Nanjing SN2

Description

A very interesting early chinese movement is the caliber SN2 from the Nanjing Watch Factory, which was released in 1968.

Unlike the other chinese movements of that time, it was a much simpler construction for cheaper production to make a wristwatch obtainable for the poorer people.

On the base plate of this pillar construction, you won’t find any bearing rubies except for the bearings of lever and balance. All other axles are beared in simple metal drillings.

The gear train is more or less a Roskopf type construction. The mainspring barrel, which is open on the movement sode, drives the second wheel, followed by third wheel, center seconds wheel (which is, unlike on a true Roskopf movement, directly driven) and the steel escape wheel.

It’s noteable, that the SN2 uses a real swiss pallet lever escapement!

Also surprising is the fact, that the three leg anular balance, whose shape should remind of a Glucydur balance, is beared in two Incabloc shock protecion bearings. Usually, you would expect either a simple chinese shock protection or no shock protection at all.

The balance beats with 18000 A/h, which can be adjusted at the hairspring key only.

As usual on Roskopf-type movements, the mainspring barrel has got on the dial side a double wheel, mounted with a slipping clutch, to drive the cannon pinion and hour wheel simultaneously.

The ratchet, however, is located on the outer side of the gear train brige.

On the yet empty dial side, you see, that this movement even uses a yoke winding system.

Easy to spot is the double wheel of the mainspring barrel, into which cannon pinion and hour wheel engage. Additionally, the transmission wheel from the keyless works engages here in case of time setting.

The cannon pinion engages with the outer, lower teeth, and the much larger hour wheel into the small, upper teeth of the mainspring barrel double gear.

Technically, the SN2 is a rather rare, but much more interesing movement, compared like other chinese calibers, like the so-called “Chinese Standard movement”.

In the lab

Timegrapher result

For such a simple Roskopf-type movement, the rates are in the espectable range.

Technical data

Usage gallery