American Railroad Chronometer Standards
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  1. #1
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    American Railroad Chronometer Standards

    Hi all, new to this forum but intrigued by the railroad chronometer traditions. It looks like the official standards of many railways specify (among other things) a sub-seconds dial. Does anyone know why this would be better than sweep seconds? The vast majority of railroad pocketwatches are indeed subseconds movements/dials. Presumably sweep seconds would allow more precise timing right?

    Thank you!

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    Re: American Railroad Chronometer Standards

    Quote Originally Posted by KtWUS View Post
    Hi all, new to this forum but intrigued by the railroad chronometer traditions. It looks like the official standards of many railways specify (among other things) a sub-seconds dial. Does anyone know why this would be better than sweep seconds? The vast majority of railroad pocketwatches are indeed subseconds movements/dials. Presumably sweep seconds would allow more precise timing right?

    Thank you!
    My first thinking is that while the accuracy was paramount all timetables were to the minute not second. The requirement for accuracy was for safety not for the pure need for accuracy only. Consider it more or less similar to the need for accuracy to a marine chronometer in a way. They were accurate for functionality not just to be a piece to show off the skill is a company.


    So navigation needed accuracy to the second. Trains needed accuracy to follow timetables for safety to avoid accidents.

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    Re: American Railroad Chronometer Standards

    Was there any sweep seconds pocket watches back then? Easy to think in today's world, but sometimes you have to step back and think of how it was back then. Learn from history, don't let the present blind you
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    Re: American Railroad Chronometer Standards

    Quote Originally Posted by tinknocker View Post
    Was there any sweep seconds pocket watches back then? Easy to think in today's world, but sometimes you have to step back and think of how it was back then. Learn from history, don't let the present blind you
    There have been sweep seconds on pocket watches made in England as far back as the mid 1800's. Most of the time they had a switch to stop them.

    The other thing to remember is the emphasis placed of readability of the watch. The bold hands and numbers were utilitarian. The addition of anther hand may have given to a mistake in time reading. At least that is what I think.

    Look at a railroad watch less like a piece of matchmaking skill and more like a high precision tool.

    Edit.... 1825

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    Last edited by thoth; November 14th, 2017 at 05:21.
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    Re: American Railroad Chronometer Standards

    Thank you! That makes sense - sweep seconds would obstruct/distract from reading the minute/hour.

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    Re: American Railroad Chronometer Standards

    And I just think this meant that the watch was to have a sub seconds dial, as opposed to two hand watches that did not. I think the authors might simply have omitted sweep seconds, not even thought about it's existsnce. I believe this could be because a watch with a second hand is more obviously stopped (that is not-working) than a two hand watch. The non moving second hand is striking :)
    Have a great day!!!

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    DON
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    Re: American Railroad Chronometer Standards

    Most likely the purpose of the hand was to show that the watch was running and for chronometer timing when the watches were taken in for service as you needed the hand for accurate timing.

    Having a sweep wasn't a needed function

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    Re: American Railroad Chronometer Standards

    While we keep saying chronometer timing and such we need to remember there was and is no such thing as chronometer testing in the US. The timing standards were set by the railroads. It was not a competition and was not done by any centralized organization. The factories produced watches that could meet the standards required and most of the time they left the factory to that standard. When they needed to be serviced they were given to watchmakers who could put the watch back into the requirements.

    If I remember right most of the greats when it comes to chronometers in Europe were watches like the Zenith 135 and almost all that were entered into observatory competitions were all sub seconds. Marine Chronometers were not central sweep seconds movements.

    While a sweep seconds could show the watch has stopped, comparing the time on your watch to that at a station would also indicate that it had or has stopped without seeing the seconds at all. But a watch without a seconds hand could not be timed to the strict requirements that the railroads had set.

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    Re: American Railroad Chronometer Standards

    Railroad time standards generally called for watches to run within 30 seconds a week, or 2 weeks depending on the railroad. Watches needed to be adjusted for temperature and isochronism, as well as 3-5 positions. Railroad workers who were required to carry a watch were also required to bring it to an inspector every week or two to compare to the system time. Only inspectors were allowed to set the watch, for obvious reasons. And of course, timing to within 30 seconds a week requires having a second hand.

    In watches with subsidiary seconds the second hand simply fits onto the extended 4th wheel arbor, which goes around once a minute. It moves and stops with the time train because it's driven directly.

    While there were 16 and 18s pocket watches with sweep second hands, they were uncommon. One sees them referred to as "Doctors' Watches". In these, the center seconds hand is driven indirectly, by a wheel fit onto an extended 3rd wheel arbor. This indirect drive is jerky, with the hand leaping ahead and stopping till the gear catches up, unless there is some slight friction to hold the pinion back. Setting the friction on these can be tricky - too little and the hand moves in jerks and jumps. Too much and it reduces balance amplitude and adversely impacts accuracy.

    Since railroad watches prior to the late 1950s were all 16 or 18s pocket watches, the subsidiary dials are large and the hands easily visible.
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    Re: American Railroad Chronometer Standards

    Thanks for the discussion! To make sure I'm understanding the rationale:
    1) Central seconds is a complication that wasn't all that mature - although it visually might have made it easier to track seconds, jumping seconds due to indirect drive is costly to precision.
    2) Pocket watches are large anyway so sub seconds are sufficient
    3) Maybe railways didn't even think about central seconds since they were rare
    4) The fact that observatory chronometers were all subseconds likely reinforces point 1).

    My aim was to understand if sub-seconds was in fact a feature of railroad watches integral to function rather than accidental, and it seems like there is sufficient reason to think there was in fact meaning to it.

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