Felsenthal Range Deflection Protractor
Felsenthal Range Deflection Protractor
- Description
- This clear plastic sixth-circle protractor is graduated into 10 groups of 20 divisions, each labeled with the number 50. The unit of angular measure is mils, which was utilized in artillery applications. There are 6,400 mils in a circle (i.e., 1 mil = 0.05625 degrees). The arc on this instrument is 1,000 mils, or 56.25 degrees, in length.
- An arm extends from the left side of the protractor. The arm is divided to half-units and marked by five (scaled) meters from 160 to 10. Two holes with diameters of 5mm are next to the 145–140 and 30–25 marks. The vertex of the protractor bears a small notch.
- The interior of the protractor is marked: PROTRACTOR, RANGE DEFLECTION (/) SCALE 1:25,000 (/) RANGE 16,000 (/) METERS. Stamped inside a box is the text: THIS TRAINING AID WILL BE RETURNED (/) TO THE FIELD ARTILLERY SCHOOL (/) UPON COMPLETION OF THE SUB-COURSE (/) WITH WHICH ISSUED. Donor Ben Rau dated the instrument to 1965.
- See also 1977.1141.01, 1977.1141.02, 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.
- Location
- Currently not on view
- date made
- 1965
- maker
- Felsenthal Instrument Co.
- Physical Description
- plastic (overall material)
- Measurements
- overall: .2 cm x 41 cm x 66.5 cm; 3/32 in x 16 5/32 in x 26 3/16 in
- ID Number
- 1977.1141.03
- accession number
- 1977.1141
- catalog number
- 336387
- Credit Line
- Gift of Ben Wharton Rau and Margery Felsenthal Rau
- subject
- Mathematics
- Protractor
- Artillery
- See more items in
- Medicine and Science: Mathematics
- Science & Mathematics
- Protractors
- Data Source
- National Museum of American History
Comments
The right side of the RDP rests on a pin on a 1:25,000 scale blank gridded chart. The pin represents the firing battery location. A second pin is inserted at the target location. The range to target is determined along the left side of the RDP. A third pin along the arc of the RDP determines the azimuth or direction of fire to the target. Quadrant elevation for the howitzers are determined using a specialized computer, or Tabular Firing Table (book), or Graphical Firing Table (slide rule). An observer will send subsequent corrections to the battery by radio or land line.
Detailed explanation in US Army pub at link:
http://www.bits.de/NRANEU/others/amd-us-archive/FM6-40%2884%29.pdf
Neil O'Connor
Fri, 2019-03-08 08:27
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Lionel
Fri, 2015-12-11 09:13