In the bowels of my library is an elusive book that mentions a “Prorating Machine,” and describes how it was used to calculate freight charges when multiple railroads were involved. The illustration that is included shows a device that was marketed, in 1915, by Keuffel and Esser Company (K&E) as a “Thacher Calculating Instrument.” In 1921, the Railway Accounting Officers Association published a book of accounting procedures that included a description of this device, but does not refer to it as a prorating machine:

“426. Cylindrical Slide Rule. Consists of a cylindrical slide having both rotary and longitudinal movement within an open frame-work of equi-distant bars. Slide contains two logarithmic scales, one on each side of center, on the bars are two other scales arranged in same manner. Used to advantage in interline division work, in rating, computing and applying percentages.
(Thacher Calculator)”

This instrument was a versatile device that had many applications far beyond the railroad accounting office.

According to the 1915 edition K&E’s catalog, “The useful applications of the instrument are almost unlimited; among them may be mentioned finding the stresses and sections in trusses and girders, mensuration, estimates of work and material, solving trigonometrical formulas, making and applying tables, problems in mechanical powers, machinery and hydraulics, problems in simple and compound interest, discount, prorating, the conversion of weights and measures, cost of merchandise with per cent. of duty or profit added.” (Emphasis mine.)

The book, Bridge Engineering, in 1916, described this device as “A slide rule of the revolving type having an exterior frame of twenty graduated bars attached to rings at their ends. The slide is an interior cylinder and is capable of both rotation and sliding inside the bars. The exterior frame of bars is also capable of rotation. A most valuable instrument in any bridge engineer’s office.

One of the benefits of this machine was its exceptional accuracy. The 20 bars, each 18 inches long, with scales on each side, were equivalent to a conventional slide rule 60 feet long. As far as I know, this is the only slide rule that was considered to be accurate enough for use in an accounting office.

The only example that I have found of this device in a railroad museum is in the California State Railroad Museum, in Sacramento. It is labeled simply: Calculating Instrument, Keuffer and Esser Co., Used by Western Pacific Railroad, c. 1910 – 1950. It can be seen in the photo displayed alongside a steam engine indicator, a pocket compass, and various dining car artifacts.

Does anyone here know of any others that are displayed and interpreted in a railroad museum? Did nearly every railroad accounting office have one? I have seen several Thachers in other types of museums, but have not seen any mention of their use on a railroad as a prorating machine.

http://s1055.photobucket.com/user/slide ... %20Machine

Bruce E. Babcock

Like this one?:

http://www.ebay.com/itm/K-E-Keuffel-Ess ... SwWnFWCXpd

Disclaimer: I have nothing to do with this auction. This is posted for discussion of the type of slide rule. eBay auctions are dropped from the database after a period of time and this link may not function in the future.

PC

PC,

The Thacher that is for sale on eBay is one version of the type of instrument that I was describing. From the several examples that I have seen, including the one that I own and the one in the California museum, this is the most common. The version shown in the illustration from the 1915 catalog includes a 3-inch diameter magnifier. The magnifier increased the cost of the device from $35.00 to $45.00.

According to an on-line inflation calculator, this is equivalent to $813.70 to $1,046.19 today. That must have been a very nice magnifier!

Bruce

Well, back before mechanical drawings and such where prepared on computer screens folks used to have a collection of 3 Sided Architectural Rulers with 6 scale factors, one on each edge of a side. These came in common drafting scale factors (3/32", 1/8, .... 1, 1 1/2, 3" = 1 foot, etc.) K&E made a bunch of these.

I had a typical collection of several of these to cover the scales I needed as an engineering student in the 70's. They where also available with log scale graduations used to plot signal strength (i.e. dB's) for electrical engineers (AKA "Sparkies").

Seems if you put a bunch of these around a cylinder with maybe 5% increments (5%,10,15....85,90,95,100%) of gradation you can quickly calculate the bits for separate railroads. The PRR gets 65%, the B&O gets 30% and the "East Podunk and Pacific" gets the remaining 5%.

You can still buy these if you have no access to computer aided drafting/design tools;

http://www.diamondtool.net/p/scale-rule ... ural-ruler

Looks like the prorating machine is just a bunch of these glued onto a cylinder.

If you could get 25 of these around a cylinder you could have 1% resolution (assuming you can see 4 of the six scale edges).

Looks like you slide an indicator left/right to the "total cost" and then just spin the cylinder around to read off 3%, 54%, 26%, 11% and 6% (totals 100%) to get each of the prorated charges for the interline accounting.

Pretty clever, yes kiddies there was life before computers.

Cheers, Kevin

Hi,

I still have the Archetects scale and Engineer's scale I purchased for my Freshman year at Ga Tech (1973). I also have a true slide rule.

People seem to forget that a calculating machine does not have to be electrically powered. I think one of the earliest that can multiply and divide as well as add and subtract is the abacus.

The trajectory computers used on the battleships in WWII were amazing machines.

I still tell people that if you can not do something with paper and pencil, you can not do it in a computer. ( Like the healthcare system <GRIN> )

Doug vV

The old mechanical calculators (such as those built by Marchant, Monroe, etc.) were intricate machines. The earliest ones were hand-cranked, later models were electric.
http://www.vintagecalculators.com/html/mechanical_calculators.html

Hi,

That triggered a memory of the earliest drawings for a mechanical calculator. They were done by Leonardo Da Vinci. It was hydro (water) powered and did not work correctly. The reason was he did not know about frictional losses when things rotated. If it had been an ideal universe (no friction losses), his machine would have worked correctly.

The history of technology is a fascinating topic and railroads are an iron age technology.

Doug vV

OT: The Ocean Tide prediction machine linked below was used for several decades in the US and is now on display in the Science Center at NOAA Headquarters in Silver Spring, MD. It still works. On one occasion was able to spin the dials:

https://tidesandcurrents.noaa.gov/predma2.html

Bob

Most people don't realize there was mechanized data processing before electronic computers, namely the unit record system that used punch cards. They were used in this way long before they became an input/output medium for computers. Key punches, sorters and tabulators was how it was done back in the day. Tabulators were "programmed" for different jobs via hundreds of wires inserted into holes that carried data from readers to counters and counters to printers etc. Tedious to set up so it was arranged that the entire board with holes and wires could be removed and another one inserted, prewired, for a different job, say payroll.

From that ebay auction

Looks like a Da Vinchi Code artifact to me.

At one time the word "computer" meant a person who did mathematical computations.