Mechanical calculators not made with pin-wheel mechanism, like ones made with buttons and ratchets mechanism.
Flying Fish calculator
This is a Chinese more-or-less clone of Monroe L-series calculator, the one from 1940s, although some sources (compvter.it, 2018) claim that it was a license copy (at least under name "Shanghai Calculator JSY-20"), there are too many modifications to the original so it's most likely a clone. These mechanical differences include a clock-like chassis instead of frame-like, orientation of relase plate, bell mechanism, but generally the principle, appearance and operation is the same. I have no idea how old my unit is, but I can estimate it. In some websites we can read that this machine was manufactured in 1950s, while in other that even in late 1970s. It is also known that there were a few versions - gray with black keys was probably a late version, brown with dark-brown, a bit matte keys made of some plastic, but my unit is brown with brown, shiny keys. Additionally gears and levers are machined, not sheet-cut which excludes 1970s, as mass production then was developed enough to quickly cut many parts of mechanism from metal sheet. The material used for plastic finishes was a puzzle to me, but by some experiments I found that in my unit it is a celluloid. So definitely 1950s, maybe early 1960s from surplus. Celluloid was one of the first plastic materials, but is not very good as a general-purpose material: it is extremely flammable, it cracks when exposed to light and releases gasses when exposed to temperature, so as better polymers became invented in 1950s and 60s, it was used less and less frequently.
The mechanical principle of operation is simple: When you press a key, a lever is pressed in its specific place. This place has a protrusion bent in angle specific to digit. So, when you press a key, the lever moves a distance specific to the value, there are about 5 distances per lever, for one digit one lever moves to the left, another one moves to the right, so there are 9 levers positions like 9 digits per one 0-9 "key set". These levers shift specific gears, which have teeth of different length in their cylindrical length, as a result, forming a gear with specific number of teeth. By turning crank, these gears transmit their value into upper counters.
Additionally, after the transmitting action, a cam can be engaged to push the release plate to make keys pop back up. If the +/- key is depressed, the cam operates normally. If a multiplication key is pressed, the lever is pulled from the cam and release plate won't be pushed - keys will not pop back and it will be possible to perform another multiplication. Additional lever connected to zeroing key can push the zeroing plate from keyboard.
To change decimal places, a valve-like knob is used. This knob turns the small internal lever which just tumble the upper part back and forth. It is also possible just to grab a handle and move the carrier manually.
The smaller crank located on the carrier allows to zero the main or turns counters. This is done not by rotating all digits which are not zero to zero as in later machines, but by rotating all digits and stopping the rotate at zero.
My unit's history is not known, comes from flea market. Some keys are missing, but I made their models for 3D print. It had a few problems related to crank lock mechanism (not operating at all) and release plate (lever not pushing the plate to a full extent), but now they are fixed.
The key models can be downloaded here, but they are untested and I think they definitely require some machining after printing.
Monroe calculators description
http://www.rechenmaschinen-illustrated.com/pictures_1951.htm - Photo of the later unit at the end of page.
http://www.rechnerlexikon.de/en/artikel/Shanghai_Calculator_JSY-20 - In German collection
http://www.vintagecalculators.com/html/busicom_and_broughtons.html - A story of an importer of different machines, mentioning Flying Fish in press article.
|General view||Front engravings||Main crank|
|Bell mechanism||Counter gears||Transmission mechanism|