frame flex with anti sway bar

Aluminum will flex more than steel (3x more) unless the design is changed.

Unibodies flex oh yes they do. But usually quite a bit less than separate frame and body.

Some of the engineering behind this is that torsional rigidity is proportional to the area enclosed by the structural member (among many other things). The "C" section of a channel frame does not enclose much area and isn't very rigid torsionally. Box the "C" into a "D" and it encloses a large increase in area and becomes much more rigid. Take the whole body and turn it into the frame and you have enclosed many, many times the area.

It is the engineer's job to ensure that the flex resulting from normally encountered conditions does no harm. So unibodies are made stiff enough that the torsional flex is not enough to pop the windows out for example (though under stress you can often hear them creak). And in a C frame pickup, make sure that the other components are not damaged by the greater flex you will see. There is nothing wrong with any of these construction methods, they simply result in different characteristics, both desirable and undesirable.

Reddog1 wrote:
I think the flex in Unibodies is very little to none. If it flexed, the windows would be popping out.

Wayne

On Mercedes I often jack up whole side using only side front jacking point.
The front lifted wheel is about 8" higher than the rear at this point, while other side is on level pavement.
Some of that is suspension travel, but some has to be body flex.

I think the flex in Unibodies is very little to none. If it flexed, the windows would be popping out.

Wayne

hedgehopper wrote:

Reddog1 wrote:

ugh wrote:
If the frame does not flex at all, the ride will be harsh! it also increases the chance of cracked frame. It is made to flex to some degree.

Ya really think so? Does the body of a uni-body vehicle flex? Have you ever ridden in a citron? I may stand corrected, but I think they are uni body. It has been many years since I have ridden in one, but the ride was as smooth as it gets.
Wayne

I would argue that a uni-body does flex. The question would be: how much does it flex? In another lifetime, when I worked for Ford, our group did a stress analysis of a uni-body automobile. If there were no flex, there would be no stress to analyze.

Unibodies flex more than box or channel frames. The term unibody just means that the frame and body are integrated whereas the "standard" frame is made as one unit and the body is another separate unit.

Kayteg1 wrote:

Aluminium makes much stiffer frame, so I wonder how 2016 models compare.

Ford is still using a steel frame, they're just using aluminum body panels.

54suds wrote:
Does an rear anti sway bar add to or reduce __ frame --- flex ???

Not in any way that matters.

Good find Nautique200


Almost 1" of displacement and Ford is still #1 selling truck.
Aluminium makes much stiffer frame, so I wonder how 2016 models compare.

You guys are out of control on your absolutes. As I have tried to point out, these frames are designed to resist twist and flexing, thus the intent of being rigid. Not like a C-Channel frame that is designed to flex and twist.

http://media.chevrolet.com/media/us/en/chevrolet/news.detail.html/content/Pages/news/us/en/2014/Oct/1015-silverado.html

to the OP's question, a beefier sway bar will technically increase frame twist, but should not do so to a concerning degree.

Reddog1 wrote:

ugh wrote:
If the frame does not flex at all, the ride will be harsh! it also increases the chance of cracked frame. It is made to flex to some degree.

Ya really think so? Does the body of a uni-body vehicle flex? Have you ever ridden in a citron? I may stand corrected, but I think they are uni body. It has been many years since I have ridden in one, but the ride was as smooth as it gets.
Wayne

I would argue that a uni-body does flex. The question would be: how much does it flex? In another lifetime, when I worked for Ford, our group did a stress analysis of a uni-body automobile. If there were no flex, there would be no stress to analyze.