Auxillary Air Tank?

SDR76 · 09-27-2016, 06:24 PM

I am thinking of putting an extra air tank under my bus between the frame rails. I have a tank that is about 15 inch diameter, and just shy of 4 feet long. I am planning on plumbing it into my onboard compressor, then once it is full, use a valve to isolate it so it will not affect the brake or air-ride systems. I'm a dirtbike guy, so i am always needing air. Is there any reasons not to??

Brad_SwiftFur · 09-27-2016, 06:36 PM

As long as it will not interfere with the driveshaft, or access to anything you may need to get to ...
As long as it is rated for the air pressure you expect it to hold (typically around 120) ...
And as long as you use plumbing up to DOT specs, the brackets are plenty strong (as you don't want it coming loose at 60 MPH) ...

Then go for it. It may take quite some time for the compressor to fill that big of a tank. You might want to consider finding a valve that will only charge it above a certain pressure (say, 80 PSI); that way your primary and secondary systems don't drop too low.

turf · 09-27-2016, 06:37 PM

you wont need an extra tank although you could put one in for an extra tank of air without starting the bus.

the airbrakes already have tanks that you can plumb off of. i'm no expert, but maybe one will chime in.

there are 3 tanks with air brakes, a wet tank, then your dry front brake tank and a dry rear brake tank. i think you can plumb off either dry tank. my tanks have multiple plugs in them you could unscrew and install a valve and air fittings.

$50 in fittings should give you an air supply, when you're parked and the engine is running.

a few have done that on here, and i forget who. its been on my to do list for a long time.

SDR76 · 09-27-2016, 06:41 PM

Quote:

Originally Posted by turf

there are 3 tanks with air brakes, a wet tank, then your dry front brake tank and a dry rear brake tank. i think you can plumb off either dry tank. my tanks have multiple plugs in them you could unscrew and install a valve and air fittings.

.

I was thinking of running right out of the drain valve on the rear dry tank. I cannot see a big downside at all. I would only charge it while at idle, then would have trap door in the side of the bus's skirt with a hose and fittings for tires and such...

Brad_SwiftFur · 09-27-2016, 09:37 PM

I've driven a couple trucks set up with air fittings on the original factory tanks (typically one of the "dry" tanks). Never saw or felt the need for adding an additional tank - but then again, anytime I needed to use the air pressure, was with the engine idling or idled up a bit. Even with big trucks, I have a "glad-hand" with appropriate adapters to fill a tire or run small air tools.

That said, I do not see any other downside aside from what I have already posted. BTW, does this tank have a provision for draining moisture? Even if supplied from the "dry" tanks, it may still accumulate moisture over time and you'll want/need a provision for purging it.

Booyah45828 · 09-28-2016, 10:29 AM

Legally, you can't use just any old air tank onboard a vehicle. It has to comply with federal regulation(FMCSA) in order to be used, and will be certified as such. Most truck stops should have something, you can also get something online or out of a junkyard.

Also, I'm not sure if it's because of a law or not, but most accessories run off either the wet tank, or the secondary tank. I've never seen anybody plumb anything but the rear braking system off the primary and I'd assume that's for safety reasons.

If you do add an additional tank, add a pressure protection valve for the reasons that brad mentioned. You don't want any additions you add to cause you to be stranded somewhere. As far as the valves, you can get them in fixed and adjustable pressure versions. If you do get an adjustable, make sure it's below your governor cut in pressure.

turf · 09-28-2016, 10:44 AM

hmmm,

could you just add a T to the drain port? keeping the drain vertical and have ball valve and a quick coupler on the horizontal leg of the T?

the ball valve just to keep any quick coupler from a possible malfunctioning?

SDR76 · 09-28-2016, 07:02 PM

I started the mockup of this and it is seeming to work out well. What I've done: Removed the Drain Valve on the rear bus tank, and replaced it with a ball valve. Ran from the valve with Stainless line and Swageloc fittings (parts left over from CNG projects). Then the new line goes into a a TEE. One side of the tee has a quick air connect (to connect my auxiliary airline to), and the other side goes to ANOTHER ball valve right before the auxiliary tank. Using the two valves should allow me to let the system pressurize at idle, then once up to pressure I would shut off the first ball valve and isolate the original system back to the way it was except a different valve on the drain). I would also keep the valve on the tank closed except when I needed air. I may cut an access door into the skirt, or I could just reach up under there really easy... I think it will work well. Best part- Ive had to buy ZERO fittings and lines- I don't have a lot of plumbing fittings, but had exactly the stuff needed--serendipity.

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