Re: [Leica] Immune to brassing!

[MicroGrid@aol.com]

Well, I'll take a shot at second guessing Leica's design engineers. My 
company expands brass and zinc among other metals. We expand all ductile 
metals into very fine precision grid structures (often used in batteries). 
Zinc alloys are widely die cast. The alloy can be tailored to maximize the 
desirable physical properties such as tensile strength, ductility, resistance 
to physical shock, etc. Most of these zinc casting alloys can be cast in 
modern high sped machines, that will yield parts with high accuracy, 
resulting in much less secondary operations, such as finish machining, than 
brass -- itself a zinc alloy. These designs can be much lighter than brass 
(although not as pretty when the black paint wears off, I hate "brassed" 
chrome cameras). The technology to alloy zinc is quite old, and the alloying 
compounds numerous. It would be as mistake to generalize one zinc casting 
used elsewhere to my Leica M top.
Materials choices are a key component of design. A designer looks at the 
requirements of the device, the environment it will be placed in and the wear 
and tear it will face. As Steve well knows, his problem with his lights was 
corrosion, inevitable when your environment is salt water. So, our lesson is 
... when your Leica (brass or zinc top) gets immersed in salt water, rinse it 
off fast! I am serious.
It seems to me that Leica did the right thing for us users by switching to a 
zinc alloy. It keeps the cost down, weight down, and by choosing an 
appropriate alloy, presumably gives better "shock protection," all desirable 
things for me. 

Bruce Bowman
Killingworth CT

In a message dated 6/13/00 8:24:00 AM Eastern Daylight Time, icommag@toad.net 
writes:

<< > I certainly cannot speak authoritatively on this but one of the
 > justifications Leica used when they switched from brass to the zinc
 > composite top plates was zinc's superior ability to absorb shock. This 
would
 > imply that it actually is softer and would dent or mar more easily than a
 > brass top plate.
 >
 > John Collier
 >
 >> From: "Steve LeHuray" <icommag@toad.net>
 >>
 >>.......it has never been mentioned that brass is actually a very soft metal
 >> which is easily dinged, scratched or crushed. Zinc is probably better.
 >>
 >
 John,
 Likewise, I cannot speak from any authority about this subject it is just my
 impression from my old beat up and dented M2's. Also after installing a
 motor drive on the brass bottom plate of my Nikon FM2n it became crushed
 from the tightening down of the mounting screw. And also from my many years
 experience with sailboats. For example many years ago I installed 8 shiny
 new brass port lights (windows for those land lubbers). They were 1/4" thick
 but within two years the brass screws had turned pink and in another year
 literally turned to dust. I replaced the screws but in two more years the
 port lights themselves started to crumble. Zinc on the other hand is also
 used for many boat related things including attaching to the hull below the
 water line to prevent electrolysis. My only knowledge of these two metals is
 from holding them both in my hands and the feeling that zinc to be the
 stronger metal. The port lights on my boat for many trouble free years now
 are silicon bronze.
 Steve
 Annapolis
  >>