DEC switch handles (use FDM?)

Vincent Slyngstad vrs at msn.com
Mon Aug 27 01:25:11 CDT 2007


From: "Chuck Guzis":
> On 26 Aug 2007 at 21:10, Vincent Slyngstad wrote:
>> Here's a nice side view of one of the ones for some of the PDP-8's.
>> There is also a long rocker style, and a sort of triangular style 
>> that was used on some of the PDP-11's.
>> 
>> http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=290149624244
> 
> Ah, many thanks--now I understand.  Would it be possible to mill out 
> the profile in a big hunk of polycarbonate and then slice the paddles 
> off like slices of bread?  The result could then be painted.

Sort of, but a couple of the magic bits would be lost that way.
Fashioning the pivots, at the rotational center of the things, would 
require additional work.  In addition, the parts you hit with your 
fingers aren't square -- they are tapered, so there is actually 
space between the tips, but not between the bases:

 \ /
  =
(but not so pronounced).  That turns out to be an important part 
of the user interface, making it easier to hit just the switch 
you want.

> I wonder if you could cast some out of zinc-aluminum alloy using a 
> lost-wax process?  Metal ones would be more durable.

I think that would work, but it sounds like more work that the 
silicone molds and plastic resins.  Durability isn't much of a 
problem, except with the pivot pins.  (The pivots can easily be 
drilled out and replaced with a length from a large paper clip, 
when they break off.)

The URLs I gave earlier for the replacement Straight-8 paddles 
had some nice pictures, which would illustrate the taper and 
show one with the pivot pins replaced with a metal axle.

    Vince

(Do not attempt to cut a paper clip with your favorite diagonal 
cutters, as the metal is often tougher than the cutters, and will 
deform the cutting surfaces.)



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