the basic keys
The first trick with the actual typewriter was to get all the regular
keys to produce letters. Shift, Space, and Enter I would worry about
later.
A quick look at the underside of the typewriter provided the answer.
Every time a key is pressed, the "lever" is pushed down and
connects with the "crossbar" (the other end of the lever raises the
hammer to strike the paper). The crossbar seems to both keep
the levers from moving too far and provide the force to advance the
carriage for the next letter.
So I figured I could use the contact there to complete a circuit.
Obviously, each lever and each part of the crossbar that it would
contact would have to be electrically insulated. Then I would need
something to act as the actual contact. For insulation I used gaffer's
tape, which worked admirably. For the contact patches I initially tried
aluminum foil but was having a bit of trouble soldering the wire to it.
I spoke to my fencing
coach, who has plenty of electrical soldering experience. He told me
that you simply can't solder to aluminum but offered me a rather
interesting bit of material: copper lamé with an electrically
conductive adhesive on the back, which I did not even know existed. The
stuff is perfect for repairing fencing lamés and seemed to be
just what I needed. He got it from a former student who said it was
manufactured my a rival electronics comapny and he had never seen it in
stores. This leant a certain mystique to the project- working with rare
and somewhat mysterious material and so forth.
My first thought was to simply put the wire under the lamé and
let the adhesive conduct and hold it in place, but the adhesive wasn't
strong enough to keep the wires from moving around. It would have held
for a while, but I needed something I could really move around, so I
decided it would have to be soldered in place.
After removing the crossbar and covering it with gaffer's tape, I
replaced it in the typewriter and used a silver glitter pen (you can
tell this was a labour of love) to mark exactly where each hammer
touched it. Then I cut triangular strips of lamé and stuck them
on over the contact areas. I used alternating triangles so that each
one could have some spot large enough to solder the wire in place- the
even ones on one side, odd on the other.
Next up were the levers themselves. Oy, what a job. Each lever was
wrapped first in gaffer's tape then in lamé. Soldering onto this
lamé material works, but the problem is that the stuff is so thin that is burns/melts
really easily, so any more than a minute touch of the soldering
iron would put a hole in it and I would have to start again.
From here I returned to the crossbar, soldering on wires (this illustration shows only one side done).
Once this was done, it was just a matter of putting it all together. But first: the special keys.
erik@SPAM-ME-NOT.multipledigression.com (minus the spam filter)