Felsenthal FAE-19A Artillery Protractor
date: label: date attributed by donor
content: 1950
label: date made
content: 1970s
name: label: maker
content: Felsenthal Instrument Co.
notes: label: Description
content: While many protractors simply measure angles in degrees, others have been adapted for more specialized contexts. For instance, they may be combined with other drawing instruments, such as rulers or templates for flow chart components. Or, they may make measurements in other scales for angles, such as radians. Before computerized and satellite navigation equipment was in wide use, protractors were employed in military applications, including positioning artillery.
label: Description
content: Thus, this clear plastic protractor, which is in the shape of a sixth-circle, permitted the user to plot the distance traveled by a projectile from the time that elapsed before the sound of the projectile was heard. The outer edge of the protractor's arc is divided by hundredths and marked by tenths from +3.4 to +0.1 (in black print) and from -0.1 to -3.4 (in red print). The scale is labeled: TIME INTERVAL, SECONDS and MIDPOINTS FOR 4-SECOND SUB-BASE, 1/25000.
label: Description
content: A scale marked DEGREES is further inside the arc. It is divided by minutes and marked by fives from 55° to 0°. Finally, a scale for MILS is divided by tens and marked by hundreds from 1000 to 100. 1000 mils is equivalent to 56.25°. A scale for THOUSANDS OF YARDS 1/25000 is along the right edge of the protractor. It is divided by five-hundredths and marked by ones from 14 to 1.
label: Description
content: The maker's mark is near the vertex: 4 SOUND SECONDS (/) FELSENTHAL INSTRUMENTS CO. (/) MFR'S PART NO. FAE-19A (/) MFR'S CODE 22040.
label: Description
content: The Felsenthal Instruments Company was the leading supplier of mathematical instruments to the U.S. Army Air Force and the U.S. Navy Bureau of Aeronautics, particularly during World War II (when the firm was known as G. Felsenthal & Sons). After the company ceased operations in approximately 1976, it provided a large sample of its products to the Smithsonian.
label: Description
content: See also 1977.1141.02, 1977.1141.03, 1977.1141.05, 1977.1141.08, 1977.1141.09, 1977.1141.10, 1977.1141.11, 1977.1141.12, 1977.1141.18, 1977.1141.19, 1977.1141.20, 1977.1141.21, 1977.1141.22, 1977.1141.23, 1977.1141.24, 1977.1141.30, and 1977.1141.39.
label: Description
content: Reference: Deborah J. Warner, “Browse by Maker: Felsenthal,” <I>National Museum of American History Physical Sciences Collection: Navigation</I>, http://amhistory.si.edu/navigation/maker.cfm?makerid=173.
label: Location
content: Currently not on view
place: label: place made
content: United States: Illinois, Chicago
topic: label: Subject
content: Mathematics
label: Subject
content: Protractor
label: Subject
content: Artillery
setName: label: See more items in
content: Medicine and Science: Mathematics
label: See more items in
content: Science & Mathematics
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content: Protractors
creditLine: label: Credit Line
content: Gift of Ben Wharton Rau and Margery Felsenthal Rau
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: 1977.1141.01
label: accession number
content: 1977.1141
label: catalog number
content: 336385
objectType: label: Object Name
content: protractor
physicalDescription: label: Physical Description
content: plastic (overall material)
label: Measurements
content: overall: .2 cm x 54.5 cm x 56 cm; 3/32 in x 21 15/32 in x 22 1/16 in