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Ebosa 86
Manual · 8.75‴ · Switzerland · 1960
Dimensions
19.74 mm
Height
4.50mm
Jewels
17
Power reserve
—
Timegrapher
Beat rate
18,000bph
Frequency
2.5Hz
Lift angle
63°
Reference: healthy amplitude ≈ 270–315° fully wound (>200° at 24 h); beat error ideally < 0.5 ms.
Movement
| Movement type |
Manual
Purely mechanical movements wound by hand via the crown, which tensions the mainspring to store energy. As the spring unwinds, it drives the gear train at a controlled rate set by the escapement and balance. Typical power reserves range from 38 to 80 hours, requiring daily or near-daily winding to keep the watch running.
|
|---|---|
| Winding type |
Stem Winding (Crown)
Winding the mainspring by turning the crown attached to the stem, transmitting torque through the winding pinion. Patented by Adrien Philippe in 1842, it replaced key winding and remains the standard manual winding method for both pocket watches and wristwatches.
|
| Setting type |
Stem Set (Crown Pull)
The dominant modern system: pulling the crown out to a setting position engages the hand-setting mechanism. Introduced in the late 19th century and refined into multi-position crowns (date, time, GMT). Used in virtually all modern wristwatches and most 20th-century pocket watches.
|
| Escapement type |
Pin Lever
Also known as the Roskopf escapement, this is a simplified, low-cost variant of the Swiss Lever using steel pins instead of jewelled pallet stones. Less accurate but inexpensive to produce, it democratized mechanical watchmaking in the 20th century, populating affordable alarm clocks and entry-level watches worldwide.
|
| Control type |
Balance Wheel
The heart of mechanical timepieces, the balance wheel is an oscillating component that, together with the hairspring, forms a harmonic oscillator regulating the gear train's pace. Its steady back-and-forth motion ensures the even release of energy from the mainspring, governing the watch's accuracy.
|
| Regulator type |
Pinned Regulator (or Index Regulator)
The most traditional regulator, consisting of a movable index pointer fitted with two curb pins (or a pin and a boot) that embrace the hairspring. Sliding the index along its scale changes the spring's active length, adjusting the rate. Simple, reliable, and easy to service, it remains the workhorse standard across countless mechanical movements.
|
Specifications
| Lignes | 8.75‴ |
|---|---|
| Shape |
Round
It is the most common form that we can find.
|
| Complications |
Sweep Second
Contrary to the ticking motion of quartz watches, the sweep second hand in mechanical watches moves smoothly around the dial, offering a visual representation of time flowing continuously. This has become synonymous with the precision and craft of mechanical horology.
|
| Hand count | 3 |
| Hand sizes | 1.40 x 1.00mm |
| Further measures | Nominal Diameter (Dn): 19.74mm |
Origin & References
| Manufacturer | Ebosa |
|---|---|
| Country | Switzerland |
| Launch year | 1960 |
| In-house | No |
| COSC certified | No |
| Signature | ca. 1960: Swiss parts 417, 1 Jewel |
Notes
Remarks: pin-lever escapement
indirect minute, hand friction clutch on barrel (Roskopf type)
Other data: balance staff: differing specs Flume, Ronda: U1983, Ronda 3725: pivots, roller Ronda 3687: pivots, finger U3051: pointed, finger (only Ebosa 86) stem: W2194 mainspring / battery: 1.10 x 9.5 x 0.09mm balance staff ronda: 3687 (8,75) balance staff ronda: 3725 (8,75) balance staff ronda: 5251 (8,75) stem ronda: 573 (8,75)
Ranfft mentioned about this caliber: There are variants with this quantity of jewels 1, 17
indirect minute, hand friction clutch on barrel (Roskopf type)
Other data: balance staff: differing specs Flume, Ronda: U1983, Ronda 3725: pivots, roller Ronda 3687: pivots, finger U3051: pointed, finger (only Ebosa 86) stem: W2194 mainspring / battery: 1.10 x 9.5 x 0.09mm balance staff ronda: 3687 (8,75) balance staff ronda: 3725 (8,75) balance staff ronda: 5251 (8,75) stem ronda: 573 (8,75)
Ranfft mentioned about this caliber: There are variants with this quantity of jewels 1, 17
Family
Compatible Parts
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