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ETA 1256

 

ETA 1256ETA 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.

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

top view selfwinding mechanismtop 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 mechanismbottom 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 mechanismmovement 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 clutchdetail: 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 platemain plate

On the dial side, you see nex to the Benrus inhouse shock protection the yoke 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.

 

ETA 1256 dial side viewETA 1256 dial side view

 

 

 Technical data

ManufacturerETA
Caliber1256
Number of jewels17
EscapementAnchor with pallets
BalanceNickel screw balance
Shock protection(s)???
Balance cock directionclockwise
Hairspring studfixed
Regulator typeHairspring key
Movement constructionFork
Escapement wheel, Fourth wheel, Third wheel
Center wheel
Mainspring barrel
Construction typesolid construction
Bridge shapeTriange, 3 gears + mainspring bearing
Winding mechanismyoke
Setting lever spring1 holes
FeaturesSCD,AUT
FunctionsHour, minute, second, selfwinding
Beats per hour18000
Size111/2''' (measured: 25,5 mm)
Production time1950-1954
Image in Flume Werksucher 1952 64
ETA 1256ETAETA12561950-195411 1/2''''''ETA 125617 Jewels, 11 1/2'''''', 18000 A/h, SCD,AUT
Factsheet

 

 

Test results

The specimen shown here, was completely gummed and showed signs of water damage. It had to be cleaned and overhauled competely.

 

Timegrapher protocol

crown rightcrown right crown topcrown top crown leftcrown left crown bottomcrown bottom 
dial topdial top dial bottomdial bottom 

On the timegrapher, the ETA 1256 showed excellent results, especially, when you know, that this movement is more than [[datetoage:1950] years old.

It was even possible to generate the timegrapher outputs in double precision!

 

 

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