The Curta.org Bulletin Board

[TheThirdMan1949]

I have a Curta II - it is, I believe, in mint condition. BUT, the carriage only seems to go to positions 1-8, although there are demarcations on the carriage all the way up to 15. Am I doing something wrong? Thank you.

[Jack]

On a Type II the numbers 1 - 15 refer to the 15 digits of the result register.
(On a Type I the numbers 1 - 11 refer to the 11 digits of its results register.)

There are, however, only 8 digits in the Type II counter register. The carriage can be moved to 8 positions that correspond to the 8 digits in the counter register. If the carriage is in position 1, a turn of the crank increments (decrements) the 1st digit in the counter register. When the carriage is in position 2, a turn of the crank increments the 2nd digit in the counter register, etc.

(6/15/2007...Just to clarify...On the Type I Curta, there are only 6 carriage positions, each of which corresponds to the 6 counter register digits. The perimeter of the carriage has the digits 1 - 11 labeled to identify the 11 results register digits.)

Note the arrow on the "back" of the Curta. [ed: Some older Curtas do not have the backside arrow.] That arrow is pointing to the digit in the counter register indicated by the arrow in the front. That is, the 1st digit in the counter corresponds to the "1" pointed to by the front arrow, etc.

Your confusion is VERY common. Personally, had I designed the Curta, I would not have put digits 9 through 15 on the front. This only causes confusion when first learning the machine's operation.

Many people have applied extreme force to turn the carriage too far. The repair costs are very high when you force the carriage beyond the 8th position.

The only reason Contina included digits 9 - 15 was because they felt that every digit and slider must be numbered for reference. I suspect they felt the numbering would also make it easier to identify groups of three in the results register.

FYI...on extremely early Type I machines, each of the eight sliders were numbered along the lower edge of the black collar (below the engraved name "CURTA"), as well as below each slider slot on the main body shell. In fact, on the earliest of Curtas, there were no numbers below the slider slots, only above the sliders. And on those very early machines there were numbers vertically next to each slider for each position of the slider's "pin" knobs. Here's a photo of Curta 970:


Photograph by J. Schranz

Jack
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Jack Christensen
Timewise
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[TheThirdMan1949]

Jack,
Thank you for your detailed reply. It was hugely helpful!
David