oxologic

Do any racers fill their tubes with helium gas or any other gas?
If they do, what are all the benefits? If they don't is it because it diffuses easily?

velocipedio

No. This would constitute cheating under UCI rules.

Moreover, given the volume, such gasses would have a negligible effect. Besides, it is very possible to build sub-6 kg bikes without resorting to such tricks using conventional technologies, hovever according to the UCI's equipment rule #1.3.019, "The weight of the bicycle cannot be less to 6.8 kilograms." So it wouldn't be legal for THAT reason.

Soberone

If you reduce the weight, with a gas, would that help up hills, maybe?. But if you haven't reduced the objects mass, or how dense the object is, you would/ or would not still have the same problem with exeleration? *scratching head* :confused:

Spire

IF you could reduce the mass on the tire (by the couple grams that helium would save, at most) that would have a larger effect than taking off the same mass from the frame because the wheel turns and inertia starts having an effect..... (Spire starts mumbling physics equations). All other effects of reducing weight remain the same.

oxologic

Is it really cheating? Since it won't really take off much weight from the bike, the bike should still be over the minimum weight.

Another thing, does the helium gas diffuse easily, you all know it from chemistry and physics classes. The same things will apply anywhere. So is it due to easy diffusion that no one uses helium to fill the tubes?

Soberone

Would you need presta valves, or schraders?

roadbuzz

Many riders fill their tubes with CO2 (carbon dioxide). I've heard that it diffuses more quickly than air.

D*Alex

Nitrogen used to be used by formula 1 racing teams, for 2 reasons:
First, it is a less reactive gas than air, so therefore, pressure doesn't change quite as much as air does when it is heated.
secondly, it is a non-oxidizer, so a tyre containing nitrogen is less likely to burn.
so they tell me.........
Of course, nitrogen is slightly heavier than air.

poululla

The 1984 US Olympic track cycling team filled their tires with helium.

Richard Cranium

I heard about the "helium" thing in 1984 too. A physicist friend maintained that due to the nature of gasses under pressure that the volumes of gas used in bicycle tires was so little as to render the difference insignificant. He claimed the reduced relative-density of helium would require a larger volume for tire stiffness.

There is very real possibility of getting heavy air from bike shops.
Air compressors in humid enviroments, and hoses that pass from one room and temperature to another room (shop) can collect moisture and pass this "wetness" into innertubes.

A good old floor pump on a dry day is the best way to inflate a tire.

I think, maybe, I don't know.....

Pat

I mole of gas at standard temperature and pressure is 22.4 liters. A mole of helium weighs 2 grams and a mole of nitrogen weights 28 grams. And a bicycle tire holds no where near a mole of gas (not even both of them). Sure they are at what? 6 atmospheres of pressure which means you multiple the volume by 6. Say you have essentially .5 moles in both tires (being generous). You get to save 12 grams.

fujimo

If you have had chemistry, CO2 (1.97g/Liter at STP) weighs more than Air (12%Oxygen, 4%CO2, 78%Nitrogen) (1.28g/Liter at STP) simply because you are adding an extra carbon atom to the already heavier than air molecule. Fill up a balloon w/air then fill a balloon w/air that you exhale and see which one hits the floor first.

Hope you understand this coming from a softmore in HS

fujimo

NOT TRUE,
Nitrogen does oxidize but it is not a component to combustion (02 + Reactant =>CO2 + Energy). Oxidizing is the ability to lose electrons, similar to ionization energy. Unless it is a noble gas (which it isn't being in group 15) it can lose electrons meaning it is an oxidizer. A tire does not burn inside, it burns from the air surrounding it. Reactivity has nothing to do with compressability. Pressure and tempurature affects all gasses the same P1V1/T1=P2V2/T2. Therefore, nitrogen or any other gas has the same compressability. If that is how you think, you mine as well fill it up with water or mercury. Nitrogen is LIGHTER than Air.

Just fill it with Hydrogen gas, it is very light but it diffuses faster since it is lighter. The lighter the gas, the faster it diffuses so CO2 diffuses slower than air. Just use Air, it is better to have the weight in the tires since that gives you momentum while spinning although that has a negative effect that is the more weight in the wheels, the harder it is to accelerate or stop.

fujimo

He2, is 8grams/mol, not 2g/mol which is the molar mass of H2

This all comes from a softmore who topped his chemistry and physics classes last year.

D*Alex

Actually, after re-examining my notes from thermodynamics ( a course which us mechanical engineers all have to take), nitrogen is slightly lighter than air (28 g/mole compared to 29.?? g/mole of dry air), BUT, air is niether noble or pure. When heated, a very small amount can react, causing a greater increase in pressure (due to the reactants having a higher total molality than the components of air originally) than would happen in a noble gas. Remember, PV=mRT is called the IDEAL gas law.

fujimo

that is only when combustion takes place but it can't happen without a reactant to burn

oxologic

Fujimo, please note that Helium exists as a monoatomic gas. It is not He2 as it is already a noble gas. Note that a noble gas has a stable electronic configuration, thus it will not react with another helium atom or any other thing for that matter. Thus, the weight of He is 4g, not 8g for He2.

Also, I also want to know who is that softmore who topped his chemistry and physics classes last year. Even someone who doesn't do that well should well know that helium is a noble gas.

fujimo

yes, I believe you are right, forgot about the octet rule

oxologic

Don't worry fujimo, it is common for people to make mistakes. Your effort to help other people in this forum is very admirable. Hope you will continue to be involved in this forum.

fujimo

do you know if there is a post concerning what cadence to select if I want to improve my leg speed for running. I'm not looking to improve my biking efficiency, I am trying to increase my running turnover rate to 252strides/min, so I am thinking of training on my bike at 150rpm. Is that a good idea for training my legs to be fast without going anaerobic?

Pat

He was replying to my post. Freshmen chemistry was a long time ago for me. I forgot about the neutrons in helium so I messed up on the Atomic weight. But I was right on it being monoatomic which Fujimo messed up on. But the main point is, you are not going to save any significant weight by filling your tubes with helium or hydrogen.

fujimo

yeah, :

kewlrunningz

I don't see why there is such a big discussion about filling bikes with gas. No one here is at the level that a few ounces off of the bike would make a difference. If you want to get faster, I suggest you hit the road and rack in a few more miles perhaps .

())_CRAYOLA_))>

WorldIRC

unless urr racing use good ol oxygen.

and ahh i just passed gr 10 science. had to learn all that chem stuff.. more to look forward to next year

fujimo

amen