................ as I'm trying to repair a vintage Omega desk clock. The original electrical movement powered by a "D" cell was an intricate "Portescap" hybrid, where a transistor controlled electric motor kept a mechanical balance wheel/escapement moving, this in turn actuated a lever which kicked a shaft with a rubber "tyre" into engagement with a pinion on the motor shaft. The "axle" of the tyre ended in a worm gear which turned a normal set of hour/minutes/seconds wheels. A very well made little bit of 1950s engineering to almost watchmaking standards. However.... The rubber tyre was prone to degradation, possibly due to early synthetic rubber not being as stable as it is now, and the contamination of oils and cleaning chemicals only served to hasten its demise. Being of unitary construction, the tyre, rims and axle are not replaceable and repair can only be done with reasonable difficulty. In addition to this inherent design flaw, the transistor circuit was also prone to failure of components, most notably the germanium diode. Then there was the issue of the spring loaded lower jewel on the worm drive etc etc. An ingenious little caliber in its time, but destined to sit in the departure lounge well ahead of it time. So the issue arose, what to replace it with? A modern quartz movement? These range in price from AUD$5.00 to $50.00 or more per unit and quality is aligned with the price. There's only one problem. The original clock, being made as I said to almost watchmaking standards, only had 6.5mm clearance between the surface of the dial and the underside of the glass and many of the modern movements, having plastic hand mounting shafts, require at least 10mm clearance to prevent the hands from touching the glass. After a lot of experimenting I found a movement that might work, but as the hands supplied with it are unsuitable, the original hands would have to be re-purposed. First problem, the modern movements all have big shafts for fitting hands and the original had extremely fine ones (did I mention "watchmaking" quality?). So, after pulling apart a few of the quartz movements I though I might have an answer. I removed the seconds hand shaft, chucked it up in my lathe in my lathe and turned it down a few 10ths of a millimetre. I then took the original seconds hand a broached out the pipe until I had a nice interference fit and "Presto!", the first part of the problem solved. So enough for today, I'm going to have a beer and watch footy on the box.
PS: If anyone is interested I can put up some pics and details of the Portescap of the movement. As I said, it's a great little bit of early hybrid horology.
I would love to see some pictures. I've always been one to open things up and have a look at what makes it work and how they may have done it differently than others.