Andy,

The following are excerpts from data sheets of a plastics manufacturer;

Concerning Teflon: virgin PTFE has exceptional electrical and dielectric
properties. Since it is a soft
material it is somewhat limited for mechanical applications. It will
creep or cold flow
when a compressive load is applied. PTFE can also experience a high rate
of wear when
used in a dynamic application.

Concerning UHMW: UHMW is an ultra high molecular weight polyethylene.
It offers a broad range
of properties such as a low coefficient of friction, superior abrasion
and corrosion
resistance that make it ideally suited for industrial applications where
material hang-up
and accelerated wear due to abrasion or corrosion is a concern. RedcoT
UHMW has
proven to outlast mild and hardened steel by as much as 10 to 1.

So, for load bearing applications, because of Teflon's softness and
tendacncy to creep UHMW is the
material of choice unless the application is for high temperatures
(cookwear, etc.) or where
Teflon's extremely good electrical characteristics are required.

One advantage that Teflon has in many applications is that it can be
'grown' in place on the surface as a thin film
which retains most of the properties of the bulk material.

Randy Marsden


----- Original Message -----
Sent: Saturday, November 01, 2003 1:48 AM
Subject: RE:[M]: Re: Re: Superwedge - HDPE vs Teflon for bearing


> Randy, surely the stiffer materials like this only amplify the casting
imperfections that you mentioned before? The tripod heads seem smooth
and most of the roughness is on the underside of the cast wedge base.
With the properties of teflon, all minor roughness of the base is
absorbed by one side of the teflon leaving the other side perfectly flat
and smooth as the bearing surface on the tripod head. How can a stiffer
material possibly do this? CDs etc are a quick fix only and they do work
but nowhere as efficiently as teflon. You mention cost which is a fair
point, but it is like having quality optics and using cheap eps, you
would not do it out of choice, the same goes for this, amplifying the
roughness of the wedge with harder materials leads to a knock on effect
of your scope base not sitting flat on the tripod thus making it harder
to polar align.
>
> Best Regards,
>
> Andy 51.19N
>
> Nil Satis Nisi Optimum
>
> (Nothing's Satisfactory Unless It's The Best)
>
> On Fri, 31 Oct 2003 21:29:52 -0800 "Randy Marsden"
>

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