Friday, 2 March 2012

The engineering workshop

Here are some images of work in progress. Geoff Mitchell, Technical Services Officer, has been hard at work designing and then making replacement pinions for the clock movement. The new parts are properly uniform, without any of the inaccuracy associated with those they are replacing (see below). They will mesh more effectively, making better use of the the original wheels and placing minimal stress on portions of the original teeth that are already badly worn.

Design notes for the new count wheel pinion

The original pinions were fastened to their respective arbors (see glossary) by peening, meaning the edges of the arbor were hammered to pinch the pinion tightly. As we do not want to reproduce this technique (which would further damage the original arbors) Geoff has designed the new pinions with retention screws which can be undone at any time.

The new countwheel pinion alongside the original, and the countwheel itself

We know that, given the advanced wear suffered by some of the original wheels during the last 50 years, our restoration work presents a final chance to retain the Castle Rushen Clock in working order. Any further pronounced wear in the original wheels would render them inoperable without very invasive treatment, such as re-profiling of the teeth with new metal. We will watch the clock movement very closely indeed for signs of such wear over the coming ten to twenty years.

The new fly pinion in situ. Note also the new pivot for the fly arbor. I am holding the old pinion