[200q20v] RE: [s-cars] Delrin/ urethane bushing alternative

Trevor Frank tfrank at symyx.com
Wed Oct 3 12:03:57 EDT 2001

Unmodified Teflon would be much worse than Delrin.  Teflon has a tendency to
creep and therefore is not suitable for bushing applications that would take
much if any real load.  I have manufactured bushing for different race cars
over the years and in one case made replacements for Teflon bushings that
had deformed in a very short time.  Delrin is inexpensive and tough, it is
easy to machine and is well suited for a bearing material, I have seen it
used successfully on everything from a Mini Cooper to an IMSA GTP/ Group C
car.  Modified nylon bushings in my opinion are one step better, they are
harder but when modified with Moly or Kevlar or ??, have a lower coefficient
of friction than Delrin, i.e. Nylatron GS.  Peek is very expensive and not
well suited for our application.  It is brittle and because of this it tends
to chip and scale under high loads.  Peeks real strength is in its chemical
inertness.  If you want to spend this kind of money and match the
coefficient of thermal expansion better than nylon or Delrin or Peek then go
to a bearing grade of Torlon $$$$ or even better yet use Vespel $$$$$.
Coefficient of friction is a reference to but not totally corollary to the
abrasiveness of a material.  Plastics can and will wear on the steel and or
aluminum that makes up the suspension components.  This could over some time
loosen the suspension of any race car.  It is important to look at what the
"k" factor is or Wear Resistance.   I have found that to get a good fit with
these harder material, anything other than urethane or rubber, it is
necessary to custom fabricate each bushing to match each component.  This is
due to the fact that these components where never machined to much precision
or accuracy.  This is probably overkill for the street car and I feel that
only a few race car drivers would notice the difference, but for those who
must have it I have done it.  Another trick is to use as little bushing
material as possible, instead fabricate an aluminum or steel sheath that
covers the outside or inside of the bushing, then press fit the bushing
material on to it, then press fit the assembly onto the suspension.  The
disadvantage is that you may never get it out again.  In this interest it is
always best to use a dissimilar material.

To be an informed consumer, pick up a DSM Engineering Plastic Products
Design and Fabrication Reference Guide.  They have many if not all of the
materials worth considering for this application.

-----Original Message-----
From: Kaklikian, Gary [mailto:gary.kaklikian at compaq.com] 
Sent: Tuesday, October 02, 2001 7:46 PM
To: Audi 20V (E-mail); s-car-list at egroups.com (E-mail); 200q20v (E-mail);
Brandon Hull
Subject: RE: [s-cars] Delrin/ urethane bushing alternative

I spoke with Shine Racing earlier this year about control arm bushings
for my 4000tq.  They said they could fit their Teflon bearings to this
application.  At the time, I had poor luck with urethane bushings and
switched to delrin.  Well, after less than 10 track days, the delrin
bushings have begun to creak and apparently there is some deflection
occuring since handling does not seem quite as precise as before. Yet,
all of the control arm bolts are tight. So, I plan to contact Shine
Racing again to see what they can do and, if necessary, send them a new
set of control arms to fit their bearings to.
I'll keep you posted on how this works out, but since I've also got
engine problems with the car now, it will be a while.

Gary Kaklikian
'86 4ktq
'92 S4 

> ----------
> From: 	Brandon Hull[SMTP:brandon at cardinalventures.com]
> Sent: 	Tuesday, October 02, 2001 7:31 AM
> To: 	Audi 20V (E-mail); s-car-list at egroups.com (E-mail); 200q20v
> (E-mail)
> Subject: 	[s-cars] Delrin/ urethane bushing alternative
> I happened upon this fascinating site today:  Shine Racing, a VW tuner
> in MA
> makes a needle bearing bushing insert for suspension control arms.
> The
> advantage would be near zero friction in the suspension movement, with
> zero
> play.  (maybe a bad thing as has been discussed, if we assume mass
> production engineering factors in some slop here to accomodate
> production
> variances)  
> In any event, I'm curious to know if anyone has pursued this for Audi
> applications.
>  http://www.srsvw.com/basic.htm
> A step by step Porsche installation:
> http://www.all914.com/projects/ScottY/Part1/index.htm
> Brandon Hull
> eS2
> 911SC
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