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

[Bernie Benz]

Hi Trevor,

You are obviously a well informed plastics application engineer, and I agree
with your comparison of the various plastic bearing properties.  Well
stated.

Recently, I have taken issue with the concept of applying either a plastic
bushing or linear antifriction bearing in a situation requiring more than
one degree of freedom, i.e. one requiring a ball bushing or an elastermeric
flexure bushing to handle the second degree of freedom.  One must understand
the systom requirements and constraints before materials selection is a
meaningful factor.

Bernie 

> From: Trevor Frank <tfrank at symyx.com>
> Date: Wed, 3 Oct 2001 11:03:57 -0700
> To: "'Kaklikian, Gary'" <gary.kaklikian at compaq.com>, "Audi 20V
> (E-mail)"<audi20v at rennlist.org>, "s-car-list at egroups.com
> (E-mail)"<s-car-list at yahoogroups.com>, "200q20v (E-mail)"
> <200q20v at audifans.com>, Brandon Hull <brandon at cardinalventures.com>
> Subject: [200q20v] RE: [s-cars] Delrin/ urethane bushing alternative
> 
> 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.
> 
> HTH
> 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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>> 
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