Perrygraf Load Center Unit-Sub Slide Rule for Allis-Chalmers
date: label: date made
content: 1943
name: label: maker
content: Perry Graf Corporation
notes: label: Description
content: This rectangular gray and orange cardboard rule has a cardboard slide and is held together by six metal rivets. The front of the rule explains that the calculator helps users select and test the proper air circuit breakers for electrical substations constructed by Allis-Chalmers. The front of the slide provides reasons why breakers were essential in old and new substation systems. The back of the rule has four logarithmic scales for reading the key number (from the transformer rating), then the index number, then the circuit capacity, and then the amp load. The scales on the slide are color-coded so the user could easily see which level of interrupting capacity was needed.
label: Description
content: According to a mark on the slide, Perrygraf Corporation made this instrument, which Allis-Chalmers copyrighted in 1943. While the company is perhaps better known for manufacturing farming equipment, it also built generators, turbines, compressors, and other machinery for heavy industry. Additionally, its engineers designed electrical substations. The company ceased manufacturing operations in 1998. For more on Perrygraf, see 1979.3074.03. For another slide rule made by Perrygraf for Allis-Chalmers, see 1983.3009.04.
label: Description
content: Reference: Allis-Chalmers, "Three 'Not-so-Secret' Weapons," <i>The Ohio State Engineer</i> 28, no. 2 (December 1944): 16–17.
label: Location
content: Currently not on view
topic: label: Subject
content: Mathematics
label: Subject
content: Rule, Calculating
label: Subject
content: electricity
label: Subject
content: Engineering, Electrical
setName: label: See more items in
content: Medicine and Science: Mathematics
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content: Science & Mathematics
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content: Slide Rules
creditLine: label: Credit Line
content: Transfer from Smithsonian Institution Libraries
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: 1983.3009.06
label: catalog number
content: 1983.3009.06
label: nonaccession number
content: 1983.3009
objectType: label: Object Name
content: calculating rule
label: Object Name
content: slide rule
physicalDescription: label: Physical Description
content: metal (part material)
label: Physical Description
content: paper (overall material)
label: Measurements
content: overall: .2 cm x 23 cm x 9.6 cm; 3/32 in x 9 1/16 in x 3 25/32 in