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Cardboard Engineering & Science Slide Rule Calculators
The Original Mobile Apps™

October 2020 Update: Mr. Joseph Birsa, N3TTE, recently donated yet another of his vintage cardboard calculators to the RF Cafe collection. This one is the "Type B" version of the ARRL's "Lightning Calculator" series.

Long before there were smartphones and software 'apps,' engineers and scientists carried around portable 'apps' of another kind. These apps were made from printed heavy cardboard stock and typically had either a sliding section sandwiched between two outer layers, or a rotating layer on a fixed base layer. They even sported rivets to hold them together - like the original Levis dungarees. I and guys much older than me [ ;-) ] routinely carried them in our shirt pockets, securely snugged behind our plastic pocket protectors. You definitely always wrote your name on them in indelible ink since there was a tendency for those cardboard slide rules to sprout legs and walk away while you were at lunch or in the can.

These cardboard slide rule calculators used to be included on the Traditional Slide Rules page, but thanks to generous RF Cafe visitors who either sent me hard copies or high-res photos, the number has grown so large that they required their own page. You are invited to submit examples of your own collection for inclusion in the informal Cardboard Calculator Museum.

The American Radio Relay League (ARRL) sold a variety of these "Lightning Calculator" slide rules in the days before electronic calculators. This "Type B" version (copyright 1932, W.P. Koechel) calculates Ohm's Laws values for resistance, voltage, current, and power. As shown here, it indicates an alignment of 1 V, 1 A, and 1 Ω. The Lightning Calculators" were rather large at 8½" wide by 11" high. Being the size of a sheet of paper, it is surprising they did not come with holes for a 3-ring binder. There were six varieties of "Lightning Calculators," as shown in the 1939 QST magazine advertisement.

Thanks to Joe Birsa (N3TTE) for the donation - Added October 19, 2020

Thanks to Neil Blaho for the donation
(copyright 1991) Added July 6, 2017

Thanks to Neil Blaho for the donation
(copyright 1976) Added July 6, 2017

Thanks to Neil Blaho for the donation
(copyright 1957) Added July 6, 2017

Thanks to Neil Blaho for the donation
(copyright 1977) Added July 6, 2017

Thanks to Neil Blaho for the donation
(circa 1950s) Added July 6, 2017

Thanks to Neil Blaho for the donation
(copyright 1968) Added July 6, 2017

Thanks to Neil Blaho for the donation
(copyright 1951) Added July 6, 2017

Thanks to Neil Blaho for the donation
(copyright 1991)

Thanks to Neil Blaho for the donation
(copyright 1968)

Thanks to Neil Blaho for the donation
(looks a little like the Starfleet Command logo)

Thanks to Neil Blaho for the donation
(copyright 1968)

Thanks to Neil Blaho for the donation
(copyright 1975)

Thanks to Neil Blaho for the donation

Thanks to Neil Blaho for the donation
(copyright 1982)

Thanks to Neil Blaho for the donation
(Annapolis, MD, was my childhood home town)

Thanks to Joe Cahak for the donation
(copyright 2009)

Thanks to Joe Cahak for the donation

Thanks to Joe Cahak for the donation
(copyright 1976)

Thanks to Joe Cahak for the donation
(copyright 1973)

Thanks to Joe Cahak for the donation

Thanks to Joe Cahak for the donation
(copyright 1999)

Thanks to Joe Cahak for the donation
(copyright 1968)

Thanks to Joe Cahak for the donation
(copyright 1995)

Thanks to Joe Cahak for the donation

Thanks to Joe Cahak for the donation
(copyright 2010)

Thanks to Joe Cahak for the donation
(copyright 1995)

Thanks to Joe Cahak for the donation
(copyright 1972)

Thanks to Joe Birsa (N3TTE) for the donation
(copyright 1986)

Thanks to Joe Birsa (N3TTE) for the donation
(copyright 1991)

Thanks to Joe Birsa (N3TTE) for the donation
(copyright 1977)

Thanks to Gary Steinhour for the donation
(copyright 1953)

Thanks to Gary Steinhour for the donation
(copyright 1975)

Thanks to Gary Steinhour for the donation
(copyright 1964)

Smith Chart Side

Slide Rule Side
Thanks to Gary Steinhour for the donation)

I. Sea-Level Reduction (left), II. Altimeter Setting (right)
These were used by air traffic controllers back in the Stone Age This particular model was auctioned off when the Bedrock Airport closed
Thanks to Don Hicks for the donation

Sage Wireline/Wirepac Calculator
(copyright 1992)

I have a spreadsheet available for the Wireline Calculator.

GE Mobile Radio, Range and Transmitter Power Calculator
(copyright 1977)
Thanks to Alan Kealey for the donation!

Classic Format Slide Rules

Pickett N600 ES Log-Log Slide Rule
(this is the same model that went to the moon w/the Apollo astronauts)

K&E Model N4080-3 Log Log Duplex Trig, S/N 467192, Copyright 1947 Slide Rule
(wooden frame & bar w/metal ends)

K&E Model 4081-3 Slide Rule, S/N 087105
(wooden frame & bar w/metal ends)

Sterling 684 White Plastic Slide Rule
(I bought this for my first algebra class in 1976)

Skala Wilcza 32 Wooden Slide Rule (Poland)
Thanks to Alan Kealey for the donation!

Pickett N1010-T Slide Rule
(found in my father-in-law's basement)

Cleveland Institute 515-T Slide Rule (made by Pickett)
Send me an e-mail if you want a PDF file of a partial (10 pages) copy of the instruction manual.
[Buy the complete manual set here]

This advertisement appeared in the August 1967 edition of Electronics World magazine. The unique slide rule, leather case, and 4-course instruction booklet was "...deliberately underpriced at less than $25."

K&E Beginner's Slide Rule, Model 4058C
(all-wood frame & bar)

Lawrence Slide Rule Instruction Book
(copyright 1952)

Cleveland Institute of Electronics Slide Rule Product Feature
January 1965 Popular Science

Gong Se He Ying
Metalworking calculator for Iron materials

Slide Rule Wallpaper
Click on the image to open it in a new window, then right-click on it and choose Set as Background

Texas Magnum, World's Longest Slide Rule
(352 feet long, 300 pounds)

Soviet Slide Rule Watch

Projection Slide Rule




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RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while typing up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived... All trademarks, copyrights, patents, and other rights of ownership to images and text used on the RF Cafe website are hereby acknowledged. My Hobby Website: AirplanesAndRockets.com Please Support RF Cafe by purchasing my ridiculously low−priced products, all of which I created. RF Cascade Workbook RF & Electronics Symbols for Visio RF & EE Symbols Word RF Workbench (shareware) T-Shirts, Mugs, Cups, Ball Caps, Mouse Pads These Are Available for Free Calculator Workbook Smith Chart™ for Excel

Cardboard Engineering & Science Slide Rule CalculatorsThe Original Mobile Apps™

Classic Format Slide Rules

Cardboard Engineering & Science Slide Rule Calculators
The Original Mobile Apps™