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Charles Babbage's "Difference Engine"

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  • Charles Babbage's "Difference Engine"

    Not exactly new news to many here, I'm sure, but there was a story about this on NPR this AM (I hadn't heard of it before). Apparently two were built... one for the Science Museum in London and one for Nathan Myhrvold (of Microsoft) who funded the project. Myhrvold's is the one currently on loan to The Computer Museum in CA. Not really ANY talk of the machining involved, unfortunately, but it's a fascinating story and machine nonetheless:

    LINK to NPR

    Link to the Computer History Museum








  • #2
    Oh wow, I've been wanting to see the London Difference Engine -- I didn't know they made two!

    Time to visit the home office (in Santa Clara, about 4 miles from the Computer History Museum in Mountain View)!

    Edit: they didn't make two. The London Science Museum constructed Babbage's Difference Engine in 2002, and the guy from Microsoft commissioned a copy of it, that was just completed last year.

    The Difference Engine in London isn't a replica -- Charles Babbage never built it, so the version the Brits made 150 years later was the first one
    Last edited by lazlo; 12-10-2009, 10:00 AM.
    "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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    • #3
      It is a lot more complex than that Robert.

      Physical Legacy
      Aside from a few partially complete mechanical assemblies and test models of small working sections, none of Babbage's designs was physically realized in its entirety in his lifetime. The major assembly he did complete was one-seventh of Difference Engine No. 1, a demonstration piece consisting of about 2,000 parts assembled in 1832. This works impeccably to this day and is the first successful automatic calculating device to embody mathematical rule in mechanism. A small experimental piece of the Analytical Engine was under construction at the time of Babbage's death in 1871. Many of the small experimental assemblies survived, as does a comprehensive archive of his drawings and notebooks.


      http://www.computerhistory.org/babbage/engines/
      There were three engines. Two difference engines which are mechanical calculators, not computers, and the Analytical engine, which is a computer.
      Free software for calculating bolt circles and similar: Click Here

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      • #4
        I'm very familiar with Babbage's machines Evan. The Difference Engine calculated tables of polynomial functions. That was the reason for the printer.

        He designed his Analytical Engine (a more general purpose computer) after he designed Difference Engine No. 1. This machine, Difference Engine No. 2, was the last machine he designed, although he tweaked the design for the Analytic Engine up to his death.

        The London Science Museum made models of both the Difference Engine No. 2 and the Analytical Engine. The Microsoft copy is the Difference Engine No. 2.

        Still, machine art (and compute science brilliance) at it's finest.

        I can't link to the video in Magee's second link, but it's highly recommended. Watching the gears in motion, and the carry chains spiraling upward is mesmerizing.
        Last edited by lazlo; 12-10-2009, 10:26 AM.
        "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

        Comment


        • #5
          I'm very familiar with Babbage's machines Evan.
          Then you should know that he actually built a working portion of the first difference engine.

          Free software for calculating bolt circles and similar: Click Here

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          • #6
            Yep, it was a prototype module (essentially a single carry chain) built by Joseph Clement, Babbage's machinist for the Difference Engine No.1 under contract to the British Government.

            Babbage shared a lot of traits with Edison, and was a prick to work with. Clement left to run his own machine shop, and no further work on the Difference Engine No. 1 was ever completed.

            Clement was a pioneer of standardizing screw threads, and had a young journeyman who worked for him, by the name of Joseph Whitworth
            "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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            • #7
              Anyone interested should check out a book - The Cogwheel Brain by Doron Swade (isbn 0-316-64847-7)

              I think that I had blabbed about Babbage before but...

              I read the book and found the history of this interesting. Babbage can be given credit for pushing machines and machinists for more accurate and precise parts for his time. He needed gears that matched each other very closely and he struggled to find shops and people that could do this.

              I was lucky enough to have seen the machine that was built in the museum in London and also the starts for the second machine. The info at the museum noted that the second machine was to be sent to the US. They gave the impression that the machine would tour US museums before being on permanent display on the west coast somewhere.

              Here is a photo that I took (I could have done a bit better) Difference Engine #2

              rock~
              Civil engineers build targets, Mechanical engineers build weapons.

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              • #8
                Originally posted by rockrat
                Babbage can be given credit for pushing machines and machinists for more accurate and precise parts for his time. He needed gears that matched each other very closely and he struggled to find shops and people that could do this.
                There was an excellent Scientific American article about the London Science Museum's construction of the Analytical Engine back in early 2000. They noted that the British government pulled funding for the Difference Engine No. 1, partly because it was very prone to jamming. Gears were hand-cut back then, so getting long chains to inter-mesh was hopeless.

                IIRC, the London Museum's gears are CNC cut?

                Thanks for the book citation Rock -- I remember that from the last time we discussed Babbage's machines. I'll have to get a copy.
                "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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                • #9
                  Originally posted by lazlo
                  IIRC, the London Museum's gears are CNC cut?
                  I dont believe so, the book states otherwise. But I didnt see them being cut either.

                  The book does parallel the building of the machine in London with Babbages challenges. So looking at a time line the reader jumps back and forth as the chapters change. The writing is god enough that you know where you are on the time line. But, they do note that the funding required that the machine be built by a specific date and it must be built using processes of the time. They did allow current manual lathes and manual mills to be used. But there was so much hand fitting.

                  It was finished only hours (or a day or so) before the unveiling and when Doron tried to turn the handle the first time it froze up a bit. After a little checking they realized that it took just a bit more force than he was applying. After the first turn or so things set in and it was reported to turn fairly easily.

                  I really become enthralled with the book, I just couldnt put it down. This is rare for me. Normally the only books that will content me are old machine manuals or books on casting, induction heating or something.

                  I found the book for a few dollars at a local computer store that was selling all of its books off. It was well worth the price.

                  rock~

                  edit - a few more photos

                  Difference engine #2 second shot

                  The machine being made for the US

                  And I talked to Charles Babbage! Well I talked to his brain at least Brain

                  Sorry for the focus, I must have been too excited and just didnt get my camera set correctly for the lighting. Gawd I'm a geek.
                  Last edited by rockrat; 12-10-2009, 11:16 AM.
                  Civil engineers build targets, Mechanical engineers build weapons.

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                  • #10
                    There was an excellent Scientific American article about the London Science Museum's construction of the Analytical Engine back in early 2000.
                    I kept that copy :-) I'm a Babbage fan!

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                    • #11
                      How things change. There are working Difference engines made with Lego blocks and an Analytical engines made with Mechano.

                      Check out this over-achiever.

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                      • #12
                        What will future hobbyists be able to do?

                        Seeing these hobbyist versions of famous machines of the past, one wonders what will future hobbyists be able to do? Using Meccano, hobbyists have recreated Vannevar Bush's Differential Analyzer, and others have recreated parts of Babbage's various Engines. The original projects taxed the resources of major universities and even sovereign governments.

                        Now, using commercially available toys(!), an individual can build working replicas. What will hobbyists be building in 100 years?

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                        • #13
                          Originally posted by Tony Ennis
                          How things change. There are working Difference engines made with Lego blocks and an Analytical engines made with Mechano.

                          Check out this over-achiever.
                          Meccano computers are hardly a recent development!

                          http://computerworld.co.nz/news.nsf/...257317001AA6D1
                          Used to design hydro dams, and to knock them down, also to track rabbit populations!

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                          • #14
                            so the second one is at the computer museum in mountain view right now?

                            i'll have to go check that out. it's just a 15-20 minute drive up the road from here...
                            -paul

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                            • #15
                              Originally posted by lazlo
                              Yep, it was a prototype module (essentially a single carry chain) built by Joseph Clement, Babbage's machinist for the Difference Engine No.1 under contract to the British Government.

                              Babbage shared a lot of traits with Edison, and was a prick to work with. Clement left to run his own machine shop, and no further work on the Difference Engine No. 1 was ever completed.

                              Clement was a pioneer of standardizing screw threads, and had a young journeyman who worked for him, by the name of Joseph Whitworth
                              There was a falling out between Babbage and Clement, Babbage complained that Clement was spending more time and money perfecting his machine tools instead of working on the engine.
                              Clement's reply was that there were no machine tools accurate enough to do this work so the tools had to be done first.

                              A bit of a chicken and egg situation but the bugbear was that these were Clements tools and any work done on them benefited Clements more than Babbage.
                              .

                              Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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