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Analog Computers - General description

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  • joshbensadon
    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
    Message 1 of 18 , Sep 7, 2012
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      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.
    • David Gesswein
      ... It wasn t intended to be that strong a statement. I don t have an analog computer so don t have direct knowledge. From other electronics the lower speed
      Message 2 of 18 , Sep 7, 2012
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        On Fri, Sep 07, 2012 at 11:50:32PM -0000, joshbensadon wrote:
        > Are you saying the transistors in the old analog computers are robust?
        > I haven't looked at part numbers yet, but they look like the old
        > germanium TO-05 case style.
        >
        It wasn't intended to be that strong a statement. I don't have an analog
        computer so don't have direct knowledge. From other electronics the lower
        speed stuff tended to use transistors with breakdown voltages higher than
        the supply. Also that a quick look assuming the parts are easily visible
        will give you an idea of if overvoltage is likely to damage the unit. if
        the breakdown voltage is somewhat higher than the preregulated voltage
        then your unlikely to fry all the transistors if the supply looses
        regulation.

        > 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'm not that familiar with them.

        They aren't computers in the modern sense. They simulate linear and
        some nonlinear continuous time systems. They don't do steps and programming
        is patch cables to wire the analog components in the correct configuration
        for your problem and setting pots to set your coefficients. I think they
        also had parts such as capacitors on plug in units to set the right values.
        I think we have people on the list who have more knowledge than me who
        hopefully will chime in.

        Some promising links for info.
        http://en.wikipedia.org/wiki/Analog_computer
        http://ericarcher.net/devices/analog-computer-bouncing-ball/
        http://courses.engr.illinois.edu/ece486/labs/lab1/analog_computer_manual.pdf
      • Dave
        ... I have never used an analog computer in anger but I was taught to use them as part of my Mathematics degree in 1972/3 and latterly I am part of the team
        Message 3 of 18 , Sep 8, 2012
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          > -----Original Message-----
          > From: midatlanticretro@yahoogroups.com
          > [mailto:midatlanticretro@yahoogroups.com] On Behalf Of David Gesswein
          > Sent: 08 September 2012 01:23
          > To: midatlanticretro@yahoogroups.com
          > Subject: Re: [midatlanticretro] Analog Computers - General description
          >
          >
          > On Fri, Sep 07, 2012 at 11:50:32PM -0000, joshbensadon wrote:
          > > Are you saying the transistors in the old analog computers
          > are robust?
          > > I haven't looked at part numbers yet, but they look like the old
          > > germanium TO-05 case style.
          > >
          > It wasn't intended to be that strong a statement. I don't
          > have an analog computer so don't have direct knowledge. From
          > other electronics the lower speed stuff tended to use
          > transistors with breakdown voltages higher than the supply.
          > Also that a quick look assuming the parts are easily visible
          > will give you an idea of if overvoltage is likely to damage
          > the unit. if
          > the breakdown voltage is somewhat higher than the
          > preregulated voltage
          > then your unlikely to fry all the transistors if the supply looses
          > regulation.
          >
          > > 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 have never used an analog computer in anger but I was taught to use them
          as part of my Mathematics degree in 1972/3 and latterly I am part of the
          team that maintains and demonstrates the Hartree Differential Analyzer at
          the Museum of Science and Industry, Manchester England. If you have browser
          other than IE you can see a flash video of the Hartree here:-

          http://www.cs.man.ac.uk/~chl/hartree.html

          I include this as the Hartree is a mechanical analog (analogue in the UK)
          computer and a direct parent of the Electronic Analogue Computer. On the
          Hartree we use the number degrees a shaft has turned to represent a variable
          in our "program" , in an Analog Computer we use a voltage to represent a
          variable.

          The feature of what are vernally termed "analogue computers" (or
          "differential analysers" in early references) is being able to "calculate"
          the area under a curve, which mathematicians call "integration". This might
          not seem a very useful thing to do, but in fact this ability will be needed
          to solve a wide range mathematical problems involving "time".

          At a simple level if we have a graph of say the speed of a car, and plot
          this, then the area under the curve will give the distance travelled. If we
          have a graph of acceleration then the area under that is speed. So if we
          have two "integrators" then from acceleration we can calculate speed and
          distance. This becomes interesting when we have equations that connects
          these together. So if you fire a projectile (much nicer word than shell)
          from a gun and you know the angle of the gun, the initial velocity of the
          shell, the mass of the shell and its coefficient of drag then using Newton's
          Laws of motion we can develop equations that link these together. These are
          called differential equations. We can then set up a "program" on our analog
          computer than shows where the shell is at any point in time. Of course
          usually we are only interested in where it actually lands, but if we include
          air resistance in the equations we typically need to do the whole
          calculation to figure this out. Historically this calculation is what drove
          analogue computer design and development.

          So as part of its commissioning testing the Hartree was used to simulate
          coal consumption in Railway Engines (I am told Hartree was a bit of a Steam
          nut), calculate cooling rates in steel ingots, simulate noise in
          transmission lines and model the stability of aircraft. Of course the
          driving force behind the initial development of all this stuff is gunnery
          calculations.

          The plug in capacitors mentioned below are what perform the integration, the
          amount of charge stored in these capacitors represents the area. For a low
          voltage it will charge slowly, for a higher voltage more quickly. There are
          high gain circuits (operational amplifiers) around the capacitor so its
          charge doesn't dissipate. They are often on plug ins and switchable as
          changing the values of the cap allows the program to run at different
          speeds. For a problem such as the cooling of an ingot, we probably don't
          want to wait several hours for our program to run, so we speed it up by
          using smaller capacitors which charge more slowly. For problems like noise
          in transmission lines where we are dealing in pulses travelling at close to
          the speed of light then we will have to slow things down a bit. If we are
          using one as part of an aircraft simulator for training pilots then
          essentially we want real time.

          They were widely used as they were much cheaper to make than a digital
          computer and they could solve the problems in real time. In 1972 at college
          we had three commercial analogue computers and I think 12 or 14 constructed
          by the lab technicians.


          > I'm not that familiar with them.
          >
          > They aren't computers in the modern sense. They simulate
          > linear and some nonlinear continuous time systems. They don't
          > do steps and programming is patch cables to wire the analog
          > components in the correct configuration for your problem and
          > setting pots to set your coefficients. I think they also had
          > parts such as capacitors on plug in units to set the right
          > values. I think we have people on the list who have more
          > knowledge than me who
          > hopefully will chime in.
          >
          > Some promising links for info.
          > http://en.wikipedia.org/wiki/Analog_computer
          > http://ericarcher.net/devices/analog-computer-bouncing-ball/
          > http://courses.engr.illinois.edu/ece486/labs/lab1/analog_compu
          ter_manual.pdf


          Dave Wade G4UGM
          Illegitimi Non Carborundum
        • s100doctor
          ... I m really pleased, as an engineers of the 1970 s, to see a brief presentation of mechanical analog (differential) computers in the MARCH discussion. This
          Message 4 of 18 , Sep 8, 2012
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            --- In midatlanticretro@yahoogroups.com, "Dave" <dave.g4ugm@...> wrote:
            >
            > I have never used an analog computer in anger but I was taught to use them
            > as part of my Mathematics degree in 1972/3 and latterly I am part of the
            > team that maintains and demonstrates the Hartree Differential Analyzer at
            > the Museum of Science and Industry, Manchester England. If you have browser
            > other than IE you can see a flash video of the Hartree here:-
            >
            > http://www.cs.man.ac.uk/~chl/hartree.html
            >

            I'm really pleased, as an engineers of the 1970's, to see a brief presentation of mechanical analog (differential) computers in the MARCH discussion. This is truly "lost technology" by my standards and I'm glad it's getting support in the UK.

            To answer the original question, about the nature and use of electronic analog computing. If you are interested enough, obtain some books on the subject from the era. Many engineering books about analog computing are available cheaply from Amazon - cheaper than those books on eBay that aren't listed by title, in order to sell them at higher prices. In addition, you can get many of those same books by loan through your local library, from university collections. That service is called "interlibrary loan" and you can talk to your local library about that service.

            While it's fun to talk about these things and discuss questions and answers thru email - it's more PRODUCTIVE to do the homework of reading the available literature, and that means paper books. They won't be available for many years longer; that's another discussion. They were designed to explain the use of these analog computers, to people would use them "in anger" as the poster described. You will need to understand differential equations, just as any binary programmer of microcomputers needs to understand Boolean logic and binary arithmetic.

            But differential equations STILL describe processes and model systems, from chemical to economic, that are still modeled today. These machines can STILL do some "work" that means something. They won't play Adventure, but you can have an adventure in learning about and using them.

            Herb Johnson
            retrotechnology.com
          • Mike Loewen
            ... You might start with The Handbook of Analog Computation : http://www.analogmuseum.org/library/eai_handbook.pdf Also on that page are dozens of manuals,
            Message 5 of 18 , Sep 8, 2012
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              On Sat, 8 Sep 2012, s100doctor wrote:

              > To answer the original question, about the nature and use of electronic
              > analog computing. If you are interested enough, obtain some books on the
              > subject from the era. Many engineering books about analog computing are
              > available cheaply from Amazon - cheaper than those books on eBay that
              > aren't listed by title, in order to sell them at higher prices. In
              > addition, you can get many of those same books by loan through your
              > local library, from university collections. That service is called
              > "interlibrary loan" and you can talk to your local library about that
              > service.

              You might start with "The Handbook of Analog Computation":

              http://www.analogmuseum.org/library/eai_handbook.pdf

              Also on that page are dozens of manuals, handbooks, tutorials and
              lectures about analog computing:

              http://www.analogmuseum.org/english/library.html


              Mike Loewen mloewen@...
              Old Technology http://sturgeon.css.psu.edu/~mloewen/Oldtech/
            • joshbensadon
              ... Thanks Herb, Your good words are always a welcomed sight. Yes, I have much reading to do. The online book referenced by Mike appears to be a real gem,
              Message 6 of 18 , Sep 8, 2012
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                --- In midatlanticretro@yahoogroups.com, "s100doctor" <hjohnson@...> wrote:
                > To answer the original question, about the nature and use of electronic analog computing. If you are interested enough, obtain some books on the subject from the era. Many engineering books about analog computing are available cheaply from Amazon - cheaper than

                Thanks Herb,

                Your good words are always a welcomed sight.
                Yes, I have much reading to do. The online book referenced by Mike appears to be a real gem, especially since this Analog Computer is an EAI model. I did a search for "Analog Computer" on Amazon and got 3,000+ hits. Can you help me out with a known title?

                Further, would you know if schematics can be found for these old computers, sorry I don't have the exact model number. If you do have these schematics in your collection, please name your price.

                Cheers,
                Josh
              • joshbensadon
                ... Mike, Thanks! That s a great place to start. As usual, I have much homework to do... so I ll be here in the corner, quietly reading if anyone wants me.
                Message 7 of 18 , Sep 8, 2012
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                  --- In midatlanticretro@yahoogroups.com, Mike Loewen <mloewen@...> wrote:
                  >
                  > You might start with "The Handbook of Analog Computation":
                  >
                  > http://www.analogmuseum.org/library/eai_handbook.pdf
                  >
                  > Also on that page are dozens of manuals, handbooks, tutorials and
                  > lectures about analog computing:
                  >
                  > http://www.analogmuseum.org/english/library.html
                  >
                  >
                  > Mike Loewen mloewen@...


                  Mike, Thanks! That's a great place to start. As usual, I have much homework to do... so I'll be here in the corner, quietly reading if anyone wants me.

                  I'm going to search around that site to see if they might even have schematics for this EAI computer.

                  Cheers!
                  Josh
                • s100doctor
                  ... I just saw your message, about two weeks after you posted it. Contact me privately, if you want specific things from me, Josh. I don t read this MARCH list
                  Message 8 of 18 , Sep 24, 2012
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                    --- In midatlanticretro@yahoogroups.com, joshbensadon wrote:
                    >

                    > Thanks Herb,
                    >
                    > Your good words are always a welcomed sight.
                    > Yes, I have much reading to do. The online book referenced by Mike appears to be a real gem, especially since this Analog Computer is an EAI model. I did a search for "Analog Computer" on Amazon and got 3,000+ hits. Can you help me out with a known title?
                    >
                    > Further, would you know if schematics can be found for these old computers, sorry I don't have the exact model number. If you do have these schematics in your collection, please name your price.
                    >
                    > Cheers,
                    > Josh

                    I just saw your message, about two weeks after you posted it.

                    Contact me privately, if you want specific things from me, Josh. I don't read this MARCH list on any regular basis, or engage in long discussions on it in general. That's simply not what I do, why that may be is not particularly relevant except to say it's nothing to do with you.

                    Also, I can't follow exactly what schematics you are looking for, and how on the one hand you have some kind of EAI computer, but on the other hand don't know what model it is.

                    I'm sorry you find the learning situation about them, to be complicated and with an unclear path. That's the nature of technology which is obsolete, generally used only by scientists and specialists, and largely documented only in books from the period. And from a period before personal computers and digital networking of any kind - not that most of that would help.

                    Since I'm of that obsolete and ancient time, and I was an engineer, I know something about it. But not something I can point to easily, that's in one book, or that can be learned by reading one or two books.

                    Sorry, but that's not my fault. It's old, it's complicated, it involves knowledge about things. Without that knowledge, operating an analog computer will make no sense at all, and seeing it run will be incomprehensible. It was difficult at the time, that knowledge is still difficult today. I can't reasonably think of an easy way to get around those circumstances - either about the background knowledge needed, or the operational knowledge to use such things, as they are almost IDENTICAL - and entirely unlike personal computing today.

                    herb
                  • joshbensadon
                    ... Please let me explain. It s not my computer, but it belongs to the York Univeristy Museum operated by Zbigniew Stachniak. I only get to work on this
                    Message 9 of 18 , Sep 24, 2012
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                      --- In midatlanticretro@yahoogroups.com, "s100doctor" <hjohnson@...> wrote:
                      >
                      > Also, I can't follow exactly what schematics you are looking for, and how on the one hand you have some kind of EAI computer, but on the other hand don't know what model it is.
                      >

                      Please let me explain. It's not my computer, but it belongs to the York Univeristy Museum operated by Zbigniew Stachniak. I only get to work on this machine once a week or every two weeks, and I didn't get to see the exact model of it. Zbigniew told me the model number last week, but my lack of short term memory strikes again.

                      I'm not in any rush to learn all about it, I'll just take my time and enjoy the ride. I've already found some information online (thanks to the posts in this group).

                      PS. My contact with Zbigniew should also be credited to Bill and Evan's Hope presentation. I live 10 minutes from York and have been visiting the campus for years but have never known about their Vintage Computer Museum until now.

                      Cheers,
                      Josh
                    • Evan Koblentz
                      ... Awesome. Tell Zig I said hello.
                      Message 10 of 18 , Sep 24, 2012
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                        >>> My contact with Zbigniew should also be credited to Bill and Evan's Hope presentation. I live 10 minutes from York and have been visiting the campus for years but have never known about their Vintage Computer Museum until now.

                        Awesome. Tell Zig I said hello.
                      • B. Degnan
                        ... Univeristy Museum operated by Zbigniew Stachniak. I York, PA? ... Hope presentation. I live 10 minutes from York and have been visiting the campus for
                        Message 11 of 18 , Sep 24, 2012
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                          > >
                          >
                          > Please let me explain. It's not my computer, but it belongs to the York
                          Univeristy Museum operated by Zbigniew Stachniak. I


                          York, PA?

                          >
                          > PS. My contact with Zbigniew should also be credited to Bill and Evan's
                          Hope presentation. I live 10 minutes from York and have been visiting the
                          campus for years but have never known about their Vintage Computer Museum
                          until now.
                          >

                          I live kind of close and would be interested to drive out some time to
                          check it out.

                          http://www.cse.yorku.ca/museum/

                          What's actually on display there?

                          Bill
                        • Evan Koblentz
                          ... Toronto, Canada.
                          Message 12 of 18 , Sep 24, 2012
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                            >> York, PA?

                            Toronto, Canada.
                          • joshbensadon
                            ... No, York University in Toronto, Ontario. ... I m a newbie at old computers, so I ll probably miss a few key systems. I think Zbigniew s favorite is the MCM
                            Message 13 of 18 , Sep 24, 2012
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                              --- In midatlanticretro@yahoogroups.com, "B. Degnan" <billdeg@...> wrote:
                              > York Univeristy Museum operated by Zbigniew Stachniak. I
                              >
                              >
                              > York, PA?
                              >

                              No, York University in Toronto, Ontario.

                              > What's actually on display there?
                              >


                              I'm a newbie at old computers, so I'll probably miss a few key systems.
                              I think Zbigniew's favorite is the MCM 70 computer, he wrote a whole book on it. There are lots of other systems as you saw in the web link you provided, but I'm not sure what's worth mentioning? Dynalogic systems? There's some of the the more familiar common systems, but several word processors and obsure ones I don't remember the names of. But there is a whole line of MCM computers. These were based on the 8008 and when that processor became too slow, they went the way of emulating the processor with faster logic chips so they wouldn't have to re-write software.

                              Anytime you're in Toronto, I'd be happy to show you around.

                              Cheers,
                              Josh
                            • Jim Scheef
                              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 14 of 18 , Dec 8, 2012
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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 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.


                              • Bob Schwier
                                ________________________________ From: Jim Scheef To: midatlanticretro@yahoogroups.com Sent: Saturday, December 8, 2012 9:44 AM Subject:
                                Message 15 of 18 , Dec 8, 2012
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                                  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


                                • Ken
                                  ... 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 16 of 18 , Dec 8, 2012
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                                    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.
                                    http://www.youtube.com/watch?v=s1i-dnAH9Y4

                                    - Ken
                                  • s100doctor
                                    ... 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 17 of 18 , Dec 10, 2012
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                                      --- 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.
                                      > http://www.youtube.com/watch?v=s1i-dnAH9Y4
                                      >
                                      > - 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
                                    • William Donzelli
                                      ... 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 18 of 18 , Dec 10, 2012
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                                        > 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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