Hamilton 992 railroad pocket watch

size 16
21 jewels
double roller
5 adjusted positions
temperature compensated
gold center wheel
lever set

This example has a Montgomery dial in open faced Fahys Montauk gold-filled case

Serial no. of watch is 1298440
Serial no. range 1,298,001 - 1,299,000 was grade 992L
Serial no. range 1,200,000 - 1,300,000 was manufactured in 1915

Therefore, this is a Hamilton grade 992L railroad watch made in 1915:

The inside of another Hamilton 992L, this one from 1916 (I didn't want to reopen mine for the photograph!)


First Wheel (Main Spring)  78 Teeth   1 Rev. in 6 Hours, 30 Minutes.

    *6.5 ratio:
    Center Pinion  12 Teeth  1 Rev. in 1 Hour = Minute Hand attached here (through a friction fit, see below).
    Center Wheel  80 Teeth  1 Rev. in 1 Hour.

        *8 ratio:
        3rd Pinion  10 Teeth  1 Rev. in 7.5 Minutes.
        3rd Wheel  75 Teeth  1 Rev. in 7.5 Minutes.

            *7.5 ratio:
            4th Pinion  10 Teeth  1 Rev. in 1 Minute = Second Hand attached here.
            4th Wheel  80 Teeth  1 Rev. in 1 Minute.

                *10 ratio:
                Escape Pinion    8 Teeth  1 Rev. in 6 Seconds.
                Escape Wheel  15 Teeth  1 Rev. in 6 Seconds.
                                                         Moves 1/15 Rev. (1 Tooth) in 2/5 Seconds in 2 half-steps (tick-tock sound).
                                                         or 1/30 Rev. in 1/5 Second each half-step (one tick sound).

                    Balance Wheel    Oscillates back and forth (1 complete cycle) in 2/5 Second = 2.5 Hz frequency, releasing Escape Wheel tooth 2 half-steps,
                                                Swings    1 time in 1/5 Second in 1 direction, releasing Escape Wheel Tooth one half-step,
                                                                2 times in 2/5 Second
                                                                5 times in 1 Second,
                                                                30 times in 6 Seconds,
                                                                300 times in 1 Minute,
                                                                18,000 times in 1 Hour,
                                                                432,000 times in 1 Day,
                                                                157,680,000 times in 1 Year,
                                                                630,720,000 times in 4 Years (between oilings).

The rim of the balance wheel travels travels about the equivalent of 9.75 miles in 1 day or 648,000 equivalent complete revolutions (+/- 270 degree swings).
If the wheels of a car turned the same number of times, they would travel 300,000 miles in a year.  The car would just about fall apart on a trip of that mileage, but your watch, some of whose parts move an equivalent distance, might not need repairs for years.

Center Wheel Shaft

    *1 Friction fit (to allow setting the hands):
    Cannon pinion shaft         1 Rev. in 1 Hour = Minute Hand attached here.
    Cannon pinion  14 Teeth  1 Rev. in 1 Hour.

        /3 ratio:
        Minute Wheel  42 Teeth  1 Rev. in 3 Hours.
        Minute Pinion  12 Teeth  1 Rev. in 3 Hours.

            /4 ratio:
            Hour Wheel  48 Teeth  1 Rev. in 12 Hours = Hour Hand attached here.

Accuracy, once correctly balanced to 5 positions, cleaned and lubricated, will regulate to +5 to -5 seconds per day depending on position.  My personal error, the way I carry the watch, positioning the watch face up during the night for 9 hours, then winding the watch in the morning and carrying it vertically stem up, or stem right, or stem left depending on how it sits in a pants pocket during the day for 15 hours, results in +1 seconds per week total error, well within the +/- 30 seconds per week requirement of the General Railroad Timepiece Standards of 1893.  My watch has maintained this accuracy since the service date Sept. 12, 2008.  Although the main spring will run the watch for 44 hours or so, it must be wound every 24 hours to maintain the above accuracy.
I purchased the watch on ebay for $240 plus shipping, and the servicing cost $194 -- a bargain for a historical mechanical watch that keeps time to within 2 seconds a week!  One can only imagine how many steam locomotive trains my watch was used on since 1915.

Railroad chronometer history

The rise of railroading during the last half of the 19th century led to the widespread use of pocket watches. Because of the likelihood of train wrecks and other accidents if all railroad workers did not accurately know the current time, pocket watches became required equipment for all railroad workers.

The first steps toward codified standards for railroad-grade watches were taken in 1887 when the American Railway Association held a meeting to define basic standards for watches. However, it took a disaster to bring about widespread acceptance of stringent standards. A famous train wreck on the Lake Shore and Michigan Southern Railway in Kipton, Ohio on April 19, 1891 occurred because one of the engineers' watches had stopped for 4 minutes and then started again. The railroad officials commissioned Webb C. Ball as their Chief Time Inspector, in order to establish precision standards and a reliable timepiece inspection system for Railroad chronometers. This led to the adoption in 1893 of stringent standards for pocket watches used in railroading. These railroad-grade pocket watches, as they became colloquially known, had to meet the General Railroad Timepiece Standards adopted in 1893 by almost all railroads. These standards read, in part:

    "...open faced, size 16 or 18, have a minimum of 17 jewels, adjusted to at least five positions, keep time accurately to within 30 seconds a week, adjusted to temps of 34 to 100 F (38 C). have a double roller, steel escape wheel, lever set, regulator, winding stem at 12 o'clock, and have bold black Arabic numerals on a white dial, with black hands."

Railroad employees to this day are required to keep their watches on time, and are subject to spot checks by their superiors at any time. Failure to keep their watches on time can lead to disciplinary action, due to the gravely serious safety issues involved.

Additional requirements were adopted in later years in response to additional needs; for example, the adoption of the diesel-electric locomotive led to new standards from the 1940s on specifying that timekeeping accuracy could not be affected by electromagnetic fields.

About the five positions

Traditional five-position adjusting specifies positions in the following order, from most to least important: dial-up, dial-down, crown-up, crown-left, and crown-right. Although dial-down is an important position in terms of diagnostics (of faults in the watch), it is relatively unimportant in the daily use of a watch. When a watch is held in different positions, gravity will cause the various parts in the watch to rest on different spots. If the friction isn't exactly the same in all those positions, then the watch will run at different rates. This is because the balance wheel will take more time to swing back and forth when it is making a wide arc than when it is making a narrow one. This is true even when a Breguet overcoil hairspring is used to try to increase the isocronism of the watch.

While in theory there are infinitely many positions that a watch can be in, in practice there are only 6 different positions that generally show different results. Those 6 positions are the faces of a cube or die. The dial can be face up, the dial can be face down, the pendant can be pointing up, to the left, to the right or the pendant can be pointing down.

Most of the time, pocket watches are either being carried and have their pendants up, or they are laying flat, with their dials up. Since pocket watches are rarely in the pendant down position, that position is generally not checked.

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