11e Clodoveu Davis

Mechanical calculators: Brunsviga 11e

I purchased this machine in October 2015 at an online auction site. It's my first electric calculator.

This calculator has been manufactured by Brunsviga in Braunschweig (Brunswick), Germany. Its factory was originally dedicated to sewing machines, and obtained the rights to manufacture calculating machines using Odhner's design in 1892. Brunsviga, however, continued improving the design: according to John Wolfe, Franz Trinks, Brunsviga's engineer, registered more than 40 patents in the U.S. between 1905 and 1925, and received a honorary doctorate from Braunschweig University.

The Brunsviga 11e was manufactured between 1952 and 1955. Based on its serial number, my machine was probably made in 1953. The machine is a little smaller than the FACIT C1-13, but with lower capacity: 7-digit input, 6 digits in the counter and the accumulator has 11 digits, as opposed to the FACIT C1-13's 13 digits. Some later 11e machines have clearing buttons marked 'I, II, III', but mine is older and has 'E, Z, R' buttons instead – I am yet to learn the meaning of the letters. Many machines out there are 220V, but mine is 110V.

This machine predates some full-keyboard ones, and although it is electric, keyboard machines were more expensive. It has been estimated that the list price of this machine in the 1950s would be equivalent to 1,500 euros today.

I received the machine in working condition, but rubber feet and the roller at the rear were gone, and the electrical wiring needed to be revised. Of course, a full cleaning and lubrication were especially needed. Some functions were not working, such as the clearing of the counter, and some were hampered, possibly due to old lubrication. The belt that connects the motor to the mechanism has been replaced by a leather strip, the kind used in pedal-driven sewing machines. The loop is closed using a piece of string!

In January 2017 I started working on the mechanical parts. I made it another belt, first trimming down an automotive one, but it turned out the sewing machine option was much better – now closed with a wire clip. A bakelite switch, used to reverse the direction of the motor, was broken, and I fixed it with a thin metal strip, superglue and tweezers. All wiring was coming apart, so I replaced everything I could, and in the process replaced the cord connector.

However, in the first few tests, one of the coils of the motor burned out. Oh well, insulatin must be bad all around, I guess. Now is time to find someone to rewind the coils in hopes the motor will work again. Next chapter coming up.

c1953 Brunsviga 11e s/n 286336

As purchased, in October 2015