One of the last ETA selfwindig movement, which is, unlike the 2824 familiy, already
out of production, is the ETA 2873, which debuted in the 1970ies.
It is a rather simple mass production movement, but still shows the familiar ETA quality.
There's no decoration on the movement, only the oscillating weight got its checkered pattern.
Technically, it doesn't matter, whether a movement is decorated or not.
movement view without oscillating weight
The ETA 2873 uses the million times proved ETA selfwinding mechanism with its double click wheels.
All gears, with the exception of the slowly running transportation wheel to the click wheel, are beared
in rubis.
bottom view selfwinding mechanism
Since the oscillating weight winds in both directions and the two click gears are always driven
by the weight, the click mechanism of these gears takes care, that the transmission wheel is always
turned in the same direction. For that, it's always one of the click gears, which spins freely, while
the click of the other ensures its power transmission.
movement view without selfwinding mechanism
The construction did not change since decades:
The large, here three-leg, ring balance (of course Incabloc-shock-protected) uses a hairspring, whose
one end is attached to a moveable stud. Its effective length is adjusted with the hairspring key.
The movement itself uses a swiss pallet lever escapement. The center second is directly driven and there's
no minute wheel, but the minute wheel on the dial side is indirectly driven by the third wheel.
This construction is used in ETA movements since the 1950ies until today!
A place, where you can see the "red pencil" is the click mechanism: It consists only of a specially shaped
spring, which works on the horizontally(!) moveable crown wheel.
The different tooth types of crown wheel and mainspring wheel is neccessiary because of the
selfwindig mechanism, but it can be easily imagined, that it is not a good idea to wind this
watch manually every day.
main plate
The date mechanism advances the date instantly and allows manual correction on the second (of three)
crown positions. The driving wheel is even jewel-beared!
dial side view
At "8" you see the pinion of the third wheel, which indirectly drives the center minute wheel, which
has to be set onto the large center axle.
At "3", you see the setting lever spring with its three positions (manual winding, date correction, time
setting).
dial side view without date mechanism
Technical data
Manufacturer
ETA
Caliber
2873
Number of jewels
25
Escapement
Anchor with pallets
Balance
Nickel
Shock protection(s)
Incabloc
Balance cock direction
counterclockwise
Hairspring stud
moveable
Regulator type
Hairspring key
Movement construction
Fork Escapement wheel, Fourth wheel, Third wheel, Large driving wheel Mainspring barrel
Construction type
solid construction
Winding mechanism
yoke
Setting lever spring
2 holes
Features
SCD,AUT,QG,RDR
Functions
Hour, minute, second, day, selfwinding
Beats per hour
21600
Size
111/2''' (measured: 25,5 mm)
Factsheet
Test Results
The movement can only with its dial into the studio and hence was completely disassembled,
cleaned and oiled.
Timegrapher Protocol
On the timegrapher, this movement showed exactly, what was expected from a simple
ETA mass production movement: Rock solid results in all positions with low variance. Very hard
to top!
It was even possible to generate the timegrapher outputs in
double precision!
