โAug-27-2021 06:55 AM
โAug-29-2021 04:11 PM
vtraudt wrote:
Lifting at the 2 rear corners (the front is already lifted at the corner, the A frame (front jack) lifts the 2 front corners, and all the static bending is/has taken place every time you put your front jack down, or hook up your trailer to the car)
โAug-29-2021 04:06 PM
Huntindog wrote:
People also ask
What is a cambered chassis?
In the structural engineering world, camber is known as having a slight arc or bend induced in a beam.
โAug-29-2021 04:04 PM
vtraudt wrote:Huntindog wrote:
[img] Click For Full-Size Image.[/img]
The few lines of surface welds induce some heat stress to the beam, which then bends up. This helps to end with a someone flat beam when load is applied and axles put underneath to push up.
It does NOT add any strenght. It only changes the bending line (crooked before weight, somewhat raight when loaded 'dry', somewhat crooked again when additional load is added (full tanks, food, storage, stuff on the rear bumper, stuff on the A frame, etc).
There may ONE very special/rare load condition when this beam is STRAIGHT. For practical terms, it will NEVER be straight. The amount of bending depends ONLY on a) the stiffness of the frame (fixed, and NOT influenced by the pre bending) b) the load and load distribution.
Lifting at the 2 rear corners (the front is already lifted at the corner, the A frame (front jack) lifts the 2 front corners, and all the static bending is/has taken place every time you put your front jack down, or hook up your trailer to the car), will add equal (but in reality less) than the normal static flex. Less, because A the axle is not in the middle of the lifting point and be the load is heavier on the front section ('tonque weight').
So lifting on the rear corners will ADD static bending (in the opposite direction. NO QUESTION.
The AMOUNT of bending could be the range (but opposite direction of the 'empty load' (the weight of the chassis itself, plus weight of the empty 'house'). In my case: 4400 lb weight empty, assumpe 2200 on 'rear' half. Lets call this the 'flat static' (assuming pre bend frame to make it 'flat' with this load). Now adding 120 gal of fluid (black, grey , fresh water) (on earth, roughly 1000 lbs) near the rear bumper. That ADDS 50% to the static bend.
Now we bounce it over a speed bump at 3 g. That is now an additional 2 g or 2000 lb near the rear bumber for a total of 3000 lbs. That is 1.5 TIMES the bending amount of the static 'assume flat with pre bent beam).
Now if we push UP the rear end of the empty trailer, that is 2200 lbs. This will result in roughly 50% LESS bending as the 'bump' with full tanks'.
Ditto, if the trailer is full (here: 7500 lbs, or 3750 on the rear portion), if we lift the rear, the bending is about equal to the amount exerienced during every 3G bump no the road (but only done once every time to jack it up, so say one per vacation, vs xxxx during driving).
Just some perspective on the issue.
โAug-29-2021 03:35 PM
Huntindog wrote:
[img] Click For Full-Size Image.[/img]
โAug-29-2021 03:04 PM
valhalla360 wrote:Huntindog wrote:
It certainly is what cambering is. Do some googling as I did. There is more than one way to do it. But I found articles of some really big semi type stuff being cambered by welding. In addition at one time, Northwoods RV had a picture of welds on one of their frames stating it was cambering for more strength. I also toured the Palomino Sabre factory back in 2010 when I bought my Sabre. I took a lot of pics. One of them shows the cambering welds. I have that pic, but I haven't posted a pic in so long, I forgot how to do it
And welding certainly does change the way a length of steel feels.
I tried it and felt it it myself. If you still don't believe me.... Break out a welder and see for yourself.
Flatbed semi's, the beams are often cambered. If you see them running empty, the curve is easy to see but they are built for many tons of load. Far different from your average travel trailer.
I've seen a fair number of travel trailer frames and not seen cambering...at least not enough to visually see anything. They will sometimes reinforce where the axles connect but that's different from cambering.
I suspect what you are confusing is looking at the strength of flat sheets vs an I or box beam working together but that's different from cambering.
โAug-29-2021 02:30 PM
valhalla360 wrote:
Flatbed semi's, the beams are often cambered. If you see them running empty, the curve is easy to see but they are built for many tons of load. Far different from your average travel trailer.
I've seen a fair number of travel trailer frames and not seen cambering...at least not enough to visually see anything. They will sometimes reinforce where the axles connect but that's different from cambering.
โAug-29-2021 02:12 PM
Huntindog wrote:
It certainly is what cambering is. Do some googling as I did. There is more than one way to do it. But I found articles of some really big semi type stuff being cambered by welding. In addition at one time, Northwoods RV had a picture of welds on one of their frames stating it was cambering for more strength. I also toured the Palomino Sabre factory back in 2010 when I bought my Sabre. I took a lot of pics. One of them shows the cambering welds. I have that pic, but I haven't posted a pic in so long, I forgot how to do it
And welding certainly does change the way a length of steel feels.
I tried it and felt it it myself. If you still don't believe me.... Break out a welder and see for yourself.
โAug-29-2021 09:09 AM
โAug-29-2021 07:28 AM
vtraudt wrote:GrandpaKip wrote:
Why not use Andersen types of levelers? I put the camper where I want it, put the levelers down, roll forward or backward a few inches, watch my level, and, presto!, itโs done.
I may give that a try. Are those type levels tire size dependent?
I have 14" tires.
โAug-29-2021 06:54 AM
vtraudt wrote:
That same hammer hitting upward at the suspension points is also hitting DOWN on the frame along to the ends (pressing down so it does not fly to the moon).
Or looked at the other way: if there were no force on the beam pushing down, they wouldn't need a beam going to the ends.
Note: a beam to only hold static load could actually be tapering down assuming an even weight distribution.
โAug-29-2021 05:50 AM
JRscooby wrote:
Well sure gravity is a force on the whole unit. But the force I'm talking about is the equivalent of a 7000 lb hammer hitting upward where the suspension mounts.
โAug-29-2021 05:10 AM
vtraudt wrote:JRscooby wrote:
But the design expects force applied upward from the suspension and tongue. That force increases and decreases, but the location does not change.
Nope!
The bad thing about gravity: it works everywhere.
The force is NOT induced just at the tongue and suspension. There is mass (force) induced into the frame at any point along the length of the house (as long as there is gravity).
โAug-28-2021 06:09 PM
โAug-28-2021 05:36 PM
โAug-28-2021 04:15 PM
Huntindog wrote:vtraudt wrote:I would not be certain of that. They can induce cambering wherever they feel it is needed.GrandpaKip wrote:
As said by HDog, frames are cambered and you really shouldnโt be screwing around with that.
No plans on screwing around with the frames, or change anything if they are cambered (need to check, haven't noticed; if so, would only be in the axle area, certainly not forwards/backward from there).