Air bag pressure

[Jerry Liebler]

I'm finally actually going to install my leveling system but I have a question.  What is the maximum safe pressure for the airbags on my bus?  I'm retaining the stock ride height system and it's leveling valves but intercepting the lines from the 3 valves.  I'll install a 3 way valve, spring return but operated by air pressure, in each of the lines between the leveling valves and the air bags. With no pressure on the air operated valves they will connect the bags to a pair of solenoid valves for 'stationary' leveling.  A single solenoid valve will operate all 3 air operated valves and connect the normal ride height leveling valves.  Normally turning on the engine run switch will select 'ride height' mode (doing it this way uses no electrical power while parked).   I'll initially use 3 3position switches to raise and lower for manual leveling but plan on adding a fully automatic mode using some 'tilt sensors'. The reason for the question is so I can set the regulator supplying air to the solenoid valves so nothing gets hurt while I'm 'debugging' the automatic mode. 
Regards
Jerry 4107 1120

[jjrbus]

Jerry  when i replaced the bag on my MCI5C, the bag had a sticker that said 100 psi max.   HTH Jim

[Jerry Liebler]

JR,
   Thanks for the data, it's better than what I had.  Does your bus use 'rolling lobe' air bags? 
Regards
Jerry 4107 1120

[akbusguy2000]

I have a similar home-made system on my 4106 that I am pleased with.  It uses Clippard gages, max reading 100psi for each of the three zones, front, left and right.

When in the automatic positions the front gage reads almost exactly 60 psi, the left about 75, and the right about 78.  In the manual position the front fully extends at 77psi, and the rears at just under 100. 

I have the manual supply regulated at 100psi but I find that the rears will raise very slowly after they reach about 90psi.  This is probably because the differential pressure is just too little to do the job as quickly as I'd like.  I may end up increasing the supply pressure to 125 as I always watch the gages when raising or lowering any or all of the three zones.

hth

tg

[jjrbus]

My air beams are still good, so I am sticking with the old fashioned bags. If the air beams ever fail I will go to rolling lobe.

[Stan]

jjrbus: Was there a previous thread on this that I missed? What is the connection between air beams and a 4107?

[jjrbus]

 Stan I do not know a thing about 4107's, I was refering to my MCI5C.

[Stan]

jjrbus:  To help you out a little, a 4104 uses an air ride system very similar to your MC-5. 4106, 07, 08 have a completely different system that doesn't use air beams and uses a different style of bag. A 4501 uses the same style as the 4104 but has 8 bags on the rear.

I believe this is correct information for the way the buses left the factory. How it is equipped 50 years later is anybodies guess.

[JackConrad]

      When I installed the rolling lobe air bags from Mohawk Industries on our MC-8, I called Mohawk and asked what they thought the maximum pressure should be.  The person I talked to said an engineeer would call me back.  About 1 hour later, I received a call from an engineer at Mohawk. He told me that he could not recommend exceeding 85 PSI.  In acutal use, we have found that about 80 PSI gives us full lift when using our manual leveling system.  When using the OPEM leveling valves while driving, pressures never exceed 60 PSI.  Jack

[Jerry Liebler]

Jack,
     Thank you very much!  I'll set the regulator at 85 PSI.
Regards
Jerry 4107 1120