How important are leveling jacks?

[John From Detroit]

When it comes to broken windshields I do not see how a 3-jack system is any different from a 4-jack where the two front jacks are connected in tandem via a "T" fitting.

You still put the front jacks down first (this was not properly explained to me by the dealership) and this provides a pivot point as fluid can move jack to jack as you do the side to side leveling using the rear jacks only.

It also splits the load of the front end between the two jacks, putting a lot less stress on things down under

Now: If you want to talk about true 4=jack systems where every jack has it's own valve and their combined actions are computer controlled.

The MTBF for computers is way way lower than the MTBF for a "T" fitting.  In fact where as T fittings have but one practical failure mode (Leak)  Computers have many and some of them can be a real PITA

 

[Bob Buchanan]

When it comes to broken windshields I do not see how a 3-jack system is any different from a 4-jack where the two front jacks are connected in tandem via a "T" fitting.

Not sure if the front jacks "are" connected -- but even if they are, what difference would that make? You still have a distribution of the load between two jacks vs. one. Your legs are both connected to your hips -- but you are more stable with both feet on the ground vs. standing on one leg. That would even be true if holding on to someone else that has both feet on the ground (making a 3 point system).

 

[Ned]

I don't know of any jack system that operates the front jacks in unison.  That would be a very poor design as it would not allow for different ground levels on the two sides.  The better systems, like HWH, operate the front jacks together, but don't begin to raise the coach until both are solidly on the ground.  Similarly for the rear and sides pairs.

 

[Bob Buchanan]

>> Hmm, it would seem that HWH are the "experts" when it comes to leveling, but I sure don't agree with that quote.  For 8 years I had a motor home with a 4-point system (front worked in tandum), then last year I bought a Monaco with a 3-point system.  At first I was concerned, but I've grown to appreciate it much more. 
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As long as you are a happy camper with your current system, that's all that matters. I'll stick with the explanation (that makes sense to me) of two major company's that are successful and have installed systems on thousands of MH's -- via major MH vendor dealerships.

>> First of all, the purpose of Monaco going to the 3-point jacks was NOT to save money, it was to save windshields.  You put the front jack down first and you automatically have a pivot point for the front of the coach to revolve on during both leveling and jack retraction.  That saves an awful lot of frame twisting that might otherwise pop a one-piece windshield.
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Do you have a reference for that? My understanding (and I don't have a specific reference) was that the 3 point system came after the 4 point system that allowed each jack to operate separately. The 4 point system HWH and Bigfoot use is a bi-axis system that replaced the earlier versions that led to 3 point systems. The jacks only operate in pairs -- the front two, the left side two, right side and rear two. So no twisting of the frame can occur.

>> Also I've found it much easier to level with three jacks.  It's so easy, I don't even use the automatic leveler anymore.
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Yes, as I mention in an earlier post, a tripod is easier to set up than a quad pod -- however, a quad pod is more stable.

>> As for stability, I found a very slight amount of additional movement while walking within the coach, but hardly enough to notice and certainly not enough to be bothersome.
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Thank you for making my point. That movement, however slight in your mind, is twisting your coach on the single front jack pivot point. Add to that a 50 mph wind, and a house full of guests . . .

Anyway, Robmorg, thanks for jumping in. I say again, it's all a matter of personal preference -- just as is the case with toad braking systems. I recall asking a class of clerical personnel years ago which Word Processor that preferred. After the heated discussion that followed I decided to never ask that question to such a group again. The bottom line is, "The product folks prefer is the one they have bought and paid for and are currently using".

 

[ArdraF]

Phil,

Getting back to leveling blocks used with jacks and your specific unlevel site.  If you don't want to purchase blocks, it's relatively easy to make your own.  Jerry made some great ones that we needed for a couple of driveways.  He used 2 x 10 boards because we have 22-inch tires.  Two x 8s are fine for 19.5 inch tires.  He cut three boards.  One is approximately 22 inches long, one is about 17 inches long, and one about 12 inches long.  One end of each board was cut square.  The other end of each board was cut at a 45-degree angle.  Each one was stacked on the other with the shortest being on top and the flat ends placed flush.  He then drilled down through the boards so he could drop nails in to hold them together.  This allowed him to assemble the leveling blocks as one, two, or three boards high, depending on what is required for the site.

When we have the same situation you mentioned, we drive the front wheels up onto the leveling blocks to raise the coach (having graduated ends make the upward drive easier).  This brings it much closer to level.  Only then do you use the front jacks to perhaps raise the front end a little more.  You also may need a couple of square boards to put under the front leveling jacks because they will then be much higher off the ground.  This should allow you to level the coach and still keep several hundred pounds of weight on the front tires just as though they were on the ground.  See attached drawing.

ArdraF

 

[Phil Hendrix]

Thanks ArdraF.... great idea. When you try to drive up on the boards do you have any trouble with the boards sliding back as the tires try to climb up on the first board? In my situation I will need to back up on the boards because I have to back into my site but same principle.

Thanks, Phil

 

[Wendy]

In my situation I will need to back up on the boards because I have to back into my site but same principle.

Not necessarily. You can back into the site, farther back than you intend to be, and then pull forward onto the blocks. We do this all the time.

Wendy

 

[Jeff]

Ned:

I believe both HWH and Powergear have the front jacks fed by a single T'd line. (That's why after one jack reaches the ground it goes nowhere until the other also starts lifting and builds pressure on both of them. The purpose is to insure that the front jacks aren't twisting the coach in one direction while the rears are torquing the frame in the opposite. The result is identical to a three jack system but distributes the front weight out on the frame rails instead on on a single point in the middle.

 

[Wendy]

I can get level without leveling jacks (boards, blocks, etc). But do leveling jacks make a substantial difference in stability? We rock a lot walking around in the MH.

Wendy

 

[Tom]

The only time anyone has commented on our coach moving was when Ron Maribito boarded on our first trip tp Moab and we hadn't deployed the jacks. Contrary to the marketing and other hype, there really is no movement when all jacks on a 3 jack system are deployed. Having never had a 4 jack system, I wouldn't have the audacity to suggest that one is better than the other, although I see, from a technical perspective, advantages and disadvantages to both.

Based on everything I've read, limited personal experience, and numerous conversations with owners and suppliers, if we ordered a new coach we'd order air leveling.

I have no idea if the content of a user manual would be considered marketing hype, but my Monaco owners manual states:

"The front jack will be the pivot point for the chassis and is always lowered first. This reduces torsion stress on the body of the motorhome."

There's no mention of the frame. Why would there be any need of it?

While we were at two of Monaco's service centers, they were replacing numerous windshields in pre-Monaco products such as Beaver and Safari, some for the umpteenth time. It would be interesting to know if those coaches had 3 or 4 jack levelers. (It didn't occur to me to ask.)

 

[Ned]

Jeff, if the front jacks were fed via a "T", then it wouldn't be possible for the two side jacks to work in tandem.  Each jack must have a separate feed from the hydraulic pump.

See the attached diagrams from HWH for the 2 most popular 4 jack systems.  It's clear that each jack is controlled individually.

 

[Alaskansnowbirds]

While we were at two of Monaco's service centers, they were replacing numerous windshields in pre-Monaco products such as Beaver and Safari, some for the umpteenth time. It would be interesting to know if those coaches had 3 or 4 jack levelers. (It didn't occur to me to ask.)

In our pre-Monaco Safari Zanzibar, we have had three windshields replaced. All of them for stress cracks coming up from the bottom of the windshield. The first one was replaced by the dealer and the second one was replaced at the Safari factory. The last one we had replaced was done by a glass shop that came over from Cottonwood, AZ. and did it here at the house. When they put it in they said they didn't think the window opening was the right size and that was the reason the windshields kept cracking. So the next day they came back with tools and took out the windshield and cut the opening to fit the glass. Haven't had a problem since.

 

[Karl]

Wendy,

I can get level without leveling jacks (boards, blocks, etc). But do leveling jacks make a substantial difference in stability? We rock a lot walking around in the MH.

When leveling with boards or blocks under the wheels, you still have the body suspended over the springs and it will move. The jacks are connected to the frame, which takes the springs out of the picture and provides a solid footprint on the ground.

 

[Tom]

Hi Don. The "fix" I saw them employing for repeated windshield breakage or popouts was to grind away some fiberglass around the opening. That would tend to support the comment the glass guy made to you.

 

[Alaskansnowbirds]

Hi Don. The "fix" I saw them employing for repeated windshield breakage or popouts was to grind away some fiberglass around the opening. That would tend to support the comment the glass guy made to you.

That's what they did Tom. I don't know why when Safari replaced it they didn't do it right. I know there was a lot of windshields that were replaced. The only one I didn't pay for was the one the dealer replaced. He had to do that or I wouldn't have bought it.

I think the window openings were too small from the start. I don't know if they were designed that way with the intention that they would be cut to the right size when the MH was assembled or if the design was wrong and nobody ever bother to correct it.

 

[Tom]

Don,

I heard somewhere that the glass supplier changed something. Methinks it could be all, some, or none of the above.

 

[motojavaphil]

bernie, I have to agee with you about blocking under the tires.  The jacks can only do so much.  I know I have been in some Colorado campgrounds that need a little TLC to get rigs leveled.  I think you have to work within the lmitations of your system. 

We have been longtermed parked in Alb.  The manual suggests you level weekly which I do.  Apparently my left rear jack sank in and the wood decided to slide to the outside taking the jack  with it.  It tweaked the system so the jack would not retract.  I dug it out and I got the mobile RV guy over to get it retracted.  We will be spending a couple nights at the RV repair shop for the jack.  In the meantime we are leveling without jacks.  I like the jacks better, hands down.

Tom, Our Beaver has the three point system.  The manual makes it a point to lower the rears first and then the front.  In another thread this was discussed and it was determined we should put a little pressure on the front first and then the rears.  We do get some rocking but we are in soft soil.  Its good for a day or so after leveling.
Phil   

 

[Jeff]

Jeff, if the front jacks were fed via a "T", then it wouldn't be possible for the two side jacks to work in tandem.  Each jack must have a separate feed from the hydraulic pump.

See the attached diagrams from HWH for the 2 most popular 4 jack systems.  It's clear that each jack is controlled individually.

Ned:

I read the second diagram as pressurizing both front jacks at the same time and adding pressure to both fronts when left or right rear is pressurized??

The Power Gear Manual explains how their system works.

 

[Ned]

Jeff, the jacks are always operated in pairs, front, back, left, right, but in no case are any two connected together.  Each has its own control valve.  When extending the left side, only the left side jacks are extended, similarly for the right.  It would make no sense to extend 3 jacks at a time.

The full set of manuals and schematics for the HWH systems is available at this web site.

 

[Ron]

Don,

Sounds like your local glass company has better engineering capability than the manufacturer did. ;D ;D  Probably just removed a smeggin or two to allow the windshield fit properly. ;D