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Mechanical analog computers

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Offline Phil

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Mechanical analog computers
« March 27, 2017, 03:27:02 PM »
In addition to the topic on Babbage's Difference Engine and Analytic Engine, there have been mechanical analog computers since at least the early 20th century. These finely crafted devices were used, among other places, in naval gunnery directors to calculate where to point and elevate a gun to hit a distant target. Fire-control teams had to input ship and target headings and speeds, air temperature and humidity, wind speed and direction, and shell size and propellant charge (initial speed of the shell). Even the Coriolis Effect had to be taken into account at long ranges. In return, the machine would tell them the azimuth and altitude needed to hit the target.

The famed Norden Bombsight also took many of these factors into account, to tell a bombardier how far ahead of the target to release the bombs (and how much to the side the bomber should be to allow for crosswinds). It was hardly top secret, being quite famous among the public, although aircraft crews were to make sure the device was destroyed before bailing out and saving themselves. The problem was, the Norden required a clear view of the target (difficult over Europe, with frequent clouds, ground smoke, and fog) and a knowledge of all the winds at various levels down to ground level. Thus, it rarely lived up to the hype about being able to put a bomb into a barrel. In addition, Norden insisted on hiring European craftsmen to build the things, and it turned out that several were Nazi agents who passed the plans along to Berlin before the US even entered the war!

Discussion of other specialized mechanical calculating devices for specific purposes (as opposed to slide rules or small calculators) is welcome here. Circular slide rules with specialized scales (like the one used in Dr. Strangelove to calculate radiation exposure) aren't all that interesting.

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Offline Phil

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Re: Mechanical analog computers
« Reply #1: May 17, 2017, 01:36:06 PM »
Let's not forget the famed Antikythera Mechanism (https://www.realmofhistory.com/2017/01/30/3d-reconstruction-ancient-antikythera-mechanism/ and https://www.bibliotecapleyades.net/ciencia/esp_ciencia_antikythera02.htm) a 2000 or so year old orrery/astronomical calculator.

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Offline Phil

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Re: Mechanical analog computers
« Reply #2: May 02, 2018, 09:17:04 PM »
Another great analog computer was the US Navy Torpedo Data Computer for its submarines. A good documentary on Fleet Submarine operations in the Pacific in WWII, https://www.youtube.com/watch?v=RR8s1zRdylo, includes quite a bit of material on the TDC (although the innards are not shown or discussed). As usual with analog computers, it was built to do one thing and do it well. It was not a general purpose computer like your laptop machine.

The TDC was shown in action in https://www.youtube.com/watch?v=nnlKl6KrnU4 (USS Cod SS 224, Part 2). Part 1, if you also want to watch it, is https://www.youtube.com/watch?v=3HuGbD8mBUM .
« Last Edit: July 18, 2019, 06:02:38 PM by Phil »

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Offline Phil

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Re: Mechanical analog computers
« Reply #3: November 09, 2018, 05:27:53 PM »
I'm not sure if the Friden STW10 mechanical calculator is internally analog or digital, but here's a fun video about trying to make it divide by zero, and going crazy. Now, what's that "DIV STOP" button for? I would imagine it's well-worn on some units!

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Offline Phil

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Re: Mechanical analog computers
« Reply #4: December 22, 2019, 12:50:10 PM »
An article on the Boeing B-29 Superfortress and its General Electric model 2CFR55B1 centralized fire-control system. Pretty amazing stuff for 1943 vintage. It was visually controlled (not by radar), but multiple gun turrets could be controlled from one of several control stations, for redundancy and flexibility. All a gunner had to do was keep the enemy fighter in the sights, and the computers did the rest of figuring exactly where to aim the guns.

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Offline Phil

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Re: Mechanical analog computers
« Reply #5: December 22, 2019, 01:21:26 PM »
There's also the Curta calculator (article) that could fit in your hand and was quite popular until the advent of small electronic pocket-sized calculators. Note that this device was a calculator and not a programmable computer, but still a neat piece of gear. Be sure to watch Adam Savage's presentation on a 3D printed replica. The story of its inventor, Curt Herzstark, is one of amazing survival of the Buchenwald concentration camp.