Community Forums

marjoa · 07-05-2017, 11:37 PM

Quote:

Originally Posted by chief5631

The Coachmen manual says never use the jacks to "completely" put the entire vehicle in the air

1st - Tejay thanks for hat factual information

2nd - Coachman probably says that for safety reasons more than anything else. Some people think that since you can raise it up on jacks that's a great and fast way to work on the RV or change tires. So, I'm thinking they just made this blanket statement for overall safety & liability concerns.

From Tejay's data, it's clear the leveling jacks are designed to support the weight of the MH off the ground and MORE. In fact from his research, they are over designed to lift & support.

I'd like to know what Bigfoot told you. Please let us know.

Dtwallace · 07-06-2017, 12:25 AM

Don't forget the frame.

Not all coach frames are as rigid as Spartans, or Freightliner. That's more of the limitations we should be concerned with (IMO).

Stabilizing, and leveling is not always the same thing. Leveling may require lifting the coach at some point, stabilizing just firms up the stance taking the bounce moment from the rubber tires, (jacks just in contact with ground)....

My hydraulic jacks are close to 3" round at the shaft, and firmly bolted to the frame. I've seen jacks on other coaches that remind me of tooth picks.

So many opinions are drawn from the tooth pick size ram systems, that we forget that all coaches are just not built equally.

Know your equipment, and follow the coach builder's guidance.

DTW

ThePowells · 07-07-2017, 10:54 PM

Here is my 1.5€ worth.
The hydraulic system under our coaches would be more than enough to at least torque the frame out of alignment given resistance points. The scissor jack systems are exactly the opposite and the frame is much stronger than the jack.
Regardless of the terrain, anything less than the chassis being level is adding stress to the frame. Everything is designed based on the premise that the coach is level. What does the suspension contact? The chassis frame. Supporting the chassis with the hydraulics is no different than being on the suspension or on jack stands. You actually create much more frame twist by jacking up one wheel to change a tire.
You are going to get onto either a very serious or unstable incline to get a coach to move while on hydraulic jacks. I have had to slide equipment supported on hydraulic jacks / pads using a wrecker and it wasn't very easy and have actually used the rear jacks to make a wrecker sit still to recover something. Look at some off the equipment used off road that has hydraulic supports and works in mountain terrain.
There really isn't much difference between having park brakes that apply to the driveline as opposed to the rear wheels and actually the ones that apply to both rear wheels are more effective than the driveline as getting one rear tire off the ground or in soft contact where is can slide renders the entire parking brake useless if the rear differential isn't locked. Also having the park brake on the driveline used to be the norm for medium to heavy duty trucks without air brakes. The most effective park brake for a hydraulic system is the microlock followed close behind by the rubber wheel chock.

Boomertx · 07-07-2017, 11:04 PM

Quote:

Originally Posted by TeJay

chief5631,

Did some research and determined this. We have a WBGO Vista 30T built on an 18,000 lb chassis. The service manual for our leveling system made by Lippert lists three jacks. A has a 1.500 inch piston and is rated for 8,000 lbs. B has a 1.875 piston and is rated at 14,000 lbs. The C jack has a piston diameter of 2.250 and is rated at 20,000 lbs. That means that the the total of:

Four A jacks can lift 24,000 lbs.
Four B jacks can lift 56,000 lbs
Four C jacks can lift 80,000 lbs

Our coach has the B jacks. So each corner jack can lift or support 14,000 lbs for a total of 56.000 lbs. I guess my educated guess was waaaay off. Instead of being able to lift only 10% to 20% more than the max weight of the RV is can lift/support 300% more than the RV's total max weight of 18,000 lbs.

Chief that information should settle any questions or issues concerning the jacks and if they can handle the weight. Yes the manual states their concerne about having the rear wheels off the ground and therefore not having locked wheels touching to prevent rolling of the RV. That is exactly why Ford has the parking brake around the driveshaft instead of on the rear wheels as almost every vehicle has done for 50 years.

Glad I did this research. Now I know exactly how much the system we have is designed to lift and support. I hope this information is of benefit to others as well.

I appreciate the good data above except for what I've highlighted in red. If both sides of the rear axle are in the air, the driveshaft brake will be just as useless as the wheel brakes in preventing rolling off the jacks. That does bring one question to mind though, do any of you use wheel chocks?

Thanks to all for the interesting discussion!

TeJay · 07-08-2017, 06:00 AM

I agree with having both rear wheels off the ground. In all our years of camping I don't ever remember even one rear wheel being lifted off the ground.

Most often I see wheel chocks under TT's and 5ver's. Yes some MH'ers will use chocks but they are usually friends that we know who are almost always deciding that for them if something can go wrong it will so they take every precaution known to man, women & child. Don't get me wrong they do have their place and while I don't carry them I do have wedges of wood slabs that I'd use to create a chock.

We camp all over the state of AR in all kinds of CG's both public and private. Seldom do we encounter questionable sights as far as not being very close to level. If we do we usually move to a different sight.

Dtwallace · 07-09-2017, 03:04 PM

Quote:

Originally Posted by TeJay

I agree with having both rear wheels off the ground. In all our years of camping I don't ever remember even one rear wheel being lifted off the ground.

Most often I see wheel chocks under TT's and 5ver's. Yes some MH'ers will use chocks but they are usually friends that we know who are almost always deciding that for them if something can go wrong it will so they take every precaution known to man, women & child. Don't get me wrong they do have their place and while I don't carry them I do have wedges of wood slabs that I'd use to create a chock.

We camp all over the state of AR in all kinds of CG's both public and private. Seldom do we encounter questionable sights as far as not being very close to level. If we do we usually move to a different sight.

X2, I've only encountered a situation where my rear wheels clear the ground at home in my back yard where we park the coach.

The wheels will clear by an inch and I have no reason to be concerned with the coaches stability there.

When I roll out of the yard in preparation for a trip, I'm sometimes delayed and need to level the coach in the front yard.

When that happens, it's nose high and I'll need a step stool to make up for the excessive height to get in and out.

I would never except a camping spot that is so far out of level, that I would need to use an extra step up front to get in and out of the coach.

I see lifting the rear wheels no more than an inch as a non issue, and using chocks as unnecessary unless I'm working on the coach without the brakes set.

I do keep chocks in the trailer for when it's parked, or needed for any other reason not planed for.

But chocks placed at a wheel on the coach that will move and pinch them in during leveling is not something I see as useful.

DTW