Roof rack mounted air tank?

MojaveKJ · **Posted:** Fri Jan 15, 2010 3:23 pm

So I had the thought of mounting an air tank on the (eventual) roof rack rather than inside the KJ. Something like this one...

http://www.viaircorp.com/OffRoad/Parts/2_5gallon.html

Maybe mount it near the front so the hose reaches easily to all 4 tires. I could fill it with my home compressor when needed.

Thoughts? Safety issues? Will it look stupid? :ROTFL:

In general I'm trying to keep the lighter stuff on top of the Jeep and heavier stuff (like spare wheel bearings!) lower. :JEEPIN:

All comments welcome, thanks!

tommudd · **Posted:** Fri Jan 15, 2010 3:47 pm

would that even hold enough air to air up 4 tires from say 15 lb to 35 ? I wouldn't think it would really . You need a compressor or CO2 to have adequate air pressure.

durangotang · **Posted:** Fri Jan 15, 2010 4:31 pm

I don't know where the pics are... but I know there is at least one Landcruiser guy running around with his entire OBA setup on his roof. Compressor was in a sealed box and the tank was up there as well. IMHO, if you are looking for a sneaky place to put the air tank, stash it underneath by the fuel tank :mrgreen:

What are you doing with your compressor? If you're hoping to run only the air tank, Mudd is right... won't be enough volume for your tires.

MojaveKJ · **Posted:** Fri Jan 15, 2010 4:34 pm

Ya Tom, that was one of the questions I thought of as well. The tank is rated to 150 psi but the amount of air that would fit (compressed) into the tank is a scientific mystery to me. It very well may not be enough to fill four (or less?) 245/70 16 tires.

I hope someone in LOST will have the math skills to come up with a viable opinion on your question.

Thanks!

MojaveKJ · **Posted:** Fri Jan 15, 2010 4:39 pm

Thanks Durangotang, that's what I was hoping for...getting an educated answer, not necessarily the one you gave but it is what it is.

Just an idea... that needs more research.

So the compressor needs to stay out of the weather or is it just better for the life span of the compressor that way?

FreedomKJ · **Posted:** Sat Jan 16, 2010 12:28 am

MojaveKJ:

I have that same 2.5gal Viair tank, and while having it pre-filled will certainly speed up the air up process it doesn't hold near enough air to dill up 4 tires on its own. I usually kick my compressor on as I near the end of a trail and by the time we're off and stopped the tank is full, cutting my air up time almost in half. This will of course vary, depending on the size of your tires.

Your compressor will last longer kept out of the weather and dirt. Mine is mounted under my front passenger seat, but will soon be getting returned to its original install location: behind the panel in the passenger side of the cargo area.

Durangotang:

Where underneath by the fuel tank do you think a tank could fit?

MojaveKJ · **Posted:** Sat Jan 16, 2010 1:28 am

FreedomKJ, thanks for the good information. It occurred to me at some point today that the tank's 2.5 gallons is not enough for the volume of the 4 tires (if all 4 needed to be completely filled at the same time, worst case) so I am revising my thinking that an on-board compressor will be needed. My first course on any project is on the path of least resistance, KISS for the sake of the budget and sanity.

I really appreciate the tip about the compartment in the back for mounting the compressor. Getting it out of the way is nice but hidden behind a panel adds much to the cool factor for sure.

I"ll have to check that out and see what size compressor will fit best. Then there is the wiring. I do not like wiring. Bad experience in my younger days...don't ask. :frankie:

Where is your tank mounted now? I'm thinking with the compressor back there it might be feasible to still have the tank on the roof and run the lines out to the tank in a similar way to how I routed the CB coax into the same area from my roof top mag mount antenna. But then again with the tank mounted by the gas tank it would again add to the cool-ness

of OBA and make it much easier in the future should I ever go to ARB lockers. Thanks to Durangotang for that tip.

Much to think about... :!:

FreedomKJ · **Posted:** Sat Jan 16, 2010 3:22 am

Right now my tank is just bungee strapped to my toolbag which is bungee strapped to the tie downs in the driver's side of the cargo area.

All of the hoses and wiring are run under the carpet and behind panels though, with just about 6 inches of hose and a quick disconnect coming out of the back seat hinge area to connect to the tank.

I haven't hard mounted it as I've not found a place I really like it. I don't want to bolt it to the cargo area floor as I occasionally need to move it for hauling larger items. I couldn't really find anywhere under the Jeep where it didn't stick down really low.

JeepinJarhead03 · **Posted:** Sat Jan 16, 2010 3:59 am

if you really hate wiring, most any car audio place is willing to wire stuff for you and typically they do a pretty good job

MojaveKJ · **Posted:** Wed Feb 10, 2010 2:56 am

FreedomKJ wrote:

... but will soon be getting returned to its original install location: behind the panel in the passenger side of the cargo area.

FreedonKJ, what compressor do you have? It doesn't seem like there's much room back there to fit a compressor. What about the noise? It would be great if you could post some pics at some point. :pepper:

I'm thinking it might be a little better to run air lines through the body to a tank, where ever the tank ends up, rather than have the whole set up external. I'm mainly a desert guy so I'm thinking that the find silt that I run across out there is probably not good for a compressor to intake from the dusty trail. :JEEPIN:

The roof rack is on the back burner for now so I think this may be my next project.

Thanks...

LibertyFever · **Posted:** Sat Feb 13, 2010 12:19 am

A 2.5 gallon tank won't do for storage tank but it will do as a reservoir for an OBA system.
Before my OBA I tried a 12 gallon air pig but it wasn't enough to air up my tires to 22 lbs from 8 lbs.

Boiler · **Posted:** Sat Feb 13, 2010 12:47 am

Though there are going to be some losses due to temp differences & leakage, I would think:

Volume of tires x change in pressure = volume of tank x change in tank pressure.

Through rough quick calculation for a 31 x 9 tire on 16" rim, volume would be about 20 gallons, per tire. If you're airing from say 8 psi to 23 psi, you need 15 psi change. If you go from 150 psi in your tank, to 23 psi (any lower and the tires fill the tank...), then you have a pressure change potential of 127 psi.

127 x Vtank = 80 x 15 -----> Vtank = 9.4 gallons. Assume probably 60% efficiency due to air leaking out during the exchange, temperature variations, and the fact that air is not an ideal gas, as this equation is derived. 9.4 / .6 = 16. That's where I'd start, a 16 gallon tank. Basically you're talking a 12" diameter tank 33 inches long.

Roof rack mounted air tank?

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