[HN Gopher] I Built a Mechanical Calculator [video]
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I Built a Mechanical Calculator [video]
Author : lispybanana
Score : 114 points
Date : 2025-03-12 21:31 UTC (1 days ago)
(HTM) web link (www.youtube.com)
(TXT) w3m dump (www.youtube.com)
| whyage wrote:
| Great work, excellent video.
| tombert wrote:
| I love thinking about the "what if?" universe where we never
| figured out semiconductors and transistors, but still had roughly
| the same level of human progress. Would everything be clockwork
| like Syberia [1]? Would we have something akin to iPhones but
| done entirely with electro-mechanical stuff with antennas? I
| guess this is sort of the appeal of something like Steampunk.
|
| 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.
|
| [1] https://en.wikipedia.org/wiki/Syberia
|
| [2] https://en.wikipedia.org/wiki/Curta
| sebzim4500 wrote:
| You don't have to be a billionaire, I got a Curta mark I for
| ~PS850 on ebay and it's like the world's greatest fidget toy.
| tombert wrote:
| PS850 is actually cheaper than I thought it was, but it's
| still a bit much for me to justify right now. If I spent a
| grand on a fidget toy, I think my wife would be pretty mad at
| me.
|
| 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.
| MatthiasWandel wrote:
| I'm sure they would not have been less than PS850 in
| whatever currency it was sold in back then, inflation
| adjusted. But the justification was much better than being
| a fidget toy.
| tombert wrote:
| Oh definitely, prior to having cheap computers that can
| compute gigaflops, I would definitely have bought one to
| do number crunching.
|
| 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.
| econ wrote:
| Update it with USB so that it can take input and return
| results. Hook it up to a cash register for something like
| an antique store. Ideally one selling small items so that
| the customer can marvel at the display adding things up.
| tombert wrote:
| I also have always wanted one of those mechanical vintage
| cash registers, for the same reason I have always wanted
| a Curta. They always seemed like they would be fun to
| play with.
|
| 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.
| ddulaney wrote:
| It doesn't help that they made an absolute ton of them:
| something like 140,000! That means that they're not
| particularly rare, and it holds the price down.
|
| 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.
| fooker wrote:
| Maybe without semiconductors we would stumble upon something
| better sooner.
|
| Maybe optical/biological/quantum computing.
| bnkd_ wrote:
| Great work !
| renlo wrote:
| Great video, I really enjoyed how down to earth it was. It
| reminded me of The Secret Life of Machines [1], where we get to
| peek behind the curtain and see how seemingly "magical" machines
| (in your case a digital computer) emerges from simple fundamental
| concepts.
|
| [1] https://en.wikipedia.org/wiki/The_Secret_Life_of_Machines
| theendisney wrote:
| You can just continue the division by inputting the remainer i
| think?
| rtkwe wrote:
| I don't know if he mentioned, the name doesn't show up in the
| transcript, it but this seems to be very close to an unrolled
| Curta, the main difference being that it doesn't use 9s
| complement for subtraction so it has a more complex bidirectional
| carry mechanism. Otherwise the function is very similar down to
| shifting the turns and output accumulator to multiply the entry
| number. The big drum he makes many of is just one in the Curta
| that actuates every output dial through a full rotation.
|
| 9s complement makes subtraction extremely satisfying on the Curta
| because it causes a carry on (almost) every single output and
| turn accumulator dial.
| WilliamG52 wrote:
| Hi, I made the calculator and this video. As I discuss
| throughout and particularly towards the end of the video, my
| design is based on Thomas de Colmar's Arithmometer (~1820-1860)
| and Leibniz's Stepped Reckoner (late 1600s), both of which
| predate the Curta (1930s). Or rather, the Curta is a super cool
| and elegant refinement of those (and other) designs. I think it
| is more accurate to say the Curta is like a rolled up version
| of those (and my) calculator.
|
| 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.
| gregschlom wrote:
| Just wanted to say, fantastic work and video. I really
| enjoyed watching it.
| glth wrote:
| Great video! Very instructive.
| mjd wrote:
| Your machine, and the video, are astounding. The complexity
| and precision of your design, and the clarity of the
| explanation were all marvelous.
|
| Thanks so much for bringing this to us.
| MrMcCall wrote:
| I just want to say that this is one of my favorite YT videos
| of all-time. Content, presentation, project, execution, pace,
| music : all perfect. That is _NO_ exaggeration. You have made
| my day better, young man.
|
| 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!
| Animats wrote:
| The carry propagation hardware is the hardest to make work
| right. The low-digit add has to power the entire chain of
| carries. As the number of digits increases, it gets harder to
| do that, because so much mechanism has to be pushed.
|
| 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.
|
| [1] https://youtu.be/vdra5Ms__9s?t=247
| rtkwe wrote:
| You can definitely feel it when doing subtraction on a Curta,
| there's significantly more drag involved in it both because
| you're generally adding a larger number so more teeth
| interact but also the wave of the carries going around.
| However the low digit doesn't have to power all the carries
| though on a Curta because all the carry does it shift a gear
| up that then interacts with a single tooth (or 9 during
| subtraction) on the drum that performs the carry for the next
| digit up.
|
| 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.
|
| [0] https://www.vcalc.net/cu.htm
|
| [1] https://www.satadorus.eu/x_ite/yacs_2_0/yacs_2_0.html
| Animats wrote:
| Yes, as the number of wheels scales up, powered carry
| becomes necessary.
|
| 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/SecondFlo
| or/To...
| orbital-decay wrote:
| What is the simplest way to do mechanical logic? Without all
| those fancy looking gears. I wonder how far it can go if you
| actually optimize it.
| tocs3 wrote:
| I have had an interest in building a mechanical computer for a
| long time. It has not ever gotten farther that some research
| into what route to take. There are lots and lots of simple
| logic mechanisms (many, many in use in real world
| applications). It can go as far and be as capable as you have
| time for.
| jecel wrote:
| An interesting option is rod logic, which is the mechanical
| equivalent to a PLA (programmable logic array).
|
| https://www.jamiekawabatarobotics.com/?p=40
| pgarza00001 wrote:
| https://www.youtube.com/watch?v=G_SC7oWL78A
|
| The Whiffletree was used in mechanical calculators. It's an
| interesting way to encode digital data mechanically.
| drcode wrote:
| the madness of cutting hundreds of gears by hand, many with a 45
| degree bevel, I couldn't even imagine.
|
| madness!
| simonjgreen wrote:
| For a second video, this is amazing. It also took me to their
| first video which is a mechanical hand, also out of wood
| https://youtu.be/gxT8TfI5DaE
| lo_zamoyski wrote:
| Mechanical computers are a great reminder of what computation is
| and what it isn't.
|
| 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.
| Joker_vD wrote:
| > Computing devices are not _objectively_ computing. They
| simulate the formal construct.
|
| 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.
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