Both my total knee replacements in 2007 are made up of components made of
titanium and a meniscus replacememt in the form of a 'plastic' plate - a
high density polyethylene - that separates the titanium pieces on the femur
and the tibia. The major concern for longevity of the new joint is from
impact of the two titanium pieces on the plastic piece - so I shall not be
taking park in those activities that produce excessive impact on the knees.
Kenneth Waller
http://www.pentaxphotogallery.com/kennethwaller
----- Original Message -----
From: "P. J. Alling" <[email protected]>
Subject: Re: New DA50/1.8 Plastic Mount
Plastic in hips and knees doesn't last forever either. Last I knew
replacement knees and hips were made out of titanium. There may be Teflon
"lubricating" pads between bearing surfaces but I don't know for sure.
Different engineering problem altogether.
On 5/23/2012 5:10 PM, David Parsons wrote:
Plastic is good enough to be used in hips and knees. I'm sure that a
lens mount will hold up fine.
On Wed, May 23, 2012 at 12:20 PM, P. J. Alling
<[email protected]> wrote:
Lenses are a long term investment, at least they used to be, plastic on
a
bearing surface implies the opposite. No matter what plasticizers are
lost
over time and the material becomes brittle and subject to cracking.
Eventually something important will break. Heat will exacerbate this
process. If the lens was cheap enough to be disposable that would be
fine
but it's not really.
On 5/23/2012 10:02 AM, Charles Robinson wrote:
On May 23, 2012, at 8:25, Tom C wrote:
Come on Pentax! How else are you shaving costs? Talk about making
yourself look cheap.
I have no complaints with the nice crisp images coming from my
all-plastic
DA 35 f2.4. It seems to be holding up quite well and frankly I don't
give a
rat's patootie what the mount is made of as long as it works. And it
does.
-Charles
--
Charles Robinson - [email protected]
Minneapolis, MN
http://charles.robinsontwins.org
http://www.facebook.com/charles.robinson
--
Don't lose heart! They might want to cut it out, and they'll want to
avoid
a lengthily search.
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