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Which is powered by this differential. test (28).jpg
On the opposite side are a set of gears which then drives with metal tapes this post with a ball on it - THWACK onto the paper. test.jpg
And then this cord on a ball bearing pulley actually moves the whole ball assembly. test (19).jpg
This is where things get really crazy. The ball has to be rotated to the exact spot that the key indicates. One side of the ball is for Caps, the other for lowercase. test (17).jpg
These bars, called Whiffletree Linkages, are used as a primitive digital input to tell the ball what position to go to. test (30).jpg
From Wikipedia entry on the IBM Selectric.
The mechanism that positions the typing element ("ball") is partly binary, and includes two mechanical digital-to-analog converters, which are basically "whiffletree" linkages of the type used for adding and subtracting in linkage-type mechanical analog computers. Every character has its own binary codes, one for tilt and one for rotate.
When the typist presses a key, it unlatches a metal bar for that key. The bar is parallel to the side of the mechanism. This bar has several short projections ("fingers"). Only some of the fingers are present on any given code bar, those present corresponding to the binary code for the desired character.
When the key's bar moves, its projections push against a second set of bars that extend all the way across the keyboard mechanism; each bar corresponds to one bit. All bars for the keys contact some of these crosswise bars. Those bars that move, of course, define the binary code.The bars that have been moved cause cams on the driveshaft (which is rotating) to move the ends of the links in the whiffletree linkage, which sums (adds together) the amounts ("weights") of movement corresponding to the selected bits. The sum of the weighted inputs is the required movement of the typing element. There are two sets of similar mechanisms, one for tilt, one for rotate. The reason for this is the type element has four rows of 22 characters. By tilting and rotating the element to the location of a character, the element could be thrust against the platen, leaving an imprint of the chosen character.
Bill Hammack, professor of Chemical and Biochemical Engineering at the University of Illinois
The main thing I wanted to communicate though is that much of the satisfaction of using a machine like this is that satisfying snap as the cam slips just enough to let the power of that motor take over.
Next up. It's Oil Can Henry time.
Now this typewriter has been used periodically but not serviced in at least the 20 years my dad had it. It works fine for me but I thought I'd take it apart and have a look.
First remove the side knobs with a 1/16" hex, remove the correcting and ink tapes, and disengage the platen with the levers on the side. test (2).jpg
Open the top and reach down on either side to disengage these levers to lift off the entire top. test (25).jpg
Down by the bell is a lever to unlock the assembly from the bottom plate. At the back of the assembly are some L plates - loosen the screws and jiggle them to the side to release the back. test (16).jpg
First thing you'll see is a bunch of half dissolved 30 year old foam. DSC_2486.jpg
A putty knife and some mineral spirits should clean all that gunk up. Otherwise it'll get into the mechanism eventually and really cause a mess.
This is what we'll clean up next. 30 year oil is really congealed nasty stuff that will gum up a typewriter beyond repair if you let it go. The typewriter should be warmed up and used once a year at least to help prevent it getting too bad. test (14).jpg
Gather up rubber gloves, some mineral spirits, and I even went all Fallout3 since I had a respirator. Tape off rubber/plastic parts with painters tape. Professional techs used to take the typewriters and dunk them in a vat of solvent with compressed air blown in to bubble the whole thing. Not going to do that. test (11).jpg
I sat the assembly on a plastic tray and sprayed on mineral oil and just gave the whole thing a bath and left it to soak for a bit. Then scrubbed off any congealed oil with stiff paint brush. Now I read on the Internet that you should do this while running the motor and using the keys. I kept the fire extinguisher handy - can't believe what you read on the Web. Got it nicely clean though. test (10).jpg
Let it all dry out in the sun. Then visit you local car parts supply place and get this stuff. Another crazy Internet tip. This Marvel Mystery Oil is interesting. Looks like transmission fluid. Makes sense since what you're looking for is a 10W lubricant with lots of preservative stuff to prevent gumming up in 30 years time. test (23).jpg
I applied it with a drip oil pen. It's better to under lubricate in the beginning then put too much on. test (24).jpg
Clean up the plastic with some softscrub like stuff, load up on typing tapes, and you're ready to go another 30 years. It felt good before and feels great now. Ah, the smell of Mystery Oil in the Morning! test (12).jpg
Good luck if you decide to tackle this yourself. You got a little bit of IBM history there. Take care of it. test (18).jpg
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