Air Tanks & Fire Extinguishers

Cool thanks, I'm wondering if I would need some kind of one way valve to stop the air back pressure leaking through the compressor? Anyway, will take some experimenting I spose.

Truck Tank will tank some enginerring to fit somewhere, the fire extigushers only 2L and will first easy under the bonnet next to the blue tounge, just enough for a quick blast, I'm not interested in filling tyres with it, I'm happy with the Blue Tounge Nativly for that, I just want to have a quick blast of air to clean out pips, air filters and to blast my air horns and possibly in the future activate some Dif Lockers.

Good to see you are still on the ball Truckster

Not all truck tanks are huge,some European trucks (Mercedes,Volvo)have tanks which would be barely 2L. - Steve

A truck tank would take no more engineering, infact less.

They would come with the mounting straps that fit them, relief valve, and train valve for fluid buildup, and you only need to join your compressor into it, no drilling, welding to add an outlet, its already there.

They do come in all shapes and sizes, some similar to 3ltr coke bottles, (too small for our application but just the point).. Look at some MAN and other import trucks which are long tube shaped, would be excellent against a chassis rail.

YATMV ;)

John, It's not volume I'm after, it's the small burst of high pressure I was after. I have a high flow low pressure pump for my air beds, bugger stuffing around with the bluetounge to blow up an air bed.
I'm intersted in this theory and I'm no rocket scientist so I hope I don't sound tooooooo dumb.
If I never let the pressure in the air tank empty right down, will it still effect my tyre pumping speed. ie Obviously the small amount of air in the tank will be used up very quickly into the first tyre, but as long as I don't let all the pressure out of the system in won't need to recharge to maintain pressure and just work as normal? Correct? Or am I wildly mistaken. Otherwise I will need to fit some kind of bypass for pumping up tyres and then flick it back again when I'm finished, maybe another 12v solinoid would do it...

No worries Jeff, not a dumb question.
This topic always seems to get people a bit confused.
I work in the diving industry and pressure volume relationships are something I do everyday.

The issue of the air bed was only to give you an example of how much air you would get out of the cylinder in a practical aspect, In other word very little.
Hence my comment about it being not worth the effort or the hassle and expense for that matter.

The thing to remember is the more air line or cylinders fitted to the air line then the more volume you have to fill.
If you then attached your flat tyre to the end of the air line then your compressor has to now put out sufficient volume to fill the airlines, the cylinder and the tyre.
Since we use very low volume pumps then it will take longer to fill the whole volume now attached to it to the required pressure.

The only way to get more volume into the cylinder is to pump it to a higher pressure, the diving industry uses a common pressure in scuba cylinders of about 200 bar or 3000 psi.
These pumps we use in our trucks are regarded as Low Pressure at around 100 to 120 psi.
Also the issue with compressors is that when the pressure increases then the volume will decrease hence the output ratings on all pumps will decrease as they build to a higher pressure.

for our application you either have to have a high volume compressor or a very large cylinder anything else is a waste of time.

I am not sure of the volume of a typical 4wd tyre but it would have to be at least 20 liters WC, this would mean to fill it to 50 psi would require about 70 liters of free air, your cylinder has about 16.

Hope this helps.

Thanks John, makes more sense now, not only are you pumping up the tyre but your pumping up everything in the system, the tank, the hoses etc etc.

Left hand threads on gas bottles may be a problem!

Yes indeed!!
I happened have an "expired" 5kg cyl (the taller, skinnier variety, not the short fat one) "lying about", so removed the valve (pri*k of a job, they are in there so t-i-g-h-t !!), drilled a couple holes, welded fittings for relief valve, press. gauge, water drain etc., & mounting lugs...
Have it mounted on the A-frame of my CT.. not plumbed, reserve air only at this stage.. have not (yet) had to use it to re-seat a bead, but certainly very handy for "dusting off" before setting up camp after several K's of bulldust! .. Usually there is enough air in reserve to re-inflate (4) trailer tyres from 14 to 20 psi, while I do the vehicle tyres straight off the pump...
My "Bushranger look-alike" will pump it up to 100psi without difficulty, will go to 120psi, but by then it's starting to struggle...

The thread in the cyl. itself (once you get the d&$n valve out) is 3/4" BSP.. this is the POL type valve... Primus & companion type valves have different size fittings, of course..

Before anybody jumps down my throat for cutting & welding on a gas cylinder, it had been empty for, like, y-e-a-r-s, and I flushed it thoroughly (several times) with water before working on it... Visual internal inspection showed shiny, like-new metal, so I am comfortable with the safety aspects...

Regards, Ed. C.

The pressure switch I have will cut the compressor out @ 105psi +/- a few. I will be fitting a pressure valve (as a backup) in line also. The Extinguisher was charged to 125psi before and sat like that for years, it also has up to 200psi on the guage, not that I'm planning to go there. I think an explosion with those items in place would be very unlikley.
But on that note I've been down to HosCo and it turns out the extinguisher has a funny thread on it that they can't match anything up to, so might be back to the ol' drawing board anyway.
I'm comited now as I've spent the money on the pressure switch and fittings so might try Truckster's idea of getting a truck tank, problem is there is only one truck wrecker I know of in Perth and it's friggin the other side of the city!
Oh well... Will keep you all updated...