Thread: Major Chassis Issue

Originally Posted by JDNSW

I would expect overloading over rough terrain. However, if it is a trayback, cracking can result from bad installation (design or execution) of the tray. Also possibly carrying very concentrated loads.

I would be very surprised to see this from operating unloaded, or indeed, from operating on smooth roads, even if overloaded. (although some people can manage to drive roughly on the smoothest roads!)

John

I would bet tray design over overloading on rough terrain, all my 130 tray tops operate at (or above GVM ) in serious off road work and have cracked tray mounts but never chassis issues. They tray needs to be strong enough to take flex, but at some point between the tray and chassis, there needs to be some where for movement, other wise it's transferred to somewhere else to either flex or crack..if you end up taking it somewhere, go to a truck body building shop or an industrial engineer that specialises in heavy welding and fabrication. Good luck!

Originally Posted by occybruce

Noticed this on the rear left chassis this morning!! is this the end of my 03 defender ??

Photo 1 outside
Photo 2 top view
Photo 3 inside

Please Help, I dont know if it can be welded and plated or its a lost cause.. how could this happen on such a strong frame?

Regards

Bruce

The key with any crack is to drill a hole 3/16 at the end of each crack to prevent it from spreading further.
Technically it looks like a easy fix...drill...clean surface with wire brush...weld....perhaps add a few flat bar plates....paint....get dirty again so it looks original.

Originally Posted by ozrob

The key with any crack is to drill a hole 3/16 at the end of each crack to prevent it from spreading further.
Technically it looks like a easy fix...drill...clean surface with wire brush...weld....perhaps add a few flat bar plates....paint....get dirty again so it looks original.

Well, yes and no. If you did that, the same forces that caused the initial crack, plus the shrinkage forces caused by the cooling in the HAZ will cause it to crack again in no time. In some metals this is literally minutes and can make quite a noise while you are packing up your gear. This will also occur if you use a plate with the welds parallel to the crack (and for the same reason).

If you rotate the square plate so that the welds are 45 degrees to the crack, the stress risers will be at 45 degrees to the original crack - effectively spreading them out.

Well pretty much what I had seen previously behind the cab. As has been stated the fishplates which should be a diamond pattern with the same thickness material. Ratio of about 3 times length along the rail to height Make sure all edges are smooth after cutting and the welds are terminated correctly with no scalloping otherwise you will be back again.

We suspected this may have been caused by using stiff steel trays that don't flex much. Have look at an ally tray on a vehicle that lives on gravel roads or works for a living. They will have black lines on the adjoining surfaces where the tray flexes.

My 110 has a cooma steel tray which is now bolted onto the chassis with some conveyor belt pads to allow a little movement.

Maybe the Indians will do a finite element analysis one day. Technology wasn't around for the original design!

part 2...

My local bushfire brigade built a new truck for offroad and onroad use. Image ended up the MAN calendar for this year.

What came to light not long after introduction was the tank of 4000 litres plus tank mass came loose. At a recent job we watched the flex between the aft bodywork and the front cab. The flex was nearly a foot between the two boxes and that's on air rear suspension !

No I won't drive it.....

All off road trucks of that capacity are designed to flex that much..body builders need to match tray and body building with chassis dynamics.