kcabpilot
CA
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Joined: 04/07/2008
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Pull the scrhrader valve out and see how long it takes your air bags to deflate.
1994 Lance 990 on 1997 F350 PSD Dually
We also have a 'truck' that FLYS
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landyacht318
Near a large body of water
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It doesn't take very long to deflate an airbag just by fully depressing the needle on the Schrader Valve. I do it several times a week. I bet it would take about a second if one were to quickly, cleanly cut the air line. I will not test this hypothesis.
I know how much lean I can expect at a certain PSI in a top heavy "B" Van. I imagine if the outside one blew during a hard turn it would get ugly quick. That's obviously a more extreme example than one bag inflating the other during a turn but it paints a picture. Now imagine an emergency avoidance maneuver where it takes a second to turn from a hard lean right to a left.
Obviously a top heavy B van would feel it more than a Dually TV.
It's my opinion that the airbags would accentuate the roll if 'T' d together. Run 2 separate lines. How long does it take to switch valves, 3 seconds, 5, 10? Is that not the only advantage of 'T' ing the lines? The compressor would run for the same amount of time. Sometimes we go overboard when trying to make things convenient even when it's possibly to the detriment of our own safety/security.
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fndrbndr
NE GA
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On my Freightliner it has 4 air bags and no rear springs. All the air bags are tied together. If I blow an air bag or line all 4 lose air and it would sit down. If you had the air bags on your TV with a T if something happened it would just settle down on the springs. If you have 2 lines if you blew a line or air bag one side would drop down. It would seem to me that would be more dangerous than what little you would feel going around a curve if the air bags are tied together. If I ever put them on my 2500 HD they will be tied together.
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az99
N.Y.
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fndrbndr wrote:On my Freightliner it has 4 air bags and no rear springs. All the air bags are tied together. If I blow an air bag or line all 4 lose air and it would sit down. If you had the air bags on your TV with a T if something happened it would just settle down on the springs. If you have 2 lines if you blew a line or air bag one side would drop down. It would seem to me that would be more dangerous than what little you would feel going around a curve if the air bags are tied together. If I ever put them on my 2500 HD they will be tied together. You are talking about two totally different suspension systems. For this to be even a similar comparison in your example of blowing an air line on the airbag equipped vehicle the spring would also have to collapse at the same time to equal the effect of you losing a airline on your air ride suspension that has no springs.
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wolfe10
Texas
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fndrbndr wrote:On my Freightliner it has 4 air bags and no rear springs. All the air bags are tied together.
Actually, on most air suspension coach (including yours) you have THREE ride height valves that control air to your bags. So two on one axle (generally the rear since it is materially heavier) are independent. With the other axle (front in this example) being independent of the rear and controlled by its own ride height valve.
But, as suggested, your system is so different from the one being discussed that it is likely to cloud the issue, not clarify it.
Brett Wolfe
1993 Foretravel 36' U-240
Cat 3116, Allison 3060
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Dave H M
IL
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I am leaving this post becsuse of too much rocket science for me. 
I am leaving mine T'd
However if i ever gets old enough to run in one of those figure 8 races, I just may put a set of cheap vice grips on each line to flatten out the turns.
I will se you un T's folks doewn the road.
We will all get there.
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fndrbndr
NE GA
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wolfe10 wrote:fndrbndr wrote:On my Freightliner it has 4 air bags and no rear springs. All the air bags are tied together.
Actually, on most air suspension coach (including yours) you have THREE ride height valves that control air to your bags. So two on one axle (generally the rear since it is materially heavier) are independent. With the other axle (front in this example) being independent of the rear and controlled by its own ride height valve.
But, as suggested, your system is so different from the one being discussed that it is likely to cloud the issue, not clarify it.
I have one height valve on the rear for 4 air bags. If you know where the rest are I would like to know.
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wolfe10
Texas
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Fndrbndr,
I could not tell from your profile what Freightliner motorhome chassis you have, but every one I have worked on has three ride height valves for the 4 wheel positions.
If this is not a Freightliner motorhome chassis, my comments may not apply.
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joshuajim
Mojave Desert
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az99 wrote:joshuajim wrote:az99 wrote:joshuajim wrote:
I would disagree with the "air pressure" shift for several reasons. First, when the vehicles rolls, the bag on the higher side will be compressed less and actually decrease pressure. This same thing will happen wether the bags are linked or not. Second, the pressure will only equalize between the bags, it will not increase pressure in the high side. Finally, the 1/4" line will not transfer enough air in the couple of seconds that the vehicle is leaning to make any difference at all.
Another urban legend. You better go take a pneumatics course if you really believe what you posted.
Since you have obviously taken the "pneumatics course", perhaps you could elucidate not obfuscate. I don't know what those big words mean but I think I get your point.  I will look up those big words and you lookup how much air a 1/4" OD airline will flow in 2 seconds at 100 PSI. To get you started a standard 1/4" airline has a .035 wall thickness so the true inside flow diameter is .180 inch. Once you calculate that you will see what I mean. Now where is my dictionary.
Consider that when the vehicle leans the worst probable case is about a 2" compression of one bag and 2" extension of the other. If you run Bernoulli's formula for pressure change due to volume change you will discover only about a 35# to 40# differential even if inflated to 100#. I think this may be higher than most people run, so use 40% of you normal pressure. This is the number you have to use to calculate the flow. I'll help you out and tell you that the volume of air transfered is about 2 cubic inches per second at the pressure I run. i.e. the transfer is insignificant. For a practical test, set your compressor at 40% above your standard running pressure and inflate the bag for several seconds (lower the pressure by 40% before you test to simulate the lean situation). Note the change in ride height.
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gouldc
Edmonton, Alberta Canada
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Question, with the check valves installed, how do you deflate? I'm assuming you'll need separate valves from each bag for that? Using electronic valves, each bag would need it's own relief valve. Just tie those valves to the same switch?
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