Homebrew Drum Computer (magnetic heads)
mloewen at cpumagic.scol.pa.us
Fri Dec 14 13:25:25 CST 2007
On Fri, 14 Dec 2007, jim s wrote:
> Also all the drums I ever saw had a sort of flying head with a horizontal
> head in a hole with a small spring mechanism that would hold it in position.
> I don't if the head normally was out of contact with the drum while the head
> was stopped and was then sucked in, or if it landed and was pushed back, but
> that whole affair was delicate as well.
Just for reference, here's some information about the drums used in the
SAGE (AN/FSQ-7) system:
Length: 12.6 inches
Diameter: 10.7 inches
Weight: 85 lbs
Speed: 2914 RPM
Recording Surface: nickel-cobalt alloy
Word Length: 32 bits (typically, plus various control and parity bits)
The heads were fixed, on 6 pairs of mounting bars, with a critical air
gap between the head the drum surface. The Q7 drums had two sets of
heads to support simultaneous r/w operations between the computer and
drums, and outside equipment (radar info, xtel, etc).
Here's a picture from the Computer History Museum:
... and a very small picture of r/w head:
The head is in the lower right hand corner.
Specifics were taken from pp 125-131 of the "Theory of Programming"
Mike Loewen mloewen at cpumagic.scol.pa.us
Old Technology http://sturgeon.css.psu.edu/~mloewen/Oldtech/
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