Description
Video
Simulation
History
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Patents
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The Fraction Of an Inch Adding Machine, or Fractron, is simple disc adder. It consists of three discs made of aluminium. The front and the back disc are riveted together. This sandwiches the middle disc though it is still able to rotate because it is really a ring rather than a disc. The moving disc has 64 holes evenly spaced about its rim, representing the fractions of an inch from 0 to 63/64. The stationary front disc shows these fractions in lowest terms and in a decimal representation. Using a stylus you can dial in any number of these fractions, and the total amount is displayed through a small window in the front disc. To reset the display to zero use the stylus on the hole that is marked in black.
The machine does not have a carry mechanism, but there is a notch in the outer disc and a tab on the moving disc. When you hold the disc you can put one finger in the notch. When the addition reaches a whole number of inches, the tab can be felt moving past the notch, alerting you to the fact that the result overflowed.
The machine came with an instruction leaflet.
Below is a video I made that demonstrates the Fraction Of an Inch Adding Machine.
You can try out the Fractron in the simulation below, or open this simulation in a separate window.
The Fraction Of an Inch Adding Machine was designed by Kurt P. Jaeger. He started making and selling them in 1951, and patented the design in 1952. The first ones he made came in a cardboard box, and the centre of the disk was black and had his name on it.
The most common version is the one I have which came in a plastic sleeve. Its centre is blank with the design patent number in small letters along the bottom. From at least as early as 1956 the adder was made by Sheridan Advertising Specialities, also known as Sheridan Printers, Sheridan Advertising, and Sheradco, Inc., located at 26020-26032 Grand River Avenue, Detroit. These adders were ideal for promotional use, so there are many which have a logo or advertising slogan printed in the centre, and Sheridan offered this service.
At some point the adder was given the more catchy name Fractron. Mine has a sticker on the instruction sheet and one on the back of the machine, both bearing that new name. The address on those stickers is in Fort Lauderdale, very close to Kurt Jaeger's Miami address, and in the metal is stamped "Sheridan Printers, Fort Lauderdale". Note that Sheridan was based in Detroit until at least 1961 according to the adverts below.
A certain Anthony Pickios may also have been involved in the manufacture, as in 1969 he was granted a patent for a draftsman kit that included the Fractron in its contents. In 1982 he received a patent for an improved method of manufacturing them, and from then on the centre of the disc included the new patent number and had the name Fractron was written diagonally across it.
I found a few advertisements for this machine in online archives, lasting about 10 years from 1951 to 1961.
Here are the patents relating to the Fractron, including some predecessors.
| Patent | Filing date | Priority date | Name | Description |
|---|---|---|---|---|
| US 1,344,190 | 07-08-1917 | 22-06-1920 | Carlos Ruiz | Fraction-adding machine |
| US 1,382,331 | 22-11-1919 | 21-06-1921 | James Thomas; Morse Twist Drill & Machine Co. | Computing device |
| GB 649,488 | 23-09-1948 | 24-01-1951 | Edric Raymond Brooke | Fraction of an inch adder |
| USD 169,941 | 05-11-1952 | 30-06-1953 | Kurt P. Jaeger | Design for a calculator |
| US 3,481,452 | 11-12-1967 | 02-12-1969 | Anthony G. Pickios | Draftman's kit |
| US 3,511,438 | 13-05-1968 | 12-05-1970 | Ralph E. Melendez | Fractron with units wheel |
| US 4,450,615 | 07-06-1982 | 29-05-1984 | Anthony G. Pickios | Method of fabricating a hand calculator See also: CA 1,189,039. |
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