|Slide rules HOME page||COLLECTION||NON-STANDARD RULES|
|Make||Russian circular rule|
|Model||Matsky (?) My best guess at the Cyrillic script.|
1. This slide rule was made in Russia.
2. It has effectively got 4 scales: on one face it has a one-cycle and a two-cycle logarithmic scale and on the other a sine and tangent scale. The sine scale goes from 5.6º to 90º degrees and the tangent scale from 1º to 45º. As, for angles less than 5.6º the tan and sine values are effectively identical, this extends the range of the sine scale to 1º as well.
3. Both faces of the rule have a moveable red cursor, which can be used by turning a knob with a small red mark in the middle. The front face of the rule also has a short fixed cursor. The front face of the rule can be turned, by a knob with a black dot in it. To multiply, set 1 on the face under the fixed cursor and set the moveable cursor to the first of numbers, move the 1 on the face to the cursor, move the cursor to the second of the numbers, set the 1 on the face under the fixed cursor, the answer is found under the red cursor.
4. The scale on the rule is only 3.7 cm (1.6 inches) diameter. This is less than 12 cm (5 inches) in length. I was told by the Russian hydrologist who gave me the rule that they used it on fiied trips as it was much more convenient that a straight rule but that they recognised that it lacked accuracy.
|Manufacturing date||c 1960|
|Length||External diameter 5 cm (2 inches)|
|Scales||A,B,S, T (not marked as such)|