Sea-Gull ST1902

Description

One of the most readily available modern chronograph movements is the Sea-Gull ST19, specifically the Sea-Gull ST1902 version featuring a 12-hour standard time display.

This 13¾-ligne manual-wind movement originates in China and is a replica of the swiss Venus 175. Visually, it is quite attractive, featuring blued screws and striped finishing, often disparagingly referred to as “Shanghai stripes.”

The base plate does not yet allow any conclusions to be drawn regarding a chronograph caliber. Just as with a standard manual-wind movement, the jewel bearings for the seconds wheel and the third wheel are visible; this implies there will be no directly driven center seconds hand.

Regarding the jewels, it should be noted that all critical pivot points are fitted with synthetic rubies.

The gear train of the base movement consists of the mainspring barrel, the directly driven center minute wheel, the third wheel, the seconds wheel at 6 o’clock (featuring a dual-wheel design, with the upper wheel driving the chronograph gear train), and the escape wheel.

A Swiss pallet lever escapement is used.

The Sea-Gull ST1902 features a gold-colored, three leg anular balance wheel that beats with a semi-fast frequency of 21,600 A/h. It is mounted using a pair of Chinese shock-protection devices designed to resemble Incabloc bearings, though they are more crudely finished, particularly the lyre-shaped spring.

The movement can only be regulated at the hairspring key.

The wheel-train bridge, which is, unfortunately, rather crudely finished, reveals that a chronograph mechanism is to be installed here. The double seconds wheel also points to this, of course.

The chronograph mechanism of the Sea-Gull ST1902 comprises a central seconds wheel, a column wheel, and a minute wheel for the display, enabling the timing of 30-minute intervals.

The distinctive feature of this caliber is its column-wheel mechanism; this not only makes the stop function more precise but should also offer a significantly better tactile feel compared to a cam-actuated caliber. Unfortunately, this is not quite the case here, as the start/stop lever, which has to sweep across a third of the movement, is loosely mounted, resulting in a rather mushy feel during operation.

On the other hand, it is clearly visible how the reset mechanism (on the left) and the start/stop mechanism (on the right—which engages the transmission wheel) interface with the column wheel via their respective levers.

Unlike the start/stop mechanism, the reset mechanism requires activation via the lower lever; the column wheel merely serves to prevent a reset from occurring while the chronograph is running.

The dial side, currently bare, reveals only the yoke winding system; the pinion for the chronograph minutes is visible emerging from the center of the setting lever spring at the 3 o’clock position.

In the ST1902 caliber variant, a 12-hour display mechanism is also visible; however, this is not linked to the chronograph but simply runs synchronously with the standard time display. Consequently, no real practical benefit is apparent.

The Sea-Gull ST1902 is fitted with a printed cover for the 12-hour mechanism, featuring numerous cutouts and apertures. Here, one can also discern the function of the sub-dials.

In the lab

Timegrapher result

The values ​​without parentheses are with the chronograph function switched off; those in parentheses are with it switched on. Without the chronograph, the movement runs quite accurately and with very high amplitude; with the chronograph function engaged, the amplitude drops sharply, and the timekeeping performance is significantly worse.