- Ranfft’s page on the Buren 1280
The movement is interesting for several reasons. It is one of the first movements with micro-rotor, it is only 2.7mm thick despite being self-winding, and it has no centre wheel. The shift of the centre wheel to a decentralized position (and therefore now called main wheel) was also used by Piaget in the caliber 9P. In both instances, the goal is to avoid an overlap. In the Piaget, it is to avoid an overlap of the centre and balance wheels and in the Buren to avoid an overlap of the centre wheel and micro-rotor.
The second wheel has a pinion reaching through the base plate and indirectly driving the cannon pinion.
Under the micro-rotor, after a first transmission gear, there are 2 gears in parallel. Depending on which direction the previous wheel turns, it drives one of the other of these 2 parallel wheels, which results in the wheel on the right always turning in the same direction (reverser system).
Another interesting point is that 2 wheels removed from the ratchet wheel, there is a wheel with 2 layers and some holes. This allows the top layer to slip over the other without driving it when the ratchet wheel is manually turned so that the micro-rotor system is not engaged.
