Basic Mechanics in Fire Control Computers

February 14, 2010 2:04 PM

I've never really had a clear understanding of how mechanical computing worked, until today when I watched these US Navy training films from 1953. Part 1 focuses on shafts, gears, cams and differentials. Part 2 explains mechanical component solvers, integrators and multipliers. More information about ship gun fire-control systems here.
posted by drmanhattan (28 comments total)

Wow, drmanhattan, awesome. I always wanted to know how mechanical computers worked. A differential, whaaaaa?

Love it.
posted by ctmf at 2:30 PM on February 14, 2010

I thought Dr. Manhattan knew how everything worked.
posted by pashdown at 2:58 PM on February 14, 2010 [4 favorites]

Great great find!
posted by DavidandConquer at 3:47 PM on February 14, 2010

Oh wow, can't wait to dig into this. The notion of mechanical computing never really hit home for until I saw the Babbage Difference Engine at the Computer History Museum in Mountain View, CA. That's one hell of a stunningly complex and utterly gorgeous machine. And it presses the (decimal!) results of its calculations into a tablet of soft plaster. All done with mechanics you can watch crank and turn like the craziest clock ever conceived. They give live demos of it almost daily, if I recall correctly.
posted by treepour at 3:52 PM on February 14, 2010

I haven't clicked on anything and I've already messed my pants. (Also, the library at work as some contemporary books on this that I'm afraid to check out for fear I'll never have time to ever do anything else. [There's like 15-20 books in the set.])
posted by DU at 4:02 PM on February 14, 2010

So I've got my grandfather's WWII era metal lathe all set up in the basement and I'm looking at this and drooling. So now the question - cutting these irregular cams with a CNC system would be easy. Cutting a second one with an old fashion style lathe and mill wouldn't be too bad once you had your first.

How did they make the first one circa 1953? Just carefully turning feed knobs based on a big table of numbers, or what?
posted by Kid Charlemagne at 4:48 PM on February 14, 2010

Kid Charlemagne -- they used a gear mechanism that moves the cutting tool in and out as the shaft rotates, much as the one on your lathe will probably move it back and forth to cut screw threads.
posted by localroger at 4:59 PM on February 14, 2010

This is unbelievably cool. These videos should be compulsory viewing for final year Mechanical Engineering students (to teach "novel" applications for what they've learned) and first year Computer Science students (to teach how some of what they are about to learn used to be elegantly implemented).
posted by Simon Barclay at 5:13 PM on February 14, 2010

i will show these in the programming class i teach. awesome find!
posted by Paleoindian at 5:40 PM on February 14, 2010

first year Computer Science students (to teach how some of what they are about to learn used to be elegantly implemented).

CS students don't learn much analog computing.

So I've got my grandfather's WWII era metal lathe all set up in the basement and I'm looking at this and drooling.

I'm reading this comment and drooling.

...cutting these irregular cams with a CNC system would be easy.

I have the same question about the equation of time cam from the Long Now clock. The Clock is supposed to be repairable by all future civilizations, including ones with very low technology. How are they supposed to compute, alone manufacture, this cam?
posted by DU at 5:47 PM on February 14, 2010

Watching video #2 makes me think of Andrew "Slipstick" Libby.
posted by DU at 6:11 PM on February 14, 2010 [1 favorite]

I have the same question about the equation of time cam from the Long Now clock. The Clock is supposed to be repairable by all future civilizations, including ones with very low technology. How are they supposed to compute, alone manufacture, this cam?

You didn't notice the slot in the base where you feed bar stock in and the clock mills out cams for daughter clocks? It's right next to the card reader.
posted by sebastienbailard at 6:49 PM on February 14, 2010

These videos should be compulsory viewing for final year Mechanical Engineering students (to teach "novel" applications for what they've learned) ...

No kidding! The notion of using cams that way blew my mind a little bit. I couldn't help but get that special feeling of dismay that comes with seeing the amount of ingenuity that humans invest in devices built to kill people, but it was fascinating anyway.

Also, I could watch differentials move around for hours. There's nothing else that moves that way.
posted by invitapriore at 7:52 PM on February 14, 2010

How are they supposed to compute, alone manufacture, this cam?

I'd include a tungsten mold for the cam, which they can pour brass into, maybe. Dunno if it would work.

Or they can ask the AI running ask.metafilter.com: "Prithee, oh Lord, how do we make another timing-spiral for the Great Clock? Cats stormtroopers, curse them 1024 times, destroyed it while raiding our nest and slaying tens of thousands of our hatchlings."
posted by sebastienbailard at 7:59 PM on February 14, 2010

How are they supposed to compute, alone manufacture, this cam?

Astronomers were calculating the numbers into the future long before mechanical or electrical computers. But yes it was a big task. I assume they'll include an engraved table of values. Then, much like a model aeroplane hobbyiest, you can construct from the table the series of cross-sections you need to build a 3d cam. Smoothing the shape across all the cross sections will yield the correct interpolations for the unknown values that lie between known cross sections.
posted by -harlequin- at 8:21 PM on February 14, 2010

CALCULUS FOR MACHINES AIEEE
posted by tehloki at 12:40 AM on February 15, 2010

This post turns me on.

I shouldn't have said that, but I can't help it. ZOMG mechanical computers fap fap fap
posted by Alex404 at 2:17 AM on February 15, 2010

This is just great.

Tinkertoys are superb for training yourself in the mechanical arts, I might add.
posted by Sukiari at 3:26 AM on February 15, 2010

So, so awesome.
posted by cavalier at 3:34 AM on February 15, 2010

One commenter in another thread about this said they were still using these in the first Gulf War.
posted by Enron Hubbard at 5:50 AM on February 15, 2010

Can you run emacs on it?
posted by wobh at 7:37 AM on February 15, 2010 [2 favorites]

I wonder if they can (and do) make stuff like this. I mean.. electronics is all nice and stuff, but when the nuclear shit really hits the United States-shaped fan, this mechanical stuff seems very, very sturdy.
posted by Harry at 7:57 AM on February 15, 2010

I mean.. electronics is all nice and stuff, but when the nuclear shit really hits the United States-shaped fan, this mechanical stuff seems very, very sturdy.

Yes, although that's not the whole story. Think about this: They are explaining the fundamental operations of the fire control computers to Navy "new hires". Whereas today, you can't even find out how much the Navy pays for their weapons, let alone how they work.

Transparency and simplicity.
posted by DU at 10:15 AM on February 15, 2010

There is a bit here about mechanical computing.
posted by Nyrath at 10:19 AM on February 15, 2010 [1 favorite]

Bonus points for spotting the two mistakes in the second video.
posted by JoJoPotato at 10:29 AM on February 15, 2010

Can you run emacs on it?

Hmm? Someone doesn't know about M-x fire-control?

Wait a second. M-x fire-control on my machine just outputs:
"Yow! Legally-imposed Demilitarization-of-text-editors is CABBAGE-BRAINED!"

wtf? When did that happen?
posted by sebastienbailard at 10:22 PM on February 16, 2010

http://en.wikipedia.org/wiki/File:Lorenz-SZ42-2.jpg
http://en.wikipedia.org/wiki/File:16th_century_French_cypher_machine_in_the_shape_of_a_book_with_arms_of_Henri_II.jpg

via: http://en.wikipedia.org/wiki/Cryptography
posted by sebastienbailard at 10:30 PM on February 16, 2010

A beautiful demo of Babbage's Difference Engine at the Computer History Museum.
posted by drmanhattan at 8:41 AM on February 17, 2010