technical advise

Good day to all the experts again.
What should one conclude from the following statement:

"When the chronograph is activated the intermediate chronograph lever rotates slightly in order to ensure that the intermediate

chronograph wheel engages the center chronograph wheel.

Unfortunately it can happen, that the teeth of both wheels hit each other at the tip. Due to that the Chrono stops." ?

I do not have any technical knowledge, and would appreciate any assumptions.
Especially the part: UNFORTUNATELY IT CAN HAPPEN-is this similar to a Porsche getting stuck between 3rd and 4th gear .. but it could happen and be accepted?

All the best

Chris

Hello Chris,

I think the following might explain the cause of the problem you describe.

In the Valjoux 7750 based chronograph movements there are two springs, one mounted on the sweep chrono runner and the other on the minute-recording chrono runner. The sweep chrono runner spring, upon a full minute revolution, must be precisely positioned so that it will advance the minute recorder. At the same time, the minute-recording spring must also be carefully positioned so that it holds the wheel in proper place.

If any one of these springs aren't positioned properly then the chronograph wheels will either not record accurately or they can cause the watch to stop when the chrono mechanism is engaged.

Please note that this information is offered without my having seen your watch and the specific points you mention.

I hope the above may be of help.

Regards,
Jack Freedman

Jack, thank you for your detailed explanation. From what you mentioned I gather that a correctment in the positioning will be the remedy. From what you mentioned, will this hold true for an in-house chrono as well? Also the "stop" you referred to, is that a "stop" of the whole watch movement?
Regards
Chris

Other chrono movements are designed and constructed differently so I can't answer your question in any definitive way. The "stop" spring is not to be confused with the "hack" lever which stops the watch when the crown is pulled to setting position.

For a remedy to your watch problem it is suggested that you contact an authorized IWC service facility which you can find through this website.

Regards,
Jack Freedman

Hello. A quick question - Why does the chronograph large second hand sometimes "wobble" a little (backward then forward) when the chronograph is started on my Aquatimer? Other times it starts smoothly. Is this just depending on how the gears are lined up when it starts? Not a big deal, I was just curious is this is common to the movement (a modified Val 7750 on my AT). Thanks.

My current understanding of the mechanical chronograph is that it is a fancy complication to mimic a stopwatch's function. If you intend to record exact time fragments, you are waisting your time and should use a digital stopwatch.
It seems to be more 'wow' factor than functional.
I am open for correctment.

Sure; I'll use the stopwatch app on my cell phone to time something precisely. I was just wondering if my experience with the movement was a common one or specific to my watch.

Chronograph wristwatches have been made successfully since the late fifties with good accuracies. Bear in mind that Apollo 13 Astronauts used their NASA flight approved Speedmaster to time their burn in order to get their craft into the correct trajectory for re-entry. That's good enough for me :-) I'm a sucker for chronos and have at least 9 in my collection. Just love that mechanical wonder.

Please see Andy's excellent post on Chronos...
www.iwc.com/forum/en/discussion/62561/?page=1

Thank you Mark, valued comment and a good article by Andy!
As iwcyates referred to the slight delay at starting the chrono, that is a loss in recorded time. I myself are having a chronograph issue which iwc is struggling to correct... And with some research one finds numerous chronograph specific issues reported - this is what is forcing my current opinion and experience of the (modern?) chronograph.

Hi WATCHJUNKIE,
Yup, I am aware of the problems you have been having. I have read about your frustrating time and could feel that Your opinion was influenced by your Current experience. I hope you get resolution soon. I on the other hand have had excellent and reliable service from my chronos and I have pieces ranging from 1950 to 2012. Here are some

Hi Mark, nice collection Indeed!
You are correct about my ongoing issues, this however lead me to the following - although chronos are very popular, how many are actually used and benchmarked by their respective owners?
Owning 20 "chronograph" watches , and using them as standard time tellers, unfortunately do not relate to the reliability of the complication.
Regards
Chris

Mechanical chronos are very nice for telling elapsed timne, but keep in mind that there are two steps in recording precisely elapsed time before the chrono hand starts running:

1) human reaction time in seeing the start and "telling" fingers to depress the pusher
2) human reaction time in having the muscles work to depress the pusher

Unfortunately, for those who are exacting these two factors vary both from instance to instance and person to person. Electronic triggers are far more exact and consistent.

As such, I wouldn't worry about a fraction of a second jump at the beginning of any mechanical chronograph interval. It is relatively meaningless.

Thanks, Michael.