Manual air system....

[Ncbob]

Being a relative newbie I sometimes have a problem 'thinking outside of the box'.  I've noticed some references to manual air systems, assuming that means removing or bypassing the leveling valves, and that's something that  Fred Hobe and I talked about a couple of weeks ago when I stopped there.

As far as I'm concerned it's a foregone conclusion that before changing anything in the air suspension system it would be necessary to test each air beam/bag combination to make sure there are no leaks.  That being done then install the manual system.  The advantage being that the bus suspension system (like a tire) would hold air and not settle.  Mmmm, sounds good to me.

But, as always, that brings up other questions.  How then does one determine what pressures to run front/rear or side/side?  Too then, without the levelers there's no recovery in cornering as with the valves
(albeit slow in recovering...it does recover).

Any thoughts? Remember..I have a MC5 so probably don't encounter some of the problems you big fellas do with the 40'ers and the tag axles.

NCbob

[tekebird]

Only reason I can see for a manual system would be to make the coach level on unlevel ground.

I think as far as ssettling, which is cause by leaks you still have that possible failure in a manual system.

You also will likely lose some of your ride comfort......the system as designed is  constantly adjusting things via the leveling valves.

Just my opionion

[JackConrad]

    When parked, movement of the coach causes the leveling valves to adjust the air volume in the bags. With no air in the system, air flows out of the bags, causing the bus to settle.
     I made a system for our MC-8 that still uses the OEM leveling valves when driving, but takes them out of the system when parked. My set-up closes the air line between the air bags and the leveling valves using solenoids. 2 additioinal solenoids on each corner add or remove air form the air bags to level the coach (within the limit of air bag travel).  We also installed a dump on the tag axle.  Jack

[tekebird]

jacks system makes sense.

you could also just get a small electric compressor and plug it into shop air inlet........and add a redundant compressor.  I lost a compressor once and bought a cheap electric compressor.......which more than  provided the needed air to get home where I could make the repair myself.

[TomC]

I highly recommend you keep the original leveling valves for driving down the road.  Otherwise, you'll have to be constantly measuring the ride height (or the height of the bus from the road) for proper ride height in relation to loads taken in and released (like when you dump your tanks, fill with fuel, use fuel, fill propane, etc).  I also made my own leveling system that uses Skinner 12v continuous duty solenoids.  One is in the line between the current leveling valve and air bag that cuts off the air supply to the air bag when activated, then tee'd inbetween the solenoid and the air bag two more solenoids for either adding or exhausting air from the bags.  Works well, and can level the bus in less than a minute at the campsite, or just dump them altogether to get it low enough where I don't need an additional step to get into the bus.  Plus if you do blow a leveling valve, can go on down the road in manual mode.  Good Luck, TomC

[H3Jim]

Jack, are those solenoids you used constantly on when driving or do they only use power when they are being switched?

[Stan]

I used a Skinner 3-way valve to switch between leveling valve and manual control. They default to manual so that no power is used when parked. They automatically switch to the leveling valves when the master switch is turned on. On 24 volts they draw less than one-half amp when energized while driving.

[JackConrad]

   Jack, are those solenoids you used constantly on when driving or do they only use power when they are being switched?  

     They are using power when in the open position, similar to the engine stop solenoid (except these have a larger orifice).
     The ones used to keep the air flowing from the leveling valves when the master switch is on, are using power all the time the master is on (like the engine stop valve). When parked, the only time they use any power is during the leveling operation. We have stayed for 2 weeks with no "air drain down".  Jack

[TomC]

There are always two sides of the coin.  I understand Jack's system, but my theory is to have everything off when driving down the road so that nothing can fail causing inconvenience (although those solenoids are very reliable).  So mine are activated when you want to use them in manual mode.  The down side is that as long as you are camping they are activated, but they do use very little current.  Same idea, just different actuation theory.  Good Luck, TomC

[H3Jim]

Do they make solenoids that only use power when switching, but not when in either position?  the electrical analogy would be like a latching relay?

[Stan]

Latching Solenoid Valves: Most of the standard Skinner valves are available with a "Magnelatch" operator. This operator uses a 20 msec pulse to operate the solenoid and then it is held by a permanent magnet.

[DavidInWilmNC]

Doesn't a member of this board (I can't remember his name) offer a pre-made system for air levelling?  I seem to remember reading a post by another member who used his system.  If one were really concerned about reliability, a couple of manual ball valves in the front and rear bays could be used to level the system when parked and to switch it back to automatic when travelling.  I believe J.R. has a system like this.

David

[JackConrad]

Pete Pappas (Daytona RTS) sells a system that is very similar to the one I made.  Jack

[jjrbus]

 I do not know about 40 footers, RTS ect. But on our little 35 ft MCIs there is no reason to leave the original system intact. Ride quality and handeling are not affected by the change.
Load the bus up the way you are going to travel in it. Then get out the service manual go to the suspension section, look for the pictures of the front and rear suspension. You will see dimensions at the axle bumpers. Add or reduce air pressure to obtain these dimensions, note what they are on each individual gauge. Use that # each time to level your bus for traveling. Unless you have a 400 lb freshwater tank or a 1000 gal fuel tank, or something else to cause sever weight changes, you will encounter no problems. When you purchase valves for the system buy one extra to carry with you, this will ensure that you never have a problem.
I did leave the original system in the bus. It is still there just unhooked.
When doing the change do not use 2 seperate valves for the front of the bus, this will cause unpleasent cornering! .
  . I've used this system for about 5 years and 20K miles with no problems. I have left this bus sitting for 5 months and returned to find it almost the same as I left it!
All of this is of course only my opinion and experience. It is no way intended to sound like it is the right way to do it. Or the only way to do it. I explored the options and did what made the most sense to me. HTH

[NJT 5573]

Kenworth uses an inexpensive valve that is frame mounted. It uses an arm that then connects to the  differential to control the amount of air needed to obtain the set height.(Length of arm). If you are loaded or mt the ride height never changes.