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 > Adding scissor jacks for side to side leveling

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opnspaces

San Diego Ca

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Posted: 08/28/21 08:30am Link  |  Quote  |  Print  |  Notify Moderator

Give it a try with a cheap bottle jack or two and see if everything works out. I know on my trailer if I get too aggressive with the corner jacks it warps the frame and the bathroom door won't close or latch. The first time I experienced this the striker was a full 1 inch above the hole in the door jamb. And my trailer is an older Jayco with a pretty stout one piece I-beam frame.


2001 Suburban 4x4. 6.0L, 4.10 3/4 ton
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vtraudt

Brighton, MI

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Posted: 08/28/21 09:03am Link  |  Quote  |  Print  |  Notify Moderator

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!, it’s done.


I may give that a try. Are those type levels tire size dependent?
I have 14" tires.


Ordered a pair. Hope that pushing around 7000 lbs a few inches to achieve a desired level works as advertised.
On loose ground, drive on 2x6 first then on levellers? ditto if more than 4" (theoretical) lift is needed? How well (with rubber mat) do they 'stick' on boards?

The advertised 4" is pretty much the effective height of 2 boards.

vtraudt

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Posted: 08/28/21 10:58am Link  |  Quote  |  Print  |  Notify Moderator

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).

Likely not linear (more mass close to axles, since water tank, fridge, etc are often placed there). But not always (and more than likely, the manufacturer uses the SAME FRAME for the various floor plans, sometimes with fridge in the rear, or in my case the heavy (when full) black water tank all the way at the rear of the chassis.

Now that (lets say 200 kg) weight WILL put a lot of dynamic force onto the chassis all the way at its end. Just for kicks using this number (published in a paper on speed bumps): "In one case, driving 32 MPH over a standard 1.5 foot long/roughly 4 inch high speed bump produced a maximum g-force of about 2.2.(gravity included). (Measurements were taken from inside the vehicle).".

So 200 kg mass with 2.2 g (rounded to 22 g/m2 acceleration) will give us 4400 N force (or about 880 lbs weight). That is the force JUST FROM THE FULL BLACK WATER TANK going over speed bump.

With that said: there is flex (any force even the smallest will flex a beam (unless it is infinitely stiff).

There is a lot of DYNAMIC force causing flex.

There is static flex.

There is DIFFERENT flex from model to model (assumption: manufacturer uses the same frame for various floor plans (and gives a hoot about the more or less flex).

Putting a jack at the corners CAN actually reduce the flex (compensating the static flex from the 'house' weight).

But that is all theoretical since I don't have the frames bending stiffness (and not even the frame's beam dimension to calculate the stiffness).

vtraudt

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Posted: 08/28/21 11:04am Link  |  Quote  |  Print  |  Notify Moderator

Huntindog wrote:


There is more to this than what meets the eye.
Most trailer frames are "cambered".


Haven't heard the term cambered, but from your description it sound like they are inducing stresses into the beam (pre stressing) by putting weld beads down. Never seen it done that way.

Inducing stress into the metal it a very common process, typically achieved by other means (think of it has a heat treatment, typically done on high carbon content steel).

I will look for signs of such 'cambering' (I would expect to see it on top of the beam or upper flange)?

Grit dog

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Posted: 08/28/21 02:06pm Link  |  Quote  |  Print  |  Notify Moderator

I don’t see the advantage to this, but to the Op, you may and that’s all that matters.
Personally, I carry 3ea 2x4s about 4’ long. If that’s not enough to level or close to level the camper then too bad or move the camper somewhere more level.
It’s just too easy. Pull into desired spot. Eyeball how much leveling needed. Either move fwd or back a few feet, lay down boards, pull camper onto them.
Or just put boards down if location isn’t that critical


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vtraudt

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Posted: 08/28/21 04:00pm Link  |  Quote  |  Print  |  Notify Moderator

opnspaces wrote:

Give it a try with a cheap bottle jack or two and see if everything works out.


yes, either on axle or on frame near axle straight lift with bottle jacks I have.

Also ordered the 'anderson' style curvy ramps, see if they work well enough to allow 'quasi in place' levelling.

And ordered 'curved' level with marks for a 'scaling'

Huntindog

Phoenix AZ

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Posted: 08/28/21 04:33pm Link  |  Quote  |  Print  |  Notify Moderator

valhalla360 wrote:

Huntindog wrote:

There is more to this than what meets the eye.
Most trailer frames are "cambered".
This is running weld beads at specific locations and patterns on the frame rails. This process slightly bends the frame, and more importantly strengthens it while adding a springyness to it. This allows for a lighter frame to be used, as the cambering puts the strong points just where it is needed. The locations/type of cambering are determined by the engineers,based on the expected loads for each trailers design. I became somewhat educated on this when having a sidebar dialog with Jbarca on a frame repair project he was undertaking. Curious about what I was reading, I grabbed some 10' metal stock from my pile and sparked up the welder. It was very enlightening. Each weld bead I ran caused measurable movements in the straightness of the stock compared to an identical unwelded control piece. More importantly the feel of the cambered stock changed dramactically. It felt more alive, with a definant springness that made it want to bounce back to its unloaded state as load was applied to it. The control piece felt dead and weak in comparisson. with out the "bounce back property of the cambered piece. IOW, applying enough force to permanently bend it was much easier.

As to what this means to what you plan on doing: I would only apply such force at a location that it was designed to take it. A jack as close as possible to the wheels should be pretty safe. Other than that, is a roll of the dice. You could end up applying force in a direction where the cambering is in the wrong direction to the force you are applying. Nothing good could come of that.
Your frames cambering can be in different locations and directions, and can be impossible to see once the trailer is built.


That is not what cambering is.

Cambering is building an unloaded beam with a curve such that when it is loaded, the load bends it back to straight.

I've never seen a travel trailer frame with cambering...certainly no geometric weld patterns and it doesn't add springiness.

That said, I do agree that if you are going to lift the trailer, doing it at the intended support points is the best idea.
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.



Huntindog
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Huntindog

Phoenix AZ

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Posted: 08/28/21 04:40pm Link  |  Quote  |  Print  |  Notify Moderator

vtraudt wrote:

Huntindog wrote:


There is more to this than what meets the eye.
Most trailer frames are "cambered".


Haven't heard the term cambered, but from your description it sound like they are inducing stresses into the beam (pre stressing) by putting weld beads down. Never seen it done that way.

Inducing stress into the metal it a very common process, typically achieved by other means (think of it has a heat treatment, typically done on high carbon content steel).

I will look for signs of such 'cambering' (I would expect to see it on top of the beam or upper flange)?
It is pretty much impossible to see with the TT box sitting on it.

Huntindog

Phoenix AZ

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Posted: 08/28/21 04:43pm Link  |  Quote  |  Print  |  Notify Moderator

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).

Likely not linear (more mass close to axles, since water tank, fridge, etc are often placed there). But not always (and more than likely, the manufacturer uses the SAME FRAME for the various floor plans, sometimes with fridge in the rear, or in my case the heavy (when full) black water tank all the way at the rear of the chassis.

Now that (lets say 200 kg) weight WILL put a lot of dynamic force onto the chassis all the way at its end. Just for kicks using this number (published in a paper on speed bumps): "In one case, driving 32 MPH over a standard 1.5 foot long/roughly 4 inch high speed bump produced a maximum g-force of about 2.2.(gravity included). (Measurements were taken from inside the vehicle).".

So 200 kg mass with 2.2 g (rounded to 22 g/m2 acceleration) will give us 4400 N force (or about 880 lbs weight). That is the force JUST FROM THE FULL BLACK WATER TANK going over speed bump.

With that said: there is flex (any force even the smallest will flex a beam (unless it is infinitely stiff).

There is a lot of DYNAMIC force causing flex.

There is static flex.

There is DIFFERENT flex from model to model (assumption: manufacturer uses the same frame for various floor plans (and gives a hoot about the more or less flex).

Putting a jack at the corners CAN actually reduce the flex (compensating the static flex from the 'house' weight).

But that is all theoretical since I don't have the frames bending stiffness (and not even the frame's beam dimension to calculate the stiffness).
I am sure that they use the same frame for many models. But the cambering is likely different.

Huntindog

Phoenix AZ

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Joined: 04/08/2002

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Posted: 08/28/21 04:47pm Link  |  Quote  |  Print  |  Notify Moderator

vtraudt wrote:

GrandpaKip wrote:


As said by HDog, frames are cambered and you really shouldn’t 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).
I would not be certain of that. They can induce cambering wherever they feel it is needed.

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