Nitrogen vs Oxygen

[PMK]

Regarding the oxygen concept. I assume the misunderstanding is someone using their oxy acetylene welding oxygen to pressurize the resivoir. This would be bad. Using compressed air (not oxygen) be it by a Fox or other pump or compressor if enough pressure, will work though nitrogen is better.

I am old and ran the Fox dual airs, in the manual fox said use a N2 tank or bicycle pump. As for all the MTB dampers I've done, I can use either N2 or pump air, most get air, as this is what the manuals recommend. Remember this is for MTB's and they typically won't get near as hot as a mc damper.

As an aircraft mechanic oxygen is considered different from air, we service the O2 from bottles, and service the tires and hydraulic accumulators and such with N2. The air is either ambient or bleed air. Unless you're British with pneumatics instead of hydraulics.

PK

 

[marcusgunby]

I think its down to the heat of a shock that we should use N2-i would use air in a emergency but i would get it replaced with N2 for the next ride.

 

[jmics19067]

My theory in a picture perfect world is that the bladder separates the gas from the oil so yor air won't oxidize anything but the inside of the bladder and the bladder cap. The oil shouldn't oxidize anymore then the time it takes to fill the shock unless you have trapped air in the body.

I also think that the main reason nitrogen is used is the fact that it is clean compared to compressed air. The whole any moisture in it getting hot and expanding throwing off any semblence of pressure regulation when it gets hot out the window. I also believe that nitrogen has a relatively linear rate at which it expands with tempature.Otherwise inert gases such as argon helium or CO2 would be just as recommended.

 

[NGE]

I think the corrosion issue is moot... The schrader valve is DESIGNED for air.. the bladder will not corrode, given a reasonable length of time... the oil doesn't even mix with the air... the ammount of water trapped in this tiny ammount of air (about 5 or 6 pumps with a pump the size of a hotdog) is inconsequential seeing as you only do it vary rarely, and everything inside can handle a drop of water... the aluminum can handle it with ease, as is demostrated with Mtn Bikes and MX forks... and finaly, should the bladder burst, the ammount of oil in the shock would not be condusive to an explosion, and it would requre a complete rebuild before reuse either way...

Am I right here?

I know an aircraft structural engineer for Northwest Airlines who told me that they use N2 in the tires of planes because it is inert and, should the tire blow, the gas from the inside of the tire would help to avert flame outs as opposed to fueling it. Not because it prevents corrosion. The corrosive effect of a stagnant ammount of air is limited due to the limit of air access.. (i.e.- oxidization consumes oxygen and is a slow proccess to begin with... you're dirtbike will die before the corrosion takes any noticable effect due to the very limited amount of fresh air to fuel the oxidization.)

 

[marcusgunby]

I think people are getting a bit too in depth here, if you want to use air you can, but its safer to use N2 as its inert.What it costs to get a N2 setup you will save in one service compared to taking it to be serviced.

 

Heres what i did, i got a N2 bottle(from work luckily for me)then i bought a recon regulator from a welding supplier(£25), i got the tyre adapter from a compressed air supplier that was 3 doors away from the welding supplier(£10) the N2 bottle will last a lifetime for most users and you dont need one this big.

 

[bclapham]

i use argon, so put that in your pipe and smoke it!:confused:

 

[Jaybird]

Just to add a bit here.....compressed air will not create oxidation of the aluminum unless there is moisture present.

It is very uncommon to see an affordable means of getting the compressed air completely dry. I think that is the main reason alternative gasses are preffered.
When I say dry compressed air, I'm not talking about running it through a 40mic Watts filter.

When we fill a tire with compressed air, we can see ~10-15lbs change with the temps. Using completely dry compressed air you may see a change of ~.5 lbs....granted the nitrogen would probably see a bit less than that, but not much.

 

[scroskrey]

I think most of you have overlooked Morphs reply at the top of this thread. Aside from moisture content, nitrogen is highly desireable due to its ability to maintain a constant pressure while undergoing large temperature changes. Air cannot match this feat or even come close. A shock that has a constantly changing intenal pressure has affectivley made all external adjustments useless.

 

[marcusgunby]

mx eagle posted this after that however-all gasses follow boyles law.

All gases must abide by the equation PV=nRt. Nitrogen increases pressure just like a combination of N2, O2 & CO2 (ie air)

 

[scroskrey]

I stand corrected. To be more precise, I was refering to the thermodynamic properties of gasses, of which, nitrogen has a low coeficient of linear themal expansion. Lower than most other safe and inexpensive gasses.