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Mechanical Computer (All Parts) - Basic Mechanisms In Fire Control Computers

Excelsior10000
Documentaries
YouTube
13 HN users recommended this documentary12 months2014–2025 score 13.5
Years with an HN recommendation, 2007–2026

HN commenters repeatedly recommend it as a beautiful, approachable explanation of analog mechanical computation, and many have rewatched it.

A 1953 US Navy training film explaining the basic mechanisms in mechanical fire control computers aboard ships. It shows how gears, differentials and cams solved mathematical problems in permanent mechanical form.

“It illustrates the problems and solutions near perfectly, and I've watched it way too many times.” (HN, 2018)

4 strong recommendations · 9 recommendations · 7 citations · Documentaries · intro

20 Hacker News comments

From the HN archive; up to 20 kept per video, favoring different commenters. Recommendations first.

@coreyp_1 May 2017 Strongly recommends
on HN thread The Turing Tumble lets you and your kids build real mechanical computers
[this video] This is an old military instructional video about fire (artillery) control computers, explaining the mechanical aspects of how they work. It's beautiful in its elegance! I have watched it on multiple occasions just for the sheer beauty of the mechanisms involved. And, yes, of course I'm a nerd!
Explains mechanisms of fire control computers; beautiful and elegant.
@boomlinde Nov 2018 Strongly recommends
on HN thread When mechanical analog computers ruled the waves (2014)
The whole training film on mechanical computers, for navy mechanics I believe: [this video] It illustrates the problems and solutions near perfectly, and I've watched it way too many times.
Illustrates problems and solutions near perfectly; rewatched many times.
@Bjartr Nov 2018 Strongly recommends
on HN thread When mechanical analog computers ruled the waves (2014)
I did not see any link to the full training video[0] the clips in this article were taken from. I highly recommend it. It's a fascinating trip into engineering, computing, and the past. [0] [this video]
Full training video behind the article's clips.
@kibwen Oct 2024 Strongly recommends
on HN thread Knocker uppers: Waking up the workers in industrial Britain (2016)
Everyone reading this right now needs to check out this 1950s naval training video on the mechanical fire control computers of battleships: [this video] For fun, before you watch, think for yourself how you'd implement addition, multiplication, squaring, etc. with only gears and other mechanisms.
Must-watch 1950s film on battleship mechanical fire control computers.
@NamTaf Mar 2014 Recommends
on HN thread Gears of war: When mechanical analog computers ruled the waves
Obligatory link to youtube video of a 1950s training video on the mechanical fire control computers (which I stole from HN last time this sort of topic came up): [this video] edit: This video is the same footage featured throughout the article, in fact.
1950s Navy training film on mechanical fire control computers.
@Sharlin Aug 2016 Recommends
on HN thread Optical solutions to NP-Complete problems
This old US Navy training film on mechanical fire control calculators (called "computers" back then, used to calculate firing solutions on warships) is pretty fascinating: [this video]
Old US Navy film on mechanical fire control calculators.
@kqr Aug 2017 Recommends
on HN thread One of the most complex wristwatches ever made
I recommend watching this video if you're interested in learning about multivariate analysis using mechanical computers. It's very approachable and informative. [this video]
Approachable, informative intro to mechanical analog computation.
@leggomylibro Mar 2019 Recommends
on HN thread The Comdyna GP-6 analogue computer that I use daily at work
Apparently the Navy also used mechanical 'computers' on old battleships to calculate firing solutions. Sailors would adjust cranks and shafts to set the input values, and those inputs were connected to cams which were machined in the shape of solutions to the equations that needed to be solved. You can watch an old training video about it from the '50s: [this video]
1950s training video on battleship firing-solution computers.
@adrianN Jun 2019 Recommends
on HN thread Wootz steel
Mechanical computers for fire control where the standard solution until very recently. Here's a very interesting video about them: [this video]
Very interesting video on mechanical fire control computers.
@ddulaney Nov 2022 Recommends
on HN thread The Bendix Central Air Data Computer (CADC)
If you’re interested in some of the individual components, there’s a great 1950’s US Navy training film on the individual components of analog fire control computers here: [this video] The ideas are the same, but the technology is about a decade earlier than the CADC, so everything is noticeably more primitive.
Great 1950s Navy film on individual fire control computer components.
@eigenvalue Mar 2024 Recommends
on HN thread Telegram for America (1956) [video]
Yes, these are awesome. There is another one of these old films about them which is a great explainer: [this video]
Old film that is a great explainer of these computers.
@mrandish May 2025 Recommends
on HN thread Millihertz 5 Mechanical Computer (2022)
I just smile hearing the term "Millihertz Computer". I'd love it if building and designing mechanical and analog computers grew as a hobby/educational activity as I find them both fascinating and somehow satisfying. Also, this 1950s Naval Training film explaining the fundamentals of how mechanical fire control computers work to solve complex problems is excellent. [this video]
Excellent 1950s film on fundamentals of mechanical fire control computers.

Citations, criticism and jokes

@Animats May 2019 Cites it
on HN thread Five Hundred and Seven Mechanical Movements (1908)
A differential is an adder.[1] This is a differential hooked up as a doubler. Mechanical analog computers, especially gun predictors, had lots of setups like that. [1] [this video]
Cited for differentials acting as adders in gun predictors.
@asciimov Mar 2022 Cites it
on HN thread The Nimatron: first 'video game' debuted in 1939
Read more
Over the years we have evolved the meaning of computer from something that calculates or reckons to a electronic device that runs software. In reality any black box that has a one-to-one relationship between inputs and outputs can be considered a computer. It might be easier to think of mechanical computers, such as the WW2 fire control computers aboard Navy Ships[0] or more famously the Antikythera mechanism[1]. These are fixed devices, they compute values from inputs. The "program" is stored in the gears camshafts and differentials and ratios between them. Similarly, fixed digital computers such as the Nimatron have their operations stored in relays and digital logic. These sorts of computers don't have a list of instructions. They just have schematics, inputs going through electronic circuits that wind up at outputs. You can do a lot of calculating with just simple logic gates. [0] - [this video] [1] - [link]
Example of fixed mechanical computers with program in gears.
@RichardCA Sep 2024 Cites it
on HN thread Founder Mode, hackers, and being bored by tech
The engineering knowledge that went into the WWII fire control computers was clearly a form of programming. You will also notice the words "computer", "input", and "output" are used without needing to be explained. [this video]
Shows WWII fire control engineering as programming, using computer terminology unexplained.
@7373737373 Apr 2025 Cites it
on HN thread Vacheron Constantin breaks the world record for most complicated wristwatch
I do hope watchmakers start to integrate "computational" (instead of temporal) complications into their watches, like a mechanical turing machine or other tiny mechanical computers or calculators which I believe have never been constructed this small. Inspiration: Wooden Turing Machine: [link] Curta Calculator: [link] Zuse Z1 Computer: [link] Maybe also analog ones!: [this video]
Offered as inspiration for analog complications in watches.
@ants_everywhere Sep 2025 Cites it
on HN thread Is life a form of computation?
analog computers don't generally compute by operating on symbols. For example see the classic video on fire control computers [this video] OP's specific phrasing is that they "map symbols to symbols". Analog computers don't do that. Some can, but that's not their definition. Turing machines et al. are a model of computation in mathematics. Humans do math by operating on symbols, so that's why that model operates on symbols. It's not an inherent part of the definition.
Classic example of analog computers not operating on symbols.
@lmm Sep 2025 Cites it
on HN thread Is life a form of computation?
Read more
> analog computers don't generally compute by operating on symbols. For example see the classic video on fire control computers [this video] > OP's specific phrasing is that they "map symbols to symbols". Analog computers don't do that. Some can, but that's not their definition. How is that not symbolic? Fundamentally that kind of computer maps the positions of some rods or gears or what have you to the positions of some other rods or gears or what have you, and the first rods or gears are symbolising motion or elevation or what have you and the final one is symbolising barrel angle or what have you. (And sure, you might physically connect the final gear directly to the actual gun barrel, but that's not the part that's computation; the computation is the part happening with the little gears and rods in the middle, and they have symbolic meanings).
Cited as example in a debate over symbolic computation.

Video list and Hacker News comment labels from HackerTube (prompted by @karpathy), released under ODC-By 1.0, built on the open-index/hacker-news archive. Hacker News data is provided by Y Combinator; comments remain the work of their authors. Video titles, channel names and thumbnails belong to their creators and are shown via YouTube. HackerTube Watch is an unofficial edition. Data export of 2026-10-31.

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