Guidance needed to build a box on a Pinzgauer 710M

Hugues

Member
Hey guys,
New here, Canadian engineer living in Switzerland for the past 34 years.
I just acquired a 1982 Pinzgauer 710M from Swiss army,
The plan is to convert it to an expedition vehicle for a 10 years world tour starting in 2024.
I'm going to remove the rear panels, structure and tarp and build a box.
Currently I'm thinking of using polyurethane foam panels sandwiched in FRP and glued together with Sikaflex 252 and fiberglass L profiles.
(similar to what is decribed in Unicat expedition vehicles video)

Now, the floor of the Unicat box is mated to the frame using 3 pivots, to avoid too much torsion on the box.
I'm not sure I can use a 3 pivots system like this, the "flatbed" of the Pinz is actually not flat but U shape. (and I want to keep total height to 258cm so it can fit in a 40' high cube container)
But in order to avoid too much stress on the panels when the bed is deformed due to a wheel going significantly up or down compared to others,
I'm thinking of ways to allow the front and 2 side panels to be able to move up and down relative to the frame,
so not having these panels attached rigidly to the frame. I don't know if this makes any sense.

Anyone has experience building a box on a Pinz 710M ? Should I expect a lot of torsion on the bed ? The central tubular frame is quite rigid, and the axles are articulated on this central frame, but...

Below you can see a first rendering of my project, following a volume study.

Pinzgauer 710 volume study v135.png

And the video below shows the flatbed of my Pinz.
I'm thinking of re-using the "metal lip" around the bed as a base to fix a L or U shaped aluminium (or fiberglass) profile,
then the base of the FRP panels would also be fitted with such profile and would be able to move up or down in the fixed profile.
Difficult to describe in words, i'm adding a drawing below showing a transversal cut of the Pinz bed and side wall.
Black is the Pinz bed,
red is the fixed alu profile to the bed,
green is the fixed alu profile to the FRP panel,
blue is the FRP panel
the green profile can slide up and down into the red profile.
Orange is a thick rubber or neoprene band that runs all along the base of the wall on the outside. It is glued and screwed to the base of the wall and screwed to the red profile. It's role is to prevent
ingress of water and dirt into the moving joint, and prevent the FRP panel from going out of the fixed profile.
Maybe a crazy idea...
But I don't think I can fix the base of the FRP panels to the Pinz frame in a rigid manner. Torsion of the frame will put stress in the panels corners and break the joints I guess.
(alu to metal bonds can cause corrosion so a membrane would be inserted between the 2)
profile.png
 

Peter_n_Margaret

Adventurer
Currently I'm thinking of using polyurethane foam panels sandwiched in FRP and glued together with Sikaflex 252 and fiberglass L profiles.
Can't help with the torsion issues, but I used the above on my builds (except I used aluminium L profiles) and it is the premium choice, in my view. With one small exception. The urethane foam in the floor tends to crush a little over time under high traffic loads so in my second build I am using PET foam instead of urethane, just for the floor. It is denser and just a tad heavier.
Good luck.
Cheers,
Peter
OKA196 motorhome
 

Hugues

Member
Thanks Peter,
I was planning to use Thermo-Lite Tough boards for the floor, 18mm. I did not know about PET foam boards, will certainly check it out.
Did you fix your box rigidly to your frame or you had some kind of system to allow for play ?
 

Peter_n_Margaret

Adventurer
The OKA is almost unique in that it has a very rigid ladder chassis. The box has a steel sub chassis of its own and that is mounted onto the truck chassis via a dozen rubber isolating blocks that allow about 10mm of movement maximum.
My new build will delete the steel sub chassis.
Cheers,
Peter
OKA196 motorhome
 

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