## Re: [midatlanticretro] Analog Computers - General description

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• Josh, Did you ever get any response to your question? I think of an analog computer as a device that models a problem and thus calculates the answer by
Message 1 of 18 , Dec 8, 2012
Josh,

Did you ever get any response to your question?

I think of an analog computer as a device that models a problem and thus 'calculates' the answer by varying inputs to the model and then measuring an output. Accuracy depended on the accuracy of the model which could be rods and gears or electric circuits or both. Analog computers that are used today include tide clocks or the more common clocks what show the phase of the moon (location is one of the inputs). Big analog computers in the 30's were used to 'solve' multiple differential equations. Artillery tables are the most common example from WWII.

The Wikipedia article is http://en.wikipedia.org/wiki/Analog_computer

Jim

On 9/7/2012 7:50 PM, joshbensadon wrote:

I'm trying to learn something about these old computers. First of all, do they actually follow program steps? I always equated the term computers with something that can follow directions, calculate numbers, make decisions based on the results. How were these old computers used? Who used them? etc.

• ________________________________ From: Jim Scheef To: midatlanticretro@yahoogroups.com Sent: Saturday, December 8, 2012 9:44 AM Subject:
Message 2 of 18 , Dec 8, 2012

From: Jim Scheef <scheefj@...>
To: midatlanticretro@yahoogroups.com
Sent: Saturday, December 8, 2012 9:44 AM
Subject: Re: [midatlanticretro] Analog Computers - General description

Josh,

Did you ever get any response to your question?

I think of an analog computer as a device that models a problem and thus 'calculates' the answer by varying inputs to the model and then measuring an output. Accuracy depended on the accuracy of the model which could be rods and gears or electric circuits or both. Analog computers that are used today include tide clocks or the more common clocks what show the phase of the moon (location is one of the inputs). Big analog computers in the 30's were used to 'solve' multiple differential equations. Artillery tables are the most common example from WWII.

The Wikipedia article is http://en.wikipedia.org/wiki/Analog_computer

Jim

On 9/7/2012 7:50 PM, joshbensadon wrote:

I'm trying to learn something about these old computers. First of all, do they actually follow program steps? I always equated the term computers with something that can follow directions, calculate numbers, make decisions based on the results. How were these old computers used? Who used them? etc.
We still used analogue computing systems in the Navy in the 1970's.  Each synchro could be adjusted with a pot which
one tweaked in with a small screwdriver.  When one got the last pot tweaked in one went back and started over to
make sure that the whole system was still in alignment.  The system was hard wired with no significantly changeable
components.
bs

• ... I just happened to have discovered this great video a couple of days ago. It s a 50 s US Navy instructional film about the mechanical computers they used.
Message 3 of 18 , Dec 8, 2012
On 9/7/2012 7:50 PM, joshbensadon wrote:
>I'm trying to learn something about these old computers. First of all, do they actually follow program steps? I always equated the term computers with something that can follow directions, calculate numbers, make decisions based on the results. How were these old computers used? Who used them? etc.

I just happened to have discovered this great video a couple of days ago. It's a 50's US Navy instructional film about the mechanical computers they used. It's really eye-opening and very high quality. (It gets to the meat about two minutes in.) For me, it demonstrated the analog/mathematical approach, in contrast to the digital/logical approach I grew up learning.

- Ken
• ... http://www.eugeneleeslover.com/VIDEOS/fire_control_computer_1.html It looks like the site linked above is a primary Web source for WWII and later Naval
Message 4 of 18 , Dec 10, 2012
--- In midatlanticretro@yahoogroups.com, Ken <kenzolist@...> wrote:

> I just happened to have discovered this great video a couple of days ago. It's a 50's US Navy instructional film about the mechanical computers they used. It's really eye-opening and very high quality. (It gets to the meat about two minutes in.) For me, it demonstrated the analog/mathematical approach, in contrast to the digital/logical approach I grew up learning.
>
> - Ken
>
http://www.eugeneleeslover.com/VIDEOS/fire_control_computer_1.html

It looks like the site linked above is a primary Web source for WWII and later Naval fire control computer documents. It may be the original source for the video referenced above, or certainly an earlier one.

These control computers used rotational position (radius vs angle) as means of expressing an analog function. One input variable was a cam on a shaft; two input variables was a surface on a cylinder. By cascading, you could have several variables per output. The video series shows this, and the Navy textbooks on the site above explain further.

Mechanical computers like this were "programmed" by manufacture; one design equals one program. Electronic analog computers were programmed by wiring panels and adjusting components, as well as by design or by hard-wire. Hybrid analog computers, made the connections and adjustments digitally.

I knew nothing about the above, until I did some Web searching based on the reference first given. It's good to see more ancient technology on the Web. In this case, advanced WW II technology, digitized from books and films.

Herb Johnson
• ... I think some of these are originally from the Historic Naval Ships Association. There is a group of us ship geeks that are also trying to save and archive
Message 5 of 18 , Dec 10, 2012
> http://www.eugeneleeslover.com/VIDEOS/fire_control_computer_1.html
>
> It looks like the site linked above is a primary Web source for WWII and
> later Naval fire control computer documents. It may be the original source
> for the video referenced above, or certainly an earlier one.

I think some of these are originally from the Historic Naval Ships
Association. There is a group of us ship geeks that are also trying to
save and archive the technology, bitsavers style.

> These control computers used rotational position (radius vs angle) as
> means of expressing an analog function. One input variable was a cam on a
> shaft; two input variables was a surface on a cylinder. By cascading, you
> could have several variables per output.

There is also a class of fire control computers that used linear
displacement of levers and linkages, rather than rotation. These
machines were much cheaper to make, but not quite as accurate. And of
course, there were hybrids of all sorts. I had a small collecton of
small machines and assemblies at VFC East number 2.

Trivia - there are two Mk 4 Torpedo Data Computers still in active
service, in the Taiwan Navy. They have been in near continuous service
since 1946.

--
Will
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