Mechanical Analog Computers
Mechanical Analog Computers
(OP)
I recently watched a documentary on battleships built during the 1930's-1940's. I was fascinated to learn that the fire control computers were 100% mechanical analog devices that considered 10 or more input variables to compute in real time the gun aiming. Does anyone know of any books that discuss mechanical analog computers? Aparently they were superior to electrical devices in the 1930's to 1950's time frame.





RE: Mechanical Analog Computers
www.historychannel.com
A search for mechanical analog computers brought up 2 results. Below is a snip-it from the first.
Although the development of digital computers is rooted in the abacus and early mechanical calculating devices, Charles Babbage is credited with the design of the first modern computer, the analytical engine, during the 1830s. American scientist Vannevar Bush built a mechanically operated device, called a differential analyzer, in 1930; it was the first general-purpose analog computer. John Atanassoff constructed the first semielectronic digital computing device in 1939. The first fully automatic calculator was the Mark I, or Automatic Sequence Controlled Calculator, begun in 1939 at Harvard by Howard Aiken, while the first all-purpose electronic digital computer, ENIAC (Electronic Numerical Integrator And Calculator), which used thousands of vacuum tubes, was completed in 1946 at the Univ. of Pennsylvania.
You'll probably want to continue your search with Charles Babbage (in 1830 -- WOW!) and his analytical engine or Vannevar Bush (100 years later!) and his differential analyzer.
--Scott
RE: Mechanical Analog Computers
The other analogue computers that I know of were the torpedo controllers, used to program the torpedoes in WW2. They were called TDCs, if you ask on the subs board at the same site then you will learn much.
Cheers
Greg Locock
RE: Mechanical Analog Computers
Just a note about the first electronic digital computer ever built. John Atanassoff actually built the first one in, I believe, the early 50's with a graduate student named Berry at Iowa State University....called, obviously enough, the ABC (Atanassoff Berry Computer). The computer science building in Ames, Iowa has a re-creation of his device on display. It preceeded the ENIAC.
RE: Mechanical Analog Computers
RE: Mechanical Analog Computers
is a history of Hannibal Ford's analog computers, you will probably find the reference list interesting, and the photos terrifying.
Cheers
Greg Locock
RE: Mechanical Analog Computers
http://www.eugeneleeslover.com/USNAVY/CHAPTER-19-A.html
Fascinating stuff
Cheers
Greg Locock
RE: Mechanical Analog Computers
First: Mr. Babbage is well known on methods to dechiper cypher. He worked in the middle of the 1800's.
His story is told by by professor Ole Immanuale Franksen of the Danish Technical University. He retired recently, but his work: Mr. Babbage's Secret, The Tale of a Cypher - and APL, has 315 pages with information on what and how he did. IBM Denmark funded his writings. The book is frem the Strandberg, Birkeroed, Denmark editors.
Second: In 1965 I, as a student organisation representative took over some rooms in the basement of the Institute for Applied Mathematics, to be used for a printing office. These rooms were perfectly suited because a Professor Richard Petersen build a mechanical, differential calculator, with many components in brass. It was heavy and required a reinforced floor.
They finished the construction in ten years time, and left the project, because they began to build the first electronic computer, DASK, which came into operation 1959.
Regards
Carl Christian Lassen, M.Sc.Mech.Eng.
External Associate Professor, Danish Technical University
President C.C. Lassen Consulting Engineers
RE: Mechanical Analog Computers
RE: Mechanical Analog Computers
RE: Mechanical Analog Computers
Having struggled with these non-linear differential equations I knew what immense work it was to do one of these calculations (round´s rotation, wind, speed of round, earth's rotation, speed and angles of target and and..)and there it was! The machine that did it in seconds. Impressive.
I remember differential gears, integrator disks, some cams with non-linear functions, servo-motors and selsyns. The result was plotted on a gridded frosted glass that could be photographed and wiped clean after each calculation. I remember no numeric output. There was probably none.
The producer of these machines was (I think)Svenska Aktiebolaget Tradlos Telegrafi (SATT), a subsidiary of Svenska Radiobolaget (SRA), which was the Ericsson radio company. It is possible that the Arenco company was doing most of the mechanical work.
The computer that I write on now has the ability to do the work of hundreds or thousands of those several hundred kilograms heavy mechanical wonders. It is fascinating.
RE: Mechanical Analog Computers
No more things should be presumed to exist than are absolutely necessary - William of Occam
RE: Mechanical Analog Computers
http://www.sciam.com/
I was told that until the advent of radar to input the range to target more accurately to the fire control computer it was still "one over and one under and then bang"
Any of the Battleship monuments have a tour of the fire control center and you can see the computer along with its' input systems. This is one case data input had to be accurate the first time.
Didn't Babbage have a female mathematician as an assistant in his work?
Most of the money for the first electronic computers was from the Ordinance Department to help with the computation of artillery tables which were then being calculated with logs.
I was working when the change was made from mechanical desktops to big IBM mainframes.
The mechanical desktops had got to the point that you could extract a square root and have accumulating totals. Another mechanical marvel was the bank tabulating machinery.
RE: Mechanical Analog Computers
RE: Mechanical Analog Computers
Funny, I thought Colossus was the first digital computer.
And Manchester Mark One was first stored program computer.
And LEO (Lyon's Electronic Office) was first commercial computer.
And that German chappie had a good go at digital computers using relays during the last global conflict...
RE: Mechanical Analog Computers
RE: Mechanical Analog Computers
It was digital, but used valves and relays. Built by the (British) Post Office - makes sense.
Cheers
Greg Locock
RE: Mechanical Analog Computers
It was designed to decode German encrypted transmissions.
It used paper tape to hold the data being decrypted and various types of thermionic valve (vacuum tube) as processing elements.
It was not a general purpose computer as such, but was designed for one specific task.
All details of this machine and others like it were secret until 1974(ish), when a books describing the UK/USA code decyphering activities were published.
Much of the actual machinery and blueprints etc. were destroyed after the war on the orders of Winston Churchill.
A working model of Colossus is being recreated at Bletchley Park in the UK.
RE: Mechanical Analog Computers
Era-1) Early devices which manipulated by hand include abacus B.C.3000, Napier’s bones, the slide rule A.C. 1600. Then mechanical Calculators - Pascal’s calculator A.C.1642, Jacquard’s loom 1801,Babbage’s difference engine (A.C.1822), Programmable machines Babbage’s analytical engine (1834), Hollerith’s punch card equipment (A.C.1890).
Era-2) Covers years 1920-1950: Atanasoff Barry Computer-ABC, 1942, Electromechanical MARK-I, 1944, First full-scale electronic computer ENIAC (1946), and Stored program computers UNIVAC (1951), first commercial computer IBM 650, 1954. First integrated circuit computer is operated on (1958), then main frames (1965). Minicomputer 1963. First personal computer 1977,
Era-3) Microprocessor age starts after 1980. The Pentium and multimedia technology came out in 1993. The World Wide Web and Internet browsers appeared in 1994.
The computer age begins Mark-I computer in 1944. Then the evaluation of computers classified by technological generations: First generation 1951-58 the vacuum tube, second generation 1959-64 the transistor, the third generation 1965-70 the Integrated Circuit, the forth generation 1971- Present, the micro-processor (1971) And Minicomputers (1975), Microcomputer (1981). Personal Computer age and network Mobil communication is sated.
Computer technology started as computing machine including the invention of transistors and development of integrated circuits, the establishment of communication satellites, and advance in optic technology. To day, desktop-size has more computing power than the room-size machines of the 1940s and can exchange Information quickly via global communication systems.
Computer machinery improved as modern computers by the use of microelectronics. Microelectronics made them law cost, high speed, and small in size. So computers may roughly classified by size and computing capacity: Mainframe computers have greater computing capacity then do personal computers.
They are varying in size and capability. Supercomputers are most powerful computers that are used for special cases as space research activities. Workstation has power between mid size mainframe and PC. Personal Computers go into different categories as Desktop, Laptop or Notebook, or Hand size-Palm Computer. Communication and computer Networks: At the mid of 1975 the major changing in computer usage was Communication be come network systems which link machines and people with companies and countries. After 1980’s PC be come as a network terminal. The computer networks are evaluated as Local Area Networks (LAN) and Wide Area Networks (WAN).
RE: Mechanical Analog Computers
During my time in the RAF, as an Instrument Technician (NAV), I worked with two electro-mechanical analogue computing devices. One type was a bombsight calculator (MkXIV and T2), the other was A.D.R.I.S (Automatic Dead Reckoning Indication System) that was pneumatic/mechanical in nature. There were several airborne devices of this type used in the 1950 - 1970 period by the RAF. I think the USAF used to use a K7 bombing system that was similar to H2S with a couple of differences? Ground Position Indicators (GPI Mk1 to Mk7) were 'all gears and cogs! Does anyone else remember these airborne devices? One day I want to be able to gain access to the UK Dept of Defence records and write a book describing the design and research that went into such devices.
Regards
RE: Mechanical Analog Computers
It showed a reconstruction of the fire control mechanical computer in use, but without going into any detail, which was a pity.
The gunlaying information was relayed to the turrets electrically.
rgds
Zeit.
RE: Mechanical Analog Computers
Very interesting and a truly prescient design.
rgds
Zeit.
RE: Mechanical Analog Computers
There is a great shot in this film of a real differential analyzer doing the supposed orbit calculations which will confirm armageddon, and it seems to be hooked up to some sort of early pen plotter, complete with Barbara Rush in a white coat playing the obligatory "beautiful daughter of the professor" role. It's referred to as "D.A." ("send this data to D.A."). It must have been state of the art for the time - possibly faster and more reliable than the digital computers of the day, and certainly far more visually impressive of course - especially for us mechanical guys. There are some other technically interesting talking points in this film, but that's another story.
RE: Mechanical Analog Computers
Regards
RE: Mechanical Analog Computers
In the US is a show is coming on The History Channel about the "Antikythera Mechanism" discovered in Greek ship wreck.
Here is website for information on this mechanism
http://homepage.mac.com/casewright/essays/antikythera.html
RE: Mechanical Analog Computers
RE: Mechanical Analog Computers
rmw
RE: Mechanical Analog Computers
RE: Mechanical Analog Computers
Interesting trivia on the cards themselves: When Mr. Hollerith developed the punch card system for the 1890 USA census he had to make a decision on the dimensions of the cards. He picked 7 3/8" x 3 1/4" which was the size of US paper money at that time. The money "shrank" to its' current size in 1929, but the cards are unchanged.
RE: Mechanical Analog Computers
Actually, I never used paper tape until much later, and not in computer situations, because computers were well past that, but in telex machines, which were still in vogue at the time. (ain't e-mail great??)
And, yes, it was the late '60's, and the early '70's.
rmw
RE: Mechanical Analog Computers
Had only one class that used the IBM370, but found the WONDERFUL utility called RJE. Remote Job Entry from the PDP-10, allowing me to edit the program in a REAL editor and just shoot the stuff into the ether and get the printout from the computer desk minutes later.
AWESOME
TTFN
RE: Mechanical Analog Computers
After one term at Princeton, when to my horror I discovered that they weren't ready for me (they still don't have a counterpart to MIT's UROP! Hope to encourage them...)
and I wasn't ready for them, either, I licked my wounds and became a Navy fire control technician. At FT school (Bainbridge, Md.), I really thought Heaven had come to earth when, well ahead of the class, I saw something with custom transparent-plastic covers replacing the cast-Al-alloy ones: it was the...
[Mark 1A mechanical analog computer:]
<http://dcoward.best.vwh.net/analog/ford.htm>
(Doug is traveling, and looking for work, btw!)
Those pages show the WW II version, the Mark 1. (Apparently, there were different Mark 1s?) The WW II version had a mechanical resolver working backwards that didn't work too well; sometimes needed operator help. Post-war, a design re-thinking fixed that. That was the Mark 1A.
As to specs: Current consumption is apparently worst-case, all synchro receivers locked at worst-case angle. (Educated guess). The computer, itself, ought to run easily on a 20 A. 120V 60 Hz circuit.
I have a mechanical schematic of that machine, bought from Doug, which is about 19in. by 48 in. or so. I still understand maybe 2/3 of it.
===
[Web page]
One really-good Web page on the Mk.1 is at the DE220 Web site:
<http://tinyurl.com/ljv5>, which came from:
<http://www.de220.com/Armament/Fire%20Directors/Mk%201%20Computer/Mk%201%20Computer.htm>
I recall reading that page some time ago, and could make some comments about it, but iirc, it's solid. No silly quasi-religious nonsense about True North.
There are some splendid National Archives images of some of the innards, although not of the really interesting sections.
Chop off the right end of the full URL some, to read a lot of very good material. Thank the site's creator!
[Btw, the 1.1-ich gun mount, also described (photos, at least) at that site, has a traverse axis; apparently it doesn't develop gimbal lock when firing straight up. IIrc, its drive servos were maintenance nightmares.]
{Repairs!]
I was extremely lucky to have occasion to repair a Mark 1A; there was a fabulous two-volume set of very-detailed instructions on disassembly, field repair (iirc), and reassembly/realignment. (HELP! Does anyone remember/know the OP number?)
We took off about 15% of the top to get at the loose screw. It was a rare treat to gently exercise the individual mechanisms, clean and lube if needed, wrap them in quite-clean rags, and put them behind the fire control switchboard.
Despite their formidable complexity, these computers were remarkably reliable; they were designed and built by very capable engineers.
===
[Misinformation, elsewhere]
There's some misinformation on the Web, as well. The integrator discs were *not* an inch thick; more like 1/4 or 3/8 inch. (Also double-sided, so they could be reversed if worn.)
The original of the article, in the Annals of the History of Computing, about Ford and Newell, has an excellent photo of an integrator. However, copies of that article do simply wretched things to the gray scale on that photo.
Also, True North, mentioned in almost religious tones on one Web site, is simply bogus. Own Ships Course was a synchro input from the gyrocompass. There was no Coriolis Effect calculation, either.
See also earlier comments about power consumption -- not really misinformation, just incompletely-defined info. (The high current was probably part of a spec. for determining power requirements and wiring for the worst case.)
===
[Some details]
The Mk. 1A has four 3-D arbitrary-function cams that hold the ballistic information for the gun and projectile the machine was built for.
The integrator outputs (through a chain of servos) drove the sights in the gun director to help keep it on target (aided tracking); tracking errors went through clutches to position the integrator carriages.
[Electromech. servos]
There's a quite-detailed description (sorry, no images) of the electromechanical position servos in the Mk.1/1A in the YahooGroups archives on the Howthingwork list, which I have contributed a great deal of material to.
It was written roughly six months ago, I think. Sorry not to have a link, now.
Really briefly, bang-bang, tungsten contacts, reversible two-phase cap.-run motor, velocity-feedback stabilized by magnetic drag* and spring. (Think high-torque-output traditional speedometer.) Large errors were stored in intermittent gearing; null was like odometers at the all-nines/all-zeros carryover.
*PM and squirrel cage, really likely
Jitter at null was minimized by flywheels on the motor shafts, free to rotate on the shafts but coupled to them by magnetic drags.
The motors were modified squirrel-cage ball-bearing induction motors with linear torque/speed curves, just about sure. They were available from Ford Instrument Co. after WW II.
As to servo bandwidth, I have no figures, but I do know that from "playing" with them that it might be as good a 10 Hz; that's a crude guess, though!
There were also a few with more-sophisticated stabilization (free flywheel connected to a differential inserted into the feedback, iirc). These had no velocity error.
===
[Photo shoot?]
I have great hopes for arranging a session (or a few) to take the covers off one of the museum-ship machines (they're too big and heavy to remove!) and take some really-good photos (scanning digital camera?) of the innards. See above for a mention...
Once done, I'd put in a few bags of dry silica gel, button it up again, maybe leave a love note to future generations, and give it a blessing.
[Materials]
Stainless steel shafts (and most gears, I assume); most of the rest, Al alloy plates. Some major mechanism support plates (Al alloy) were an inch thick, as I recall.
Housing was big Al alloy castings.
[Sounds]
The sound of these machines was distinctive and memorable. Static, there was a tinkle of gears now and then as the servos fixed tiny errors. A servo that was suddenly enabled, with a big error, made gear-train noises as it slewed and settled; full scale might take a few seconds.
The unforgettable sound, though, was that of the time motor starting and running. It took a few seconds to accelerate, with a hint of siren-like whine. Once at speed, an interesting escapement, cam, and contacts, combined with a jewel-bearing spur-gear differential did effectively a pulse-width modulation (5 Hz?) of the AC power. The torque reversals happened twice per tick (power on, power off), and were rough on the gear reduction at the motor.
The combination of the very regular "chunk-chunk", some semi-random tooth noise, and a frosting of tinkling gears was memorable. In all, maybe 60 or so (very crude guess) meshes contributed to the sound. The cast-Al alloy covers muffled some of the sound, of course.
[Range and rangefinders]
Btw, before radar, range was determined by optical rangefinders. The r/f operator turned a knob to make the target seem to be the same apparent distance away as the little open lozenge-diamonds in the reticle. (These were not split-image types; those didn't work out, in practice.)
A central wide button on the knob told the computer when the rangefinder was on target.
The view through a rangefinder was stunning. Scenes miles away seemed to be like a tabletop scale-model diorama, because the sense of depth was so strong.
Those long ears that stick out of the sides of some older gun turrets and all earlier gun directors are the ends of the rangefinder.
[Hopes]
I dearly hope to write up these machines in lots more detail on a planned Web site -- <nbodley.us> is parked, for now; nothing there (end of March, 2004).
CLASSES OF M.A. F.C. COMPUTERS
[There were essentially two main classes of mechanical analog fire-control computers. One variety, such as the Mk. 8 Range Keeper, which did just fine in 1991 for battleship shore bombardment, and the Mk.1/1A, carries computational quantities from one place to another by way or rotating shafts. Typically, full scale implies many turns of a shaft.]
[These machines, called tachymetric (not "tachometric") (Greek: "tachys" = speed, iirc), effectively determined the target speed (implicitly, I'd say). Combined with one angle, and rate of change of altitude, they defined the target motion vector.]
(For the other class, linkage, please scroll down; I'm not quite organized! :) )
[Prediction]
From that target-motion vector, along with range to the target, the computer could predict where the target would be when the shell reached it. The gun lead angles aimed the shell to that point, and the mechanical time fuze setting made the round explode at that time.
Yes, there were prediction multipliers, thin things, in a stack, iirc, of four. Big, too; maybe a foot square?
A simplifying assumption was that the target vector wouldn't change. (An anti-sub machine (Belock?) was built with constant radius-of-turn, as well, but that was disabled because of serious reliability problems. Don't blame Harry(?) Belock! Not his fault!)
More fun was calculating the angles required to keep the guns on target as the ship's deck tilted. Exact calculations wer not passible in the Mk.1/A; there were too many terms.
The Mk 47 Computer, mentioned below, did exact calculations, using resolver chains.
Unfortunately, these tachymetric machines were not fast enough in converging to a solution when kamikazes (late-WW II suicide bombers) came in.
[Grace Hopper]
RAdm. Grace Murray Hopper apparently did some of the fundamental math. for the (post-WW II redesign?) of the Mk. 1(A?). The Mk. 1 (WW II) design started in the early 1930s, I'm told.
[Evolution]
These tachymetric machines did evolve, however; the Computer Mk. 47, another magnificent machine, was an hybrid. It did multiplication with precision pots, and trig functions with electrical resolvers (similar to synchros). That computer was part of the GFCS Mk. 68, iirc.
The whole gun director was gyro-stabilized in one axis; it sat in a huge yoke. Trunnions were toward and away from the target. The USS Wilkinson, DL5, had that system.
A further evolution was the Computer Mk. 100 (?), for the Terrier (probably) ship-borne missile. IIrc, that computer did mostly electronically what the disk-ball-roller integrator did mechanically.
THE OTHER KIND ==================
at last
If the rotary-shaft/tachymetric variety are hard to find out about, even more obscure are the phenomenal linkage analog computers. One good look at their mechanisms, and you'll never, ever forget it.
I can only compare these to a sofa-bed linkage, or some linkages for an auto. convertible top. However, a fire control computer has more elements, and each is
by no means anywhere near to being as complicated as the two examples I cite.
I have seen two linkage computers, open to my eyes; one was in the Mk. 56, and the other was a Librascope sonar fire control computer.
[Kamikazes and the GFCS Mk.56]
The Mk 56 Gun Fire Control System was a real masterpiece. I'm essentially sure it was a very-fast-reacting system that was developed to cope with kamikazes. There are illustrations on the Web of its critical innards, very clever, and the most not-to-scale drawings I've ever seen... :)
However, scale drawings of its linkage computer seem exceedingly difficult to find; that's my current viewpoint. Not the least-remarkable aspect is that the ballistic calculations were done by linkages, not 3-D cams!
The Mk. 56 system's linkage computer (it had its own Mk. no.) consisted of an upper "tray" (in a casting, iirc), maybe 4 or 5 inches deep, maybe a yard (meter) wide or a little more, and maybe 20 inches from front to back. The linkage components moved sidewise; all pivot axes were straight up and down.
At the bottom of the tray were high-precision racks and pinions for rotary mechanical input and output. A substantial space below the "tray" held servos and synchros for the I/O.
There was a remarkable 3-D mechanism ('dummy gun", loosely speaking, that had a rod pointing straight down (home position). The rod fitted into a ball with a hole through it (ball: likely).
The ball moved an x-y carriage with linear-pot pickoffs, and the whole x-y assembly rotated through a limited angle as the gun director rotated around the line of sight as the deck tilted.
The assembly was nicknamed the finger of Omar. :)
The system design was by Ivan Getting; oral history transcripts, iirc by the IEEE, were on the Web and probably still are. One of those transcripts has the U.S. patent number on the Mk. 56 system, although there is no mention of "Mk. 56" in the patent, which was long classified. IIrc, the patent number is in the 3,400,000..3.6M range. It contains a detailed mechanical schematic, using symbols you won't easily forget.
Detailed linkage design was apparently by Antonin Svoboda, one of the authors in the MIT Radiation Lab. Series.
[Sonar linkage computer]
The sonar computer was mounted on a bulkhead (wall), and linkage movement was in a vertical plane. It was smaller than that of the Mk 56 system's computer. It contained enclosed disc-ball-roller integrators; they were on the market, once, as mechanical components.
Its sine (or cosine, but not both!) mechanisms were hypocycloidal (iirc) gears, exact 2:1 ratio between a ring gear with internal teeth, and a smaller gear on a disc crankpin, so to speak.
The inner gear rotated Spirograph fashion inside the ring, but the 2:1 ratio meant that any point on its pitch circle moved in a straight line. The output was a pivot exactly coincident with the pitch circle.
These mechanisms were also offered commercially. They were theoretically perfect, neglecting tooth errors and backlash. (This mechanism was used on some early steam engines. Don't confuse it with another somewhat-related scheme that made several flywheel rotations for one stroke.)
For just a little taste, a computer that probably did only scaled addition and subtraction, see <http://dcoward.best.vwh.net/analog/libra.htm>. That machine converts rotary knob inputs to linear motion, and uses cascaded "whiffletree" linkages to do scaled addition and subtraction, with the results displayed on the two large pointer dials.
(Love that spare parts collection :) )
Linguists will see where Librascope got its name; remember the astrological sign for Libra? Balance? ("skopein" (to see?) is Greek, iirc)
If you know the IBM Selectric mechanism (a good part of it is mechanical binary!), its tilt and rotate combining linkages are the same idea; identical in principle, except for binary inputs.
Btw, steam-engine valve gears (afaik, all) are low-accuracy analog multipliers. The Baker valve gear is closest to those used in linkage computers, although physically simpler; a Baker's castings are not the easiest to understand.
[Other personal interests; off-topic.]
Other extreme interests include mechanical calculators, with particular attention to the later Marchants, (Silent Speed) that used the proportional gears principle, essentially a 9-ratio preselector transmission for each of the ten columns(!), about 39 spur-gear differentials in the carriage, and a multi-digit *analog* magnitude comparator!!
They ran at 1,300 cycles/min. and were the speed champs for decades.
My apologies for some inconsistencies in style and editing; I'm tired, just now, and this was a piece of work! If someone as crazy as I am :) actually wants to edit/rearrange this, I won't mind, but I'd want to check the text.
As to factual reliability, this should be rather good. I try very hard to either be as correct as I can, or include some qualifying remarks (which, in other docs., I often do).
In closing, I am rather poor about replying to e-mail (I'd prefer to be different!), but one never knows. Try anyhow. If I'm not snowed under, I'll give my best.
Nicholas Bodley
Waltham, Mass.
RE: Mechanical Analog Computers
I'll be back to all your links many times.
RE: Mechanical Analog Computers
What a fascinating read. Thanks for sharing that with us. I did other jobs on ships, boilers, turbines, mundane things like that, and only observed the FC systems in passing. At that stage of my life, I did not have the mental capacity to understand what you just said. Now I do, and had no idea of the sophistication.
Thanks again.
rmw
RE: Mechanical Analog Computers
Thanks for that epic post. It gives me an insight into things I've only seen in books or on the History Channel. Please keep posting.
-----------------------------------
Start each new day with a smile.
Get it over with.
RE: Mechanical Analog Computers
great post. Had you thought of posting it as an "FAQ"? This would be a good way to preserve your response in the fora without having to track down this thread (as mpore threads are added it will become displaced, then lost).
JMW
www.viscoanalyser.com
RE: Mechanical Analog Computers
If I ever get to the point of setting up my Web site (<nbodley.us>, which is parked at <www.godaddy.com> (it's also private, by proxy or such)), then I'll surely include at least this much.
If it's not hopelessly long, I could post this big one to FAQ, once I learn how; shouldn't be hard to do.
I do realize that a considerable amount of background has been omitted; the subject is just too big to explain in one article. I hope that the links I gave include some scanned and OCR-processed pages from a Naval training manual; that's the one that illustrates the basic F.C. mechanisms.
Best regards!
Nicholas Bodley || Eastern Mass.
RE: Mechanical Analog Computers
Anyhow, I took [jmw's] suggestion, and copied the article to the FAQ, worrying about using up space. I edited it some, fixing typos I was too tired to notice when I first wrote it. Also added some material, and restored some info (mechanical resolvers) that got lost somehow in numerous previews-and-edits in the original. However, the article is substantially the same.
My regards to all,
NB
Nicholas Bodley |*| Retired technician
Eastern Mass.
RE: Mechanical Analog Computers
The display "limit" for a posting is 4 stars, it is very likely that you have more than that from people who did not post a response directly. Enjoyable reading especially from an insider's view.
Regards,
RE: Mechanical Analog Computers
In the DE220.com article linked to here
www.de220.com/Armament/Fire%20Directors/Mk%201%20C...
it states that the Mk. 1 fire-control computer was installed in cruisers "after CL51 and CA68." This leaves me wondering about old CA-30, the Houston. Does anyone know what type of fire-control system was on the Houston? She was commissioned 17 Jun 1930.
Thanks very much.
James D. Hornfischer
RE: Mechanical Analog Computers
Prof.(?) Jon (not John) Sumida has written at least one book on the topic, but apparently from a general perspective. I haven't seen his book.
Related topics follow, on-thread, and maybe somewhat repeated:
Probably since my last post, I did some online research about the f.c. system on the H.M.S. Hood. For a start, see about the Dumaresq "clock"; Googling on [dumaresq fire control] gives a distracting collection of hits. (I didn't dare...) I think it's quite unlikely that the USA would have used something like the setup on the Hood. (My apologies to the Brits, but the Hood had a real kluge/kludge of a f.c. system! Somewhere there's a memorable photo of it; as well, there was, iirc, a 70-man crew in their plotting room!)
[Btw, I write on sometimes-related topics for the Howthingswork list at <YahooGroups.com>. That's where I do almost all my technical writing, and there's quite a bit of it. Fairly deep in the archives is a quite-detailed description of the position servos in the USN Mk.1/A computers; basically, tungsten contacts, miter-gear differential for obtaining the error signal, "bang-bang". Had 115v 60 Hz capacitor-run reversible induction motors with linear torque/speed curves. Large errors were stored in a train of intermittent gearing like an odometer at full carryover (all 9s <--> all 0s). At null, the train of gears was at the equiv. of being partway thru full carryover. Physical form was open, like a regular gear train, not a cylindrical cluster. Stabilization (velocity) was by high-torque (compared to speedometers) magnetic "drag"s, which might be considered to be drag (eddy-current?) clutches. Permanent magnet and squirrel-cage structure. If you consider the current in the squirrel cage to be eddy current, then the term fits.
The DE220 site has some great, but relatively-uninformative photos of some of the Mark 1's innards. They are from the National Archives, and I hope there are more.
Possible that when they were taken, the real goodies, such as the set of four 3-D ballistic cams, was still considered somewhat classified.
As my life seems to slowly fade away, I almost pray for the discipline and energy to document the Mark1/A better and further. I do hope to organize a photo expedition to one of the museum ships to set up ventilation and lighting, remove covers, and take superb shots of the innards, then drop in a few bags of regenerated silica gel and button her up again for future generations.
Superb shots: *Scanning* digital camera! See <FLAAR.org>. (If you have to ask what they cost, you can't afford one. Exposure time was many seconds; pixel count was roughly 10K by 12k or such, a few years ago. Haven't read about them, recently.)
I'm also hoping to obtain a *mechanical* schematic of the Mark 1A (any mod); I already have one of the Mark 1, from Doug Coward of the Analog Museum Web site. He might have a few more, rolled sheets. I should try to have this copy scanned professionally; with broadband, a 600-MB file download (Hooray, BitTorrent!) is no longer prohibitive; it might not be that big. (Can GIFs be in the 100s of MB? I don't know specifically why not.)
Many thanks, folks. Keep the faith!
NB
Nicholas Bodley |*| Retired technician
Eastern Mass.
RE: Mechanical Analog Computers
Bob O.