EB 8027

EB 8027 | 17jewels.info - The Movement Archive

EB 8027


The EB 8027 is a typical pin lever movement of the Ebauches Bettlach, which is considerably finer made than other pin lever movements and impresses with the extraordinary high number of 23 jewels.

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Like most other EB pin lever movements, the EB 8027 uses an extra flat and light ring balance, too. Its torque is pretty low, nevertheless even these movements are capable for daily use. The watch shown at the bottom of the page can tell you stories…

A speciality of the specimen shown here is, that the three leg ring balance is beared in two shock protections, probably Trishock. And besides that, the whole balance system with its moveable hairspring stud seems to originate from a “better” watch than an EB pin lever movement.

EB 8027: gear train

gear train

The construction of that movement, which probably originates from the 1960ies is contemporarily modern with a directly driven center second and a minute wheel, which is located under its own bridge.

EB 8027: side view of the gear train

side view of the gear train

The movement is a so called pier construction, which means, that between the thin main plate and the upper bridges, there are only pillars. This saves a lot of money, but is of course less stable and sturdy.

EB 8027: base plate

base plate

All bearings, even of the hour changing wheel, contain synthetic rubies. From a technically point of view, there’s no need for such a bearing on the mainspring barrel nor on the hour changing wheel, and even the cap jewel of the third wheel is not really neccessiary.

The escapement wheel bearing has got a cap jewel only on the movement side, but not on the dial side. The reason for that oddity is unknown, but maybe 24 jewels would have become rather implausible.

EB 8027: dial side without date indication mechanism

dial side without date indication mechanism

The EB 8027 uses a rocking bar winding system, which is much cheaper than a yoke winding system. Unfortunately, the click mechanism is also very simple made - it consists only of one single spring, which blocks the ratched wheel. It’s not a solution for lifetime…

EB 8027: date indication mechanism

date indication mechanism

The date mechanism is, apart from one detail, pretty simple and genious at the same time:
The hour wheel drives the date setting wheel with a moveable fusee. This fusee tensions the date setting lever during the whole day and reduces force from the movement. At midnight, the lever can unblock in a single step, since the fusee is moveable, and advance the date.

The other function of the fusee is, that by setting the time back and forth a few hours, the date can be corrected semi-fast.

The disadvantage of this construction are the two thin springs. They’re breaking fast and so, don’t apply tension to the date setting wheel. Without tension, the whole mechanism is dead. You can see the broken spring on the photo.

EB 8027: EB 8027 dial side

EB 8027 dial side

The date ring is very broad. Unfortunately, it is made of plastic, which discolors by sun rays. You can see, on which day, the date mechanism broke…

Technical data

Size:11 1/2''' (measured: 25,55mm)
lift angle:43°
Number of jewels:21
Escapement:Pin lever
Balance types: Nickel anular balance
Shock protection(s): ?
Balance bearing / direction hairspring:Clockwise
Moveable stud:yes
Adjust mechanism:Hairspring key
  • lever
  • escape wheel, seconds wheel, third wheel
  • center minute wheel
  • mainspring barrel
Construction type:pillar construction
Winding mechanism:rocking bar winding system
Setting lever spring:1 hole(s)
  • SCD (direct center seconds)
  • QG (date indication (aperture))
  • RDR (date corrector)

Usage gallery

EB 8027: Helsa Precision divers' watch

Helsa Precision divers' watch