FW: [DML] Front Suspension Mod's

["Chris Parnham" <chrisparnham@xxxx>]

Some technical front suspension stuff!

CP


-----Original Message-----
From: Walter Coe [mailto:Whalt@xxxx]
Sent: 06 January 2002 06:55
To: dmcnews@xxxxxxxxxxxxxxx
Subject: Re: [DML] Front Suspension Mod's


Toby & list,

You have my full attention on this one. My opinion, excuse the cliché, is
that you are trying to make a silk purse out of a sow's ear. If DMC stayed
in business, there would probably be a recall on this part. I don't think
that a simple bolt-on kit would be safe because it would change the stresses
on an already weak part. Before anything is bolted on, the bottom should
have a plate welded on to box it in and -- more importantly -- more metal
needs to be added to the outermost edge of the arm. Have you seen the
photos of Tom Long's broken control arm? If anyone were to do all this
welding, then they might as well weld on your modifications instead of bolt
them on.

There have been lengthy 'off list' discussions about designing a better
front lower control arm and making a new geometry heavy duty sway bar fit.
I wish that the moderators would allow more brain storming about ideas such
as this on the DML, but they are more interested in seeing posts about what
has been done rather than allowing the list to be cluttered with
speculation. So I'll give a summary of what we came up with so far:

To start with some name dropping, Steve Wynne of DMC Houston announced at
the SEDOC event last September that he had plans on the drawing board for
producing a new front suspension that would replace (or eliminate?) the
front sway bar. This included what he described as an "A" arm that would
replace the weak OEM lower control arm. Keep in mind that the front sway
bar works primarily as a wheel locator bar which makes reengineering very
difficult. Without the bar, the control arm would fold back. Even if the
arm were made stronger or in an "A" shape or triangulated (as you all it),
if it didn't bend then the frame surely will. Of course your idea would
reuse the old sway bar, so this wouldn't be a problem. (I'm just explaining
some background for everyone else.) From what Steve described, I think he
is proposing a weld-on fixture that would connect between the front
suspension of both wheels. Something like this could be made strong enough
to eliminate the need for a wheel locator bar. Considering that his Stage
1, 2, etc engine upgrades are not sold as kits, I assume that such will be
the case with his suspension upgrade if he ever gets around to making it.
Such a setup could add substantial strength and eliminate the need for a
wheel locator bar.

Like you, I have considered a new control arm design that would attach to
the outer points on the frame instead of at one point in the center like the
OEM does. (Many people have independently come up with this idea.) This
could still use a connection in the center making it look like a 3 ring
hinge or it could eliminate the center connection which would then need to
be replaced with a spacer. For what it's worth, I don't think this idea is
practical unless a new fixture is made to bolt or weld around the frame that
would connect between both control arms. The advantages of this is that it
could add substantial strength and eliminate the need for a wheel locator
bar (which would then make room for a more simple sway bar). And even
without a bar, it may improve handling because the OEM bar does little to
stop sway anyway as its primary function is as a wheel locator.

Taking all this into consideration, my plan is to make a new heavy duty sway
bar that could bolt up to the OEM control arms. However, I don't mean for
this to be done without either replacing the arms with improved aftermarket
ones or having the original arms substantially reinforced. My main concern
at this point is that the OEM-size sway bar studs might be too thin to be
strong enough to support the added stresses of having a real functional bar
that actually does the job of a sway bar in addition to being primarily a
wheel locator. What compounds this problem is that using a thicker bar will
proportionally make the OEM-size stud a high stress point. The engineer
suggested turning down the ends of the bar on a lathe so that they would be
gradually tapered. This would distribute some of the load away from the
stud. This sounds like a great idea to me and is the one we are planning
for now. The alternative is to use a thicker stud which would then require
a larger bushing and a custom lower control arm. And if this is the way we
end up doing it, then I would expect anyone buying the heavy duty control
arm would as a matter of course also not want to risk using their weak OEM
control arms even if they could be made to fit. Then we would sell a
complete kit that includes a new sway bar, control arms & bushings.

Considering the additional fore/aft stability that this stiffer bar would
provide (particularly if we used nylon bushings instead of rubber), it may
give all the handling improvements we are looking for and make the "A"
arm/triangulation idea a moot point. Food for thought.

I have learned a lot from the extensive conversations I have had with the
owner of Addco (who made the rear sway bar accessory for the DeLorean) and
with the engineer who designed it (he is now working for himself in Florida
and is the one who is going to make the new front sway bars.) I originally
thought that we would have to temper the new sway bars after they were made,
but this is not the case. Instead they start with certified pre-tempered
bars and cut & bend them to shape. That really simplifies the process. But
what makes this so damned difficult for the DeLorean is that this is more
than just a sway bar; it is also a critical wheel locator, so dimensions and
integrity are critical. Normal sway bars have fittings welded on the ends
which are not tempered afterwards. But since we also need it to work as a
wheel locator, any welding to the ends may weaken it too much. Then we are
looking at having to re-temper them which is a can of worms better left
unopened. So far it looks like the process is going to be: 1) starting with
a straight pre-tempered bar and turning it on a lathe to taper the ends and
cut threaded studs. 2) the bar is bent to shape such that there is more
threaded stud on the ends than necessary. This is to give some breathing
room because if the studs are made too far apart or the bends not done exact
enough, then it can't be turned on a lathe again once it is bent. 3)
spacers (washers) are placed on the ends to fill in the breathing room. 4)
bushings must be welded to the front of the bar to match the OEM design.
This stabilizes the bar laterally. Welds at these points won't adversely
affect the tempering of the bar.

The next step in this project is for me to sit down at my drafting table and
whip out some engineering drawings of the OEM bar. It would seem that I
could just send a sway bar to the engineer, but additionally he needs
engineering drawings because we are changing the shape (that's my job) to
increase the car's turning radius by stopping the wheels from rubbing the
bar. This is even more critical for those of us with wider aftermarket
rims. I have asked the list for help from anyone who is sitting on a copy
of the factory design drawings that show this bar. It could save me some
time & effort, but so far no one has come forth. Meanwhile I have other
projects that I need to finish first such as making all these convex mirrors
I have promised to so many people. (sigh) But oh what fun we are having!
Toby, you are welcome to comment, suggest & criticize on a wholesale level
all you want. You are the materials expert here. All the help I get will
be appreciated.

Walt Tampa, FL




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