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CO2 cartridges
NB: Originally posted elsewhere on the Global Riders Network and appears via syndication.
Just thought I'd share this fine link with you guys...
http://finewhip.cart.net.au/store/co2/16g-co2-ca...
They've even got N2O cartridges, wondering what that would do to your tyre.
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Make them laugh?
Seriously though as Nitrogen doesn't expand much when heated and is pretty inert it is commonly used in shocks. I guess that in a tyre the pressure would remain very constant from desert to snow...!
Helium?
Yeah - I had heard that baking shops were a good place to pick up cartridges. Nice find
We used to run nitrogen in our racing slicks on motorbikes back in the 80's,used to carry a large cylinder all over the country was great for beading tyres!
would you use these for xc for just for road???
I have used these on both road and MTB bikes. As it says on the website - one cartridge will fill a MTB tyre to about 40psi and a road tyre to about 130psi (these figures are a bit optimistic IMHO).
And if you have a 29er the 25g cartridge will do the job.
The N20 cartridges are nitrous oxide for whipping cream or getting high, not nitrogen.
do you just plug it on the vaule and fill away?
Don't all gasses expand at the same rate? Can someone prove/disprove this.
Pretty cheap here - without going outside the bicycle network.
http://www.cellbikes.com.au/Bike-Rider-16g-CO2-A...
the good old days of getting the whip cream cannisters after a dance party , we used too get 10 packs at a time , the easiest way for a cheap buzz
Different gasses expand at different rates as they have different boiling points depending on surrounding pressure.
If you cool butane at sea level it will become a liquid at minus 12, CO2 at minus 56.6 & N2O at minus 88.
Basically some gasses are more lively than others & therefore the N2O cart will contain the greatest volume of gas out of the commonly used gasses available (as long as the liquid held within the cart is the same).
That ok?
So at the sort of pressure you run your tyres at, is the N2O a liquid, vapour or gas?
N20 will change from vapour (Gas) to a liquid at 848.47082 psi at 20C
Or at - 88.5 at 1.013bar pressure(Normal sea level atmospheric)!
How's that for lively!
I don't think the inside of your tube will meet either criteria so it'll be vapour!
Don't ask me to explain enthalpy or dew point unless you're supplying beer/ Titanium or carbon goodies:-)
does that mean you get more (tyre)pressure out of a N2O 16g cartridge than a 16g CO2 cartridge??
Yes
The molecular weight of nitrous oxide is 44 which is the same as carbon dioxide. This means the same number of molecules will fit in canisters of the same weight. Disregarding any affinity between gas molecules the same number of molecules will result in the same pressure for a fixed volume, so the pressures from both canisters will be similar.
Nitrous oxide will have more affinity between molecules and therefore a slightly lower pressure will result (i.e. it will deviate from being an ideal gas to a greater extent than CO2). Nitrous oxide will also adsorb more strongly to the tyre wall, increasingly so as the pressure increases, so again this would reduce the pressure. Nitrous oxide is also more reactive which may degrade the rubber faster than CO2.
Would be fun to try, I wonder if all this adds up to a difference you could feel?
Sorry, I disagree with the similar pressure statement.
Due to the far lower boiling point (-88 N2Oas opposed to -55 for CO2). For 16g carts the pressure within the cart and within the tyre would be higher with the N2O.
Think of it this way, if both were released into a tyre at -60 the CO2 would remain liquid & wouldn't expand at all, the N2O would.
Rgds T
The boiling points are irrelevant, as long as they are both gases at the operating temperature of the tyre. The question is an application of Avogadro's rule "equal numbers of gas molecules will occupy the same volume at the same pressure and temperature.
The equation PV = rRT applies to all gases, where R is the universal gas constant (6.02x10^23), T is temperature in Kelvin (celcius + 273).
Real gases deviate from this slightly due to attraction between the molecules. Avogadro assumes no attraction between molecules. Nitrous oxide I would expect to have higher intramolecular forces, meaning that would have slightly lower pressure than the CO2. This doesn't seem in line with the relative boiling points, but there are other factors such as entropy changes which influence boiling points.
...and I thought it was hard to get two economists to agree
In simple terms, if one was to use little gas canisters to inflate one's tyres, what gas is best to use in those little canisters?
No explanations pls. Just an answer. Or should we have a poll???
I use a little refillable cartridge to fill my tyres.
For a 2.4" 29er it can be tiresome refilling the cartridge over 100 times, but the refills are 'free'.........
That's 78% nitrogen and 21% oxygen isn't it? Mind you, that's only if it's at sea level and 15°C and 101325 Pa (whatever Pa is......)
R=8.315J/K/mol. Avogadro's number; 6.02x10^23, is how many atoms there are in a mole, calculated as the number of atoms in 12g of Carbon-12. Only helpful when working out n, not R.
This thread is hurting my eyes with misinformation, same as the 29er v 26er thread.
Just buy the cheapest, biggest canister possible. You will probably end up using it wrong on the track anyway and have to resort back to a pump which will only give you 78% N2, 21%O2 and 1% Argon / CO2 /Water vapour.
Might be easier to see when writing the ideal gas law as PV = (mRT)/M
Hardly any difference in atomic weight (proportional to M) between N2O and CO2 so no expected difference in pressure at a constant mass (m), volume, pressure, and temperature.
Can't comment on tyre material degradation (yikes!), intermolecular forces, and adsorbption but the N2O could come in real handy as a trackside anaesthetic.
Brings a whole new dimension to trail fixes!
I like theses discussions, they're educational and dispel myths. At the moment I'm convinced that regardless of what gas you have in your tyre, the expansion due to temperature will be pretty much the same.
1 thing I can't see anyone mentioning is that you wouldn't get the frozen valve with NO2 like you can do with C02 if not done correctly
I would have though that the JT coefficient of N2O and CO2 was similiar at ambient conditions?
Is the N2O cartridge 'drier' than the CO2 due to the original source of the gas and/or the production method of the cartridges?
They would both freeze up to the same amount I would say. The ideal gas equation can be reduced to PV/T = constant, when expanding the pressure drops, volume increases and the temperature drops. Once again it doesn't matter what the gas is, as long as its a gas in the canister.
Yes you are correct @c3024446 - R is the gas constant my mistake there. You would want to use different units for this problem (0.082 L.atm/K.mol). Been a few years since I've had to recall that stuff.
Stand corrected @bigtom you must be an engineer
Having done my research I have concluded that I am wrong:-?
Although the pressure within the cart will vary with temperature the pressure achieved within the tyre will be almost identical.
I was going off at a tangent thinking about superheated steam & the like.
Answer for 29ers 20g cart!