Weekly Classic Computer Trivia Question (20141215)

Doug Ingraham dpi at dustyoldcomputers.com
Mon Dec 22 11:31:30 CST 2014

Thanks for playing everyone.  The answer I was looking for was vertical
displacement of the letters or wavy text.

There are two reasons this happened.  The primary reason is the critical
timing of the firing of the hammer.  The other reason would affect all
types of impact printers and that is stopping the paper motion through the
printer.  This was not usually a problem unless the weight of the paper was
very light which would allow the sprocket holes to elongate.  This would
allow the paper to continue moving around while the drum was completing its
turn.  The sprocket holes could also elongate if the paper tension was
increased too much.

None of this was of much concern on the slower 300 lpm printers but at 1000
lpm or faster timing would be more than three times as critical.

Chain, train, and band printers would tend to have mild misalignment in the
horizontal direction but could still have vertical alignment issues if the
paper continued to move around.

One of my friends reminded me of the most unusual uses of the 1000 LPM
printer on the CDC 3400 that South Dakota School of Mines and Technology
had in the 1970's and that was as a bass drum when the computer played the
Stars and Stripes forever.  I only saw this run a handful of times and it
is probably one of those things lost forever.  Even if someone had a copy
of the program no simulator would be accurate enough to run it and I am
pretty sure there is no running hardware.

Doug Ingraham

On Mon, Dec 15, 2014 at 2:07 PM, Doug Ingraham <dpi at dustyoldcomputers.com>

> OK, so somewhat weekly questions.
> Back in the days of high speed line printers there was a characteristic of
> drum style printers that made the output print style quite distinct.  What
> was this characteristic?
> I don't miss the noise of those devices and it seemed like no matter how
> careful you were when changing the ribbon you would smudge your hands.
> Doug Ingraham

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