JF Ptak Science Books *Quick Post*

There's a box in the studio that is filled with all manner of antique and semi-antique adding/calculating/etc. instruments, from slide rules to blast effects of a nuclear weapon to air speed to the gas mileage for a 1959 Rambler. Some are wood, some metal, but my favorites I think are those made of paper (a large revolving baseball from 1961 for calculating world series records is my favorite in that area....that, or the radiation measurer made of paper to place alongside A Body Part to check on its incremental-or-not growth following nuclear detonation).

The there are the little bits that maneuvered the little bits, as seen in this uncovered little gem, the "Fraction of an Inch Adding Machine" (shown above). It was patented in 1952 by K.P. Jaeger (http://www.google.com/patents/USD169941), and is stamped "Sheradco, Inc., Detroit" on the reverse of the metal plate.

It does a relatively simple task as stated--adding diverse fractions--and it does so quickly; as a matter of fact, it is far quicker than you can do it online, even with a converter. This is basically two steps--you put a pen or pencil head in the outer ring hole for the first fraction and move the dial clockwise until you come to the stop; then you do the same for the next fraction, and the result is instantly displayed. For operations above 1, you just need to keep track of the whole numbers yourself. Unfortunately it doesn't teach you anything about fractions, but neither does your digital calculator teach you about anything calculating.

This is just a smart and pretty instrument that works very nicely indeed, and I just wanted to share it.

[I did find a lovely post on how to make your own! It also provides a pdf of base plate and the rest of it as well: http://www.evilmadscientist.com/2007/make-your-own-1952-fraction-of-an-inch-adding-machine]

While looking for it on Google Patent Search I bumped into some other similar devices, and I just wanted to take a moment to note the beauty of the possibility of their interior base dials. Just one sample here for the moment: the "Dial Adding Machine" of E.T. Knopke, 1952, which is so full of numbers and potential and mathematical poetry:

[Source: Google Patents]

Feb. 19, 1952 E. T. KNOPKE 2,586,058