Latest bit of ebay tat...

[Matt]

As Harrison's splendid new (old) clock demonstrates beautifully, the secret of a great clock is minimal interference with the pendulum. The problem, of course, is that you need to perform two functions that require a degree of interference. First you need to power the pendulum and second you need to take a signal from the pendulum to the rest of the train.

My latest ebay buy takes this principle one step further than most, by powering the train magnetically rather than mechanically, using two sodding great electromagnets:


which turn on every few ticks and give the pendulum a bit of a pull when it is at the end of its swing. So how is this impressive feat of turning on at precisely the right moment and only when the pendulum is starting to slow achieved? I can almost hear you ask. Here's where things start to get gratifyingly unexpected.

further up the pendulum there's an extra arm with a jointed metal rod that swings very freely indeed in the same two dimensional plane as the pendulum. Most of the time it gently caresses over a strangely grooved jewel, attached to a setup that looks pretty well identical to the sort of contact breakers you find on old cars.




However, every so often, when the pendulum is starting to slow down, the little rod will catch in the groove in the jewel and very gently push it downwards like so:



completing a circuit powered by an old six volt battery and powering up the electromagnets to give the pendulum a tug. All in all, pretty cool, no?

But there's more:

Up at the top of the clock there's a set of brass bushed mainplates that have clearly been made up in perspex to replace the original brass ones and together with the (absent) chapter ring style dial allow a view of the escapement, or rather half an escapement, as this one is relieved the duty of powering the pendulum allowing it to be very simple and minimise interference with the pendulum:



The set up is pretty close to identical to the f300 with two pawl arms, one of which pushes the wheel forward one notch, while the other catches the wheel and stops it falling backwards. This powers a perfectly normal train through to the hands.

The clock was sold as a non runner which had been put in the loft decades before by the seller's father. I assumed that the electrics would be fried or something would be broken, but I think the truth is a little more interesting.

As you can see, the contact breaker arrangement is currently spoiled aesthetically by a couple of cheap cross head screws. and appears to be floating a centimetre or more above the back. This is because I had to replace the original short screws and shim the contact breaker setup until it was perfectly in line with the rod. It's a bodge right now, but I'll do it properly soon. Prior to this, the contact breaker setup was out of line of the travel of the pendulum and so the little rod would never get to 'accidentally' settle in the groove and push down. The most it could ever do is slip off at a stupid angle.

Working out the problem, I can only assume that the original mechanism is very old. The electromagnets appear to have been rewound prior to not being used as the windings are comparatively recent and immaculate, the case seems to be modern, handmade and very nice, but the mechanism stinks of late Victorian (over)engineering. So I think that someone spent a lot of money recasing an ancient electromagnetic clock, giving it perspex plates, revamped electrics and a new dial setup and in doing so failed to get the system set up so everything indexed correctly. They then gave up without noticing the problem and stuck it in the loft. When the son (who was a lovely Cypriot chap with the most beautiful old house) got it down again in the course of building works, he appears to have just wanted rid and popped it on ebay.

To a electromechanical clock fan like me, the problem was obvious, but unless you have spent plenty of time jumping between purely mechanical and electromagnetic components, or setting up the points on a BSA Bantam with Rizla paper, I can see trying to work out the chain of causation being utterly bemusing.

It's running now with reasonable accuracy, considering it needs a service and setting up carefully and it makes the most wonderful range of muted rustles with the tiniest little tink by way of a tick. I think I've finally found a longcase I can run in my bedroom, and what a beauty it is! Setup, service, new hands and face and a bit of all round TLC and this will be very very special. I do love Ebay!

[Donf]

Half mechanical, half electric - a concept that seems to have fascinated designers for years.

Cool find - but of course it needs a service - you got it on ebay!

[FuzzyB]

Very cool! It makes me happy to know there are people around that understand how these things work and care enough to to get them running again. Well done!

[iyonk]

Any Wrist shot?

[Colin]

Very interesting! Thanks for posting!

(I was looking for something good to read while I flossed.)

[tempocalypse]

Very cool! Would love to see a picture of the whole clock by the way