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Re: Why CO2?

Posted: 10 Aug 2019, 1:30pm
by Mike Sales
philsknees wrote:I see that the empties are recyclable alongside tin cans & the like - it's a shame the little darlings admirable concerns about climate change don't spread to responsible disposal of the nitrous cartridges they're dumping everywhere. I can foresee a cyclist being unseated by a handful of empty cartridges in the near future. (Whoops, slipped into Meldrew mode there. Apologies!)



It's no wonder that the Extinction Rebellion demonstrators have to sit down in the road. They must be unsteady on their feet after all that NO2.

Re: Why CO2?

Posted: 10 Aug 2019, 2:57pm
by Brucey


interesting and not very accurate. The main gist of it is correct but the diffusion rate of CO2 through rubber is definitely not 'minutely different' from that of air or N2; it is considerably higher.

cheers

Re: Why CO2?

Posted: 10 Aug 2019, 7:45pm
by rmurphy195
I have a Brommie with the Marathon tyres.

I use a workshop pump at home, but have found that I can pump the tyres up to a decent hardness with the pump that comes with the bike, more than enough to get around on without the tyres dragging.

Re: Why CO2?

Posted: 10 Aug 2019, 7:57pm
by Samuel D
On the topic of diffusion of CO2 or air in inner-tube rubber, Josh Poertner has alleged (e.g. in this podcast from 48'15") that Vittoria has added graphene to its latest latex tubes with the result of lower leakage rates.

Re: Why CO2?

Posted: 10 Aug 2019, 8:22pm
by GranvilleThomas
Well according to Wikipedia, by volume, dry air contains 78.09% nitrogen, so surely this car tyre filled with nitrogen business is all a scam?

Or maybe I am missing something?

Would not be the first time :D

Re: Why CO2?

Posted: 10 Aug 2019, 9:05pm
by Cunobelin
Brucey wrote:


interesting and not very accurate. The main gist of it is correct but the diffusion rate of CO2 through rubber is definitely not 'minutely different' from that of air or N2; it is considerably higher.

cheers


Hence the description "interesting"

Re: Why CO2?

Posted: 10 Aug 2019, 9:07pm
by Cunobelin
GranvilleThomas wrote:Well according to Wikipedia, by volume, dry air contains 78.09% nitrogen, so surely this car tyre filled with nitrogen business is all a scam?

Or maybe I am missing something?

Would not be the first time :D



Again ... for information as opposed[youtube][youtube][/youtube][/youtube] to a confirmation either way:


Re: Why CO2?

Posted: 10 Aug 2019, 9:21pm
by philvantwo
Aeroplane tyres are filled with nitrogen, 220psi!

Re: Why CO2?

Posted: 10 Aug 2019, 9:42pm
by Samuel D
What is the composition of the gas in a bicycle inner tube after it has leaked down, been pumped up, leaked, pumped, etc., for many cycles?

Re: Why CO2?

Posted: 10 Aug 2019, 11:57pm
by Brucey
Samuel D wrote:What is the composition of the gas in a bicycle inner tube after it has leaked down, been pumped up, leaked, pumped, etc., for many cycles?


different; smells of rubber...? :lol:

cheers

Re: Why CO2?

Posted: 11 Aug 2019, 7:15am
by Mick F
CO2 diffuses over time, so that's why after a visit from the P fairy and I fit a new tube inflated with CO2, I have to re-inflate with a proper pump after getting home.

Now, this begs the question posed.
If you inflate with bog standard air from your hand pump and the CO2 contained within it diffuses, the air left must be CO2-less. Pump up again to top it up, and the CO2 diffuses again but this time there's less of it.

Re: Why CO2?

Posted: 11 Aug 2019, 12:05pm
by Samuel D
There isn’t much CO2 in air to begin with, though. What about leakage rates of oxygen versus nitrogen, taking into account partial pressures? That would tell us more about what ends up in the tyre after a while.

I ask because I suppose the leakage rate must diminish over time. Is this effect significant?

Re: Why CO2?

Posted: 11 Aug 2019, 1:13pm
by Brucey
according to

http://people.ds.cam.ac.uk/jae1001/cus/teaching/materials/M6_Lecture_6.pdf

rubber is more permeable to oxygen than nitrogen, so the air inside the tyre ought to become oxygen-depleted over time.

cheers

Re: Why CO2?

Posted: 11 Aug 2019, 2:24pm
by Samuel D
Ah! If it had been the other way around we could have hoped for a bigger reduction in leakage over time.

Re: Why CO2?

Posted: 11 Aug 2019, 2:32pm
by RickH
Mick F wrote:CO2 diffuses over time, so that's why after a visit from the P fairy and I fit a new tube inflated with CO2, I have to re-inflate with a proper pump after getting home.

Now, this begs the question posed.
If you inflate with bog standard air from your hand pump and the CO2 contained within it diffuses, the air left must be CO2-less. Pump up again to top it up, and the CO2 diffuses again but this time there's less of it.

As has been said already there isn't much CO2 in the air around us. According to here CO2 makes up just 0.04% of the atmosphere.