Fw: [DML] Re: Trailing Arm Bolts - Engineering

["Chris Parnham" <chrisparnham@xxxx>]

----- Original Message -----
From: <tobyp@xxxx>
To: <dmcnews@xxxxxxxxxxxxxxx>
Sent: Tuesday, November 13, 2001 12:52 AM
Subject: [DML] Re: Trailing Arm Bolts - Engineering


> David - You are quite correct in your assessment that the tubes and
> sleeves will collapse if the torque is increased significantly. I
> installed the new bolts at a torque level of 50 ft-lbs, with a
> copper-based anti-seize compound applied to the shank and threads.
> That is the same value as the "stock bolts" as I recall. Forgive me,
> but I ran some numbers today on the preload in the bolts caused by the
> installation torque. I wanted to see how much tensile stress we put
> on the bolts by torqueing to that level. It revealed some interesting
> information ... without going into the calculations in detail, a
> torque of 50 ft-lbs on the TAB with grease on the threads and shank
> would create a tensile (tension) stress of about 116 KSI. (Remember
> that 1 KSI = 1,000 PSI). If the threads on the bolt and nut are
> perfectly clean and dry, the tensile stress value at 50 ft-lbs of
> torque is 48.3 KSI. Trust me on this ... it just works out that way.
> The actual preload is probably somewhere in between those two
> extremes, but it varies depending on the cleanliness of the hardware.
> The average of the two is about 82 KSI. If you are brave enough to
> muscle through a previous post of mine, the maximum allowable tensile
> yield stress on the stock bolts is 103 KSI. We are probably coming
> close to yielding, or stretching, the TAB every time it is torqued.
> The variation could also explain why some people have a problem with
> their TAB's , and others do not. My custom bolts have an allowable
> tensile yield stress of 200 KSI, so they would only get to about 1/2
> of their capability at maximum torque. Okay ... I'm done. I just
> thought that you'd like to know.
>
> BTW - What are some of these other solutions that vendors have come up
> with? I haven't seen "The Fix" for this area yet ... just a lot of
> hand-wringing, and guessing. Please advise.
>
>
> --- In dmcnews@xxxx, jtrealty@xxxx wrote:
> > All of what you wrote was interesting but it comes down to putting
> > more stress on the bolt then it will see in service by torquing it
> > above that level. If you go overboard you will collapse the metal
> > spacer in the radius arm bushing pn 106716. As is usually the case
> you
> > cannot improve an entire system by changing one part. It usually
> takes
> > a reengineering of the entire system or you just move the weak point
> > to somewhere else in the system. Before you continue you should
> > discuss this with a Delorean vender as they have all "been
> there-done
> > that" and now have a good way to fix this weak area. There is no
> > substitute for experience so before starting on a new project like
> > this you should get all of the history that you can.
> > David Teitelbaum
> > vin 10757
>
>
>
>
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