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

mt-ed
Explorer
Explorer
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.
28 REPLIES 28

HMS_Beagle
Explorer
Explorer
I hear ya, square tubes with their flat sides may have buckling modes that round do not - depends on the thickness of the wall. I've had Happijacks on two campers and I'd consider them about par for RV equipment, which let us be honest is an extremely low bar. And Lippert isn't the top drawer of that low set either. I've yet to have a Happijack catastrophically fail, I have had them slowly self destruct and need rebuilds or parts. My expectations of them - like other RV equipment - is low, so I treat them gently.

But you can find as many complaints about their competitors. Like many things in RV land, you have to build it yourself or adapt it from another industry if you want reliability and quality.
Bigfoot 10.4E, 2015 F350 6.7L DRW 2WD, Autoflex Ultra Air Ride rear suspension, Hellwig Bigwig sway bars front and rear

stevenal
Nomad
Nomad
When picking up my 1st TC in 98, the dealer demonstrated loading. No motors on the HJs, so my help was needed. We lowered the TC until it was an inch or 2 off the bed, and even. Then we dropped the front until it made contact before dropping the rear. The slant of the uploaded bed combined with the front down 1st philosophy put the TC front well below the back while in this part of loading process. The jacks survived this and every other loading without failure. Dealer approved and time tested.
'18 Bigfoot 1500 Torklifts and Fastguns
'17 F350 Powerstroke Supercab SRW LB 4X4

JoeChiOhki
Explorer II
Explorer II
HMS Beagle wrote:
There is no mystery to the engineering of steel tube, round, square, or otherwise. Both shapes resist torsion and bending. And a square tube will resist both more bending, and more torsion (and more compression while we are at it) than a round tube of the same dimensions. This is very well worn and reliable science that can be found in any properties of materials textbook.

I think these myths stem from the fact that using a given amount of material, you can make a round tube that is slightly stronger than a square one. In other words, the same amount of material used to make a 2" square tube could have been used to make a 2.5" round tube, and the round tube will be stronger. But at the same dimensions - 2" tube to 2" tube - the square tube is stronger.


I was thinking more specifically to point loading in the classic square vs a circle stress format.

Happijacs have notoriously buckled from side loads at the point where the outer tube is applying sidewall pressure to the inner jack tube, where as similar round tube jacks have bowed and deformed, but not completely buckled in on themselves (they've taken on a curve, like bending a roll cage).

They haven't been known on this forum as "crappijacs" for nearly two decades for nothing, between their tube wall weaknesses and the sheer pin problem that would literally cause the camper to plummet to earth, and all of this BEFORE Lippert got ahold of the company, a company notorious for poor quality steel trailer frames.
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HMS_Beagle
Explorer
Explorer
There is no mystery to the engineering of steel tube, round, square, or otherwise. Both shapes resist torsion and bending. And a square tube will resist both more bending, and more torsion (and more compression while we are at it) than a round tube of the same dimensions. This is very well worn and reliable science that can be found in any properties of materials textbook.

I think these myths stem from the fact that using a given amount of material, you can make a round tube that is slightly stronger than a square one. In other words, the same amount of material used to make a 2" square tube could have been used to make a 2.5" round tube, and the round tube will be stronger. But at the same dimensions - 2" tube to 2" tube - the square tube is stronger.
Bigfoot 10.4E, 2015 F350 6.7L DRW 2WD, Autoflex Ultra Air Ride rear suspension, Hellwig Bigwig sway bars front and rear

silversand
Explorer
Explorer
....round steel tubes vs. square: one resists torsional twisting; one resists load bearing when horizontal. But every application is complex, and situational.

....just adding to Matt's excellent explanation:

Also, remember that putting a (pay)load in a truck will drop the truck (and bed) from a few fractions of an inch, to 2 or 3 or more inches in the rear. Measure the slope of your truck bed before applying the truck camper load.....then after. The unloaded truck bed will sit quite a bit higher in the rear, and if your truck camper nose is a bit low, when you pull the truck forward whilst unloading, the rear bed surface may "beach", potentially severely "bending" the jack leg(s).....
Silver
2004 Chevy Silverado 2500HD 4x4 6.0L Ext/LB Tow Package 4L80E Michelin AT2s| Outfitter Caribou

HMS_Beagle
Explorer
Explorer
But, if I load 2 pallets of bricks on the roof rack at the back, then I can tip it over the back jacks too.

Unfortunately in the modern society we live in, you can't just say "don't do anything stupid", because it assumes too much.
Bigfoot 10.4E, 2015 F350 6.7L DRW 2WD, Autoflex Ultra Air Ride rear suspension, Hellwig Bigwig sway bars front and rear

mkirsch
Nomad II
Nomad II
StirCrazy wrote:
HMS Beagle wrote:

Happijacks explanation must be out of an "abundance of caution". Suppose you had a camper with the CG 4 feet off the floor and 2 feet back from the front of the box. Most large campers would sell their soul to get the CG that far forward. To tip it to the balance point you'd have to get it 26 degrees nose down. With 4' of jack travel and a short box camper, you might just be able to manage that. Not sure why you would try, it's kinda like telling kids not to put beans in their nose.


I am not rich enough to have electric jacks so I am constantly lifting the back end higher than the front and vise versa when loading and unloading as I dont have enough arms to pump all 4 jacks at the same time. I have checked to see how stable it is and it is real stable at a slight inclanation so I am not concerned with how I do it, but it would be nice to be able to do all 4 at once and eliminate that whole procedure.


OBVIOUSLY we are not talking about, "If you raise the rear even a FRACTION OF AN INCH higher than the front, you will open a portal to hell and release Satan and all his demonic minions."

It has to be some significant amount. Why they don't specify, is because it's easier to say "Don't do it AT ALL!" and not leave it open to interpretation.

"Don't raise your camper more than 25 degrees," gives the end user ideas. Plus if the weight distribution of the camper is not "standard" that number will change. Let's say they loaded the cabover storage with bricks, and it tips over at 24 degrees.

Putting 10-ply tires on half ton trucks since aught-four.

StirCrazy
Nomad III
Nomad III
HMS Beagle wrote:

Happijacks explanation must be out of an "abundance of caution". Suppose you had a camper with the CG 4 feet off the floor and 2 feet back from the front of the box. Most large campers would sell their soul to get the CG that far forward. To tip it to the balance point you'd have to get it 26 degrees nose down. With 4' of jack travel and a short box camper, you might just be able to manage that. Not sure why you would try, it's kinda like telling kids not to put beans in their nose.


I am not rich enough to have electric jacks so I am constantly lifting the back end higher than the front and vise versa when loading and unloading as I dont have enough arms to pump all 4 jacks at the same time. I have checked to see how stable it is and it is real stable at a slight inclanation so I am not concerned with how I do it, but it would be nice to be able to do all 4 at once and eliminate that whole procedure.

Steve
2014 F350 6.7 Platinum
2016 Cougar 330RBK
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HMS_Beagle
Explorer
Explorer
JoeChiOhki wrote:


I do also wonder if it has to do with Happijac's choice to use square tube jacks, as their jacks have been known to buckle at the pressure point between the outer and inner tubes before. Round tubing is naturally stronger by shape than square tubing and will take a good deal more strain without failing catastrophically than square tubing does.


From an engineering point of view, square tubes of the same dimensions are stronger in every direction than round, and not by just a little: for example a 2" square tube with 1/16 wall is 70% stronger than a 2" round tube with the same wall (though only 20% stronger if bent on the diagonal). If the round tube is bigger or thicker, then sure.

Happijacks explanation must be out of an "abundance of caution". Suppose you had a camper with the CG 4 feet off the floor and 2 feet back from the front of the box. Most large campers would sell their soul to get the CG that far forward. To tip it to the balance point you'd have to get it 26 degrees nose down. With 4' of jack travel and a short box camper, you might just be able to manage that. Not sure why you would try, it's kinda like telling kids not to put beans in their nose.
Bigfoot 10.4E, 2015 F350 6.7L DRW 2WD, Autoflex Ultra Air Ride rear suspension, Hellwig Bigwig sway bars front and rear

mt-ed
Explorer
Explorer
mkirsch wrote:


Um, okay? "Displacing gravity?"

In other words the person who answered your question had no clue. What they said is absolute nonsense. They just want you to go away.


Yes, I guess using happijacs bestows upon the user Super Hero powers! Haha. I pretty much felt dismissed. I'm really surprised by their response because they display this warning, in bold print, over, and over and over throughout their instructions. To me, such insistence would indicate failure to heed their warning would result in some catastrophic failure. Also, if it truly IS that important, how hard would it have been to put the "or else" clause after the "never" statement?

mkirsch
Nomad II
Nomad II
mt-ed wrote:
Well folks, as promised here is the official word from happijac....

If you raise the back of the camper higher than the front, you are displacing gravity on the camper. You are making the front end forward heaver which can cause the camper to fall forward.

I cut and pasted their response verbatim from their email.

Thanks for all the interest, input, advice, and conjecture everyone!!


Um, okay? "Displacing gravity?"

In other words the person who answered your question had no clue. What they said is absolute nonsense. They just want you to go away.

Putting 10-ply tires on half ton trucks since aught-four.

JoeChiOhki
Explorer II
Explorer II
HMS Beagle wrote:
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...


I do also wonder if it has to do with Happijac's choice to use square tube jacks, as their jacks have been known to buckle at the pressure point between the outer and inner tubes before. Round tubing is naturally stronger by shape than square tubing and will take a good deal more strain without failing catastrophically than square tubing does.
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Channel 17

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'1974 KIT Kamper 1106 - 11' Slide-in
'2006 Heartland BigHorn 3400RL

jimh406
Explorer III
Explorer III
Thanks for posting their response.

That’s pretty funny. Funnier is that they thought they needed to add it to the manual.

Who wants to see how much higher they have to raise the rear of their TC to get it tip forward? 😄

I’m wondering why they didn’t mention not putting one side higher than the other. 😉

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mt-ed
Explorer
Explorer
Well folks, as promised here is the official word from happijac....

If you raise the back of the camper higher than the front, you are displacing gravity on the camper. You are making the front end forward heaver which can cause the camper to fall forward.

I cut and pasted their response verbatim from their email.

Thanks for all the interest, input, advice, and conjecture everyone!!