Slide RulesIndex by Makers & Retailers
Hundreds of companies around the world were involved in the production of slide rules from the 18th to the 20th centuries. Click on one of the names below to see the objects in this collection that were associated with that firm.
"Slide Rules - Index by Makers & Retailers" showing 1 items.
- This plastic instrument consists of a white rectangular plastic sheet that slides between two white discs. The discs are held together with black plastic bars and metal grommets. The rectangular sheet is marked in green on both sides, with a polar grid and rectangular grid on one side and a polar grid on the other side. The front disc has scales for altitude computations at the top and for air speed computations at the bottom. The back disc has a scale to correct direction readings for wind and a scale for converting temperature readings from degrees Centigrade to Fahrenheit. The center of the back disc is clear for viewing the grid. A salmon plastic sheath stores the instrument.
- The device is marked on the front: DALTON DEAD RECKONING COMPUTER (/) TYPE E-6B. It also is marked: WEEMS SYSTEM OF NAVIGATION (/) (A DIVISION OF JEPPESEN & CO.) (/) DENVER, COLORADO; PAT. NO. 2,097,118. The grid is marked in pencil: FL[IGH]T OFF COURSE (/) 2 MILES/SQUARE. The back of the disc is also marked in pencil. The three lines in the clear part of the disc are illegible, but below the temperature conversion scale, the marks read: 3.5° F/1000'. A ring at the top of one black plastic bar is marked: U.S. PAT. 3,112,875.
- Naval Reserve pilot Philip Dalton, in consultation with navigation instructor Philip Van Horn Weems, developed the Dalton dead reckoning computer for the U.S. Army Air Corps and received a patent in 1937. The device was widely used during World War II.
- After the war, many manufacturers in the United States and Europe made the E-6B. Elrey Borge Jeppesen, a pilot for what became United Airlines, founded his company in 1934 and moved it to Denver in 1941. Jeppesen & Co. made aeronautical charts and navigational tools and guides. It became a subsidiary of Boeing in 2000. The patent number on the back of this object refers to the design of the computer with the gridded rectangular sheet and two discs. The patentees were employed by Felsenthal Instruments Co., which frequently supplied companies with the plastic for manufacturing Dalton computers in the 1950s and 1960s.
- The donor purchased this object around 1965 and used it for about two years in airplane navigation.
- References: Paul McConnell, "Some Early Computers for Aviators," Annals of the History of Computing 13, no. 2 (1991): 155–177, on 156; Philip Dalton, "Plotting and Computing Device" (U.S. Patent 2,097,116 issued October 26, 1937); Ben Van Caro and Burton L. Fredriksen, "Computer Slide Construction" (U.S. Patent 3,112,875 issued December 3, 1963); "E6B," http://en.wikipedia.org/wiki/E6B; "Jeppesen," http://en.wikipedia.org/wiki/Jeppesen; "On the Beam," advertisement for Dalton Dead Reckoning Computer, Felsenthal Plastics, Flying 35, no. 2 (August 1944): 10; Paul Sanik, "U.S. Army Air Corps Aerial Dead Reckoning type E-6B," Journal of the Oughtred Society 6, no. 2 (1997): 32–34 .
- Currently not on view
- date made
- Jeppesen & Co.
- ID Number
- accession number
- catalog number
- Data Source
- National Museum of American History, Kenneth E. Behring Center