Pinwheel Calculators

My collection of mechanical calculators

These are some pinwheel calculators that I bought on ebay. The golden era of these devices was from around 1890 to 1960, but all of mine happen to be rather modern designs from the 1950s. That is no mere coincidence: I'm not really fond of the worn-out look that usually comes with the older models, and I do want fully functional ones. After all I actually use them. Multiplication and division is rather quick and painless, and even square root computation is possible. Finding the square root of 11 with a precision of six decimal places, for example, takes about five minutes.

Triumphator CRN1 This one was made in the German Democratic Republic, built as if to prove that size does matter.
The reversing gear on the multiplier register must be operated manually, which is awkward and rather unusual. Most other calculators have an automatic gear that will guess from the first turn of the crank whether you are going to divide or multiply.

Walther WSR 160 If I had to choose one of these machines for doing everyday calculations, I would definitely pick the Walther.
The product register has thumbweels for manual adjustment (which can be useful in some calculations) and 16 decimal places instead of the usual 13. The cancellation lever can be set to also trigger a carriage return. And (I guess they were just being playful here) the setting levers don't rotate when you turn the crank.
Actually I used to have two of these, and the other one, which is in a slightly darker shade of gray, is the one that I kept until today.

Multo This was the first calculator that I ever bought. It took me some time to realize how poorly designed it is:
The multiplier register does not compute carry. You cannot cancel the product register alone, but either the multiplier register or both registers at the same time. And (this does no harm, but is clearly the silliest part) turning the crank not only rotates the setting levers, but also the numbers in the check register above them.
The one thing I like about the Multo though (and which it has in common with the Walther) is the way the carriage works: You can push it freely to the right, and there is a carriage return button to slide it back to the left.

Original-Odhner 239 This one was broken when I got it: The cancellation lever for the product register was stuck, and trust me, that is a serious issue, making the machine virtually useless. To fix the problem, I had to disassemble most of the carriage with the product and multiplier register, and it took me about two years before I found the time (and the courage) to finally do that.

Olympia Brunsviga 13RM The only Brunsviga that doesn't suck (and doesn't have that silly logo with the robot head full of cogwheels). Made by Olympia AG after they bought the Brunsviga brand name.

For further details on mechanical calculators, take a look at this user's manual or this excellent technical description from the Hewlett-Packard museum. And don't miss the Curta, the amazing pocket calculator from the 1940s. I can hardly believe the prices at that Curtas are still traded today, otherwise I'd already own one of those, too.

Back home

Triumphator CRN1	This one was made in the German Democratic Republic, built as if to prove that size does matter. The reversing gear on the multiplier register must be operated manually, which is awkward and rather unusual. Most other calculators have an automatic gear that will guess from the first turn of the crank whether you are going to divide or multiply.
Walther WSR 160	If I had to choose one of these machines for doing everyday calculations, I would definitely pick the Walther. The product register has thumbweels for manual adjustment (which can be useful in some calculations) and 16 decimal places instead of the usual 13. The cancellation lever can be set to also trigger a carriage return. And (I guess they were just being playful here) the setting levers don't rotate when you turn the crank. Actually I used to have two of these, and the other one, which is in a slightly darker shade of gray, is the one that I kept until today.
Multo	This was the first calculator that I ever bought. It took me some time to realize how poorly designed it is: The multiplier register does not compute carry. You cannot cancel the product register alone, but either the multiplier register or both registers at the same time. And (this does no harm, but is clearly the silliest part) turning the crank not only rotates the setting levers, but also the numbers in the check register above them. The one thing I like about the Multo though (and which it has in common with the Walther) is the way the carriage works: You can push it freely to the right, and there is a carriage return button to slide it back to the left.
Original-Odhner 239	This one was broken when I got it: The cancellation lever for the product register was stuck, and trust me, that is a serious issue, making the machine virtually useless. To fix the problem, I had to disassemble most of the carriage with the product and multiplier register, and it took me about two years before I found the time (and the courage) to finally do that.
Olympia Brunsviga 13RM	The only Brunsviga that doesn't suck (and doesn't have that silly logo with the robot head full of cogwheels). Made by Olympia AG after they bought the Brunsviga brand name.