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Topic: Travel mode leveling (Read 722 times) previous topic - next topic

Travel mode leveling

Okay, I should know this but now am unsure about auto leveling while in travel mode. 

When we were in Yellowstone, not having a toad meant we drove the coach around a fair bit.  At low speeds, with windows open, tooling around that glorious countryside, I could hear the sounds of air exhausting as we rounded curves.  I was under the impression that this was an auto ride leveling function.  Is that right?  If so, is the same sensor used as when leveling while parking or is this an air pressure balance function?  Or is the whole my imagination? 

I haven't noticed this happening lately during my limited driving time. 

Thanks, Chuck
"Not so  long ago we were a nation of risk takers, riding five million pounds of  thrust straight into space."  Joe Gresh
Chuck Pearson
1996 U295
2018 Can Am X3 TurboRS

Re: Travel mode leveling

Reply #1 –
Chuck,

Been there, done that. We also drove about the park with windows open. We could hear the leveling system working. I will provide my interpretation of what is happening. Experts will likely support the explanation, improve it, or correct it.

When you level while parked, the leveling system tries to level the coach for the comfort of people, refrigerators, water in containers, etc. While in motion, the leveling system tries to keep the chassis at a constant height above the axles.

When traveling, the ride height (leveling while traveling) will be controlled by the ride height valves. There are two in back and one in front. It is easy to see the mechanisms in the back. Look in the access doors for the batteries and isolator. The ride height controllers are the valves and mounts that look like a big Tinker Toy structures with one rod connected to the chassis and the other connected to the H frame (the frame for the axles and wheels). The valves attempt to keep the distance between the H frame and the chassis at 8" when the coach is in travel mode. When the coach goes around a turn, the chassis will lean outward, compressing the air bags on the outside of the turn and expanding the air bags on the inside of the turn. The ride height valves will attempt to correct by exhausting air from the expanded bags and adding air to the compressed bags. On the next turn in the opposite direction, the valves will again exhaust air from bags on the inside of the turn and add air to bags on the outside of the turn. Changes in attitude from front to back because of bumps and attitude changes will cause adjustments. It is a dynamic adjustment system with the purpose of keeping the distance between chassis and H frames constant.

I found it fascinating to travel in conditions where I could hear the system working.
J D Stevens
1997 U295 CAI 36' Build #5085
2002 Subaru Outback
Motorcade 16869
Bellville, TX

Re: Travel mode leveling

Reply #2 –
When activated, the HWH will level the coach whether parked or moving. While driving, activation is automatic.
1994 U280, Build 4490
Deming, NM.

Re: Travel mode leveling

Reply #3 –
JD you are right on as to how it works while driving, pretty fascinating as to how it works
previous 1984 35 ft ORED 250 HP 3208 Cat       
previous 1998 40 ft U295 CAI 325 hp Cummins
previous 2003 40 Ft u320 build #6140 450 Cummins M11.                                                         
1999 Mazda Miata
Ron, Nancy, Tipper the cat, Max The dog
1997 U 270 36 ft build number 5174 8.3 Cummins

Re: Travel mode leveling

Reply #4 –
Thanks a million J.D., for the great explanation.  Now it's clear, I didn't imagine it after all.  So, the side to side leveling would be via the rear valves exclusively, right?  The front valve would be for fore and aft leveling only.

Guess I'm going to need to go back to Yellowstone to verify proper operation.  Not near as much fun doing hard turns in the Sam's Club parking lot. 
"Not so  long ago we were a nation of risk takers, riding five million pounds of  thrust straight into space."  Joe Gresh
Chuck Pearson
1996 U295
2018 Can Am X3 TurboRS

Re: Travel mode leveling

Reply #5 –
Quote from: Chuck Pearson –
Thanks a million J.D., for the great explanation.  Now it's clear, I didn't imagine it after all.  So, the side to side leveling would be via the rear valves exclusively, right?  The front valve would be for fore and aft leveling only.
Yup. In travel mode, "level" means that the chassis is the proper height above the H frames. When parked, "level" means the egg won't roll off the counter top while you get out the other ingredients. There are valves and controls for each purpose.
Quote
Guess I'm going to need to go back to Yellowstone to verify proper operation.  Not near as much fun doing hard turns in the Sam's Club parking lot. 
Yup, indeed! Cruising YNP is WWAAYY better than cruising a parking lot. We cruised the hills of Yellowstone NP with the windows open and could hear the hiss of the suspension system as it did its job. We set the retarder on about "3" and made our way at steady speeds while enjoying the fresh air and remarkable sights.
J D Stevens
1997 U295 CAI 36' Build #5085
2002 Subaru Outback
Motorcade 16869
Bellville, TX
 

Re: Travel mode leveling

Reply #6 –
Great explanation JD.

Now for those who are curious about how FT did air leveling before HWH, here is how it works and it's quite ingenious (kudos to CM Fore or whomever invented it): 

Each of the three ride height valves (mentioned above) is mounted on a small pivot plate that rotate the whole ride height valve.
Connected to the plate is a large sheathed cable (like the kind you see on boat steering) that rotates the entire ride height valve.  When this is done it "tricks" the valve into thinking it needs to add or subtract air from the air springs.

The cables lead to 3 mechanical levers on the floor between the drivers seat and wall:
Left for left rear.  Middle for front axle.  Right for right rear.
Example: Push the middle lever forward = front drops down proportionally.

The brain of the system is between your ears: read the bubble, move the lever.
Once the coach is level, it will stay that way as long as there is system air.
The levers have a center detent (with microswitches) to illuminate the dash "air level" light.  Light goes out = travel position.
Yes, it does take an extra minute to make adjustments.  My coach has a 120VAC 3/4hp air compressor to keep system pressure up.  I put a timer on it so it doesn't start in the middle of the night.
But think of it: No electronics.  No sensors.  No extra air valves.  Not even any extra airline connections.  Elegantly simple and reliable.

John Fitzgerald
1991 U300 (SAI) Side Aisle Island Bed 40'
Detroit 6V92 with Allison Retarder
Meridian (Boise), Idaho