OTIS KING CYLINDER CALCULATOR

Otis Carter Formby King 1876-1944 patented his Cylindrical Calculator in 1922, production ceased in around 1972 when cheap electronic calculators started to arrive from Japan. Cylindrical calculators have the advantage of greater accuracy than standard rule types in that they are longer, this one 66 inches as opposed to rule types of 10 inches as the scale helix's around the tube, they are not as accurate as electronic types due to errors in reading the cursor. This version is type 'K' which is capable of Multiplication, Division, Proportion, Percentage, Constant factors, and Sterling, calculations. It has a Chrome portion which is the holder followed by a bottom scale section numbered 100 to 995. The centre section is the Cursor with two lines at each end, after which is another top scale numbered from 100 to 995 half way, then continuing again from 100 to 995 to the end. In order that the range of the scale may be unlimited decimal points are not marked. Thus the reading 212, for instance also serves for 2120, 21.2, 2.12 etc, the position of the decimal point in the answer is found by inspection of the rules given in the instructions supplied with the unit. To use, take the holder in the left hand, and open instrument to full extent. Move Cursor to set bottom arrow. Next move cylinder so that number on scale is set to top arrow. Do not touch Cursor while moving Cylinder. Then, move Cursor to set either arrow as required, the companion arrow will then point to the answer. Example. To multiply 115 X 23. Extend the unit fully. Move Cursor bottom arrow to 115 on the scale, (line not number). Move the top of the Cylinder to Unity, (letters One in the middle of the scale), Do not move the Cursor. Move cursor to 23 on top scale (above 'one'). Read answer on bottom pointer of Cursor, = 264 and a bit. which is 2465.

Donated by Tony Curtiss.

A1711