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Carlo Croce, Cogorno, Italy. 2003. 12"h x 8.5"w x 8.5"d, without dome. 15"h x 11"diameter with dome. Custom design, completely hand made. Dead bead verge - crown wheel escapement, one-half seconds pendulum. Click on the picture to go to a page for more detail. Click here for photos of the clocks' construction. This design is a closely based upon that originally made by John Joseph Merlin in 1776. It is regarded as the first true skeleton clock made in England and remains one of quite igneous and original design. During the period of 1820 - 1850 a few fine makers such as Condliff and the partnerships of Strutt and Wigston, and Parker and Pace produced some beautiful quality and highly ingenious clocks, but only in limited numbers. By the mid nineteenth century the production of skeleton clocks had increased dramatically, roughly matching the rapidly increasing industrial wealth of the country, and it was at this stage that their manufacture was largely taken over by a few specialized firms such as Smith of Clerkenwell and Evans of Handsworth.1 Merlin was principal mechanic to James Cox, the celebrated maker of of automata and musical clocks. In 1773 Merlin left Cox and established his own museum of automata known as Merlin's Necromantic Cave. His main field of activity was in the design of mechanized musical instruments. He was also the inventor of the roller skate. He used the skates in a demonstration where, as described by the source footnoted below: 'supplied with a pair of these and a violin he mixed in the motley group of one of the celebrated Mrs. Corneily's masquerades at Carlisle House, Soho Square; when, not having provided the means of retarding his velocity, or commanding its direction, he impelled himself against a mirror of more than five hundred pounds value, dashed it into atoms, broke his instrument to pieces, and wounded himself severely'.2 The shock of this incident appears to have made Merlin give up his desires to to set this invention before the public, and it was left to the Americans to reintroduce the roller skate under that name in the early 1870s.2 Unfortunately, like Congreves' rolling ball clock; while an ingenious design and interesting to look at, it is a poor time keeper and difficult to keep running. The verge escape wheel has 60 teeth and is used to indicate the seconds. Normally a verge has an odd number of teeth so the resting or dead faces of the verge are staggered on on either side of its' axis. The center wheel has 60 teeth and drives directly the vertical escapement pinion which is a worm gear. It is here that the clock exhibits it main problem in reliability. A worm driving a toothed wheel provides a reliable, low torque input. However, in reverse, a high torque from the toothed wheel to the worm is required. While this works well in the fly fans of a music box or clock fly fans which do not involve static friction (see Rahmer), this is wholly unsuitable to drive a pendulum! A pendulum involves a process of starts and stops entailing greater frictional forces known as static vs. moving friction. The profile of a normal toothed wheel driving against a worm gear results in a very small area representing the edge of the tooth driving the worm. This creates a great deal of pressure in a tiny area resulting in high friction. A helical gear instead of a conventional 60 toothed wheel would have solved this problem, but this was prior to Charles McDowalls' helical geared skeleton clocks of the 1830s. It is doubtful that Merlin's original clock ran for any length of time before lubrication failure due to the problems discussed and the deficiencies of the oils available in those days, caused it to stop. A modern, synthetic, high pressure automotive grease applied to the worm gear is used to overcome this problem. Even so, wear is apparent on the edges of the main toothed center wheel. 1. Roberts, Derek, British Skeleton Clocks, Suffolk, England 1987 2. Busby, T., Concert Room and Orchestra Anecdotes, London, England 1825
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