Do I need to worry about chassis torsion?

[Esben Bøll]

Hello everyone

My hzj75 overland camper project here in Denmark is moving along (slowly) and should have a "finished" box within a couple of months.
Then I need to fix a few things on the car. One of them is a worry I have had for some time and that I hope you can give some advice on.
Chassis torsion! Is this something I should worry about on a hzj75? What is your experience?

My setup is a demountable camper box made of 30mm GFK sandwich panels. I do not have a steel support frame in the floor in order to keep the weight down.
The box is mounted with ratchet straps onto an aluminum tray which is bolted directly to the original mounting points on the chassis frame.
Right now not even the original rubber discs are being used, just metal on metal.

I am worried that chassis torsion is going to move up through the tray and put stress on the rigid camper box.

So can anyone tell how much torsion twist there is on the classic HZJ chassis frame and does anyone have any experience combating this?

I was thinking of just using the original rubber discs that the original tray is mounted with. Or will I have to upgrade and used springs or additional rubber between the chassis frame and aluminum tray?

I have attached a couple of pictures of the setup.

 

[Shayne]

I reckon body mount rubber is intended to be a sound damper rather than anything else and your box is no more rigid than a typical car body so it will flex , you just won't see it .

 

[Shayne]

A 6" square of horse mat between the tray and the box in each corner might soak up some vibration and help the straps keep it in place .

 

[Dave_S]

Hard to say on that set up - the wheel base is so short I doubt you'd have a lot of flex in the chassis in any case.

Personally I would be looking to test this without the box in place, ideally by using a fork lift to lift one rear wheel off the ground until the opposite side is just about to lift, then check the movement in the flatbed. Any material movement will twist the box and likely you'll end up with water leaks if nothing else.

There a few solutions possible, rail on rail, three point mounts, spring loaded bolts (as you've suggested) - but I'd see if you have a problem before getting into these solutions.

Neat looking truck, BTW!

 

[Chris]

Lazz is yer man on this topic. He's somewhat of a torsion guru. @Olazz

 

[SteveJB]

Is it a homemade box or factory if factory then the suppliers should have the information you need or trawl through some of the sites of habitation box manufacturers must be information and solutions available for you