Venus 170 Musings

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I just finished a somewhat long running restoration on a Chronographe Suisse Venus 170, and as a new forum member I wanted to share some thoughts on the movement based on my experiences with it in the hopes it might be helpful or perhaps spark an interesting discussion.

First off, the Venus 170 seems to be well regarded, and it does have some nice features, including the column wheel mechanism, the use of an oscillating pinion to for chronograph engagement, and the fact that the top/bottom orientation of the subdials allows the stop/start button to be placed immediately adjacent to the column wheel, which in turn makes for very smooth and low-effort actuation of the chronograph functions.

All that said, the Venus 170 has some... interesting design choices that make this movement, in my admittedly limited experience, a somewhat cantankerous beast, even compared to later chronograph movements (for the record, I have also restored several subsequent common chronograph movements at this point including the Venus 188 and 200, Landeron 48 and 149, and a Valjoux 236). Here are some of the things I didn't like, as a watchmaker, about this movement:

First off, the chronograph operation depends on several rather small and delicate springs. Only two are of the more robust "engineered" type - the column wheel jumper and the hammer spring. The others are cheap "bent wire" springs that tend to get a little tired with age, which can lead to unreliable operation.

Most of the chronographs I have worked on have a very simple & classic train-of-wheels layout. Not so the 170, which has a offset 2nd wheel and canon pinion, which is significantly more difficult to remove than a convention center canon pinion. It also has an unusual keyless & motion works design to go with it (pictured above). The use of rocker bar mechanism for the keyless works, as opposed to the more typical (at least in swiss movements) sliding clutch makes sense, as it allows the winding wheel and click to be placed on the dial side, away from the chronograph parts. A bit more baffling (at least to me) is the design of the motion works, which uses a wigwag mechanism for the minute wheel with a spring tensioner, which you can see in the photo with the minute wheel removed.

I'm generally pretty good at puzzling out the rationale behind even odd or unusual design choices in watch movements at this point, but I have not been able to deduce why this wigwag design was necessary, and it was the source of multiple headaches when I was trying to get the watch working properly. In particular, the wigwag-ing minute wheel tends to disengage from the hour wheel if there is even a small amount of friction affecting the minute pinion or hour wheel, particularly when the setting mode is engaged and the watch is adjusted in the retrograde (counter clockwise) direction. This combined with the fact that the minute pinion (which fits around a fixed post in the center of the movement as the canon pinion is offset) and the hour wheel are closely coupled and fit together very snugly means that it is very easy to provoke this mechanism such that the minute and hour hand actually start moving together, which completely throws off the hand alignment in a way that can only be fixed by taking the hands off (at least this particular Chronograph Suisse model has a removable bezel so you can do this without uncasing the movement, but removing and re-installing the chronograph second hand is a huge PITA since it has to be aligned so carefully!). I wrestled with this problem quite a bit, ultimately resorting to polishing the interior and bottom of the hour wheel to minimize friction with the minute pinion and applying more lubrication to these parts than I normally would, before I got the watch in a state where I could set the time reliably. 

By the way, I had to steal some parts from a donor movement in order to get this watch running, and another thing I noticed is that there were some surprisingly significant design differences between the two movements, even though they were both Venus 170. This meant that, while most of the parts were interchangeable, some were not. A good thing to keep in mind if you're working on one of these.

In any event, I know the 170 is much-loved, but in general I can see why later chronograph movements by Venus and others didn't carry forward some of these unusual design decisions.

Edited September 27, 2024 by Feedback