A weighty subject.

[Tom]

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

If this is true would it be possible for a team to introduce such an element to the car during a pit stop decreasing the cars overall mass by maybe 10Kgs and allowing it to drain slowly so by the weight in it is still 600Kgs?

Thinking a long way out of the box here but I was just wondering the plausability of my idea?

[RacingManiac]

lighter than air as in less dense? It still has mass though and 600kg is mass, and acceleration is affected by mass.

[kilcoo316]

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

If this is true would it be possible for a team to introduce such an element to the car during a pit stop decreasing the cars overall mass by maybe 10Kgs and allowing it to drain slowly so by the weight in it is still 600Kgs?

Thinking a long way out of the box here but I was just wondering the plausability of my idea?

No, the mass would increase, but the weight would decrease (due to bouyancy from the helium [for instance]).

It would reduce the downward force from the car to the track, but increase (probably immeasurably to be fair) the mass of the car and thus the lateral force on the tyres in a corner.

So it would be the wrong thing to do.


Uhhhh - I think Anyone care to put me right?

[Steven]

The lightest usable material you could use is hydrogen (which is highly flammable) or helium (quite safe). Even better, you could warm these gasses up so they have a lower density, or basically take nothing and thus a vacuum.

Air has a density of around 0.012 g/cm³ at 20°C and 1013 hPa.
Helium has a density of 0.00008 g/cm³ at the same normal conditions.

Suppose you take 10l Helium in the car. You can see it adds marginal weight to the car, but it creates a slight upward force since it's less dense than air. The upward force (rho*g*V) would be less than 0.0000000000011 N, therefore also being only good for a marginal weight decrease (F = m*g)

So it's just not practically possible. Secondly, it only generated an upward force, so it does not increase braking performance (which is horizontal accelleration/decelleration) and it basically reduces the effect of downforce.

@kilcoo: yes mass would increase if that gas was an extra and not replacing air, and also idd because of the upward force weight decreases marginally

[walter]

yes all of this is true, but... what if that helium was IN PLACE OF AIR say in the nosecone... it would be a slight decreace in mass, if you considered the volume and the containment aparatus.

the fact is these cars are so tight everywhere that there is litttle if any gain in replacing air with a lighter element. it would only add extra cmplexity. and i doubt such would fly with FIA inspectors well.

[Steven]

Well a modern F1 nosecone can contain maybe 20l or something, I don't think it's much more. And even if so, that upward force is going to be very very few (even not good for a mg) so there's no point I think.

Also, teams put ballast in the tips of the nosecones to influence car balance and correspond to the minimum 600kg of a car. I can't really think of a place in the car where it is beneficial to add helium.

[RacingManiac]

think about the weight you may add to make those parts of car pressure tight....

[dumrick]

You would always had mass in that case and mass is what creates inertia in a car.
However, in the places filled usually with air you would get less mass, but having to make it air-thight, why not pumping air out as an alternative (creating negative relative pressure)? The result would be the same... and unnoticeable, anyway, I guess.

[Bender]

You could always add hydrogen to the engine, that will improve acceleration and fuel economy...and possibly create fireworks

[wowf1]

Well if you were going to do it, you'd seal off sections inside the car, and have vacuums like Tomba suggested. But seeing as air's density is 1.2kg/m^3 you'd need a large volume for any noticeable effect. I doubt there is even 1m^3 of free volume in the car, so you wouldn't even save 1kg. I realise F1 teams are striving to save grammes, but I can't see creating vacuums in the car to be a viable method.

[Tom]

Well vacums are how wings work (in a bizarre complex manner involving pressure) so is there anyway we could use this to help ground effects? All good ideas come from idiotic ones.

[vyselegend]

I can't really think of a place in the car where it is beneficial to add helium.

The idea of filling the tyres with helium has been proposed in another topic (don't remember which one) in the purpose to help braking, acceleration and perhaps decreasing inertia. Then someone pointed out that helium (and to an extent hydrogen) is a very small element, and so there is no way to avoid progressive escape of those atoms. It was about tyres, but I think the same is true for all pieces of bodywork. To keep helium inside the car, you would have to fill it in some heavy container of dense material, which would totally cancell all gains in term of weight.

[m3_lover]

I know they do not use standard air in the tyres of F1 cars, is it helium or nitorgen in the tires>?

[Ciro Pabón]

Well vacums are how wings work (in a bizarre complex manner involving pressure) so is there anyway we could use this to help ground effects? All good ideas come from idiotic ones.

Here you have a ground effect based on your idea: notice how far away is the ground! This surely qualify as an effect. As Tomba points out, the braking and accelerating grip is totally screwed:



Of course, the "flexi-wing problem" is bigger.

I have an hour to spare, waiting for a mail so, again, this is a long post, sorry.

Now, seriously: there is a part of the car that is a sure candidate for your idea. You know, as some members told us, it is difficult to find a part of the chassis or the structure to fill, which has to be cleverly designed to be concealed, sealed (no pun intended) and is probably filled with this aluminium honeycomb they use. This left us with... the tires. Have you noticed they are hollow? I did. They are full of air! They are even substituted at pit stops! Muahahahahaha!

This leaves us with the problem of the last set of tires and the uncorruptible FIA stewards... mmmmm, maybe a cousin I have in Medellín can fix even that last one. Well, at least, sticking to the theory only, you can use this for the first and second stints on a two stops strategy. But if you are ahead at third stint, after Imola and the such, you already know what will happen! Double muahahaha!

The air in the tires not only has to be carried, so it robs you of momentum: it also rotates. Any decrease in this mass gives you a better acceleration,

- not only because you need less momentum, (as you point out)
- but because you are diminishing the rotating mass on the tires, which is another energy that the engine has to give you, (as I point out), and finally,
- because you are diminishing your unsprung mass, (as I've heard this is a mantra in this forum and it sounds smart).

I guess other members can find additional reasons of why the wheel is a special place to "shave" some weight, from less solid driving axles to smaller brakes to any other thing. You know those guys...

There is a fourth effect: some of you who might understand the giroscopic effect now can see that you are also diminishing the rotational inertia (this is a tertiary effect, I concede). If you do not know about giroscopes, skip this: it is a "nerd" effect.

Anyway, I have you bored to death to convince you that this idea affects several departments in design.

Besides, the density of the air you are substituting with, let's say, helium, is increased, because it is pressurized so Tomba's calculations have to be corrected. Unfortunately, the problem here is the Boyle's law: it states that if you use a gas with less density, like helium, you have to increase the pressure of the gas to reach the same volume, but I am not sure how much and I am getting tired. You could heat the gas, which leads to problems with the rubber. But let's not be discouraged by small things like the theory of gases... we are breaking ground!

Let's see: given that F1 tires have a maximum radius of 66 cm, a maximum width of 35.5 cm and 38 cm (front/rear), and a minimum wheel bead diameter of 32.8 cm, this left us with:

V = (2*(0.355) + 2*(0.38 ))*pi*(0.66-0.328)^2
V = 0.509 m3

This is half a cubic meter or 509 liters. Looks good. The tires are inflated at 1.4 bar (or at least they are measured at this pressure, feel free to correct me... if you dare ). Using Tomba figures for density and pressure and assuming 20 centigrades (gross underestimate), this gives us a weight of air in the tires that is:

W = (0.012-0.00008) *1.4 bar/1.013 bar * 1000000 cm3/m3 * 0.509 m
W = 8.4 kg

Not bad. This is 8.4/600 * 100 = 1.4% of the total weight of the car, in the unsprung, rotational mass. Big figure. This could be substituted by around 10 liters of extra-fuel, good for 2 or 3 laps. It could shave, once you have used this fuel, on a typical 1m 30s lap almost 2.5 seconds, if times were proportional to weight, which, as I have explained to the point of brain pain, is probably an underestimate.

But Tom, this is the sad part, we are not that smart. Or maybe we are, but we are not alone. At least in drag racing, nitrogen is used instead of air. The reason is related to the pressure increase you get when you heat the tires and the change of size of the patch, not the weight of the car, I think. While I wrote this post m3_lover already spoke of nitrogen used in F1.

Sorry, mail arrived, I'm sure you can find your own links to this use of nitrogen on race tires.

The helium idea is totally new, I think, but, as an "aficionado" I'm probably wrong. What the heck, if you speak with Ferrari (suffer, Manchild!), be sure to mention my name. Don't worry, MC, I was joking! If they hire us we can sabotage something to "compensate" for their cheating! Muahahaha!

[Steven]

Well there are a few remarks I have to make about this Helium idea in tyres. First of all, I don't think the rotational mass reduction is important since we are talking about gases here. Gas molecules move freely around and will therefore not always be at the same speed of the tyre rotation.

Second, I've been looking into the reasons why Nitrogen is supposed to be good to fill tyres and compared them with Helium:

- Nitrogen does not contain the oxygen in air, so it is not prone to flammation. Helium is a noble gas and therefore also not flammable, so very good.
- Oxygen in air oxides at higher temperatures and thereby makes the tyre rot slowly from the inside, making it reduce flexibility. Nitrogen does not contain oxygen and so does Helium. Again an interesting argument.
- 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

Finally it seems like Helium tyre fill might be a good idea. Noble gases are generally very nice stuff to work with