ETA 1256

Description

The ETA 1256, which debuted 1950, was the first selfwinding movement of the Grenchen manufactury. It already used a very modern selfwinding mechanism, which winds the movement in both directions.

The ETA 1256 is the prime father of all ETA selfwinding movements ever made.

The specimen shown here was also used by Benrus under their own caliber name CF 1.

The spring less click reverser with double click wheel allowed, that the oscillating weight winds in both directions.

On hand winding, the pawl winding wheel decouples the oscillating weight.

top view selfwinding mechanism

The oscillating weight is beared on a conical shaped axle, which avoids running out bushings. This very effective type of bearing was used until in the sixties, ETA used ball bearings.

bottom view selfwinding mechanism

The oscillating weight wheel always turns the outermost winding up wheel (at "4") and the upper pawl winding wheel (at "2"). The tricky part is now, that the upper(!) pawl winding wheel corresponds with the driving gear (at "1:30"), while the lower pawl winding wheel is connected to the outermost winding wheel. According to the turning direction of the oscillating weight, both pawl winding wheel run either synchronously or the upper wheel spins freely, while the lower wheel is driven and thus reverses the direction.

movement view without selfwinding mechanism

The ETA 1256 bases on the "old" movement family with directly driven minute hand, of which for example the ETA 1081 is a member.

Its screw balance (which is beared in the specimen shown here in a patented Benrus shock protection) beats with contemporary slow 18000 A/h.

The hairspring (here in the beautiful top class Nivarox-I-type) is still fix connected to the balance cock and can be regulated due to the shock protection system on the hairspring key only.

The movement bridges look a bit like a prototype, especially with all its cutted out parts. In terms of quality, this pallet lever movement, whose 17 jewels are all used in the time works, it is very good one!

detail: coupling clutch

Under the loupe, you can see the two parts of the pawl winding wheel: In one direction, the click runs freely, in the other one, it is blocked by the "dots" and drives the other wheel.

main plate

On the dial side, you see amont the Benrus inhouse shock protection the yokw winding system, whose setting lever spring has got only one hole.

As on many old movements, a partial minute dial is engraved, which allows a regulation of the movement without mounted dial. This was helpful in times, when not every shop had got a timegrapher.

dial side view

Technical data

Manufacturer	ETA
Caliber	1256
Number of jewels	17
Escapement	Anchor with pallets
Balance	Nickel screw balance
Shock protection(s)	???
Balance cock direction	clockwise
Hairspring stud	fixed
Regulator type	Hairspring key
Movement construction	Fork Escapement wheel, Fourth wheel, Third wheel Center wheel Mainspring barrel
Construction type	solid construction
Bridge shape	Triange, 3 gears + mainspring bearing
Winding mechanism	yoke
Setting lever spring	1 holes
Features	SCD,AUT
Functions	Hour, minute, second, selfwinding
Beats per hour	18000
Size	11¹/₂''' (measured: 25,5 mm)
Production time	1950-1954
Image in Flume Werksucher	1952 64