Dimensions: 205 x 30 x 22 cm ( H x B x T )
Duration: 4 months
Price Range (inkl. VAT): 55 – 65.000,00 €
The precision pendulum clock GRAMAT is the only clock currently being produced that operates in a partial vacuum similarly to the clocks in evacuated tanks produced in the last century. After a long development period, PW has succeeded in producing hand-made, extremely delicate and airtight housings. By means of a patented process, the density of the enclosed air is kept remarkably constant, thus protecting the pendulum from atmospheric changes. The sensor is a glass ball with a volume of approx. one liter. The air’s density affects the ball’s buoyancy, which, in turn, controls a small vacuum pump located in the base of the clock. This control mechanism is so sensitive that it is triggered by density changes of less than 0.1 mg per liter, which corresponds to a change in air pressure of 1/10 hPa. The control panel is located in a drawer. When it is time to wind up the clock, the vacuum control unit is turned off and air is permitted to enter through a valve. The air pressure is indicated on a precise diaphragm pressure gauge.
The adjusting screw at the lower end of the pendulum rod is activated by means of a worm gear. It allows for very sensitive adjustment with a precision of 1/100 of a second per day. Another unique feature is the beautiful large wheel with its 400 teeth. It is a tribute to the mysterious table clock made by the famous clockmaker Jean-Antoine Lépine at the turn of the 18th and 19th centuries. As in all PW clocks, the epicyclic gearing is worked into the hub. Because the arbor of the large wheel assumes the role of spacer, the plates can be reduced to a minimum. The string barrel is activated using an offset rewinding gear.
The GRAMAT precision pendulum clock also has a long central second hand, a feature rarely seen in long case clocks. The minute wheel is located in the power train and the escape wheel arbor runs through the minute wheel’s arbor without touching it. This challenging design has never before been implemented in this form. Aside from the GRAMAT and the SARLAT, no clock currently being produced has a double escape wheel. Two wheels are used for the lift and stop functions. This design, known from astronomic precision pendulum clocks such as Rieflers’, makes it possible to provide the anchor with bearings that roll off of the lift faces, thereby preventing friction and wear. The double escape wheel also greatly improves the escapement’s effectiveness. It requires significantly less driving force, so the clock runs more gently and is more durable. The weight that provides its driving force weighs only 2.8 kg, and the clock runs for a full four months before the next rewinding.
The GRAMAT precision pendulum clock can be crafted with a highly precise gravity escapement or with the patented PW escapement that provides the pendulum with the most freedom possible. Both options make for an extremely accurate timepiece capable of achieving a deviation of less than 1/2 second per month.