The Bifora 81, which was only built for four years (1958 till 1962) is a small manual wind movement with a diameter of 8 3/4 lignes, intended for ladies' watches. The unusual on this movement is its directly driven center second, which required an enormous height and also led to a very compact construction especially in the balance and hairspring area.
The base plate already shows two things: The rocking bar winding mechanism together with the ratched, which is located on the dial side and all bearings are ruby-equipped.
On the gear train, minute- and center second wheel are on top of each other and have got the same diameter, even the diameter of the third wheel is the same. The wheels go quite far into the balance area. When you mount the movement, you have to put the hairspring below the center second wheel, while you have got almost no vertical space to do this. Maybe this was the reason, why the Bifora 81 was discontinued so fast.
On the side view you see the compact construction even better, and also the very long axle of the excapement wheel, which on its top side, engages into the center second wheel.
The balance, which is located under a small cock, beats contemporarily slow with 18000 A/h and is beared in two inhouse Bishock protections. It regulates a swiss-type pallet lever movement.
Like most Bifora movement, the caliber 81 also uses a rocking bar winding mechanism and a ratched (here a very well constructed one) on the dial side.
To get to the popular 17 jewels, two cap jewels are used, one for the escapement wheel (useful, since it works as an oil reservoir) and one for the lever axle (useless, since the lever axle doesn't use oil for bearing).
In the lab
The specimen shown here was resinified and has a loose balance cock, so it got a full cleaning treatment. Afterwards, it became clear, that the hairspring lost its shape and kind of falls onto the legs of the balance. In addition to the very compact construction around the balance, it is impossible for a non-watchmaker to fix this.
This movement and watch was kindly donated by Erwin. Thank you very much for the support of the archive!