Mechanical Analog Computers 10

[butelja]

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.

 

[nicabod]

Thanks to the e-mail notification scheme, I came to have a look, started to re-read the thread, and had a look at [authorjim]'s message. Sorry, Jim, but I don't know the history of analog fire control computers at all well, on the whole.

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.

 

[Shellback]

For Nicabod.. If my memory serves me correctly, the techman for the Mk 1A was OP 564. I also operated and maintained this mechanical (monster). In 1978 I was very fortunate and lucky to become the Top Gun USN (Surface) on a destroyer (USS Higbee DD-806) using the MK 37 Gun Fire Control System. It was a very capably and reliable system. I am certain that there are still a few in operation in countries such as Turkey, S. Korea and perhaps Columbia.

Bob O.