polar planimeter
Date: circa 1949
Inventory Number: 2004-1-0344
Classification: Planimeter
Subject:
Maker: Gebrüder Haff (1835-present)
Seller: Keuffel & Esser Company (1867 - 1987)
Cultural Region:
Dimensions:
4.7 × 23 × 8.6 cm (1 7/8 × 9 1/16 × 3 3/8 in.)
Accessories: instrument case
white card with instrument and measurement information inside instrument case
DescriptionThe planimeter is stored in a rectangular black leather case that opens with two hinges along one of the long edges. There is a single metal clip attached in the center to the front of the top half of the case that snaps onto a latch attached in the center of the bottom half of the case when closed. The inside of the case is lined with green felt cloth. The top and bottom interior are contoured to fit the disassembled planimeter pieces and keep them in place when the case is closed.
The planimeter breaks down into two main pieces: the tracer arm and the second arm. The second arm is the longest. It is a black, rectangular metal bar that sits on top of a large black puck at one end and a steel pin at the other end.
The tracer arm consists of a shorter black, rectangular metal bar. There is a steel roller whose axis is perpendicular to the bar extending from one end. Next to the intersection of the bar and this extension arm there is a hole. When the instrument is assembled, the steel pin at one end of the second arm sits in this hole. There are two short, black rectangular offshoots, one at each end of the black metal bar, each perpendicular to it. These two bars serve to frame and support two measuring devices. One device consists of a black disc with incremental measurements from 0 to 9 marked around the circumference in white numerals. The disc lies flat next to the black metal bar. There is a white arrow, pointing to the measurement markings, that is attached to the black disc with a screw at its center. Beneath the disc, parallel to the main bar, there is a thick, metal screw.
The second measurement device consists of two adjacent black wheels. The axis of the wheels runs parallel to the black bar and connects with the metal screw beneath the black disc. The bottom wheel (using the orientation of the numerals) is incrementally marked with white numerals from 0 to 9, and each increment is further subdivided into 10 sections with small lines. The top wheel is marked with a single unit, one end marked 0 and the other marked 10 with ten equally spaced lines between them.
At the opposite end of the smaller black bar from the steel roller extension, there is a steel strip attached at one end and extending in line with the bar. At the end of the strip there is a black metal extension attached with two screws. There is a steel stylus below the extension and a brass screw above it. Next to the stylus there is also a metal support screw. At the very end of the black extension there is a rotating black finger hold. There is a depression on either side of the finger hold. Users are meant to put their thumb and middle finger in the depressions and to rest their pointer finger on top of the brass screw above when directing the stylus.
The Keuffel & Esser Co. Manual for compensating polar planimeters that details the design and function of the instruments can be found here. Pages 5 - 8 deal specifically with this model, the 4236.
The planimeter breaks down into two main pieces: the tracer arm and the second arm. The second arm is the longest. It is a black, rectangular metal bar that sits on top of a large black puck at one end and a steel pin at the other end.
The tracer arm consists of a shorter black, rectangular metal bar. There is a steel roller whose axis is perpendicular to the bar extending from one end. Next to the intersection of the bar and this extension arm there is a hole. When the instrument is assembled, the steel pin at one end of the second arm sits in this hole. There are two short, black rectangular offshoots, one at each end of the black metal bar, each perpendicular to it. These two bars serve to frame and support two measuring devices. One device consists of a black disc with incremental measurements from 0 to 9 marked around the circumference in white numerals. The disc lies flat next to the black metal bar. There is a white arrow, pointing to the measurement markings, that is attached to the black disc with a screw at its center. Beneath the disc, parallel to the main bar, there is a thick, metal screw.
The second measurement device consists of two adjacent black wheels. The axis of the wheels runs parallel to the black bar and connects with the metal screw beneath the black disc. The bottom wheel (using the orientation of the numerals) is incrementally marked with white numerals from 0 to 9, and each increment is further subdivided into 10 sections with small lines. The top wheel is marked with a single unit, one end marked 0 and the other marked 10 with ten equally spaced lines between them.
At the opposite end of the smaller black bar from the steel roller extension, there is a steel strip attached at one end and extending in line with the bar. At the end of the strip there is a black metal extension attached with two screws. There is a steel stylus below the extension and a brass screw above it. Next to the stylus there is also a metal support screw. At the very end of the black extension there is a rotating black finger hold. There is a depression on either side of the finger hold. Users are meant to put their thumb and middle finger in the depressions and to rest their pointer finger on top of the brass screw above when directing the stylus.
The Keuffel & Esser Co. Manual for compensating polar planimeters that details the design and function of the instruments can be found here. Pages 5 - 8 deal specifically with this model, the 4236.
Signedin gold lettering on the case lid: Keuffel & Esser Co. N.Y.
in black lettering on white card inside instrument case: Keuffel & Esser Co.
engraved on instrument arm: K + E KEUFFEL & ESSER CO.
engraved on instrument arm: MADE IN GERMANY
in black lettering on white card inside instrument case: Keuffel & Esser Co.
engraved on instrument arm: K + E KEUFFEL & ESSER CO.
engraved on instrument arm: MADE IN GERMANY
Inscribedengraved on instrument arm: 30155
engraved on instrument arm: 88526
typed on white card inside case: 4236
handwritten on card inside case: 88529
engraved on instrument arm: 88526
typed on white card inside case: 4236
handwritten on card inside case: 88529
FunctionThe polar planimeter is used for ascertaining the area of any plane surface represented by a figure drawn to any scale, such as indicator diagrams, profiles, architectural plans or sections. The planimeter is placed over top of the diagram in question and the user traces it with the stylus at the end of the short arm of the instrument. The planimeter measures the area of the traced figure.
This is a polar planimeter because the intersection point of the tracing arm and the longer black arm is restricted to circular motion. This is the case because the other end of the second black arm is fixed in place by the black puck. For linear planimeters, the end of the tracer opposite the stylus moves in a straight line, either in a track or on rollers.
As the user traces a figure on the surface below, the metal roller attached to the tracing arm rolls and slides along accordingly. The measurement mechanisms record this motion and when the user arrives back at the starting point, the recorded motions will be proportional to the area of the figure below.
The Keuffel & Esser Co. Manual for compensating polar planimeters that details the design and function of the instruments can be found here. Pages 5 - 8 deal specifically with this model, the 4236.
This is a polar planimeter because the intersection point of the tracing arm and the longer black arm is restricted to circular motion. This is the case because the other end of the second black arm is fixed in place by the black puck. For linear planimeters, the end of the tracer opposite the stylus moves in a straight line, either in a track or on rollers.
As the user traces a figure on the surface below, the metal roller attached to the tracing arm rolls and slides along accordingly. The measurement mechanisms record this motion and when the user arrives back at the starting point, the recorded motions will be proportional to the area of the figure below.
The Keuffel & Esser Co. Manual for compensating polar planimeters that details the design and function of the instruments can be found here. Pages 5 - 8 deal specifically with this model, the 4236.
Curatorial RemarksThere is a discrepancy between the serial number engraved in the instrument arm (88526) and the serial number handwritten on a card inside the instrument case (88529).
The serial number on the second arm is 30155: different from the one on the tracer arm (88526). It is likely that the second arm came from a different planimeter.
The serial number on the second arm is 30155: different from the one on the tracer arm (88526). It is likely that the second arm came from a different planimeter.
Primary SourcesKeuffel & Esser Co., "Directions for the Use, Care, and Adjustment of Compensating Polar Planimeters", printed in the United States, 1938.