Bob and folks,
>I found the end link hanging below the family land barge (Detroit minivan)
>this afternoon. Turns out the ~4 year old sway-bar broke off about 10
>inches in from the end link. A couple questions for the list:
>
>First, it's really a sway-tube. Is it lower weight or some other advantage
>they are after in going with the hollow tube versus the solid bar as is on
>the Alpine? I suspect a solid bar would have had 3X the weight, but
>probably would not have broken off like this.
First of all, does the minivan have struts in the front?
On many cars, the sway bar has a double duty, one as a sway bar,
and another as the locator for the lower control arms.
These cars usually employ struts instead of 4 link
suspension (upper and lower control arms).
Now to the hollow bar issue.
A hollow bar has only a slightly lower spring rate as a function of its
outer diameter. Somebody told me at one time or another that its the
surface
of the bar that contributes most to the spring rate of the bar, and that
hollow bars have two sets of surfaces, outer and inner.
Since the bars size need only be increased as small amount to get the
same rate at a solid bar, and the weight can be reduced by 40 or 50%, the
hollow bar makes sense.
It is not attypical to find hollow bars of race cars.
>Second, is this kind of failure more typical than I had thought?
>The sway-bar is really low on the long list of auto parts I normally think
>of as having an aptitude for catastrophic failure. Sway-bars are supposed
>to just fade away, right?
This is not a typical failure.
A sway bar is just a torsional spring, whos twist should not be allowed to
take the bar to the yield point of the material.
A failure like this is most likely attributable to a defect in the material,
or some sort of a processing error, where the part was somehow over
hardened.
Jarrid
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