Lorsa 81
Description
The Lorsa 81, a tonneau shaped movement with 6 3/4 x 8 lignes, made in France, dates from around the mid 1970s until the early 1980s and was one of the last tiny windup movements from France.
The contemporaneous offered fully round version of this movement was the Lorsa 82. Both are technically equivalent.
base plate
The execution of this movement is standard; of course all important bearings contain rubies.
gear train
The gear train follows the usual conventions for tonneau shaped movements of this size: Mainspring barrel, directly driven center minute wheel, tiny third- and fourth wheel and finally a large steel escape wheel.
side view of the gear train
Due to the limited space, the lower bearings of third- and seconds wheel are above the escape wheel.
movement w/o center seconds
The execution of the ratchet is as easy as genious, it consists only of a single part, a spring-loaded click, which is beared below the ratchet wheel and engages into it.
gear train with center seconds
The seconds wheel is beared on top by the center seconds bridge. The center seconds pinion is driven by a flying beared, just put onto an axle, transmission wheel, located at position 4 o’clock.
The drawback of this construction is, that as soon as the flying transmission wheel touches the bridge or the slightest part of dust is between this wheel and the bridge, so much friction is applied, that the amplitude goes down dramatically.
side view with center seconds
As escapement, a swiss pallet lever escapement is used.
It is controlled by the three-leg anular balance, which beats with 21600 A/h and is beared in two RUFA Antishock bearings.
The frequency can only be regulated directly at the hairspring key.
Lorsa 81: Dial side
We have the expected view on the dial side, we see the woke winding system and we can see the two bearings of the third- and seconds wheel, which are above (seen from the movement side) the escape wheel.
In the lab
Timegrapher result
On the timegrapher, this compareatively small movement made an execllent impression; with a little higher amplitude, it would have run in all positions within the chronometer specs.| horizontal positions | |||
|---|---|---|---|
| dial up | -2 s/d | 259° | 0.4ms |
| dial down | +-0 s/d | 246° | 0.2ms |
| vertical positions | |||
| crown right (12 up) | -8 s/d | 195° | 1.2ms |
| crown up (3 up) | -+0 s/d | 195° | 0.3ms |
| crown left (6 up) | +6 s/d | 200° | 0.0ms |
| crown down (9 up) | +-0 s/d | 196° | 0.9ms |
Technical data
| Manufacturer: | Lorsa |
| Caliber: | 81 |
| Size: | 6 3/4 x 8''' (measured: 15,2 x 17,9mm) |
| A/h: | 21600 |
| lift angle: | 52° |
| Number of jewels: | 17 |
| Escapement: | Pallet lever |
| Balance types: |
monometallic anular balance (three legs) |
| Shock protection(s): |
Rufa-Anti-Shock |
| Balance bearing / direction hairspring: | Counterclockwise |
| Moveable stud: | yes |
| Adjust mechanism: | Hairspring key |
| Construction: |
|
| Construction type: | solid construction |
| Winding mechanism: | yoke winding system |
| Setting lever spring: | 6 hole(s) |
| Features: |
|
| References: |
Frankreich: 1976 |
| Inventory number: | 22060 |
Usage gallery
Prätina ladies' watch