Full Details

Name and Model Number Cox's Compressed Air
Discharge Computer
and Pump Computer, 1897
Country of Origin USA
Date of Manufacture 1897
Front Scales Discharge Computer Scales: Compressed air discharge, Pipe diameter, Initial Pressure, Length of pipe, Loss of pressure
Back Scales Pump Computer Scales: Free air discharge pressure, Air & water cylinder diameters, Lift and piston speed, Gauge pressure, Air cylinder diameter
Scale Length Varies
Type of Rule Disc
Construction Printed cardboard
Area of Use Technical
Comment Used for calculations related to sizing pipes for compressed air.
Computer bears the imprint "Designed by William Cox", who patented his design for the first duplex slide rule in 1891.
Published and copyrighted in 1897 by Rand Drill Company, New York.
Rarity RRR
Donor Collection of Mike Frey
Match Number 230
(Click Picture for Details)

In conjunction with our 'donors' we assign a rarity rating to each item, based on the system devised by Herman van Herwijnen
(1929 - 2004), renowned Dutch collector, author, and creator of Herman's Archive, a collection of 5,000 slide rule images on CD.
• RR = Rare - 1 of 25 collectors has one; it may take a year to find an example in the marketplace.
• RRR = Very Rare - only a few known to collectors; may be several years before it comes up for sale.
• RRRR = Extremely Rare - a museum piece; unlikely that an example will come up for sale.