pwv@fluke.UUCP (06/24/83)
About leaving the shutter of a camera cocked:
As I understand metals and fatigue, leaving a spring under tension
(assuming that it has not been stressed beyond its elastic point)
*does not* cause the metal to fatigue. Only repeated movement
(flexing, vibration, stretching, etc.) of metal will cause it to fatigue
and break. Therefore, leaving the shutter cocked on a camera should
have almost no ill affect on the shutter reliability.
Any mechanical engineers out there care to refute this (il)logic?
Pat Vilbrandt
John Fluke Mfg. Co., Inc.
(...decvax!microsof!fluke!pwv)
(...uw_beaver!fluke!pwv)
(...ssc-vax!fluke!pwv)
(...and others!fluke!pwv)jim@uw-beaver.UUCP (06/28/83)
As I understand metals and fatigue, leaving a spring under tension
... *does not* cause the metal to fatigue.
I think you are wrong. It has been a number of years since I took a
materials class, but as I remember it the molecules of iron in the
spring will tend to realign themsleves to relieve the tension, so that
a spring under tension will not last as long as one not under tension.
This is not what a metalurgist would call fatigue, but it does result
in a less springy spring. If anyone is really interested I will dig up
a reference.
I don't know whether this has a practical effect. I've had a Minolta
for about 12 years with the shutter cocked the whole time, and it still
works. But my 30 year old Leica, which has also been cocked the whole
time, has lost its slow shutter speeds. I don't know if this is
because the springs are week or not.