[DML] Re: Driver Side Torsion Unit
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[DML] Re: Driver Side Torsion Unit

The torsion rod topic is an old favorite of mine.

The torsion rods are highly stressed, and will all probably fail, as the stress on them is probably above the fatigue values for cyclic loading.  It's just a matter of how many cycles, and the integrity of the torsion bar.  

I agree with both Jake and Dave.  Hope I haven't paraphrased wrong.

Dave says something like "Contact with the hinge is a stress, concentrator" (my car had that problem.  I polished out the defect, and wrapped the rods in wireloom at the contact point).  

Jake says something like "Some torsion rods fail for no apparent reason in random locations."

The discoloration Jake described is typical of a fatigue failure.  Some microscopic defect concentrated the high stress, creating a crack, which over time eventually enlarged enough so the remaining metal couldn't take the stress, and "pop" it goes.

Keeping the torsion rods free from crud and surface damage will prolong them.

We're collectively lucky that someone has made replacements.  The replacements are potentially hazardous, just like the originals.  There is no "safe" torsion bar option here.  I personally am not going to grill the manufacturer of the replacements about math and metallurgy.  I feel grateful to have an option at all.  


--- In dmcnews@xxxxxxxxxxxxxxx, Jake Kamphoefner <jakekamp@...> wrote:
> I agree with you that the hinge can cause some damage, but I disagree about the metallurgy of the bars.  I think it is possible for them to have some defects.
> We've had two bars break in the past 6 months in our club (both passenger).  One broke exactly in the middle of the bar, and the other broke in the open space where the bar passes through to the adjuster under the t-panel.  Both were low mileage cars, neither were over-torqued, and they both failed shortly after closing the door (when the tension is highest).
> We examined both of the bars, and found no scratches at the point of breakage, but rather that the metal on the inside of the bar looked discolored and slightly "sandy" in sections (similar to corrosion).  Our conclusion was that the bars must not have been manufactured correctly as the metal was rather inconsistent, albeit invisible from the outside.
> Jake Kamphoefner
> 1063
> ________________________________
> From: jtrealtywebspannet <jtrealty@...>
> To: dmcnews@xxxxxxxxxxxxxxx
> Sent: Friday, September 18, 2009 11:29:10 AM
> Subject: [DML] Re: Driver Side Torsion Unit
> My theory is that the torsion bar gets scratched where it passes by the rear hinge. Since the torsion bar is so highly stressed a scratch will concentrate all of that stress, propogating a crack eventually through the cross-section of the bar. My solution is to put a small piece of rubber from an old tire tube between the torsion bar and the rear hinge. Often you have to use your fingers to pull the bar away enough to slip the rubber in between the bar and the rear hinge. Do it on both doors. Cheap insurance. It is no coincidence all of the bars I have seen broken break at the point where it passes by the rear door hinge. There is nothing wrong with the metallurgy of the torsion bars.
> David Teitelbaum
> __._   
> [Non-text portions of this message have been removed]


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