1710 Etherington Table clock with lots of bits missing

NigelW

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I am now making a new set of blanks for my cutters, this time trying my best to get all the tooling as accurately set up as possible.

First off is the drilling of the positioning holes. To do this I mounted my ER32 chuck directly onto my rotary table rather than onto a chuck adapter fixed to the table (to cut out as many "middlemen" as possible. I had to make a new set of T-bolts with 1/4" BSF threads to do this. The chuck was carefully positioned using a gauge held in the spindle and repeated taps from a hide mallet until everything was true. The arbor was then held in a collet. All went well and the set of five holes was nicely concentric (better than before).
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Next was to mount the ER32 chuck accurately in the lathe. I had tried this before but was never happy with the result. The ER32 chuck was sold with an adaptor for the Myford lathe which screws on to the lathe spindle. The chuck is then fixed on, the location being by means of a close fitting male part on the adaptor locating in a female part on the chuck, with three screws to hold it in place. Despite following the manufacturers' instructions and turning the male part in situ to ensure concentricity with the lathe I could never get the chuck itself fully concentric so I have now tried an alternative, which is to make the whole thing a somewhat loose fit on the adaptor, including opening up the countersink holes for the socket screws a shade to allow a little more movement, then tightening it down gradually with a dial indicator in place, tapping with a mallet until it is aligned. This finally seems to have worked, the eccentric mandrel has been mounted and trued up and the next stage of cutting the relief edges is underway.
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NigelW

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I was very privileged at the weekend to be allowed to remove the dial and inspect at close quarters what is probably one of the best clocks ever made by Etherington. It is far superior to mine in finish but was probably made at around the same time so it shares many of the same mechanical features. The under dial work, which you so rarely get to see pictures of in catalogues and books, is especially interesting.

In the first picture I am holding the V-shaped lever away from the quarter snail to show the "foot" which engages on the snail. This lever conveys to the quarter repeat train the information about which quarter it is. In some quarter repeat mechanisms the lever is lifted clear of the quarter snail at the end of the quarter repeat sequence and only unlocked and allowed to drop onto the snail when the quarter repeat string is pulled. Here it appears to be in contact with the snail the whole time. The potential problem with it being in constant contact is that it could jam the motion work if the minute hand is moved backward to an earlier quarter but this is prevented by having the "foot" pivoted and sprung. I have never before observed this detail.

The second picture is a close up of the other end of the V-lever where it engages with the saw-tooth like stop on the end of the main quarter repeat arbor. When the quarter repeat string is pulled (not the string you see here - that is attached to the leaf spring which pulls it back) the arbor will rotate until the appropriate tooth is stopped by the T-shaped protrusion on the end of the V lever. On release the leaf spring rotates the arbor back to its original position, strikng the appropriate number of quarters on the way. All this is quite conventional. What is unusual about this Etherington movement and mine is that there is a window in the front plate corresponding to the position of the T-shaped end of the V-lever. The exact purpose of this has long been a puzzle to me. My theory was that the saw toothed stop might have been between the plates, not in front of the plate, and that the window was to allow the v lever to engage with it, through the plate. In this clock however there is no such arrangement (for which i have found no precedent anywhere else either); the window appears only act as a stop to restrict the movement of the V lever - something which could equally well have been achieved by a pair of banking pins.

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NigelW

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This picture compares the underdial quarter repeat work of three quite similar clocks by different makers. The V-lever (B in the Gould) appears to be in constant contact with the quarter snail in both the Etherington and the Quare but in the Gould it has a pin which allows it to be lifted clear of the snail at the end of the sequence.

The unlocking arm D is attached to an arbor from which another arm between the plates extends to engage with a locking pin on the second wheel of the quarter repeat train. The configuration is the same in all three but how the arm is locked differs, the Gould being the simplest. There are also differences in the linkage mechanism C which holds the hour strike on warning until the quarter repeat sequence has been completed.

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NigelW

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This picture compares the underdial quarter repeat work of three quite similar clocks by different makers....
Another thing that all three of these appear to have in common is that the maximum rotation of the main quarter repeat arbor for any given sequence is about a quarter of a turn, which will occur when the time is between a quarter to the hour and the hour itself when three quarters will be sounded. This means that the main wheel must have 12 hammer pins (it does, in the Etherington) and if the train is locked on a pin on the second wheel that the gear ratio of the main to the second wheel needs to be 12:1 (other ratios may theoretically be possible I suppose, but this seems the most logical).

Not all quarter repeats have a main wheel with 12 pins but there is an advantage with this particular configuration of under dial work. The stop formed by the end of the V-lever is at three o'clock in relation to the main arbor and the pin on the locking arm is just before twelve. The maximum rotation of 90 degrees means that the hook or protrusion of the cam which engages the pin on the locking arm does not interfere with the interaction of the saw-toothed part with the V-lever so both can be formed from the same piece of brass sheet. If the rotation were, say, 120 degrees, then there would have to be a different, and less simple, arrangement. In the Gould the rotation needs to be a little more than the other two to allow for the unlocking of the V-lever.

This potentially sends me back to my drawing board. I originally postulated a six pin main wheel with a 6:1 ratio between it an the second wheel. With 72 teeth on the main wheel that gave a 12 leaf pinion, which I duly made. My tutor declared that this looked wrong to him and I have never found an example with this many leaves in a contemporary quarter repeat train. So I reduced the pin count to 8, giving a 9 leaf pinion which I also made. All along I was assuming the the saw-tooth like cam would be between the plates so not also be involved in the unlocking of the train, but more crucially there is limited space for the main arbor wheel given the position of the top right pillar; I had ruled out 12:1 because, using modern calculations of gear sizes and modules, that would have resulted in clearance of only half a millimetre. I am now reviewing this decision. The empty main arbor pivot holes in the plates look too much big and show no signs of wear so I feel pretty confident that they would have been bushed and the bushes subsequently removed. Since I will need to rebush the holes I think there will scope to move the centres a millimetre or so further away from the pillars to give that precious clearance which will accommodate a 12 pin wheel, a 90 degree maximum rotation, and a cam similar to that on the Etherington pictured above. A new arbor for the second wheel will be needed, with a six leaf pinion. Third time lucky, I hope!
 

NigelW

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Interesting; mine is guite good, but I've had it for years now.
The Hobson book is a facsimile of a sketchbook kept for private use and never intended for publication plus some black and white photos of only reasonable quality. There is very little description and analysis and few if any of the mechanisms are described in full. Useful, certainly, but frustrating.
 

DeanT

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The Hobson book is a facsimile of a sketchbook kept for private use and never intended for publication plus some black and white photos of only reasonable quality. There is very little description and analysis and few if any of the mechanisms are described in full. Useful, certainly, but frustrating.
Its good to help join the dots but it doesn't paint the full picture....

Would be great to write at updated one at some stage....maybe an open site where photos could be posted with explanations.
 

Mike Phelan

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Its good to help join the dots but it doesn't paint the full picture....

Would be great to write at updated one at some stage....maybe an open site where photos could be posted with explanations.
An excellent idea, Dan.
 

NigelW

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These photos compare the dials and under dial work of two Etherington clocks which I believe may be close in date. The first dial is more finely engraved and has four subsidiary dials with the alarm setting dial in the centre (clockwise from top left, strike/silent, rise and fall, day of the week, pendulum hook). The second dial (my clock) has - unusually - a rotating alarm dial in the top left, a strike/silent lever at the centre top and rise and fall in the top right.

The first under dial picture relates to the clock with the four subsidiary dials, the second to mine. The under dial layouts are different but similar. It is hard to be sure how much is original but the first is clearly much more complete. Curiously some of its elements are not as ornate as mine, for example the hour rack cock. Two under dial components on the second movement post date the removal of the quarter repeat work - the strike/silent lever and the hour lifting piece.

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NigelW

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Finally got back to making my gear cutters. To check the width and depth of the cutters I need to make I have looked again at the existing wheels. Teeth on clocks of this age are square bottomed and are formed with a more or less parallel sided cut, with the teeth only curved over at the top. The analysis shows that the teeth of the original wheels are all narrower than the gaps between them, in one case only factionally so, and at the other extreme the tooth just under about 80% of the width of the gap. The length of teeth in the trains seems pretty constant and does not vary with the diameter of the wheel, although the teeth of the finer motion work wheels are shallower. I have not yet completed the analysis but so far I have identified the need to make three different cutters. Cutter 1, being the same depth as cutter 2 but narrower, could be used instead of making a second cutter if I advance the dividing head slightly and do an additional round of cuts but I would feel more comfortable using a wider cutter I think as I will be doing all the dividing by hand, having economised by not buying an electronic one.

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NigelW

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Used my Vertex rotary table today with an ER32 collet chuck mounted on it to slash the teeth on my first gear cutter. Stages of cutter development shown in second piucture, alongside a commercial Thornton cutter. Still need to heat treat, polish and test.

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NigelW

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Just had an email from my dial and case restorer. Both are finished. The mechanism restoration is more or less designed and some tooling up has been achieved but I am far from completing it.

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