Powergear leveling system

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mrschwarz

mrschwarz

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Jun 7, 2009
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I have an 08 Meridian with a Power Gear leveling system. Unlike the HWH systems in my previous motor homes, to level side to side, the system only uses the rear cylinders. The two front cylinders only function together when the front of the coach needs to be leveled. I though something was wrong with the system until I read the manual. Its behavior was described the same way.

This makes no sense to me. When extending a single jack, isn't the chassis being twisted? It's also very difficult to manually level when I have it at home. My slab is not level. What I used to do was I would raise the low side up as high as it would go. I would then raise the other side until it was level. This leveled the coach and raised it up as high as it would go. I can't do that any more. In fact, it's pretty difficult to manually level the coach at all.

Is there logic for the system to behave this way? Is this a throwback to the 3-cylinder systems that were used for a few years? I would be curious of others' opinions about this.

Thanks in advance.
 
Wow, I don't see how that would work at all, unless like you indicated that it only had one front jack in the center of the chassis.  It seems like your system would twist the frame severly.  I too sometimes have to raise one side or the other quite a bit to level in a spot.  Heck, I've even has to throw blocks under the jacks on some sites!  Not recommended, but sometimes there is no choice.  Your system is electric, right?

Sarge
 
If the system is working as designed, that's unbelievable.  Yes, only one jack extended will twist the frame.  If you can manually control the jacks, level side to side first using front/rear jacks on port or starboard, then level front to back.
 
You guys aren't understanding how the Power Gear system works. It is actually an superb design. The front pair are served by a common hydraulic cylinder, so each front jack always has the same pressure as the other (law of physics). As the rears move, the fronts shift to keep the pressure in balance and thus always support the front end with equal pressure on each side. That totally eliminates chassis twist by allowing the front to move from side to side as needed in response to the rear jack movement. There is simply no way to torque the chassis unless one of the front jacks reaches the end of its travel before a rear extends fully. That's conceivable but extremely unlikely.

Essentially this method combines the best feature of the single front jack (no twist) with the better stability and load spreading of two front jack legs.

I've owned two coaches with Power Gear jacks and have several years experience with them. They work..
 
In the Power Gear, both fronts ALWAYS hit the ground. As soon as one touches, it stops moving until the other reaches the ground.  It is possible to make only one rear hit the ground if you use manual override, but the front still "rolls" to the opposite side to avoid twist.  That's why mrschwarz now has some difficulty in leveling in his yard - the offside keeps dropping as he lifts the other side.  To counteract that, the front has to be raised higher (increases pressure on the front jacks) until it is supporting a similar amount of weight as the rear and stops dipping. In unusual side-side leveling situations, it can be a nuisance or even require some blocks under one side to assist. That's a drawback of the PG system.  The HWH system has drawbacks in other leveling scenarios, e.g. when only one corner is low. Neither is 100% perfect.
 
Is there a logig.. Yes. there is..  First the two front jacks do operate as a single unit, however not the way you might think.

If you are interested in a fun experiment try this,  With the jacks retracted and a 2-way conservation possible between you and your partner, slip a 4x4 under one, just ONE front jack, have your partnet extend the jacks till the one jack hits the 4x4... Then have partner extend a bit more.. You will find the other jack continues down

WHY?  Because the two jacks are connected together with a "T" fitting and fluid can flow from jack to jack.. This effectively makes the system a tripod system

As you know 3 points determin a plane

So, you extend the front jacks.. You now have a system that can "Teeter Totter" on the two front jacks, as one goes up, the other goes down

Now you extend the rear jacks and then extend just ONE rear jack, to level side to side.. As the one side goes up. fluid flows from the other side front jack so the low side jack extends

NOTE: this does not work if the jacks are FULLY extended.

But it does work

You get the benefits of a 4-point jack system (Greater stability, less stress on the frame cross member where the single front jack attaches on a 3-jack unit) and the benefits of a 3-jack system (Way Simpler control system)  All in all a very good design I think.
 
John - good explanation.  It does make sense that the two front jacks are acting as the third point in the triangle.  I suppose the issue would be what, if any, advantage the system has over HWH.  Maybe a good topic for another thread.
 
THe advantage is that the Power Gear system is more fool proof.

I have heard of cases where wither the control computer, or a technician, got "Confused"

and .. Well imagine the following arrangement of jacks

2-------4
1-------3

Now to raise the "lower" side, you extend 1 and 3, but suppose someone cross wired and it extends 1 and 4 instead (or the computer gets confused and extends 1 and 4)

Has happened.

Can't happen with the 3-valve power gear setup cause as you extend 3 (3 and 4 are the rear jacks) 1 will naturally extendand 2 retract to make up for it. Keeping the harmonic balancer at exactly the same height above the ground (Pully on front of engine) if it is a front engine gasser like mine.

It is also less expensive, A "T" fitting is way less costly than a valve and the control electronics.

NOTE: the system it happened on, that I heard of, was NOT an HWH, I forget the name but it was NOT one of the more common names (Power Gear or HWH)
 
So the front two jacks are connected. Pressure will always equalize between them. I should raise the front first and them side to side. That makes sense. What doesn't though is that the front acts like a pivot. Put weight on the left and it leans to the left. Put weight on the right and it leans to the right. I could stand to lose a few pounds, but my weight is pretty insignificant compared to the weight of the motor home, but wouldn't walking around inside  cause movement and vibration? Isn't one of the purposes of the jack to create a rigid connection between the chassis and the ground?

How is this better?
 
Well, I do feel vibration when wife enters.. but the motor home is what, 2200 empty, wife is perhaps 10% of that if she's loaded down with heavy groceries (NOTE that I'm not giving away her weight here)  I can hit perhaps 20% of that if I load myself up to the max with heavy stuff (I can carry quite a bit of weight)

You won't torque the frame any.

But I'm sitting on the rear jacks when I feel it.

I do have reason to believe I might have an air bubble in one of the rear lines though.. Long story. Don't know how it got there, or how to get rid of it.. not sure I care
 
2200 lb RV..?  

Must be Detroit math.

Maybe it's because I have a mid-side entry on my Bounder, but I've never experienced any movement when someone walks around inside or enters/leaves the coach when jacks are down.  Maybe the quality of coach has something to do with it.
 
My buddy has a 28' Trek with a single jack in the front, and there is some motion when you walk around the front area.  I've been quite pleased with my HWH jacks (once we had them replaced for slow retraction.)
 
I've never seen a 2200 lb. motorhome, must get great fuel economy :D
 
John Canfield said:
My buddy has a 28' Trek with a single jack in the front, and there is some motion when you walk around the front area.  I've been quite pleased with my HWH jacks (once we had them replaced for slow retraction.)
Click to expand...

John, I wonder if having just one physical jack v/s the two that self-equalize would make a difference in motion felt from walking about.

With all power removed, I would guess that the motion will not be instantaneous due to time required for fluid to bleed from one jack cylinder to the other, on the four jack Power Gear systems.  Just a swag...
 
Lou (onaquest) said:
John, I wonder if having just one physical jack v/s the two that self-equalize would make a difference in motion felt from walking about.
Click to expand...

Lou - don't think I have ever been in a rig with the Powergear system, so no opinion here.
 
I've owned two coaches with the Power Gear floating front jacks system and have a close friend who has the 3 jack system on a 2000 American Dream. The 3-jack system has a bit of jiggle when a guy my size (240 lbs) moves from one side to the other suddenly. The 4 jack power gear moved much less, but was not totally motion free either. 

Our current coach has an Equalizer 4 jack system that auto levels by putting all 4 jacks in ground contact and then using small increments of jack pressure in sequence around the coach to avoid any chassis twist. It never moves any one jack enough at one time to do any damage.  However, I think I could generate some twist in full manual control because I can operate each jack independently that way. Nothing to stop me from doing whatever I want in manual control mode.
 
Sorry Ned. missed a ZERO

And to John Canfield.. I don't know. I doubt it

The major difference is where the jacks are attached

THe Power Gear 4-jack system the jacks all attach to the main frame rails
These are the STRONGEST rails under your motor home. They are designed to support the entire rig, and in fact, that is what they do.

On the 3-jack system the single front jack is attached in the center of a cross rail

Cross rails are not, usually nearly as strong as the main frame rail.

And what's worse.. The weakest point on that cross rail is the exact center.. Exactly where the jack is bolted.
 
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