11 May
2000
11 May
'00
7:50 p.m.
ard(a)p850ug1.demon.co.uk (Tony Duell) wrote:
I have to jump in since someone brought up the Selectric.
Has any-one here ever dismantled a Selectric? Did once
Never done a Selectric. Worked on teleprinters, though, and some of those
have some _strange_ mechanisms. Olivetti had a binary->position decoder
that consists of a series of metal cylinders each with an eccentric hole
such that each one fitted over the next smaller. These were rotated into
one of 2 positions according to the state of a particular bit (one bit
for each cylinder, all cylinders could move separately), so the
overall displacement of a follower on the largest cylinder was determined
by the total binary value of all the bits.
Creed made a paper tape reader where the holes in the tape for a
particular characeter were sampled one at a time by a series of metal
'peckers' and the state transmitted serially by a single contact assembly
operated by a link from the peckers.
Creed also had an amazing carriage feed mechanism consisting of a pair of
pawls opeated by a camshaft (half a turn per character IIRC) that 'walk'
along a rack fixed to the carriage. That one is almost amusing to watch.
and though I thought knew mechanisms at the time
it turns
out I sure didn't. The central mechanism seemed like a cross
between Dr. Nim (On Topic) and DigiComp-1.
The key presses were relayed by an almost binary series of
pushrods to a cascaded teeter-totter matrix.
FWIW, I believe the service manuals for Selectrics were available from
IBM, and maybe they still are.
The damndest mechanism I've ever seen.
Anybody else have
this reaction?
Seems like a pretty good topic so I'm chiming in with this...
John A.
P.S. Don't go breaking up working ones to find out though.
Dismantling a machine is not equivalent to breaking it up :-). It can't
be that hard to get them back together again...
-tony