Leveling revisited for MCI 102

[niles500]

Why not look at the Level Low system on Prevost VIP coaches and copy that - FWIW

[sledhead]

I would not set the system up to auto adjust to drive level when the key is in the on position as mine does that and I will change that so when I want to drive I will add a switch for when I am ready to drive .
my new coach has the all auto setting by hitting the button for level when camping but to me it works in reverse as it always starts the level cycle by dumping the air in the system . some times this is good but if I am way off level then after it has tried and failed then the on board compressor starts up to add air and it takes a lot longer then if it were to add air in the beginning .

the old simple manual push to add air and pull to remove air system on the old coach was so much faster and way simpler to use and to adjust for level . plus it never had a leak as it was so simple with no splits in the lines from the valves to the bags

dave

[Jim Blackwood]

Well first off there is no key on this bus, just the main power switch on the dash and the main disconnect in the battery bay. It would be easy enough to add another switch in a convenient spot.

The present plan has about 3 options though.
(1)-full manual leveling using air switches (valves)
(2)-manual with solenoids on the bleed side (purge)
(3)-manual with solenoids on both bleed and compressed air sides

The last two allow for automated leveling later if desired but that would come... well, later.

In all 3 of these options there is one common feature. A valve is placed in the air line going to the air bag. That's the simple version, it can get fancier as desired.

The purpose of the (selector) valve is to isolate the air bag from the coach's onboard leveling system. This has two advantages. It means the coach's original leveling system does not change in any way. It remains as the manufacturer designed it, which is generally a good thing. The second advantage is the jacking system can now disregard the OEM leveling system entirely, another good thing. This can be done as simply as by adding the most basic of on-off valves but a high flowing solenoid valve makes the most sense. It should be a Normally Closed type so that it doesn't have to draw power when sitting leveled. Typically these will draw well under 1/4 amp of current when activated which is no problem on the road and if one fails it will default to the jacking mode which is an acceptable fail safe.

Between the selector valve and the air bag is one or more "T"s in the line for the jacking system. This can go back to the driver's area to a manual leveling valve and optional gage (1) meaning that can be the only additional air line and it can be large to help with rapid leveling. The system can instead use an adjacent solenoid valve to bleed for lowering along with the aforementioned line for pressurized air for lift, allowing monitoring of pressure (2). This can allow quicker lowering if a high flow solenoid valve is used. A check valve with a 20psi cracking pressure on the outlet of the purge solenoid could be used to maintain air bag integrity, this should still allow lowering to the bump stops. Or, solenoids can be fitted for both air and purge (3). A gage line may or may not be added as desired.

In all 3 of these options the leveling operation is still manual but the 2nd and 3rd lend themselves to automation if desired and allow more options. For instance a master switch could be used for All Purge when setting up if the ground is flat and a low step is desired, allowing the bus to be dropped to the bump stops before leveling. Or perhaps purge only on the rear or front. Then any of a variety of leveling switches or devices could be used to bring the coach up to level. Maybe they have an Android app for that, who's to say. You might be able to level your coach from 3 states away. Not my concern.

I think this plan makes more sense than trying to acquire and graft in someone else's system with no idea how that is supposed to work. It's minimally intrusive, can use easily sourced components, shouldn't be too expensive, and is easily upgradeable. My initial searches indicate that acceptable solenoid valves should fall in the $10-20 price range when buying in quantity. Should be under $300 in costs plus fittings and tubing. That seems pretty low-buck.

Jim

[thomasinnv]

Dave, what brand auto level system do you have? Mine is made by Valid and can be programmed to auto-level by either first raising or lowering according to user preference. Many of the older powergear air levelling systems were a joint venture with Valid as well and most have the same programming capabilities. My system is highly configurable to just about any parameter, but the average user would have no idea about any of it, most people just push the button and forget about it.

[Jim Blackwood]

I have some more information about the bus.

First, the two front air bags are in fact "T"d together and fed by the white line coming out of the kneel controls panel (photo above). There is no other connection to that line, and the "T" is welded to the bracket the leveling valve is mounted on, making it easy to mistake it being connected to the level valve. It is not.

A 1/4" red line comes from the LH air bag into the Kneel panel. it goes to the 50psi pressure switch.

A 3/8" blue line runs from the level valve forward through the bulkhead. I believe it is the line that goes to the distribution block connected to the air tank in the left front  under the driver.

A 1/4" white line runs from the level valve into the kneel panel where it connects to the bottom valve. We could really use an explanation for how that valve operates. My guess is that it is an air piloted 2 way valve and I suspect this will prove to be compatible with the system operation explanation, although I also suspect it has an internal bleed from the pilot line to the air bags. This would enable the slow rise after fast recovery.

So first off, the lines we need to access are available from the kneel panel and there is no need to go under the bus. Analysis of the kneel panel may provide more options for connecting the jacking system. For instance, hijacking the leveling pilot line may be all we need to do, although also hijacking the pressure switch may be an advantage for faster fill rates. Bleed can be accomplished through the PPV solenoid valve and the existing regulator will limit purge to 20psi.

I think we can do this with only one small 1/4" solenoid valve and some switches, maybe a relay or two. Pretty unintrusive to the original system too. So here's how I see it working:

Put a solenoid valve in the level line inside the panel. That shuts off the level valve and disables slow level control. Use a N/C valve so that when not OTR the system shifts to jack control automatically. Or, a master switch that lets you disable leveling OTR if you prefer. Or both.

Now to purge we power up the top coil of the PPV and exhaust the bellows as desired down as far as the bump stops, limited by the 20psi regulator.

Then we power up the bottom coil of the PPV and at the same time the fast recovery solenoid to lift the front of the bus. This may require a DPDT switch so that the two solenoids remain isolated. A diode could do the same thing. Or a relay. Provided the electrical power does not come from the 50psi pressure switch, full system pressure should be available for maximum leveling range. So, electrical switches, electric controls, upgradeable.

Now it also should be possible as mentioned, to hijack the level line. For this, a 1/4" line from that valve in the panel to a dash mounted operator valve with whatever air supply is handy (Bay door latch control supply?) would give manual control with no electrics.  I think that's about as simple as it gets but I would not expect it to be fast.

Jim

[Jim Blackwood]

I have a test ready for tomorrow, using bits-n-bobs. Removed the level line and capped it, stuck another line on the valve and put a manual 3 way  on it with a line to the quick disconnect on the front tank so that's all ready to go. If it works right I might be able to lift the coach off the blocks with the airbags. Find out about noon tomorrow.

Jim

[sledhead]

Dave, what brand auto level system do you have? Mine is made by Valid and can be programmed to auto-level by either first raising or lowering according to user preference. Many of the older powergear air levelling systems were a joint venture with Valid as well and most have the same programming capabilities. My system is highly configurable to just about any parameter, but the average user would have no idea about any of it, most people just push the button and forget about it.

the level system is a vintage 2000 H W H and works well but every time it dumps air to level first . but if I know it is a not a level lot I use the manual set up and do it myself by adding air to the part that is low and go from there . the system works ok but I like the bus nut way better

dave

[Jim Blackwood]

Of course it couldn't be quite that simple.

I did manage to get full excursion so that's the good news. Otherwise it was all pretty screwball. First, in order to hijack the leveling control line I had to shut off that valve it runs into. That's going to make control purely by air a PITA and while a 1/4" line will work it is going to be unbearably slow. I can't imagine running that size lines all the way to the rear. Wood blocks would be quicker. And the controls to the solenoids didn't react as expected either and it may take awhile to sort out what exactly is happening there. The PPV solenoid for instance wasn't real useful. It seems like is just shifts from pressure to exhaust which makes it no good for leveling. The fast recovery solenoid is good for raising, but only up to a point, probably the point where the 50psi pressure switch opens. Which means that has to be overridden somehow. I can probably sort that part out in the panel, at least I hope so but the 24v source is going to have to come from the dashboard area so that's another wire to run if a relay is needed.

A good wiring diagram would help. Unfortunately the ones in the tech bulletin are too fuzzy to read and as we know aren't correct anyway for this bus. The ones in the online maintenance manual all have the legend and some of the traces missing where the drawings were truncated so they aren't much help either.

I'm going back out to have another look, particularly at the circuit from the 50psi switch to the fast fill solenoid to see if I can find an easy way past that. Then I'll need a fast purge valve of some sort that I can open and close at my pleasure.

Still making progress, just not in a straight line.

Jim

[Jim Blackwood]

OK, not so bad after all.

Of note: some PO had screwed in the adjustment on the regulator to disable Kneel. It had the effect of setting a minimum air bag pressure that was close to normal ride height. I backed it off to the point where the regulator just starts to stutter. That seems about right or maybe just a small bit low. I haven't tested the kneel function and may find other issues there but I'd heard that disabling Kneel was common among fleet owners for liability reasons. So it may be fine.

Now for the fun stuff. Once the level line is disabled, jacking control is all electrical. No changes need to be made to the coach's ride control system.  4 wires run down to the panel are all that are needed I think, maybe another wire for the leveler solenoid.

On the terminal strip at the bottom of the panel are 5 posts, 4 of which are used. To raise the coach, a ground is applied to the left hand post and 28v is applied to the (bus) front terminal of the pressure switch. This will directly energize the fast fill solenoid and raise the front of the bus as high as it can go. You can stop by simply disconnecting. So a DPDT switch works here. It is fast enough that momentary-on will work fine. To lower, momentarily apply a ground to the second terminal from the left and 28v to the second terminal from the right. This will engage the PPV valve into purge mode and it will drop the front of the bus all the way down even after you remove power. The only way to stop it is to apply power to the fast fill solenoid. (which I think also applies power to the fill side of the PPV) So, the same SPST switch can be used for both, wiring power and ground to the center terminals and connecting the other four appropriately, 2 for lift and two for purge. Now you simply hit purge momentarily (spring loaded to center is what you want here or M-Off-M) , wait until it drops about where you want it, and hit fill. Then lift to level.

Doesn't get much simpler than that. I'll be ordering a common 1/4" solenoid valve and a switch if I don't have something handy. The only remaining question is how well it will hold the set level while sitting but it seems pretty air tight. I do plan to run a test where I set the level high and leave it though.

The rear doesn't look anywhere near that simple at first blush, but I've blocked it up and should be able to get at least part way in there for a look. Unfortunately there doesn't seem to be a handy convenient panel to work from.

Jim

[Jim Blackwood]

After some trouble getting a solenoid I found acceptable here is where I'm at. (Photo)

As you can see it's a push-on style which is convenient, just slice the tube and insert. The description said it is a 100% duty cycle but isn't meant to be on all the time. Whatever that means. Probably means at some point the coil will burn out but since the failure mode should be Off, big deal.

Next job is to find switched 28v in the panel if possible, or upstairs if not. Then find appropriate DPDT switches.

Jim

[Jim Blackwood]

Ran a 1/4" air line yesterday. I drilled a hole up into the air duct in front of the baggage door and fished a line up into the electrical panel by the driver. Two lines actually. I ordered some 5 conductor cable for the control wiring and will fish it through when it comes. So since I had enough air line on hand I fished that through first, cut the red line in the kneel panel (goes to the pressure switch) and connected that up using a push-on "T". Then I ran the loose end down into the service bay below and routed it over and up with the other air lines (having pulled the bay door control lines out, leaving the two lines running down the sides of the bus), pulling the slack up into the defroster area and attached an air pressure gage.

That leaves me some nice options. Because I have the manual air valves, I can "T" off of the gage line for a manual control as well as the electric controls. Slow but sure. And I'll be able to watch for leakage.

Next I'll add a ground to the new solenoid and clip a jumper wire to the 28v bus to air the system back up, check pressure, and see how well it holds air. The wire should come in a week or two.

I've also ordered a pair of 22ton pin type jack stands, and took a chance on a new Chinese supplier selling 22ton air/hydraulic jacks for about $50 each. I ordered a pair, so we'll see whether or not I just lit a cheap cigar with a hundred dollar bill. Should know in a couple of weeks.

Jim

 

[luvrbus]

You can raise the rear of the DL 4 inches with a button on the left upper panel it only works with 100psi and over takes about 10 to 15 seconds for it to raise 

[Jim Blackwood]

Yep, did that and blocked it. That might be a clue to the control system on the rear. I'll get a look at it once the jacks arrive.

I tested the new solenoid, the gage line, and the existing kneel and recover functions today, all worked as expected. Kneel pressure is just slightly over 20psi and standard ride height is at a bit over 60.

Jim

[luvrbus]

Yep there are 2- Norgren valves back there it should be easy

[Jim Blackwood]

Finished the wiring for the switches on the controls for the front today and tested. It works about as expected with a few quirks.

Resumption of normal ride height is fairly slow and only begins after the door is closed and if power to the new added solenoid is turned on. I can't say if the solenoid restricts flow and slows it down, but it might. It's probably fast enough though.

Purge (lowering) is very fast and does not stop until the rocker switch is pressed in the lift direction.

Lift is relatively slow but considerably faster than the automatic resume. I will play with it some later, it may be that the kneel switch will do the job just fine but it is unpowered with the main switch off.

Also the lift position on the rocker backfeeds main power, so all the instrument lights come on when lifting. Didn't notice that from down at the panel. But it's not a bug, it's a feature!

Jim