Happijacs, what will happen if.........

[mt-ed]

When reading about the operation of my happijac electric camper jacks, it stated numerous places, "Never raise the back of the camper higher than the front".

Why? Is the location of the front jacks at a fulcrum point of the camper and if the back gets too high it will tip over front ways?

That's about the only thing I can think of. Anyone else know of any other reasons?

Thanks in advance.

[HMS_Beagle]

I think the reason they say this is due to the potential for forward weight shift if carried to extreme. At normal angles, not a problem*. I don't think it is due to worries about bending the jacks, certainly carried to extreme you could bend the jacks, but you are nearly equally likely to bend them tilting aft as forward - the bending moment on the jacks is nearly the same - and they do not caution against tilting aft. It cannot be due to concerns about tipping over forward, it would be a highly unusual camper that would do that even at full jack travel.



* Take a 4000 lbs camper, vertical CG 4' above the box floor, 10' between jacks and longitudinal CG 3' back from box front. Level, front jacks take 2800 lbs. 5 degrees forward slope changes this to 3080 lbs. If the jacks are that close to failing you have many more issues to address. Yes, I am an engineer...

[bigfootford]

JoeChiOhki wrote:
The logic I can see and its not just unique to Happijacks is the rear jacks in most cases have the tubes anchored the full length down the wall of the camper, allowing the camper to restrain the side to side movement of the jack tube. The fronts are only anchored on at a very small section of the tube turning them into giant fulcrums.

When you tip the nose higher the rear jacks are restrained by the camper itself and don't begin to flex to the side as the weight application changes.

When you go the opposite direction, the front legs have nothing to prevent them from flexing or twisting toward the rear, apply enough downward dog pressure and the jacks will either buckle or the anchor points will fail, because you've been applying a twisting forcing to that limited anchor area with a fulcrum. (Think of how using a cheater bar on a socket wrench amplifies the force at the nut or bolt, you're doing the same with your front jacks).

Exactly! Good explanation Joe!

Jim

[JoeChiOhki]

The logic I can see and its not just unique to Happijacks is the rear jacks in most cases have the tubes anchored the full length down the wall of the camper, allowing the camper to restrain the side to side movement of the jack tube. The fronts are only anchored on at a very small section of the tube turning them into giant fulcrums.

When you tip the nose higher the rear jacks are restrained by the camper itself and don't begin to flex to the side as the weight application changes.

When you go the opposite direction, the front legs have nothing to prevent them from flexing or twisting toward the rear, apply enough downward dog pressure and the jacks will either buckle or the anchor points will fail, because you've been applying a twisting forcing to that limited anchor area with a fulcrum. (Think of how using a cheater bar on a socket wrench amplifies the force at the nut or bolt, you're doing the same with your front jacks).

[mt-ed]

Fishbreath wrote:

If you feel that comments to your questions are not accurately answered, I would suggest contacting the manufacture for answers.
Good luck and welcome to the Forum

Thanks FB! Actually, the first place I went to was the mfgr.! I just thought I'd ask it on here as well, while I was waiting for the response from them. I intend to share their response to me on here once they get back with me. I'm more interested than ever to hear "their" response!

[Fishbreath]

What is with all of the nasty comments to a new member? Here is a person asking a legitimate question and some old timers feel it is necessary to berate him.

Mt-Ed, please do not let these negative comments deter you from seeking advice on this forum. There are a lot of knowledgeable people here. Just remember that it is advice from the Internet and some of it will be speculation, conjecture, hallucinations and just plain BS. After you sift through the comments, you might just be able to come up with the correct answer.
If you feel that comments to your questions are not accurately answered, I would suggest contacting the manufacture for answers.
Good luck and welcome to the Forum

[Grit_dog]

mt-ed wrote:

AISURFFISH wrote:

mt-ed wrote:
"Never raise the back of the camper higher than the front".

Why?

If you seriously have to ask this question then you do not need to be owning a truck camper...

Hmmmm...your response clearly indicates that you do not know the answer to my question either, and camouflage your ignorance with such a useless response!

"If" you are truely so wise and "all" knowing why are you here if all you're going to do is insult those of us that are trying to learn?

Your response added absolutely NOTHING to the advancement of truck camping!

Bingo!
I never saw that warning on our (heavy) TC and can guarantee the back was higher multiple times. Either when loading / unloading on uneven ground that sloped down to the front.
Never fingered it was an issue (within reason of course).
I'd guess it's a catch all statement due to someone, somewhere, sometime, lifting it way out of level front to back, having an issue and purporting that the issue was caused by the lack of a warning.
Similar to the don't stick you hands under a lawnmower stickers...

[mt-ed]

AISURFFISH wrote:

mt-ed wrote:
"Never raise the back of the camper higher than the front".

Why?

If you seriously have to ask this question then you do not need to be owning a truck camper...

Hmmmm...your response clearly indicates that you do not know the answer to my question either, and camouflage your ignorance with such a useless response!

"If" you are truely so wise and "all" knowing why are you here if all you're going to do is insult those of us that are trying to learn?

Your response added absolutely NOTHING to the advancement of truck camping!

[Homeless_by_Cho]

AISURFFISH wrote:

mt-ed wrote:
"Never raise the back of the camper higher than the front".

Why?

If you seriously have to ask this question then you do not need to be owning a truck camper...

PLEASE DON'T BE NASTY TO A PERSON WHO IS TRYING TO UNDERSTAND THE REASONING BEHIND THE STATEMENT!

LeRoy

[Longshore]

AISURFFISH wrote:

mt-ed wrote:
"Never raise the back of the camper higher than the front".

Why?

If you seriously have to ask this question then you do not need to be owning a truck camper...

I disagree with this statement.

[AISURFFISH]

mt-ed wrote:
"Never raise the back of the camper higher than the front".

Why?

If you seriously have to ask this question then you do not need to be owning a truck camper...

[AnEv942]

I look at it as weight transfer, front jacks already carry a lot more than rear. As the rear jacks are raised some of their weight/load moves to front. IE not paying attention I can easily raise one rear jack off the ground-
To a degree yes the fronts are at fulcrum point and the higher rear is the closer they get. Also they are mounted to camper at 90°, feet, front & rear are fixed to ground so as you raise as mentioned and load becomes less vertical thru legs (tube) is when tube failure more likely. Even with front jacks fully collapsed and rears full extended I doubt you could topple over on its nose, though mostly because either the jacks would buckle or mounts fail first.

Be interesting on camper destined for recycle to test some of these failure scenarios to see what really happens.
But not on mine, going up/down nose is always higher till it contacts bed of truck.

[jimh406]

There really isn’t any reason to when you are loading/unloading. Instead, I think the common recommendation is to raise the front slightly to be able to pull out without dragging. Off the bed, you probably would only need to barely have the front or rear out of level assuming you picked a reasonable spot.

[3_tons]

"Never raise the back of the camper higher than the front"....Why”??


“Stop, the stove is HOT, DON’T TOUCH A HOT STOVE”!!

[joerg68]

The center of gravity is roughly 1/3 of the way back on the camper floor on most campers. It will not topple.
But the jacks are not designed to take a lot of side (right/left/fwd/aft) loads. As far as I see it, you would create a forward momentum on the front jacks which would try to bend them backwards. They are under a lot of stress as is and don't have a lot of reserves. A jack mount might fail or a jack leg might bend, or a jack might loose footing and slide away. In which case you will end up with a buckled jack and a camper on the front or side...
(Sorry for potentially botched non-engineering language. Not an engineer, and not a native english speaker at this end)