Aircraft instrument i.d.

Canso42 · **Posted:** Thu Jul 10, 2008 9:39 pm

Last weekend while cleaning out the storeroom for my parents, we came across a couple of old aircraft instruments. My stepmom's first late husband flew a B-25 in the service and later flew warbird B-25 N9494Z, ex. 44-30925 "Laden Maiden" when it was owned by John C. Estes of Beaumont, Tx., 1966-68.
I have what seems to be a chronometer of some sort, with several different time scales all next to each other. The main markings go in a circle to '24' with a smaller, blue set of marks going up to sixty around the outer rim. Three hands like a regular clock. inside the circle are four small dials.
the top one with one hand goes to sixty in increments of five
the right one goes to sixty in increments of ten
at left is a 'civil date' dial going from one to thirty one
bottom- one to twelve dial with two hands and marked 'Elapsed time'
at right of that dial is '8 days'
two knobs, at one o clock and seven They are gummy and stiff. By seven o clock knob is a little bitty set screw 'set date'

on the back is a slotted screw marked 'adj'
the i.d from the back

AN 5741-1
MFRS. PART NO. E-37500
CONTRACT NXs 1301
MFRS. SER.NO. 005724
ELGIN NATIONAL WATCH CO.

GLORY! This thing still works! While i was writing this thread, one of the knobs went click-PING and the sixty second dial started turning, the 'elapsed time' zeroed and the second hand on the main clock is keeping time.

Can andbody give me some background or info on the item?? Anyone have any idea of its age or what it may have come out of?
Does Elgin Watch Co. still exist?
The other instrument was a Cessna a/s indicator that stopped at 180 knts. I'll buzz them for info on that critter.

help me out, gang.
Doug

Canso42 · **Posted:** Thu Jul 10, 2008 9:41 pm

OOPS! I meant to say simlply 'late husband.' Sorry mom.

Robbie Roberts · **Posted:** Fri Jul 11, 2008 12:17 am

FIRST late husband? How many LATE HUSBANDS she got? :shock:

Sorry, couldn't resist... lol... I'm assuming(hoping) you mean late first husband..

Robbie :wink:

Forgotten Field · **Posted:** Fri Jul 11, 2008 2:01 am

Direct from my the clockmaker who works on these for me:

Quote:

37500. Shortly after Pearl Harbor was attacked by the Japanese on December 7th, 1941, the Hamilton Watch Company, like many other manufacturers, turned their entire production facilities to the manufacture of highly specialized navigational timepieces and other precision instruments. However, The US Navy's Bureau of Aeronautics and the US Army Air Corps wanted two sources of supply which resulted in Hamilton's and Elgin's cooperative effort in designing an elapsed time clock.
The Elgin-Hamilton 8-day elapsed time clock was a 24-hour dial clock with special chronograph and civil date features designed for use as a navigational instrument in aircraft. The movement, rather than being that of as simple clock, was more like that of a large complicated, 8-day,16-jewel watch with a lever escapement. The primary differences between this instrument and an ordinary 12-hour dial watch were; 1)a somewhat more complex winding and setting mechanism; 2) two barrel mainspring assemblies instead of one; 3) the gear ratio between the cannon pinion, minute wheel and hour wheel rotates the hour hand once for every twenty-four revolutions, instead of the usual twelve; and 4) the addition of three specially designed chronograph, elapsed time, and civil date mechanisms on the front and rear plates.

The functional features of the elapsed time clock were; 1) a 24-hour dial; 2)the unusual combined winding and setting knob and the continuously running hour, minute, and second hands; 3)a chronograph system for measuring and recording short intervals of elapsed time; 4) an elapsed time mechanism entirely independent of the chronograph, for measuring long intervals of time (in both hours and minutes); and 5) a "civil date" mechanism with a calendar device for the consecutive indication of the civil date the passing of each 24 hours.

mike furline · **Joined:** Wed May 05, 2004 3:45 pm **Posts:** 2679

I just picked up one of these chronometers and manual last month.

These clocks show up on ebay fairly regularly in the $400-$600 range. The manual is very informative as well, with instructions on use, maintenance, parts, etc..

It was used in U.S. Navy aircraft from the 1940's thru 1990's. One is also installed in the "Spruce Goose". Approx. 28,000 built. Elgin is out of business.
Don't wind it up all the way, the spring can be brittle.

http://www.historictimekeepers.com/37500.htm

http://cgi.ebay.com/HAMILTON-ELGIN-5-DI ... 18Q2el1247

http://www.thewatchguy.com/pages/ELGIN.html

Regards,
Mike

Forgotten Field · **Posted:** Fri Jul 11, 2008 10:52 am

Beg to differ:

Quote:

Don't wind it up all the way, the spring can be brittle.

If the spring(s) (there are two inside the 37500) are so brittle that you can't wind it up fully, you need to replace the spring(s). All of the aircraft clocks of WWII era made by the US require full winding to the stop of the spring. This is not to say that you have to put your whole hand on it and make your muscles quiver to get that last notch out of the ratchet pawl- it means that you wind it with your thumb and index finger until the stop.

If you need a spring replaced, we offer full service to all WWII era clocks and include a 6 month warranty on parts and labor. I am not the clock maker. My friend Dave is and has been doing it for 40 years:

http://www.forgottenfield.com/amg/instr ... locks.html

mike furline · **Joined:** Wed May 05, 2004 3:45 pm **Posts:** 2679

Quote:

If the spring(s) (there are two inside the 37500) are so brittle that you can't wind it up fully, you need to replace the spring(s).

So, if a person wanted to avoid possible spring breakage and replacement, don't wind it fully. :?:

Mine keeps accurate time and I don't wind it to the stop. I give it a few turns every day or so, tick-tock tick-tock around it goes. Then again I don't need to rely on it for time/distance/navigation.

Forgotten Field · **Posted:** Fri Jul 11, 2008 4:16 pm

Quote:

So, if a person wanted to avoid possible spring breakage and replacement

There are three dynamics going on here- the spring manufacture, the operation of the spring, and the wear on the spring. Some of the original springs were not produced to standard during the way or were damaged at some point in their lives. But the overall majority of the original springs are good and were designed and heat treated to work precisely and unwind at a constant rate over the period of eight days, with the intent that the clock would be re-wound every seven days. When you are only partially winding the spring, you are not allowing the spring to fully compress, unwind and release its tension in the way it was designed. That leads to uneven wear on the whole spring, consequent potential breakage. We can tell when clocks come in and have been properly wound during their lives- One of the clocks that I had was a Waltham USN A-11 type clock with its original spring- it still keeps good time losing less than 2.5 minutes over a week. I wound it tight every week (without gorilla gripping it) and according to the new owner, it keeps good time.

You can probably keep doing what you are doing to your clock, and it will continue running- but what you are doing to it is going to cause a spring failure at some point.

mike furline · **Joined:** Wed May 05, 2004 3:45 pm **Posts:** 2679

Taken from the manual,

" Although the clock will run for 8 days without rewinding, it should be wound daily."

Depot IRAN & overhaul is at 500 hrs, about every 3 weeks if in constant use.

I wind it halfway, you wind it every 7 days. I guess we both have a little to learn.

It's just a novelty piece for me, not something I need to depend on.

Forgotten Field · **Posted:** Fri Jul 11, 2008 7:52 pm

I stand corrected.

Canso42 · **Posted:** Fri Jul 11, 2008 8:49 pm

You got me Robbie!
That's it! Thanks Mike and F.F. I'm glad to see how it mounted in the panel too. I didn't wind it, I was just messing with the knobs and must have unstuck it. This thing has been an a dresser drawer in the storeroom for about forty years.

All I really want to do is clean it up, not use it as such. It's a nice accessory for my desk but my first thought was to mount in in a plaque that looks like an instr. panel for my older stepsister, the only one of my sisters who actually remembers her dad's B-25 at Beaumont. She and I haven't spoken much about the parents we lost but I find myself in a unique position to help her connect with her dad who died in 1968.
Which knob is the windup?

Was it Navy only? Was the quantity built the total or just Elgin's contribution? Can the year-built be determined from the ser. #?
Thanks bunches guys
Doug

Forgotten Field · **Posted:** Fri Jul 11, 2008 9:38 pm

They were built during WWII and used afterwards for many years. They were built for USN use, but some saw use in USAF aircraft.

mike furline · **Joined:** Wed May 05, 2004 3:45 pm **Posts:** 2679

Canso,

The knob at 14:00 is the wind up and elapsed time control, knob at 3:00 is chronograph control.

I understood 28,000 to be total production for both companies.

I would recommend getting the manual, very informative.

Regards,

Matt Gunsch · **Posted:** Sat Jul 12, 2008 9:48 am

Here are the clocks I have, and one other odd ball if someone can ID
CLOCK, AIRCRAFT
8 DAYS, ELAPSED TIME, 12 AND 24 HOUR DIAL
MFR'S PART No 618-12-24-10
MFR'S SERIAL No 722
WAKMANN WATCH CO. INC
NEW YORK, NEW YPRK

I found it at a swap meet, I think I paid $25 for it about 15 yrs ago.

I also have a Wakmann 8 day it has W337510 10 ink stamped on the bottom edge of the face, and 820190 on the top edge FEB 13, 1967 on the back

now for the real odd ball,
TYPE B-2
SERIAL NO. AF43-1261
SPEC. NO. 27333-A
MFRS. PART NO. 5010
ORDER NO. AC-31747
JAEGER WATCH CO. INC NEW YORK

Canso42 · **Posted:** Sat Jul 12, 2008 5:25 pm

Last night while already a bit groggy, I tried to post a msg. about the Cessna ASI that came with the Elgin 37500 but apparently it went somewhere unknown.
I'm out of town on a borrowed comp. so I cant give details like model and serial but it's marked Cessna on the face, badge plate etc. and stamped 'funtional tested Oct. 1963' on the back.
The dial starts straight up at 0 and goes to 180 mph/160kts stopping at about the ten o clock position. The dial scale is white until about 56 mph when it turns green. At a hundred something it turns yellow and has a red bar at about one six two. That's all I can remember at this time. It has some other stampings and faintly embossed on the back is the warning 'CAUTION-DO NOT BLOW IN TUBES' At the bottom belown the badge plate is the word/name 'KOLLSMAN' Designer? Builder?
Any of you instrument techies have any idea on the age or a/c without better details like model #? How about a tech contact at Cessna. Their website wasn't much help there.

blue skies
Doug

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