9s complement makes subtraction extremely satisfying on the Curta because it causes a carry on (almost) every single output and turn accumulator dial.
The "big drum" you mention is sometimes called a Leibniz Wheel, though this naming convention is misleading in some ways: http://journals.cambridge.org/abstract_S0007087414000429. As that article argues (though I disagree with some points), the history of calculating machines is more nuanced than a linear progress narrative suggests. So, I tried to keep my narrative a little tighter and not go much into the calculators of the late 19th century and the designs in the 20th century like the Curta. Also, the Curta's (awesome!) story has been told many times, so I did not feel the need to go into it. Sorry to go on this long, but I think this history is fascinating and how we tell it speaks to how we understand how technology changes through time.
Well done, young sir! Thank you for your hard, difficult work, and sharing it with us.
ETA: And you got a lol from me at the end!
Thanks so much for bringing this to us.
There are carry mechanisms which use an external power source for carry propagation. Babbage's Difference Engine has one.[1] All the pending carry values are stored in a latch for each number wheel. Then a cam system applies the carries one at a time. This scales to large numbers of wheels.
While carry propagation is certainly a hard problem to solve (just ask Leibniz), I had much more difficulty getting the zeroing mechanism to work smoothly - in a way it's a similar issue because you need to move a bunch of parts all at once, which from a force perspective is difficult.
Oh I should mention that Pascal also solved the sufficient force carry propagation issue in the Pascaline with his "sautoir" mechanism.
There's a whole page of Curta info [0] and a 3d simulator [1] where you can see how similar the setup is and some of the ingenious tricks to fit all of the functions of this machine into a little larger than a grenade sized package.
Another mechanism that's been used is sort of analog - differential gears, with two inputs and one output. Race track totalizators used that to add multiple unsynchronized inputs. Here's one from Adelade.[1] The machines were huge and heavy, but reliable.
(It is a tradition and a contract term in the gambling industry that gambling equipment companies are strictly liable for errors. As a result, that industry builds unusually reliable equipment. GTech once mentioned in an annual report that they paid out about 3% of revenue in error payments.)
[1] https://www.cs.auckland.ac.nz/historydisplays/SecondFloor/To...
[1] https://en.wikipedia.org/wiki/The_Secret_Life_of_Machines
Mechanical calculators are ridiculously cool to me. If I ever become an eccentric billionaire, I really want to buy an original Curta calculator [2], just because I respect the genius and engineering required to design such a thing.
The one in this video is also very cool. Very satisfying to watch all the gears turn at once.
Maybe optical/biological/quantum computing.
Whatever patents that they had have to be expired, I kind of wish someone would make reproductions. I know there's the 3D printed ones, which are cool in their own right, but since 3D printers aren't super precise the parts have to be huge to compensate. I want as close to a one-to-one reproduction as possible, but I guess there's not much money in it.
Add in the fact that authenticity is part of the appeal, plus the fairly expensive process to make a decent replica, it’s not shocking that no replicas have emerged, even though cheap-ish CNCs mean it’s probably easier to do than it ever has been.
The problem is that if I bought one now, it would simply be a toy and nothing else. That's just a bit more than I'm willing to spend.
I could probably get one of those cash registers to play with for not a ton of money, but my house isn't huge and it's hard to justify the space.
Computation as studied by computer science is not a physical phenomenon, but a mathematical construct that claims to formalize the notion of an effective method. This claim is perhaps most tangibly expressed in the form of the Church-Turing thesis.
Computing devices are not objectively computing. They simulate the formal construct. Anything that can be used "computer-wise" can be said to be a computer in the same manner that anything that can be used chair-wise can be said to be a chair. But there is nothing inherently computational about the device itself.
Isn't it backwards? I don't think that e.g. herding sheep into the pen while making a mark on the door for each sheep "simulates counting sheep". Instead, you can use the formal construct "counting sheep" to describe this physical process: "doing this and this will count the sheep".
Otherwise you may very easily end up puzzled why maths is so unreasonably effective in natural sciences.
The Whiffletree was used in mechanical calculators. It's an interesting way to encode digital data mechanically.
madness!
