From: <dmcnews_at_dml_yahoogroups.com>
To: <dmcnews_at_dml_yahoogroups.com>
Subject: [DML] Digest Number 783
Date: Wednesday, November 14, 2001 3:31 AM

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There are 3 messages in this issue.

Topics in this digest:

1. Re: gas ran over
From: Christian Williams <delorean_at_dml_framezero.com>

2. Re: Trailing Arm Bolts - Engineering
From: tobyp_at_dml_katewwdb.com

3. Front sway bar progress (long)
From: "Walter" <Whalt_at_dml_att.net>





Message: 1
Date: Tue, 13 Nov 2001 16:04:30 -0800 (PST)
From: Christian Williams <delorean_at_dml_framezero.com>
Subject: Re: gas ran over

There's probably not a whole lot that can go wrong here (aside from the
smell), but I'd be sure to take off the access panel in the spare wheel
well to check the fuel pump and sender units. The sender has raw wire
connections on the top, and the boot on the fuel pump can "bowl". I'd just
take a rag and wipe them off, if any gas got in there.

-Christian




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Message: 2
Date: Wed, 14 Nov 2001 00:26:54 -0000
From: tobyp_at_dml_katewwdb.com
Subject: Re: Trailing Arm Bolts - Engineering

Hello Group - I though that I'd "weigh in" on two points that were 
brought out here.  BTW - I am very happy to see some "considering" and 
"pondering" going on here ... it is important for everyone's learning 
to gather different viewpoints on specific issues.

For the first point, "brittle bolt breaking", as noted in David's 
first paragraph;  This IS a concern when the bolt is "pushed to it's 
limits".  Based on my previously noted calculations, we are at, or 
above, the yield limits for the current TAB.  The inevitable result is 
bending to the point of yielding, fatigue damage, and ultimately, 
fracture due to fatigue cracking.  I also noted that the stresses are 
at about 1/2 the limit of my bolts.  You can't generate enough load in 
the system to reach the limit of 200 KSI yield strength in the Inconel 
material that I have selected.  The entire rear suspension (rubber 
bushings, washers, trailing arm assembly) will fail long before my 
bolts are stressed even close to their capability.

The second point that David brings up is the retorqueing issue for 
bolts.  He is absolutely correct in that, "When using bolts and nuts 
close to their yield point ...", retorqueing can result in stretching 
and yielding.  This allows joint loosening, which requires that you 
continue to retorque - until the bolt fails in tension.  As noted 
above, the current TAB is near it's yield stress point just from the 
installation torque.  This is before any loads are applied to it from 
driving.  When my bolts are torqued, the stresses are far below the 
"elastic limit" (sorry for getting technical again!), and there will 
be no permanent (called plastic) stretching of the material.  The 
Inconel bolts can be torqued an infinite number of times, barring any 
damage to the threads, and never suffer from "plastic deformation".  
Okay ... I'm done for now.  Thanks for your patience with me.

BTW - I have received indications of interest for 31 sets of bolts so 
far.  I will keep the list posted (so to speak) on whether this 
project will be economically feasible for myself and Specialty 
Automotive, based on being able to move the majority of the first 
batch of 100 sets that I have discussed with the manufacturer.

Thank you, David, for your sound advice below on proper maintenance 
procedures that all should follow on every car.  When in doubt, read 
the instructions!   




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Message: 3
Date: Tue, 13 Nov 2001 19:51:08 -0500
From: "Walter" <Whalt_at_dml_att.net>
Subject: Front sway bar progress (long)

I finally got to speak with Roland who is the owner of Addco.  He also owns
a DeLorean which explains why his company makes the rear sway bar for it.
We discussed at length the obstacles involved in making a heavy duty front
sway bar.  There are two main concerns:

The sway bar only works marginally as a sway bar.  It's main purpose on the
front suspension is as a "wheel locator bar".  The best way to describe its
function is to consider what happens when it is removed.  Without it, the
suspension holding the front wheels will bend backwards while the tires rub
the rear of the wheel wells.  So as a wheel locator bar, its dimensions are
critical to holding the front alignment.

The ends of the sway bar attach to the front lower control arms via rubber
bushings.  To make this fit, the ends of the sway bar look like bolts.  They
are turned down thinner than the rest of the bar and threaded.  This design
is very hard to copy accurately.  Normally this sort of bolt-like end made
onto a bar is made while the bar is a straight rod.  It is put on a lathe.
The ends are turned down (cut thinner) to match the dimensions of a bolt.
Then the end is threaded.  The problem with this method is that one must
calculate how long to make the rod so that the threaded ends show up in
exactly the right spot as the bar is bent to shape.  An alternate method is
to use something like a pipe threader that will turn the ends down after the
bar is bent to shape.  But this is a fixture that would have to be custom
made for the job.  (Cha-ching).

The next preferred method of manufacture is to shape the bar first, cut the
ends to length and then weld bolts to the ends.  This method makes it a lot
easier to make a bar of exactly the right size and proportions, but it has
drawbacks.  Butt-welding a bolt to the end of a bar is not going to be as
strong as machining the existing end of the bar into the shape of a bolt.
So to overcome this weakness, a custom-made bolt with a rather thick sleeve
for a head can be made and fitted over the end of the bar and welded.

At this point I'm feeling all warm & fuzzy except that those bolt ends on
the bar look rather thin.  Roland & I discussed two ways to solve this
problem.  1) use a very hard steel bolt.  2) use a bigger bolt.

The first method is the easiest.  I had concerns about mixing steel alloys
(the bar should be type 1045 carbon steel, and the butt-welded bolt
something different).  But Roland said that this won't matter because it is
on the end of the bar where it is not getting any twisting forces.  If this
were in the center of the bar, then it couldn't be done.  I asked about
tempering the steel, and he said that most of what he does starts out with
pre-tempered steel.  They just bend it to shape and weld the required
fittings to the ends.  No additional tempering is needed.  Even though
welding the ends removes the tempering at these points, they are not
stressed like other areas of the bar.  However, our needs on the DeLorean
are more critical because the bar functions as a locator bar as well as a
sway bar.  I'm assuming that such a bar would need to be re-tempered once
all the welding is done.  I still have some research to do here.

The second method (using a bigger bolt) gets rather complicated.  At the
very least, the end bushings would have to be made larger, and the lower
control arms do not have a lot of room for this.  To make more room would
require making custom lower control arms.  This sounds too costly, but
considering that the original supply has run out, the DeLorean vendors are
having new and improved ones made from scratch anyway.  So how much money do
you want to spend?  Now add new front lower control arms to the shopping
list.  And this of course puts me right where Steve Wynne at DMC Houston is.
He's talking about making a suspension upgrade that does away with or
replaces the sway/locator bar and the control arms with a very different
design.  (sigh)  Well, if he would just hurry up!  Some of us impatient
types want something sooner.  He said that he wants to test his setup on a
car for a year before he sells any, but I'm not aware that he even has a
prototype yet.  I offered to test his prototypes, but he doesn't want the
liability.  I even offered to sign wavers, become an employee, etc.  Just no
luck.  :)

While typing this out, I got a phone call from the engineer (John Carlson
with Saner Performance Fabrication) who designed the DeLorean rear sway bar.
We discussed all of this and more, and he wants me to send him some
drawings.  It's a good thing I did well in my Engineering Graphics course in
college.  He contradicted some of what Roland said, but has some other ideas
as well.  One thing both of these guys suggested was leaving the original
sway bar alone and adding an additional sway bar.  But this defeats half the
purpose of this project: Getting the original bar out of the way of the
wheels.

If anyone has any opinions or suggestions, e-mail me privately or to the DML
if appropriate.  If Steve Wynne is serious about this project and will
finish it soon, then I will wait him out.  Otherwise, I'm having fun with
it.  Does anyone know his progress?

Walt    Tampa, FL




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