Being a habitual frame pump devotee (not _too_ habitual... I don't pop tyres toooo often), I have just bought my first CO2 cannisters and valve attachment bits, as my particular frame pump tends to get a bit unmanageable once I've got the patched or replaced tube up to about 60-80 PSI (road bike).
What I'm curious about is why the gas cannisters marketed for this purpose are filled with (mostly?) carbon dioxide? I'm guessing it's purely economics, since unless I'm missing something (and I suspect I very well might be), re-inflating your tube with air is a better option than CO2 (i.e. you wouldn't have to re-inflate the tube with air again later if the cannister had air in it to start with).
I find it difficult to believe that it costs more to compress ambient air into a cannister than it does to compress CO2.
Is the cycling industry just decades ahead of the curve on carbon dioxide sequestration initiatives, or is there some other mystical reason at play here?
Chris
Last edited by chriscole on Wed Mar 20, 2013 2:34 pm, edited 1 time in total.
Probably because cheap CO2 cannisters existed before CO2 refillers for bikes existed, and they're just leveraging an existing (read: cheap) supply chain.
Yep. Readily available CO2 canisters..... used for soda bottles in bars and pubs, amongst other things. You don't get carbonated water with pressurised air
Isnt the CO2 cannister filled with liquid CO2? (ultimate compression) CO2 is also an inert gas, meaning that it doesnt really react with anything adversly, or ignite with a spark or flame. Nitrogen could also be an alternative, but you might not like the price. Oxygen has a tendency to intensify flames or even explode under the right conditions, so that isnt a great idea either.
"Air" is a cocktail of loads of different gasses, so compressing it to a size that fits into your pocket could be tricky. Normal compressed air, say from a home or even an industrial air compressor would require a very large canister to fill a bike tube.
Readlly available, pre-existing CO2 canisters, addapted to suit your bike, is an inexpensive and convenient solution.
rebilda wrote:Isnt the CO2 cannister filled with liquid CO2? (ultimate compression) CO2 is also an inert gas, meaning that it doesnt really react with anything adversly, or ignite with a spark or flame. Nitrogen could also be an alternative, but you might not like the price. Oxygen has a tendency to intensify flames or even explode under the right conditions, so that isnt a great idea either.
"Air" is a cocktail of loads of different gasses, so compressing it to a size that fits into your pocket could be tricky. Normal compressed air, say from a home or even an industrial air compressor would require a very large canister to fill a bike tube.
Readlly available, pre-existing CO2 canisters, addapted to suit your bike, is an inexpensive and convenient solution.
Yes its liquid, which is why they get so cold when used, the liquid is boiling off as a gas generating massive volumes of gas. You would never get the volume and pressure required with plain air.
As others have said it is simply economics. CO2 is the cheapest safest, physically easiest gas to supply in a liquid form. The other two obvious ones of O2 and N2 have MUCH lower boiling points. Also it would be an interesting experiment to see how long your inner tubes would last in a high pressure pure oxygen environment!
clackers wrote:Obviously there are safety reasons, but if we concentrate just on the economics, a measure of how costly it is to compress a gas is its boiling point.
CO2 liquefies at -60 degrees at normal pressure.
The main component of air is nitrogen (-196 degrees) and the secondary component is oxygen (-180 degrees).
Really? I thought CO2 went straight to a solid at normal pressure (and somewhat colder).
This discussion goes from the sublime to the ridiculous.
ironhanglider wrote:Really? I thought CO2 went straight to a solid at normal pressure (and somewhat colder).
This discussion goes from thesublime to the ridiculous.
I see what you did there! You quite rightly point out that liquid CO2 cannot exist at atmospheric pressure.
However the overal point still stands that it is thermodynamically easier and cheaper to create and store liquid CO2 than N2 or O2. Getting into the exact reasons is definitely outside of the scope of discussion here.
jules21 wrote:it's mostly for environmental reasons. the CO2 is sourced from the atmosphere, so it's reducing global warming.
The cost of the gas is negligible compared to the cost of the cylinder its stored in. Its a moot point as to the cost of which gas as except for rare gases such as Argon, the gas is fraction of a cent to fill a 16g cylinder
It's simple physics. When CO2 is compressed to a certain pressure it condenses into a liquid (at room temperature, this is the important part). Air would still be a gas and you would fit barely any of it in the same canister as you would with CO2. When you put your cartridge on the inflator and release it into the tire, the pressure change turns it back into a gas and inflates your tyre.
jules21 wrote:it's mostly for environmental reasons. the CO2 is sourced from the atmosphere, so it's reducing global warming.
Really? Have you got a source for that? It'd be good if it is true.
You won't get a more authoritative source than Jules21 from BNA
Perhaps Jules must be trying to wind everyone uo. As soon as you release CO2 it goes back into the atmosphere, so actually zero reduction except the amount in stored ctg . In fact it actually INCREASES the amount of CO2 emissions once you take into account the energy used to form an aluminium cyclinder, liquify the gas, transport the cyclinders etc.
On the other hand a good old hand pump has zero effect
Red Rider wrote:[quote="jules21"]it's mostly for environmental reasons. the CO2 is sourced from the atmosphere, so it's reducing global warming.
Really? Have you got a source for that? It'd be good if it is true.
You won't get a more authoritative source than Jules21 from BNA
Perhaps Jules must be trying to wind everyone uo. As soon as you release CO2 it goes back into the atmosphere, so actually zero reduction except the amount in stored ctg . In fact it actually INCREASES the amount of CO2 emissions once you take into account the energy used to form an aluminium cyclinder, liquify the gas, transport the cyclinders etc.
On the other hand a good old hand pump has zero effect
When will you greenies wake up. Global warming is inevitable , regardless of cause. As such, all the evil by products of western consumerism such as disposable nappies, plastic bags, and cyclists CO2 canisters , when turned into landfill will be a godsend. As the seawater level rises, you'll wish we had more landfill, or to use its PC title, protective dyke.
You quite rightly point out that liquid CO2 cannot exist at atmospheric pressure.
