Junghans J68

Description

In the 1930s, Junghans produced this officially 20 ligne diameter measuring stopwatch caliber, which in reality had a diameter of only 18 1/2 lignes.

As easy to see, this movement lacks bearing rubies; only the balance wheel is beared in two pairs of them (bearing ruby and cap jewel), all other pinions are beared in simple drillings.

Since a stopwatch does not run 24/7, this is perfecly acceptable.

The gear train is standard with the mainspring barrel, the excentrical minute wheel at 12 o’clock (revolving twice per hour), the third wheel, directly driven center seconds wheel and steel escape wheel.

There’s an oddity with the lever, unlike on most other pallet lever escapements, there are no ruby pallets here, but steel pallets.

There were two versions of the Junghans J68, once the version shown here, where the balance wheel beats with 18000 A/h, which allows a precision of 1/5 seconds, and one version with double speed (36000 A/h), with a precision of 1/10 seconds.

The adjustment is done with a long regulator arm.

The especially flat and wide anular balance is not shock protected and uses, like the lever, an ellipse made of steel.

Above the balance wheel, there’s a flat spring, which breaks in stop position the center seconds wheel. Connected to it is the spring loaded lever, which stops and starts the balance wheel.

On the dial side, there’s the column wheel mechanism, which only knows the positions stop and start.

The reset of the hands can be done any time, even during measuring (“flyback”) by the lever at position 11 o’clock.

At position 5:30, you can see the lever mechanism, described above.

Technical data

Usage gallery