Max air bag pressure

[gumpy]

After years of thinking and planning and acquiting stuff (most of it wrong), I finally got sick of parking on boards, and decided to
build my leveling system. I decided to build a 3-point system, using 3 solenoids at each point, rather than using the small regulators
I was going to use. I'm hoping I have all my leaks fixed between the leveling valves and the air bags, so that once set, it will remain
stable, and not have to be readjusted. The regulator system would have prevented readjustment, but I'd have had to have air pressure available all the time, which would mean a pump running periodically to keep it charged, which equates to more electric
usage. So I decided I'd build it using solenoid air valves. I had 3 which I'd bought last year for the regulator system. I had purchased them from a surplus place, and of course now that I need more, they are out of stock. I lucked out and found 7 more of the
same unit in TX, and made an offer to the guy for all 7, which he accepted. Should be here in a few days.

So, I started with the front axle, since it is the easiest to get to. Today, I got the 3 solenoids I have installed, and connected to the
air lines. I hooked up a switch temporarily to see how they work. I think it's going to work out well. I'll hvae about 4-5 inches of
travel.

My question, though, is what is the maximum pressure I can put into the air bags without overinflating them and potentially
breaking them. I'm not sure if there's a regulator on the supply line to the leveling valve or not, but even if there is, the leveling
valve would never fill to max pressure, but with my system, it would be possible to do so. I suspect 120 is way too high. For some
reason, the value of 85 psi seems to stick in my mind. Anyone know for sure?

My plan is to use one of the little regulators I was originally going to use for control to set the max pressure in the supply lines to
each control set. I'm going to install my little Harbor Freight compressor in the rear bay and connect it into the air system, so I can
turn it on when needed to air up the bus. I'm going to see if I can run the leveling system supply directly off the compressor, so I
won't have to air up the entire bus just to adjust the leveling when the air is down.

So, anyone know what the max pressure is I can put in my bags?

craig

[Ncbob]

Craig, you know well that compared to most of you...I'm a 'newbie' at this business of owning a bus. But the last time we were at Table Top for Kyle's Rally Jack Conrad, Dallas and I set out to test my left rear air bags and beam for leaks and Jack suggested 60 PSI as the test pressure as that was the normal inflation pressure for over the road use.

If that makes sense to you, as it did to me, then I'd use that as a normal number and work each way to whatever gives you the normal ride height.

Keep us posted on your progress....we're alway interested in the new horizons you broach for us.

NCbob

[jjrbus]

Fuel gauge is still working!!  Right off the sticker on a new GoodYear bag for an MCI. Do not exceed max 100psi or serious bodily injury can result.

[Stan]

Gumpy: I think you will find that you seldom have to add air to level the bus. It is easier to let air out of the high side and it is not desirable to raise the front up and make it too high to step into. Another consideration with air leveling is most don't change the pressure in the tag bags. If they leak down then you require more pressure in the drive axle bags to stay at the same height.

[LutherC]

Craig,

I don't know the max pressure, but I installed my leveling system using 24 volt Skinner solenoid Valves and seat valves. I have gauges that monitor the pressure of the bags(4- two for the front and two for the back). When driving the height is contollled by the factory leveling valves and pressure is approx. 65# in the front, 85# left rear and 80# right rear. However, my bus is loaded down now with my sons belongings that I am moving to Calif. for him.
Luther

[gumpy]

Thanks for the replies.

Jim, that's good info on the bag tag. Also, glad to hear the fuel gauge is still working. Pretty good for a kludge fix, huh.

Stan, good point. Today I found that both my tag bag valves are leaking, so I'll have to fix those to keep the tag bags inflated,
or I'll have to readjust after it leaks down. Thanks for pointing that out.

Luther, those are good numbers. I'm debating if I want to put gauges in, too. Would like to see what the normal operating pressures are, but I'm not sure it's necessary to have gauges to set the leveling. I'll be leaving the auto levelers in for traveling.
Maybe I can find some small gauges I could mount below the switches. Anyone have a lead on some small inexpensive air gauges?

[pvcces]

Craig, I think the bags should be able to hold together even with full system pressure. My reasoning is that when a leveling valve fails by leaking air into the airbag, the bag is going to reach system pressure eventually.

I realize that we hear of airbags failing occaisionally, but I don't recall of hearing of one that failed because of overpressuring it. The pressure warning quoted above could have been given because of liability reasons, and if so, it might be pretty conservative.

Also, if normal running pressure amounts to half of system pressure, what happens when you go over a bridge abutment that causes the coach to heave up and down? Some of those are pretty violent.

The only warnings that I recall about airbag damage had to do with letting the axle hang on the airbags.

For what it's worth.

Tom Caffrey

Thanks for the replies.

Jim, that's good info on the bag tag. Also, glad to hear the fuel gauge is still working. Pretty good for a kludge fix, huh.

Stan, good point. Today I found that both my tag bag valves are leaking, so I'll have to fix those to keep the tag bags inflated,
or I'll have to readjust after it leaks down. Thanks for pointing that out.

Luther, those are good numbers. I'm debating if I want to put gauges in, too. Would like to see what the normal operating pressures are, but I'm not sure it's necessary to have gauges to set the leveling. I'll be leaving the auto levelers in for traveling.
Maybe I can find some small gauges I could mount below the switches. Anyone have a lead on some small inexpensive air gauges?

[TomC]

I know I'm at the top of the travel when the air bags start to make a funny clicking sound with the air escaping around the top bead.  I think the bags were designed to leak off if too high.  That's on my AMGeneral that has aluminum cans on the tops of the air bags.  I don't think 120psi will hurt the bags for short periods.  Good Luck, TomC

[JackConrad]

Craig,
  When I installed our leveling system. I added a solenoid to dump the tag air bags.  I did this for 2 reasons. First, to give me more weight on the rear axle for traction (If necessary), and also to use when leveling the bus. My concern was that if leveling requires me to dump the air in the rear bags, I was transferring most of that weight to the tag axle air bags.   
  where are your tag air bags leaking. We were getting bubbles between the top of the bag and the plate the top of the bag attaches to. Turned out to be pinhole leaks due to rusted out top plate of the air bag.  Jack

[gumpy]

Good point Jack. I already have the tag dump solenoid, so it seems my procedure should be to dump that first, and then level the bus. Only problem, though, is that when the bus is turned off, I think that solenoid reverts back to open, which would then allow them to refill. Will have to investigate that.

The bags themselves are not leaking. They're new. I found the shutoff valves in the rear passenger compartment are leaking from around the levers. Hopefully just an o-ring fix.

[Len Silva]

There is a description of my automated leveling system here:
http://www.busconversions.com/bbs/index.php?topic=2175.msg18506#msg18506

I don't have the tag axle to contend with and used a four corner system.

In my automated system. I first dump all the bags before checking for level.  This lowers the bus, making for easier entrance and means the the bags only have to go up to level, far easier logic than trying to determine which way a particular corner should go.
FWIW,

Len

[jjrbus]

Got my gauges at www.surpluscenter.com in Linclon Nebraska 99 cents each. also bought my solonoid valves there. Everything was cheap (you expected less of me?) so I bought extras.

[RTS/Daytona]

I've sold a great deal of my leveling system over the last few years - My personal feelings about max air bag pressure are:

If my 30,000+ lb RTs BuS Conversion can withstand stand the huge pressures created on it's air bags when going over a large dip or raise on I95 at 70 mpg - then I'm not too worried if 120 lbs goes in them occasionally.

Just my opinion