Does anybody know how that speedometer works?

I just assume it's correct that it should tick also when the loco is standing still.

Very interesting! But how would it work? Here is my sepculation:

I have recorded and measured the ticking. There is a distcinct tick every 0.495.. second. I assume that is meant to be 0.500 second, but the clock in the loco which they recorded from may not have been tuned that accurately. Between this tick there are two smaller ticks, so we have three intervals. At 36 km/h anything moves 10 m per second (36000 m / 3600 seconds), 5 m over half a second. This is a little more than a revolution of the main wheels. They have a diameter (⌀) of 1.35 m, so they would move 1,35 * π  = 4.24 m in a revolution. If the speedometer is being kicked once per revolution it should show 36 km/h * (4.24/10 ) = 15.26 km/h. Thus with a fast "up" / slow "down" arrow to integrate over this length it should show about 15 km/h. If the speedometer is a wound clock I assume the ticking is to clear the integration, hold the arrow or something like that. In that case it would tick while there is a stand still. Pluss it should then show zero, to be verified by the driver.  

Worth reading is the Speedometer article at Wikipedia, but it did not make me any wiser in this regard. Or maybe even more interesting are the Tachometer or Wheel speed sensor articles. But to me, still unsolved how this one would work.

I have now got confirmed in [1] (p.20) that the speedometer of Ce 6/8 II was a indeed a Systems Hasler type. So this probably is the case for the III-version, too.

I have been thinking, maybe the ticking at stand-still might be from a paper logging mechanism? I read that the clock logged events on paper from the Integra-Signum safety system.

[1] is crammed with detail in German. Google translate and I have translated some of it into English in a blog note where I try to understand and discuss the circuit diagrams. The note is "in work": SBB Historic: Schaltplan – two circuit diagrams of the Ce 6/8 III crocodile (here) (Disclaimer)

[1] Krokodile, Legendäre Schweizer Elektroloks by Beat Moser and Peter Pfeiffer. 2.2017. A full 100 page magazine. Just wonderful.

@Unholz - Always nice with some remembering :-) Thanks!

Thanks, Tom in Oz! Very interesting! This is really fantastic!

I wish we could find a picture out there!(?)

Would there be one hand/arm with a needle, one for each value, that could cross each other? One on top of the other, in a way? And for a simultaneous change for all they would draw slightly curved lines, like 3 mm below each other?

Would they draw a line by being continuously pressed against the wax, or would they be pushed regularly?

I don't understand 2 and 6:

1. recorded speed
   
2. engine notch position
   
3. brake pipe pressure
   
4. brake pipe operation
   
5. use of whistle
   
6. vigilance operation
   
7. some other parameter
   

I remember seing the logging instruments at the transformer station I grew up by, since my father worked there, that these instruments had ink. I think these had been mounted around 1952, and they were in use until around 1980.

Ok! I should have known the vigilance word, because I have discussed (with SBB Historic) at a blog note [1] about the fact that the Märklin 55681 does not have the dead man's foot pedal, which it should have had! The history of when and why is also there.

[1] Dead man's pedal Standard disclaimer (no ads etc.)

Sounds very right!