Chinese Abacus By Tom Parker MAKE MONEY
Sometimes it costs more to buy it than to make it from the money itself.
$17.95
Wood-frame Chinese
abacus bought online.
$0.93
Chinese abacus made
of pennies, twigs, and
coat-hanger wire.
The Chinese abacus, or counting frame, is an ancient calculator using beads on rods for both
decimal and hexadecimal computation. In many
parts of the world, schoolchildren still use these
ingenious devices to do large-scale addition, subtraction, multiplication, division, and even square-and cube-root operations at astounding speeds.
The traditional Chinese abacus has seven beads
on each rod, two above and five below. These are
usually made of wood, glass, or stone, rounded for
easy manipulation. I wanted to make my beads out
of pennies, but flat disks would be hard to separate
and slide with your fingers. So I chose pre-1982
pennies, which are 95% copper and easy to deform.
Photograph by Tom Parker
I made mine in the “Adirondack porch furniture”
style, with a frame of dried chokecherry twigs. Since
twigs aren’t perfectly straight, I clamped each one in
a jig so I could drill orderly and parallel holes using a
drill press. First I drilled flat-bottomed holes for the
joints of the frame, using Forstner bits. For the rods,
I drilled carefully spaced sets of holes, sized so that
(The newer zinc pennies tend to snap when bent.)
I could press-fit coat-hanger wire. If you size your
holes right, the frame and rods just snap together.
I center-drilled each penny first. Then I fashioned
a crude deforming tool using a bench vise. To one
jaw of the vise, I glued an old cylindrical bushing the
same diameter as a penny. I sawed off a
7" hex
bolt, filed it to a smoothly rounded stub, and glued it
to the other jaw, just opposite the bushing. This gave
me a “tooth” I could use to deform each penny with
a simple clamping operation.
165 Make:
