Ancient and Modern: II Ancient

'Dead-beat' clock temporarily dead!

Here you see the works of a old(-ish) wall clock that is timed by a pendulum. It's entirely mechanical. The escapement is a modified Graham design (dead beat), with adjustable pallets.

This link is to a photograph of a clock almost exactly like ours, except that we have a 'seconds' hand in a small dial at the top.

It hadn't worked for years, but when we moved to our present home four years ago, I decided that it was time to try to get it running again. Somewhat to my surprise, I managed it...

But a couple of weeks back, it decided it didn't want to run any more, and so I took it apart again, and you see the results in this photograph.

I gave the gears a general clean-up, and lubricated them with some VERY light silicone oil. But the real problem seemed to be the pallets that tick-tock in the teeth of the escapement wheel. They had become grooved over time.

You can see the escapement wheel as the furthest-right wheel in my 'photo, and it drives the 'seconds' hand direct. One of the two steel pallets can be seen passing through the brass verge to the right of the wheel, and with some imagination you can discern the angled end touching one of the teeth. The other pallet is mounted on the opposing side of the verge, and as the pendulum (to which the verge is attached when the clock is mounted) swings, the two pallets engage with the teeth in sequence to allow the wheel to advance one step. ... And, if all is working right, a sustained tick and tock ensue. But it wasn't all working right! Please sing the Grandfather Clock song at this point...

Ninety years without slumbering, (tick, tock, tick, tock).
His life's seconds numbering, (tick, tock, tick, tock).
It stopped, short, never to go again, when the old man died.

With some trepidation, I decided that I had to grind, reface, and then polish the hard-steel pallets. The previous time I got the clock running, I had merely cleaned up the grooved faces as best I could. The 'trepidation' arises because (i) The ends of the pallet are cut to a very precise (!!!) angle on the inside faces; and (ii) I have absolutely no idea of what I am doing in this field, and no ability to cut nice faces, regardless of precision. The face angles determine how much energy gets transmitted back to the pendulum from the weight and gearing, and thus the sustainability of oscillation, that has to compensate for the losses in the bearings and gears of the clock.

To illustrate what I just wrote, here is a photograph of an escapement like our clock's, showing the angled faces of the pallets.

I also resoldered the verge to the pivot arm, so that the verge hung more symmetrically and so that the 'nibs' of the pallets engaged centrally with the teeth of the escapement wheel. Breath-holding tasks!

The long and short of it is that the clock appears to work again: at least it has run for the last eight hours or so.

Good!

But there's another side-story to be told about this clock. We inherited it from my wife's mother. My lady's parents had been Sussex artisans, with no apparent connections with academic matters whatever. But we unravelled a tale that told how this very clock had once been mounted on a wall in Oxford, not more than a couple of miles from where it now is. Great-grandfather had, according to this story, been the Bursar of one of the grander colleges. But he drank too heavily (that must have been going some in the late 19th century), and was 'relieved of his duties'. My, oh my! ...And now, by an amazing coincidence, the clock is in our house.