerogel. Sounds very brittle though. The disadvantage of the aluminium alloy is that its far heavier. I'd like to think I'm on to something with this ultra-light heat conductor though (lighter than the gold they use I'm sure and possibly as conductive) and it could possibly be used to support unimportant components that don't matter when you crash. Just thought it interesting.

Jersey Tom · Post 06 Jun 2006, 23:04

Heat insulator I think you mean..

Aluminum is more dense, yea, but its specific strength is so absurdly higher you wind up using less of it, both by mass and by volume. For example, the wikipedia thing talking about holding up a heavy car (say 2000kg) with 1kg of aerogel... you could do the same with a wrought piece of aluminum that weighs 2 grams!! Its absurd how strong engineering materials are. You could hang a car by a 5/16"-24 bolt (M8x1.25)

The other question with aerogel is how formable it is, how machinable, if you can cast it in anything but billet or sheet..

I don't see any use of aerogel in a car other than as an insulator. Cutting edge engineering as seen in top end motorsports, aerospace, and defense is often all about finding materials with super high specific strength or stiffness.

Tom · Post 06 Jun 2006, 23:13

Sorry, I of course meant insulator. I think it is workable because aircraft have them in the cabin area to keep inside heat up.

NickT · Post 07 Jun 2006, 11:49

Actually...

Commercial manufacture of aerogel 'blankets' began around the year 2000. An aerogel blanket is a composite of silica aerogel and fibrous reinforcement that turns the brittle aerogel into a durable, flexible material.

It could quite easily be used to replace the honeycomb in composite structures.