Tissot Navigator (Lemania Cal. 1341)…

Another Tissot on the blog, and another chronograph, this time a Navigator from the 1970’s…

(Click pictures to enlarge)

During the late 1960’s and 70’s, Tissot had a range of chronograph models with the titles Seastar or Navigator (or both) featuring a variety of calibres, some hand wound (Lemania 873, Valjoux 7733/4) and some automatic (Lemania cal. 134x, cal. 5012).

The movement in this watch is a Lemania cal. 1341, an automatic, three register, cam lever chronograph. What makes this calibre interesting, both technically and visually, is that the minute register for the chronograph is not presented in a subdial, but as a separate minute hand that sweeps around the dial. The subdials in this calibre are an hour recorder at six, and running seconds at nine ‘o clock.

The cal. 1341 is a simplified version of the cal. 1340 which was first introduced in 1972. The main difference between the two is that the cal. 1341 has 17 rather than 22 jewels, and has no facility for adding a 24 hr function. The 1340/1 calibres are often linked with the Omega calibres 1040/1 and for good reason as they are almost the same, apart from a few technical improvements and an Omega rather than a Lemania branding.

In the 1930’s Tissot, Omega and Lemania formed a working group called La Societe Suisse pour l’industrie Horlogere (SSIH) which was the predecessor of Swatch Group of today. Therefore,  it is not a really surprising to see Lemania based calibres appearing in the watches of all three brands.

Removing the winding rotor from the movement reveals the heart of the cam lever mechanism…

Power for the mechanism is provided by the driving and coupling wheels, just like a traditional chronograph calibre. When starting and stopping the chronograph the position of the cam controls the raising and lowering of the coupling wheel onto the centre second wheel. When resetting, the coupling wheel is disengaged from the centre second wheel and the reset hammer moves across to return the centre second wheel back to the zero position. Also attached to the cam is the coupling yoke which provides the link to the hour and minute registers on the dial side of the movement.

Turning the movement over and removing the calendar plate and mechanism bridge, you can see that the rest of the chronograph functions…

In the picture above the mechanism is in”stopped” condition. You can see that the minute recorder clamps are in contact with the minute recording wheel holding it in position, and the hour recorder stop lever is arresting the hour recording wheel.

When the chronograph is started, the hour recorder stop lever pivots around it’s securing screw pulling back the valet which prises the minute recorder clamps open. The minute recording wheel then turns along with the cannon pinion on which it sits. The hour recording wheel is also released and turns along with the mainspring barrel.

As the watch was already in good cosmetic condition, it needed no more than a service to ensure it was as good inside as outside. Here it is all back together again.

Rich.