William Renda, Paris, France. 1952. Movement net, 15"h x
7.5"w x 4.25"d, w/ dome 17"h x 9.5" diameter. One minute
period flying tourbillon with pinwheel escapement driven by a sector gear from a
2.5" diameter one second balance wheel. Count wheel strike powered from separate
spring barrel. Gilded movement and frame.
The tourbillon, (French for 'whirlwind') is recognized as one of the more difficult
complications to make. It was invented by Abraham-Louis Breguet in 1795 to compensate for
positional errors in watches. This is accomplished by mounting the escapement in a
rotating frame, so that the effect of gravity cancels out when the escapement is rotated
180°. By encasing the entire escapement within a rotating frame (the tourbillon), the
frame, as it rotates, constantly varies the position of the balance wheel in
relation to its environment. The effects of gravity were particularly problematic when
pocket watches were carried in the same pocketed position for most of the day. In a
tourbillon, the entire escapement assembly rotates, including balance wheel, escapement
wheel, and pallet fork.
Of course, this is entirely superfluous in a stationary table top clock. This fact
coupled with the difficulty of fabrication, results in few such examples having been made in the larger versions
necessary for a table top skeleton clock.
William Renda is unknown as a clockmaker. In fact he signed the movement as 'William
Renda, Ingenieur, a Paris'. Apparently he considered himself an engineer or perhaps a
machinist rather than a clockmaker. It is possible that this is a unique piece. The
quality of the work is first rate as exemplified by the gilded finish of the frame as well
as the fine bluing of the screws, clicks and their springs which are beautiful. A star
pattern was used for several of the wheels. Three points for the balance, five for the
count and six for the great wheel - an artistic balance of symmetry to the size of the
wheel. All spoked wheels are attached to their collets by screws. The dial is made from
two pieces of silvered plates that sandwich the blue enamel number plaques with a separate
engine-turned bezel. Since the tourbillon is vertically mounted, the pinwheel escapement
needed to be exactly counter-balanced on the tourbillon cage. In addition the pinwheel
escape pallets had to have their own poising weight.
Following are several video clips of the tourbillon escapement, the last showing the
clock striking: 1, 2, 3, 4, 5.