Thread: How strong is the D2 chassis?

The chassis wont achieve plastic deformation with extreme articulation, even when fully loaded and beyond. Impact loads are significantly greater than static or gradually applied loads.

I'm not definate, but I suspect the D2 chassis is made of something slightly better than mild steel although nothing flash.

Hi Slunnie, was waiting for your input, always great to read.
So the chassis structure would have been designed never to reach plastic deformation, but would surely it would reach the yield strength where deformation starts to occur?
What I am getting at, with articulation, the chassis would reach its yield strength, but would extreme repeditive articulation (I'm talking everyday flexing) start taking its toll on the chassis. You mentioned a while ago, the front body mounts seam to be a bit weak on the early D2's and do seam to bend.

Originally Posted by Hendrik

Hi Slunnie, was waiting for your input, always great to read.
So the chassis structure would have been designed never to reach plastic deformation, but would surely it would reach the yield strength where deformation starts to occur?
What I am getting at, with articulation, the chassis would reach its yield strength, but would extreme repeditive articulation (I'm talking everyday flexing) start taking its toll on the chassis. You mentioned a while ago, the front body mounts seam to be a bit weak on the early D2's and do seam to bend.

Gday Hendrik,

There may be some mix up with the definition of yield here, but plastic deformation (ie permanent deformation) occurs after max yield strength has been reached. Where deformation starts to occur, but before plastic deformation occurs is called elastic deformation. Elastic deformation (flexing without permanent bending) is starts to happen as soon as you place a load on the chassis (or anything for that matter). A chassis isn't a totally rigid structure but will to a minor extend flex around in all directions while you are just driving. If you put your fingers over the gap between the door and body in a car and drive it over uneven ground you will feel the door gap change as the body flexs. When you totally articulate the chassis and suspension you are nowhere near the point of plastic deformation, but if you impact on the chassis such as landing it after being airborne then you run a good risk of bending or twisting it as the force is significantly greater than just driving it and articulating.

The repetitive cycling of loads through the chassis is called fatigue and as the loads increase the number of cycles reduces before a failure of some descript occurs. Fatigue failures in the chassis as far as I'm aware won't show up as a bend - a bend is usually indicative of a big force like an impact. Fatigue will typically show up as cracks though and in the areas that are most highly stressed. If you drive it everyday on the road, then you will probably never see cracks in the chassis. If you regularly offroad it then the D2 will be prone to cracks in a couple of places:

In front of the Panhard mount / steering box mount - there is a weld kit to reinforce this part.
The PS body mount behind the front wheel - this was reinforced in the D2a. These crack, they don't bend.
Tops of the B-pillars - this is just a poor engineering design in my opinion and you just live with it.

Thanks for the explaintion Slunnie. I did have my wording mixed up, forgot what about elastic deformation completely, my brain is in holiday mode from Uni.

My car was airborne for an instant, and the back end on the LHS came down hard on the rear bar and hence the rail bent up slightly also causing a crease in the roof just near the turret. The fact that it was airborne as you mentioned did cause the deformation you mentioned before.
It all makes a lot more sense now

Originally Posted by Hendrik

Thanks for the explaintion Slunnie. I did have my wording mixed up, forgot what about elastic deformation completely, my brain is in holiday mode from Uni.

My car was airborne for an instant, and the back end on the LHS came down hard on the rear bar and hence the rail bent up slightly also causing a crease in the roof just near the turret. The fact that it was airborne as you mentioned did cause the deformation you mentioned before.
It all makes a lot more sense now

How big was the hit?

There has been the odd bent D2 chassis. Your bend usually happens at the spring turret at the rear, but that usually when landing it with a trailer on the back rather than landing on the rear bar!

Well I didn't have a trailer, but it bent exactly where you say, at the spring turret. One side is bent more than the other, about a 7-10mm difference in height I'd say. But you can clearly see the marks where it hit. The hit was large, the front diff is bent and both front alloy wheels buckeled. I didn't hit it with great speed, approx 40km/hr but the drop off and step up was huge.

I will take a few pictures off of it tomorow and post them up, I bought the wreck back off the insurance company.

you parting it out ?
i am in brisbane in a few weeks and looking for some odds and ends off a D2

I have cracked my chassis 2 times now, bent both front trailing arms and both front body mounts on all ocassions there was some sort of hard impact involved, and with me I had the camper on, the first being a washout on the road from Cunnamulla to the Dig tree, that was massive 2ft wide and about a foot deep at around 80 to 90ks with the camper on, my D2 has towed a camper on and off road for around 180,000ks and 5yrs on some pretty rough roads, hitting some pretty big washouts and potholes, not to mention corrigations.

When fully articulated, I can still open all 5 doors

Baz.