Speedmaster pushers: how stiff?

Archer

Is it? How so?

I'll be honest, in all the years I've been on watch forums, this is the first time anyone has brought up the issue of the start and stop forces being different as a problem that I've seen. Pretty much all discussions surround the difference between the feel of cam and column wheel chronographs. [...]

Gruesome

TL;DR : my super rough wild ass guesstimate is the systematic effect of uneven pusher force might be on the order of 20ms, and might thus matter for the fastest mechanical stopwatches, but not for our chronographs.

Long version:
Well, there's always a first time...

Hi Al, I was thinking more of short distance running, 100 to 400m, where you definitely need 0.1s (or better) precision.
I agree that this issue must be completely irrelevant for applications where 1s or 0.5s precision is good enough. (I hope you weren't pushing those poor workers for every tenth of a second...😉)

But for sporting competitions, you wouldn't want to introduce a systematic time offset because stopping happens faster than starting (assuming same speed of 'trigger finger' force buildup) and depends on the watch used, which is why I assumed that this is a solved issue.
It is already a while that mechanical stop watches were used for high profile sport events, but mechanical watches to time to 1/10th and even 1/100th of a second did exist. I found a nice article on the development work Seiko did for the 1964 summer olympics, but no mention is made of the trigger forces. It seems that at about that time the switch to electronic timing systems happened.
NIST has a document on stopwatch calibration, but they don't mention this issue either. (They do talk about reaction time.)

So then I started looking at physiology papers, but it's really not my area of expertise, and I was ready to decide I'm not that interested and to give up, when finally google decided to give me some graphs and numbers (it's all about the right search terms...). From the little I have looked at it seems (I could be completely wrong) that a muscle might take on the order of 200 ms (give or take 100ms; I used the search term 'isometric force vs time') to build up its maximum force, so assuming I can pull 50N (5kg weight force) using my index finger muscles, then a variation in force of 10% of that (5N = 500 gram) corresponds to 20ms. (The force buildup is apparently not linear, but this is good enough for our purposes.)

So what does that mean?
20ms (even with a large uncertainty factor, say 2 or 3) is small compared to variations in human reaction time.
As an offset over many timings it could matter for 1/100th second stopwatches.
20ms does not matter for time intervals measurable with our chronographs. If the effect were ten times larger, then one might be able to start seeing differences between different watches.

I'm still miffed though. They engineer cars so that closing doors sound pleasant; why can't they engineer watches so the pusher feel is even?

buramu

My original question has been answered perfectly

buramu

Using my Speedy Pro for timing engine bursts before entering Earth’s atmosphere it struck me that the tactile quality of the start/stop pusher on my watch is not particularly nice.

I have to push really hard before the chrono eventually engages. It’s a big, sudden clunk rather than a gratifying mechanical click. Hard to describe in words I guess, but I wouldn’t really describe it as pleasant - even though the stopwatch itself works reliably enough.

This is my first chronograph, so I can’t really compare it to anything. How stiff is the pusher action on the Speedmaster Pro supposed to be?

Archer

Since the pushers are identical in every way between the top and bottom,. I'm not sure this has any credence.