A request forwarded from NIST-

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Subject: Ideas for alloys for use in switch contact
Author:  [log in to unmask] at _internet
Date:    8/21/95 6:48 PM


 I have a client who is looking for a copper or copper alloy
to use in a switch-type assembly. The flat, slide contact is
half-hard ETP copper.The bowed, fixed contact is a strip of Alloy 195.
  The force on both contacts, when closed, is 160 grams. Contact
travel is about 3.2mm. Contact area varies from 0.4mm x 1.9mm to .8mm 
x 1.9mm. Voltage across contacts is 1 - 12 VDC. Current is 1 - 30 ma. 
Life expectancy of assembly is about 30,000 cycles. 
     
       Problem is that contacts must be self-wiping. Assembly may
stand for weeks without use. Oxide buildup has to be wiped off 
contact by other contact to make the contact. This causes wearing
of both surfaces, resulting in ridges, which rapidly causes increased 
resistance across the contacts. Phosphor-Bronze and conductive 
lubricants have been suggested but not yet tried. In order to remain 
competitive, cost of solution must be as low as possible. Exotic 
materials and Rube Goldberg devices for cleaning the contacts are out.
     
       The key words here are 30,000 - 50,000 life cycles and cheap.
     
Reply to: Bob Weller, CNYTDO, 1201 E. Fayette St. Syracuse, NY, 13210.
  Phone: (315) 425-5144
  FAX:   (315) 475-8460
  E-mail: [log in to unmask]
     
Please reply to the sender at the address above.  If you reply by email, 
please send me a copy.  Thanks in advance.
-
Charlie Rosenberg, TECnet, 4 Colby St. Room 153, Medford, MA  02155 
E-mail: [log in to unmask]  Tel: (617) 627-3818 Fax: (617) 623-1427