HN Theater @HNTheaterMonth

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: https://m.youtube.com/watch?v=s1i-dnAH9Y4

The ideas are the same, but the technology is about a decade earlier than the CADC, so everything is noticeably more primitive.

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] - https://www.youtube.com/watch?v=s1i-dnAH9Y4

[1] - https://en.wikipedia.org/wiki/Antikythera_mechanism

The US Navy made a great video in 1953 explaining how mechanical computers work: https://www.youtube.com/watch?v=s1i-dnAH9Y4

⬐ hungryforcodes

Wow. I actually feel SMART now -- why was I watching React videos before? :p

⬐ agumonkey

This video is so brilliant

⬐ emilfihlman

Thank you for this! I absolutely love old US military / government services produced teaching and learning material like this. Sometimes it feels like the quality peaked long before.

I guess the definition of "computer" you have is "stored program machine", but a lot of other machines were called computers back then.

https://news.ycombinator.com/item?id=15108965

https://www.youtube.com/watch?v=s1i-dnAH9Y4

⬐ russh

"Computer" was not limited to machines https://www.nationalgeographic.org/article/women-nasa/

⬐ IcyClAyMptHe

I've watched this video countless times throughout the years. It's a lovely illustration of what can be calculated by physical means, but also a great example of a concise and engaging educational video - every step is clearly animated and you understand how each component works. Fantastic stuff

⬐ chefandy

Though this video isn't among them, the Prelinger Archives at The Internet Archive have a thousands of public domain videos— many are educational videos from this era. They've got a streaming preview player but you can easily download larger versions directly, or torrent them if you want to save Brewster a bit of bandwidth.

https://archive.org/details/prelinger

⬐ pinkman68419

Every time I see this video posted I watch it again from start to finish. Amazing what could (can!) be done with purely mechanical components.

⬐ agumonkey

That is true. And also I see a direct link between coupled mechanics and reactive programming.

That vid brought a few internal chats about computing. Since it's clear those things are computing advanced function in real time (with noise though), streaming physical changes downto the linkage graph, no side effects if you haskell-squint hard.. digital computers are a different take on computing, they were timeless, memoryfull at first.. and along the decades it seems we were all seeking to bring back automatic coupling (reactive recomputation) on the foreground.

⬐ rfreiberger

I love the idea of alternative reality and what if the vacuum tubes were never invented, the same with the transistor. Would we have huge steam engines running building sized mechanical computers to calculate simple programs. Each time I visit the Computer History Museum I think of what if the path was disrupted somehow.

⬐ sidpatil

I'd prefer to think that in the alternate universe, the machines aren't building-sized.

In that alternate universe, maybe Swiss watchmakers are the ones driving innovation in computing.

⬐ agumonkey

Opening a smartphone is reminiscent of opening a wristwatch.

⬐ perl4ever

There are concepts of electronic computers that involve streaming data in a vaguely similar way:

https://en.wikipedia.org/wiki/Systolic_array

An early example of this (an electronic computer in the 1940s!) seems to have been:

https://en.wikipedia.org/wiki/Colossus_computer

⬐ agumonkey

Yes most analog "computers" were time ordered / streaming.

Hollerith and discrete calculating machines were more about unordered data analysis. Static batch of input, chunk it the way you want, forward, backward.. doesn't matter. Very freeing in a way. I can understand why digital computation wiped the market, no noise and no constraint.. how nice. Until it starts to produce spaghetti bowls and crawling insects.

⬐ daralthus

As a fun exercise add erosion into the picture as a memory mechanism. Then just imagine a river flowing, rocks tumbling, birds chirping...

⬐ dang

Sorry for offtopicness- xept could you please email [email protected]? I want to send you some repost invites.

⬐ kazinator

This video may be useful for teaching kids arithmetic intuition from non-traditional angles, including for negative numbers. E.g. the double-rack-pinion adder and especially the X-Y rack multiplier.

Multiplication is typically modeled using repeated addition, or surface areas. But when negative numbers are involved, it may be unclear. You can stick to areas if you have a Cartesian plane where the upper left and lower right quadrants are understood to contain negative area. But that may seem arbitrary, requiring explanations that seem like hand waving if you don't already have an intuition for it. The mechanical multiplier replaces hand-waving explanations of sign with a waving arm that clearly reverses slope under the right geometric conditions, to produce a positive or negative number.

Here's a video detailing some of the math and mechanisms used.

https://www.youtube.com/watch?v=s1i-dnAH9Y4

This reminds me of a 1950s training video from the US Navy that I once watched that explained the function of the mechanical computers used for fire control of the ship's guns. I found it to be a really handy primer on how mechanical computers function and may well be of interest if this concept appeals to you.

https://www.youtube.com/watch?v=s1i-dnAH9Y4

If one searches around youtube there is quite a lot of films reels people have uploaded show the devices in action.

e.g. This is a fire control mechanism for ships.

https://www.youtube.com/watch?v=s1i-dnAH9Y4

Very clever stuff indeed.

You may find yourself wondering: what would happen if the gears are not circular?

The answer is then they can implement a wide range of mathematical functions like reciprocal, tangent, square etc. and you will get a kick out watching an hour long video about a mechanical "computer" with cams building up differential calculations: https://www.youtube.com/watch?v=s1i-dnAH9Y4

Enjoy!

All parts, without annoying timestamp at the bottom:

https://www.youtube.com/watch?v=s1i-dnAH9Y4

Mechanical computers for fire control where the standard solution until very recently. Here's a very interesting video about them: https://www.youtube.com/watch?v=s1i-dnAH9Y4

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] https://www.youtube.com/watch?v=s1i-dnAH9Y4&t=757

⬐ rolandog

Thanks for the link. Those mechanical computers are really amazing; such an elegant solution.

⬐ TeMPOraL

Thanks for that video. Very informative... like many of the videos from that age. There's something about training videos and physics videos from the 50s / 60s that makes them much better than what people produce today; it's hard to say exactly what it is, but they do feel cruft-free.

⬐ dTal

Not just the 50s/60s - this video explaining differentials is from 1937 and is a marvel of pedagogy:

https://www.youtube.com/watch?v=yYAw79386WI

⬐ TeMPOraL

Oh yes, that's legendary! I forgot it was pre-war! Speaking of war, I also recall pretty well-made video explanations for bomber pilots, about how to fly the planes to avoid anti-aircraft fire.

So I guess I should extend my original statement to the 1930s-1970s range.

⬐ Grustaf

They are not trying too hard to make it fun and entertaining. But it ends up much more entertaining than modern chewing gum tutorial videos.

⬐ Anarch157a

I think you're gonna like this one [1]. The B-25 Mitchell instructional that was linked here some few weeks ago is also amazing [2].

[1]: https://www.youtube.com/watch?v=Ac7G7xOG2Ag

[2]: https://www.youtube.com/watch?v=-YQmkjpP6q8

⬐ TeMPOraL

[1] reminds me of this: https://www.youtube.com/watch?v=bZe5J8SVCYQ :).

⬐ jacobolus

> something about training videos and physics videos from the 50s

They drafted people indiscriminately into the military, and then assigned some brilliant ones to make the videos. The assigned job was to make the clearest possible explanation for an audience assumed to also be competent.

Today, similarly competent people are likely full-time professionals, scientists, or the like, instead of making educational videos (though there are a few notably excellent people making educational videos today).

Folks making educational videos today have much more pressure to be wacky or exciting. Content is much more often patronizing.

Beyond that, I would guess there were also some pretty bad military training videos from the 50s, which just haven’t survived.

⬐ jcims

I wish they would make some for convolutional neural networks.

⬐ spandexcajun

3blue1brown videos are probably the best equivalent. Maybe a little basic? But really, all his math videos are just ridiculously good quality.

https://www.youtube.com/watch?v=aircAruvnKk

⬐ Animats

The editing, pacing, and style were better.

Educational videos today tend to go to one of two extremes. Either they're a talking head with PowerPoint, like most of the "massively online" courses. Or they have way too many jump cuts, like theatrical movies which want your attention, not your understanding.

There's also an annoying tendency to have distracting music and irrelevant graphics during narration.

Here's an old Jam Handy film, "Spinning Levers", on how a transmission works.[1] There's a whole series of these Chevrolet films on the Internet Archive, covering major vehicle systems. Things to note:

- There's a narrator and a demonstrator. We never see the narrator, and the demonstrator never talks. So the viewer can focus.

- The demo models of parts are really good. They start with a simple version and add features until a full transmission has been built up.

- There's some simple animation. Animation is used to point out how power flows through the gears. This is much clearer than someone using a pointer.

- The editing and narration are very well synchronized.

- There's an entertaining part at the beginning and end, so you don't feel like they're beating you over the head with the boring stuff.

[1] https://www.youtube.com/watch?v=JOLtS4VUcvQ

There's a great 1953 Navy fire control computer training film that explains some of these: https://www.youtube.com/watch?v=s1i-dnAH9Y4

⬐ always4getpass

That's different. The original link aims at mechanical contraptions while yours at mechanical computation. Still equally impressive and interesting

⬐ tlrobinson

True, but there's a lot of overlap in the mechanisms. The video explains how they can be used for computation, which I find even more interesting.

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:

https://youtu.be/s1i-dnAH9Y4

⬐ benj111

Bombers too.

https://en.m.wikipedia.org/wiki/Norden_bombsight

The Heathkit EC-1 operations manual seems like a good start for electronic analog computers and has some examples of problem circuits: http://www.ccapitalia.net/descarga/docs/1959-ec-1-heathkit.p...

I also like to share an instruction video on mechanical computers on every suitable occasion: https://www.youtube.com/watch?v=s1i-dnAH9Y4

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] https://www.youtube.com/watch?v=s1i-dnAH9Y4

The whole training film on mechanical computers, for navy mechanics I believe: https://www.youtube.com/watch?v=s1i-dnAH9Y4

It illustrates the problems and solutions near perfectly, and I've watched it way too many times.

⬐ nick_m

Thanks, being a long-time lurker, I've just signed up now to say that's great. What a video - I've been writing software for the past 31 years, and I love the simplicity among ingenuity of this. If you've not read it already, you might like http://www.mayofamily.com/RLM/txt_Clarke_Superiority.html

One of my favourites is this 1953 explanation of the workings of mechanical analog computers used by the US Navy: https://www.youtube.com/watch?v=s1i-dnAH9Y4

⬐ JorgeGT

I was going to link this. I think we should seriously consider how the skill to produce such clear and didactic explanations to complex concepts has seemingly degraded nowadays.

Specifically I wonder: who was making these videos? how where they trained? where they attached to the different unit or was it a dedicated group that was commissioned by the different units?

I recommend watching this video if you're interested in learning about multivariate analysis using mechanical computers. It's very approachable and informative. https://youtu.be/s1i-dnAH9Y4

https://www.youtube.com/watch?v=s1i-dnAH9Y4

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!

you don't even need electronics to make a computer! here's a 1953 training film for a mechanical fire control computer

https://www.youtube.com/watch?v=s1i-dnAH9Y4

⬐ gozur88

This kind of stuff fascinates me. There's an amazing amount of intelligence you can put into oddly-shaped cams.

Some videos of a very similar computer here: https://www.youtube.com/watch?v=s1i-dnAH9Y4

⬐ exDM69

This is an excellent video about analog computer basics. I've watched it many times and it's always entertaining and educational.

It's hard to imagine, but these things were still in active service well in to the 1980s, for example in the Vulcan bomber which flew a raid to the Falklands.

⬐ rjsw

The British torpedos used in the Falklands war were designed in 1925 [1].

[1] https://en.wikipedia.org/wiki/British_21_inch_torpedo#21_inc...

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: https://www.youtube.com/watch?v=s1i-dnAH9Y4

Well, there's spaghetti sort: https://en.wikipedia.org/wiki/Spaghetti_sort

Also things like using slime mold to solve the traveling salesman problem: http://phys.org/news/2013-03-blob-salesman.html

And if you want to go simpler, there's always mechanical analog computers: https://youtu.be/s1i-dnAH9Y4 (it's long but well worth a watch IMO)

Oh, and obviously anything involving a scale model, especially for fluid dynamics (so wind tunnels, wave tanks etc), is doing the same thing in spirit.

⬐ hackcasual

Slime molds aren't guaranteed to find optimal solutions

⬐ zdkl

You'll have to break out "Moldy Carlo" simulations for that!

⬐ saurik

That analysis of spaghetti sort is incorrect as you scale N to a size larger than the hand. It will take time linear in the number of straws to move your hand across the tips to find the largest one, and this will be true for any size hand as no matter how large the hand is, there is an upper limit to the number of straws it can hover over in parallel.

One of the big points of complexity analysis is that at small scales you might see certain behavior but what we are really interested in is asymptotic complexity: this is like saying selecting the lowest value from an unsorted array is faster than a tree iif the array has so few entries that it fits into the L1 cache (while the tree's randomly scattered memory means walking its left edge could take much longer; essentially making the array O(1) in memory accesses while the tree is O(log n)). A better analysis of spaghetti sort should find it to be O(n^2), if the algorithm really continues to function at all (and it isn't clear to me that it correctly scales).

(It is also worth nothing that if you want a limited purpose linear time sorting algorithm based on the same "let's change the notion of comparison", we even have working ones that function on real world computers: radix sort is insanely epic and with a little assistance from insertion sort fix up passes I have used it to sort Unicode strings in seemingly impossibly fast times.)

I think it's this one: http://www.youtube.com/watch?v=s1i-dnAH9Y4

(it's "Basic Mechanisms in Fire Control Computers" parts 1 and 2, from 1953)

⬐ mastazi

Thank you so much! No Netflix tonight ;-)

Speaking of targeting computers, one of my favorite videos on YouTube is a training film describing the theory of operation behind a purely mechanical fire control computer by the US Navy circa 1953 https://youtu.be/s1i-dnAH9Y4

⬐ nsxwolf

Thank you for that. I just watched a few minutes, but already, watching a cam compute a reciprocal is by far the most interesting thing I've seen all week.

Analog computers were basically voodoo to me before this. Looking forward to watching the rest!

⬐ aswanson

Thanks...just goes to show how brilliant some of our pre-digital forbears were. I still give more props to old school television engineers to present day ones. The laws of physics are far more unforgiving than the laws of a compiler.

⬐ bcoates

I love that film, but it's kind of weird that it doesn't mention what's probably the most important invention that makes this type of computer possible: The torque amplifier.

All the devices shown suffer power losses between input and output, some of them severe. A torque amplifier has two shafts that are 1:1 geared for speed but the output shaft has extra power taken from a third supply shaft, like the supply to a logic gate that lets it drive more output power than it draws from its inputs.

https://en.wikipedia.org/wiki/Torque_amplifier

http://www.youtube.com/watch?v=s1i-dnAH9Y4

Interesting to see this on HN as we dug out an entrance to a WW2 German bunker yesterday afternoon here in Jersey (the British island). Like urbex and WW2? Photos here: https://plus.google.com/photos/105983129534664287827/albums/...

Some videos also on our group's YouTube page, with a quick walk-through. We already have one of these restored and open to the public, and we were after parts and a bit of exploration.

As for the accuracy, WW2 guns were good enough. This Youtube video on mechanical fire-control computers is very interesting and I've seen it come up on HN before several times. https://www.youtube.com/watch?v=s1i-dnAH9Y4

Lots of this equipment survives today. It was built to last and many people still collect it. We've also got about a dozen French and German cannon dumped from cliffs that we'll recover some day.

⬐ Luc

Great stuff, thanks for posting this.

What's being removed from the walls with the angle grinders? It looks like bits of rusty tube with little value...

How was the air in there?

⬐ Someone

Could be as simple as something to hang wooden seats or beds from. See for example the third photo in http://www.dailymail.co.uk/news/article-1041171/Violent-stor...

I wonder more about why one would, upon entering such a bunker, start axle grinding ones such structures.

⬐ Luc

Little point in leaving stuff there I suppose. It will just rust away further over the next hundreds of years. Better to concentrate resources in a few of them.

⬐ tombrossman

Sorry, I posted this and went to sleep so missed the replies. We have one complete and open to the public. We were allowed to dig out the bunker entrance to explore & recover anything interesting, then it had to be sealed back up. The last time this was done was in the 70's, as it is beach-side in an environmentally protected area.

⬐ dfc

Is it normal to fire up an angle grinder and not wear eye protection where you live? In one of the pictures you can see spark bouncing off worker's face an inch below left eyeball.

⬐ jrockway

The sparks are hot, but don't contain much mass, so I don't think they're as dangerous as they look. That said, as an official paranoid person, I always wear goggles.

⬐ dfc

Data/evidence to the contrary:

The Royal Society for the Prevention of Accidents (RoSPA) Home and Leisure Accident Surveillance Systems (HASS/LASS) lists angle grinders at #3 in their top ten list of most dangerous tools, with an average of 5,400 injuries recorded. [1]

"Angle grinders are one of the most dangerous tools in any workplace. They are used for cutting, grinding and polishing work. ... Most angle grinder injuries are from metal particles lodging in the operator’s eye. However, the most serious injuries are from kick-back, where the disc is thrust back violently towards the operator." [2]

[1]: http://www.hassandlass.org.uk/reports/2002data.pdf

[2]: http://www.commerce.wa.gov.au/worksafe/angle-grinders

Related: If you haven't seen this 60 year old US Navy training video on "mechanical fire control computers" it is definitely worth a watch. https://www.youtube.com/watch?v=s1i-dnAH9Y4

⬐ kawera

Fascinating. Thank you very much!

⬐ ANTSANTS

Came here to post this.

⬐ csandreasen

Ars Technica also did a good write-up on that subject:

http://arstechnica.com/information-technology/2014/03/gears-...

⬐ vibrolax

The Computing Mechanisms chapter of the following book illustrates many mechanical computing elements: "Mechanisms and Dynamics of Machinery", Mabie and Okvirk, Wiley 1963 ISBN 10: 0471559377 / 0-471-55937-7

I bought this book for $1 at a library book sale 25 years ago to teach myself cam design. I've kept it because of the chapter on the computing mechanisms.

⬐ Gravityloss

These were hard to construct back in the day. Now with 3d printers and computer aided design, you could create really nice and complicated mechanical computers relatively easily.

Useful for cases where you don't have electricity.

I've had a business idea or a few...

⬐ aidos

I've only watched the first half but that's possibly the most interesting thing that will be posted on HN today.

Just wanted to write a quick note to try to persuade others to watch it (I almost didn't as I avoid videos).

⬐ agumonkey

dig in hnsearch, there were many older threads with loads of videos of the same kind.

⬐ taejo

Interesting! I never really thought about cams as computational devices -- that can compute any "nice enough" function on the circle!

⬐ _archon_

This video series is much more interesting than I anticipated. Of particular interest was how the pacing, concept introduction, and simplification was handled. This video is approachable and affords a high-level overview of a very complex system, enough that I'm sure I could operate such system given some practice.

Between the demonstrations, the visuals, and the matter-of-fact narration, this is a masterpiece of informative video.

Interestingly, several months ago I came across the following 1953 training video dealing with this same subject.

http://youtu.be/s1i-dnAH9Y4

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):

https://www.youtube.com/watch?v=s1i-dnAH9Y4

edit: This video is the same footage featured throughout the article, in fact.

⬐ D9u

Ah... You beat me to it!

Reminds me of all the crazy gears they used in mechanical computers http://www.youtube.com/watch?v=s1i-dnAH9Y4

⬐ jjdro

Wow that video is cool. I'd love to see some design tools and open cad files for 3d printed mechanical computers

⬐ DigitalJack

What a fantastic video!

⬐ ssewell

To be honest, at first I saw this post and thought, "how is a simple post of the Geneva drive mechanism news?". But after reading some of the followup and various links, I've definitley changed my opinion. Some amazing mechanical engineering in here. Thanks for this great video!

> It’s easy to write a program that will do this automatically without any human input. What if the plane is changing altitude? The problem becomes slightly harder, but not too hard. It’s just a matter of figuring out how far to plan in advance.

This reminds me to some extent of Basic Mechanisms in Fire Control Computers [1]. The whole thing is worth watching, but the link will take you to the point that I was reminded of.

[1] http://www.youtube.com/watch?v=s1i-dnAH9Y4#t=612