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.
Why Hacker News points people here: HN commenters repeatedly recommend it as a beautiful, approachable explanation of analog mechanical computation, and many have rewatched it.
“It illustrates the problems and solutions near perfectly, and I've watched it way too many times.”HN comment, 2018
“It's beautiful in its elegance! I have watched it on multiple occasions just for the sheer beauty of the mechanisms involved.”
Explains mechanisms of fire control computers; beautiful and elegant.
Full comment
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!
Strongly recommendsboomlindeNov 2018
“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.
Full comment
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.
Strongly recommendsBjartrNov 2018
“I highly recommend it. It's a fascinating trip into engineering, computing, and the past.”
Full training video behind the article's clips.
Full comment
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
Strongly recommendskibwenOct 2024
“Everyone reading this right now needs to check out this 1950s naval training video”
Must-watch 1950s film on battleship mechanical fire control computers.
Full comment
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.
RecommendsNamTafMar 2014
“Obligatory link to youtube video of a 1950s training video on the mechanical fire control computers”
1950s Navy training film on mechanical fire control computers.
Full comment
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.
RecommendsSharlinAug 2016
“is pretty fascinating”
Old US Navy film on mechanical fire control calculators.
Full comment
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
RecommendskqrAug 2017
“It's very approachable and informative.”
Approachable, informative intro to mechanical analog computation.
Full comment
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
RecommendspeterkellyApr 2018
“One of my favourites is this 1953 explanation of the workings of mechanical analog computers used by the US Navy”
1953 explanation of US Navy mechanical analog computers.
Full comment
One of my favourites is this 1953 explanation of the workings of mechanical analog computers used by the US Navy: this video
RecommendsleggomylibroMar 2019
“You can watch an old training video about it from the '50s”
1950s training video on battleship firing-solution computers.
Full comment
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
RecommendsadrianNJun 2019
“Here's a very interesting video about them”
Very interesting video on mechanical fire control computers.
Full comment
Mechanical computers for fire control where the standard solution until very recently. Here's a very interesting video about them: this video
RecommendsddulaneyNov 2022
“there’s a great 1950’s US Navy training film on the individual components of analog fire control computers here”
Great 1950s Navy film on individual fire control computer components.
Full comment
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.
RecommendseigenvalueMar 2024
“another one of these old films about them which is a great explainer”
Old film that is a great explainer of these computers.
Full comment
Yes, these are awesome. There is another one of these old films about them which is a great explainer: this video
RecommendsmrandishMay 2025
“explaining the fundamentals of how mechanical fire control computers work to solve complex problems is excellent.”
Excellent 1950s film on fundamentals of mechanical fire control computers.
Full comment
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
Cites itD9uMar 2014
“the following 1953 training video dealing with this same subject.”
1953 training video on the same subject.
Full comment
Interestingly, several months ago I came across the following 1953 training video dealing with this same subject. this video
Cites itAnimatsMay 2019
“A differential is an adder.”
Cited for differentials acting as adders in gun predictors.
Full comment
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
Cites itasciimovMar 2022
Example of fixed mechanical computers with program in gears.
Full comment
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
Cites itRichardCASep 2024
“The engineering knowledge that went into the WWII fire control computers was clearly a form of programming.”
Shows WWII fire control engineering as programming, using computer terminology unexplained.
Full comment
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
Cites it7373737373Apr 2025
“Maybe also analog ones!”
Offered as inspiration for analog complications in watches.
Full comment
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
Cites itants_everywhereSep 2025
“the classic video on fire control computers”
Classic example of analog computers not operating on symbols.
Full comment
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.
Cites itlmmSep 2025
Cited as example in a debate over symbolic computation.
Full comment
> 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).
