One More Mechanical Stopwatch Math Question

[Quiet 1]

Another one that baffles me: I collect stopwatches that are either unusual, rare, 'purpose built' or a combination thereof.

I have several super high BPH beats per hour) timers. They're fascinating to watch the sweep hand zip around the dial. Several had specific WWII military uses. (The WWII A-8 (jitterbug) USAAF groundspeed timer or the Soviet Agat Sonar timer or the magnificent Soviet 2nd Watch Factory (now Slava) 1/100th of a second stopwatch that went into space mounted in the capsule's of the original Soviet Cosmonauts.)

But this little speedster I recently acquired has me stumped. A revolution of the sweep hand take only 2 seconds. As you can see the outer register has 50 indices, numbered every five, beginning with .005 .010 .015 etc. ending at .050 (the full 2 second revolution). The accumulator dial register has 40 indices numbered every 5 beginning with .250 .500 .750 1000 etc. and ending with 2

Mathematics is not my strength (that's putting it mildly). Can anyone explain what is being timed? Decimals of seconds?

If so, why accumulate in .050 segments ending at 2 (after 40 rotations - 80 seconds)

If any one here can offer any explanations (about the math), or, speculate on possible uses, military or industrial) I'd be both grateful and interested in learning.

 

[Cubist]

Nice stopwatch! And the photos are great, they reveal the brushed finish on the steel very nicely. I once produced a similar circular pattern on something I made in my metalwork class many years ago. Unfortunately I can't offer any insight into its possible use. You've probably worked out that one unit of stopwatch time = 40 seconds...

real time in seconds <=> the units on the stopwatch
2 seconds <=> 0.050, multiply both sides by 20 gives...
2 * 20 seconds <=> 0.05 * 20
40 <=> 1
40 seconds <=> one unit of stopwatch time

I guess that it's custom made to time something that ought to take around 40s. Maybe built to time someone on an assembly line? I don't know. I can't think of an obvious military application (although I found an internet post that said, "Meylan stopwatches were frequently used by the US military"). Good luck in your research, and please let us know if you find anything out about it.

 

[Quiet 1]

Once again, Cubist, great thanks for your response, explanation of it's 'unit of stopwatch time' and thoughts on possible uses. I genuinely appreciate your taking the time (no pun intended) to look, ponder and reply.

And btw, no, I did not know it's 'unit of stopwatch time' was 40 seconds. I thought since it records down to 1/25 of a second it was to time something super fast like a chemical reaction or an ultra high speed 'event'. So, I suppose it's not as "exotic" as I'd hoped. But, it's still a very rare configuration and fascinating to watch it 'do it's thing'.

 

[Cubist]

So, I suppose it's not as "exotic" as I'd hoped. But, it's still a very rare configuration and fascinating to watch it 'do it's thing'.

It seems pretty special to me. Each mark, or index, on the register represents 0.001 of that unit. In other words, each index measures 0.001 * 40s = 0.040s = 40ms (milliseconds). I don't think my reactions, to stop/ start the device, would anywhere near justify that level of accuracy! Human reaction time varies, but it's approx 200ms. IF the operator's reaction time is consistent for starting and stopping the timer, then the measured result might be pretty accurate (because the 200ms operator's delay at the start cancels out their 200ms delay at the end).

Hope you can understand this!

EDIT: In retrospect, my guess of measuring the time of someone on a production line must be WAY off the mark. You wouldn't need such a level of accuracy for something like that. I think you might be looking for something that needs to be timed, that would be expected to take around 40s, but it also requires an extreme level of accuracy for the measured time. That's just a guess though . Interesting!

 

[Quiet 1]

Hey Cubist, Great additional information. Your explanation is clear and I do understand it and I thank you for providing it.

However, it precipitates a question (sorry). I describe this as a "1/25th of a second" stopwatch. Would it be better described a "40 milliseconds" stopwatch. (Milliseconds sounds way more 'kool' and impressive. Ha, ha.) Or, does it matter?

Your comments on human reaction time are certainly correct and thought provoking too. Particularly the possibility of the results potentially being reasonably accurate due to the 'start' and 'stop' reaction times cancelling out. Good stuff. Thanks again for all your comments.

 

[Cubist]

I describe this as a "1/25th of a second" stopwatch. Would it be better described a "40 milliseconds" stopwatch. (Milliseconds sounds way more 'kool' and impressive. Ha, ha.) Or, does it matter?

"1/25th of a second" and "40 milliseconds" are equivalent time periods, but there's also another option that would be widely understood, "4 hundredths of a second". Choose your favorite! I think you're in a better position than me to know if there's any kind of naming convention, for the minimum measure, among the stopwatch collecting community. But among friends you should definitely blind them with science in order to impress and bamboozle them! You're welcome for the time, I like to see vintage tech, machines, calculation methods, etc

 

[Quiet 1]

. . . . . . But among friends you should definitely blind them with science in order to impress and bamboozle them! You're welcome for the time, I like to see vintage tech, machines, calculation methods, etc.

Ha, ha, ha! YES! I'm a life long proponent of W.C. Fields aphorism “If you can't dazzle them with brilliance, baffle them with bullshit.” But, your "blind them with science" is definitely more gentile and debonair. Thus I'm going with your suggestion of "4 hundredths of a second".

It's been a genuine pleasure communicating with and learning from you, Cubist. Best regards, Lance