pivoting frames and mounting campers

[tamangel]

Don't have a M35 handy, so I can not verify this myself and I can not find a pic of the rear mount on the web. Sure would make things easier if I went this route at the rear. I was thinking I'd need a pivot at the rear, but doesn't look like it (if M35s don't need it, I think I'd be okay).

head over to Steel Soldiers ( http://www.steelsoldiers.com/ ) you can get any info you need on M35's might have to join to see pic's but no cost.. Excellent info available..

Mike W

*******

 

[IdaSHO]

I had the truck in the shop today doing some tests.

I had hopes that I could extend the flatbed headache rack over the cab to provide some between cab and camper stowage, but it proved unwise.
Adding in the amount of flex shown between bed and cab, I have less than 5 inches to work with. To slim to be useful. Still, I may come up with something yet.


Anyhow, it did provide for some flex test photos, showing just how well a simple 3-point pivot setup works.
Ive been running this setup for a couple of years now, and have logged nearly 50k with the camper loaded.

This truck for all intensive purposes has stock suspension, so no crazy amount of flex.
But I did get it flexed far enough that a hair more lifted a tire. So this should be as far as Ill ever have it flexed.

notes:

10 inches under drivers front
8 inches under passenger rear

I added some red lines in photoshop to illustrate the bed-chassis and bed to cab changes

 

[pappawheely]

I found these photos that show a mounting system like discussed by Alastair and others.

 

[tamangel]

any idea how long the cab to end of frame measurement is on that Iveco? I like it..looking at a 12' frame truck currently but need a flatbed that will need to take a 14' Alaskan non-cabover..I guess the frame doesn't have to extend the full 14' but the flatbed does..

Mike W

******

 

[Victorian]

I found these photos that show a mounting system like discussed by Alastair and others.

Most beautiful mount I have ever seen!

 

[nick disjunkt]

wow, any idea who fabricated this?

 

[IdaSHO]

Pretty incredible.

Looks like the bed and cab share a coil sprung frame, on top of the chassis....

Then the bed is on a pivoting frame, on top of that :Wow1:

 

[nick disjunkt]

Pretty incredible.

Looks like the bed and cab share a coil sprung frame, on top of the chassis....

Then the bed is on a pivoting frame, on top of that :Wow1:

It's interesting that the fabricator didn't chose just to use just the 4 point pivoting mount. It undoubtedly isolates the body sufficiently on its own, but perhaps they were worried about it concentrating the load too much on chassis. I'm not aware of Unicat or any other similar companies having chassis problems caused by not using additional chassis rails. The secondary rails (sprung at the front) is undoubtedly the system required by Iveco's body building guide, but with the torsional isolation of the 4-point mounts, I would have thought the springs could safely be left out. Perhaps they were worried that hard mounting the secondary rails would make the chassis too stiff and prevent twisting?

 

[nick disjunkt]

I love the bearing shell design of the middle mounts

 

[pappawheely]

I think I will mount my box similar to the subframe on this truck. Fixed at the rear and spring mounted towards the front. When I think about it, it makes sense that the frame would flex between the axles because that is where it's being acted upon. The pivots on this design seem redundant unless they are planning for some major flexing on both the frame and subframe.

 

[IdaSHO]

The pivoting frame is done correctly.

Not sure what you are talking about.

 

[Victorian]

The pivoting frame is done correctly.

Not sure what you are talking about.

I believe that is the official by Mercedes Benz required subframe....

 

[IdaSHO]

Very well could be, not sure

Three pivots can never induce a bending moment or a torsion in the camper structure, but 4 can do so quite easily.

Ill say it again, the pivot frame in those photos is done correctly.

I believe you are confusing BENDING with TWISTING.

A chassis does not bend (much, if any). It twists (considerably).


When it twists the front and rear pivots as shown remain in the same plane.

 

[pappawheely]

Who here remembers that 3 points define a plane? That system has one too many mounting points. It is very, very nicely built, but it won't achieve the desired end result. It will still act like a 4 legged bar stool with one short leg when the chassis has a twist in it. In other words, it will still transmit a torsion to the camper box. A three legged bar stool never wobbles, no matter how uneven the ground under it is or if the legs are unequal length.

Unless their incorporation of the springs between the sub-frame and the truck frame is intended to relive that torsion. Which case why bother with the very nicely built pivots? They won't be needed if the spring mounts do their job correctly.

That is why I don't understand the center mount. It can't move without flexing whatever is bolted to it.

 

[julius0377]

Four point mount

The four point mounting system works as the front and rear frame mounts allow flex at both ends, while the centre mount remains fixed. Combined with only twisting at the ends this isolates the box from the frame. If the frame where to flex lengthwise, it would not work.

Unicat, Action Mobil, Bocklet, etc. all use this system on larger/longer builds as it distributes weight more evenly on the chassis than a three point mount.