Skip to main content

Search

My Visit
Donate
Home Smithsonian Institution

Site Navigation

  • Visit
    • Hours and Locations
    • Entry and Guidelines
    • Maps and Floor Plans
    • Dining and Shopping
    • Accessibility
    • Visiting with Kids
    • Group Visits
  • What's On
    • Exhibitions
      • Current Exhibitions
      • Upcoming
      • Past Exhibitions
      • Online Exhibitions
    • Today's Events
    • Online Events
    • All Events
    • IMAX & Planetarium
  • Explore
    • Art & Design
    • History & Culture
    • Science & Conservation
    • Collections
      • Open Access
    • Research Resources
      • Libraries
      • Archives
        • Smithsonian Institution Archives
        • Air and Space Museum
        • Anacostia Community Museum
        • American Art Museum
        • Archives of American Art
        • Archives of American Gardens
        • American History Museum
        • American Indian Museum
        • Eliot Elisofon Photographic Archives, African Art
        • Freer and Sackler Archives
        • Hirshhorn Archive
        • National Anthropological Archives
        • National Portrait Gallery
        • Ralph Rinzler Archives, Folklife
        • Libraries' Special Collections
    • Blogs
    • Podcasts
    • Mobile Apps
  • Learn
    • For Kids and Teens
    • For Educators
      • Resources
      • Field Trips
      • Professional Development
      • Events
    • Youth Programs
    • Fellowships and Internships
  • Get Involved
    • Volunteer
      • Behind-the-Scenes
      • Digital Volunteers
      • Smithsonian Call Center
      • Visitor Information Specialist
      • Docent Programs
    • Citizen Science
    • Work with Us
      • Office of Human Resources
        • Working Here
        • Employee Benefits
        • Job Opportunities
        • How to Apply
        • Job Seekers with Disabilities
        • Frequently Asked Questions
        • SI Civil Program
        • Contact Us
      • Affiliations
      • Global Partners
  • Support
    • About Membership
    • Become a Member
    • Renew Your Membership
    • Make a Gift
  • About
    • Museums and Zoo
    • Research Centers
    • Cultural Centers
    • Education
    • Our Organization
      • Leadership
        • Secretary Bunch
        • Advancement
        • Communications
        • Administration
        • Education
        • Museums and Culture
        • Science and Research
      • Board of Regents
        • Members
        • Committees
        • Reading Room
        • Bylaws, Policies and Procedures
        • Contact
        • Schedules and Agendas
        • Meeting Minutes
        • Actions
        • Webcasts
      • General Counsel
        • Legal History
        • Internships
        • Records Requests
          • Reading Room
        • Tort Claim
        • Subpoenas & Testimonies
        • Events
      • Equal Employment Office
        • EEO Complaint Process
        • Individuals with Disabilities
        • Special Emphasis Program
        • Supplier Diversity Program
          • Doing Business with Us
          • Policies and Procedures
          • Additional Resources
      • Sponsored Projects
        • Policies
          • Animal Care and Use
          • Human Research
        • Reports
        • Internships
    • Reports and Plans
      • Annual Reports
      • Metrics Dashboard
        • Dashboard Home
        • Virtual Smithsonian
        • Public Engagement
        • National Collections
        • Research
        • People & Operations
        • One Smithsonian
      • Strategic Plan
    • Newsdesk
      • News Releases
      • Media Contacts
      • Photos and Video
      • Media Kits
      • Fact Sheets
      • Visitor Stats
      • Secretary and Admin Bios
      • Filming Requests

Perrygraf Load Center Unit-Sub Slide Rule for Allis-Chalmers

National Museum of American History
Social Media Share Tools
    • Print

Object Details

Perry Graf Corporation
Description
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.
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.
Reference: Allis-Chalmers, "Three 'Not-so-Secret' Weapons," The Ohio State Engineer 28, no. 2 (December 1944): 16–17.
Location
Currently not on view
Credit Line
Transfer from Smithsonian Institution Libraries
1943
ID Number
1983.3009.06
catalog number
1983.3009.06
nonaccession number
1983.3009
Object Name
calculating rule
slide rule
Physical Description
metal (part material)
paper (overall material)
Measurements
overall: .2 cm x 23 cm x 9.6 cm; 3/32 in x 9 1/16 in x 3 25/32 in
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Slide Rules
National Museum of American History
subject
Mathematics
Rule, Calculating
electricity
Engineering, Electrical
Record ID
nmah_694152
Metadata Usage (text)
CC0
GUID (Link to Original Record)
http://n2t.net/ark:/65665/ng49ca746a5-1026-704b-e053-15f76fa0b4fa

Related Content

  • Slide Rules:Index by Makers & Retailers

    American History Museum
  • Slide Rules:Index by Material

    American History Museum
  • Slide Rules:Index by Purpose

    American History Museum
  • Slide Rules:Linear Slide Rules

    American History Museum
Slide rule - Allis-Chalmers Load Center Unit-Sub Rule - Front View
There are restrictions for re-using this image. For more information, visit the Smithsonian's Terms of Use page .
International media Interoperability Framework
IIIF provides researchers rich metadata and media viewing options for comparison of works across cultural heritage collections. Visit the IIIF page to learn more.
View manifest View in Mirador Viewer

Footer logo

Link to homepage

Footer navigation

  • Contact Us
  • Press Room
  • Human Resources
  • Host Your Event
  • Access Smithsonian
  • EEO & Supplier Diversity
  • Inspector General
  • Records Requests
  • Privacy
  • Terms of Use

Social media links

  • Facebook
  • Instagram
  • Twitter
  • YouTube

Email signup form

Email powered by BlackBaud (Privacy Policy, Terms of Use)
Back to Top