May-20-2021 01:25 PM
May-30-2021 08:27 PM
May-30-2021 06:45 PM
May-29-2021 07:48 PM
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.
CB
Channel 17Redneck Express
May-27-2021 08:33 AM
May-27-2021 07:46 AM
May-26-2021 12:06 PM
May-26-2021 08:35 AM
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.
May-26-2021 05:43 AM
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.
May-25-2021 01:20 PM
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.
May-25-2021 12:34 PM
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.
May-25-2021 04:58 AM
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!!
May-25-2021 12:14 AM
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...
CB
Channel 17Redneck Express
May-24-2021 04:15 PM
May-24-2021 03:42 PM