Restoration of English Longcase Clock Movement. By Robert Coster, Newbury Circa 1730-40

This is very nice five pillar (finned) movement by Robert Coster of Newbury, Berks. It is an 8 day movement, with a count wheel strike train. Robert Coster was apprenticed to Luke Wise of Reading in 1695, and worked in reading until 1707 whereafter he relocated to Newbury. Robert Coster died in 1749 in Avington, near Newbury ( B Loomes 2006)

As is ordinarily the case for English longcase movements, it has continued running on the basis that any wear and issues have been overcome by the great amount of power supplied by the 10 and 12lb weights. Any other type of clock would have stopped a long time ago. These just keep on going based on this power, and the robust nature of their parts. However when the time comes to 'make good' the movement, it always involves a great deal of work. On a movement such as this, it is important to conserve the original parts as much as possible. 

As is often expected on these movements there have been previous attempts to close up worn pivot holes in the plates by punching the brass. This has been carried out quite aggressively throughout the movement, a few examples above and below. It can also been seen on the inside of the plate, that there has been the need to have proud bushings. This has been required due, it would seem, to excessive end shake of some of the arbours

The arbour pinions show a deal deal of wear throughout. The fly arbour pinion, first picture below, being particularly worn. 

The pinions are cut from from the same piece of steel as the arbour originally. An option to rectify the wear here would be complete arbour and pinion replacement. However this movement requires a conservation approach. To replace the pinions here would be to replace all of the arbours, and is not an option. So all but the fly arbour pinion will be repaired by re-building the steel pinion leaves by micro-welding techniques. I do not have the appropriate micro-welding equipment, so this work will be given to Mr Geoffrey Walker FBHI. Once the pinions leaves have been built up, Geoffrey will grind away the excess material and reshape the pinions. 

I have chosen to replace the pinion on the fly arbour, however, the arbour will not be replaced. A fly type cutting tool was made to replicate the shape and size of the pinion leaves. Silver steel was mounted into a lathe, and centre drilled to 1.20mm. The steel was then mounted on the mill, and a new pinion length was cut with the single tooth fly cutter. The pinion leaves were cut off the fly arbour on the lathe, and the abour turned down, in order to receive a 4mm length of the new pinion.

     The pinion was finished, staked and fitted to the arbour. 

   

The steel pins on the strike pin wheel are unsurprisingly worn, with near three centuries of lifting the hammer tail repeatedly. The hammer arbour return spring on these movements gives quite stiff resistance. 

New pins fitted below.

The pivot holes in the plate are very worn. The main wheel arbour pivot hole bushings were made on the lathe, from a brass that matched the colour of the original as closely as possible, and made with a taper of 0.04mm over 4.10mm, to aid a tight mechanical fit in the re-centred and milled out main wheel pivot holes

                                

Above left, the bushing installed and chamfer can be seen in the plate in order to receive the peening of the bushing. 

Below the main wheel bushings have both been carefully peened over into the slight chamfers.

Below the excess material has been milled away from the bushings, and 'finished', and reamed to fit the polished and burnished main wheel pivots. One of the main wheel pivots before and after re-facing and polishing, below.

The arbour/pinion below is from the time train. The pivot is broken and requires re-placing, however, it has no shoulder on the arbour, which explained the protruding brass bush found on the inside of the clock plate. The shoulder was obviously cut away, short, for some reason in the past. Whilst drilling the new hole, I had no trouble drilling at 0.50mm as a pilot, then 0.75mm, however thereafter I could not get a spade drill bit to bite. What had me baffled was that the bits were coming out of the hole untouched. Ordinarily if a bit has not bitten into the steel, you'd expect to see the bit's edges slightly worn, one would also worry that you'd work hardened the steel in the hole. However the drill bits tips did not illustrate that. I looked inside the hole under the stereo microscope and poked around inside the hole, and noted that something was moving about on touch. It occurred to me it was actually the end piece of a previously inserted replacement pivot, and it was sticking to the end of the drill bits and spinning inside the hole. Thus it protected the end of the drill bit, but obviously stopped it drilling the hole further, which explained the untouched appearance of the end of the drill bits. You can see the little 'offender' in the second picture below right, next to the pinion. Once that was removed, drilling was not a problem. I only wish it had not taken so long to solve the mystery. 

This would need not only a new pivot, but also a new shoulder next to the pinion. This would mean the protruding bushing could be replaced with one that could be flush to the clock plate. I wanted to get this fabricated and fitted before all of the pinions were sent to Geoffrey Walker for restoration by micro-welding.

Below you can see the donor shoulder/pivot steel being fabricated on the lathe. The end that will be inserted into the hole in the arbour can be seen, and was cut in order that it would be 0.01-0.02mm larger than the hole, in diameter, for a tight mechanical fit. The pivot would be cut after the donor piece was fitted to the arbour. Below right, the donor piece has been fitted to the arbour.

Below the shoulder is cut to 1.25mm in length, and  the new pivot has been cut, polished and burnished.

Below is the anchor, arbour and crutch. The assembly is in pretty poor shape. Both ends of the arbour have been re-pivoted at some point in its history, however, when that was done fractures in the arbour occurred. This will have been through trying to fit new pivots that were too big for the holes made. There fractures on both ends of the arbour. The one on the right, by the yellow arrow. However, the arbour is  usable, strong enough and original. 

There is a rather unpleasant 'blob solder' on the crutch.

Below right, the crutch end of the arbour with newly made crutch collet, and a new hole of 1.32mm ready to take a new pivot of 1.33-1.34mm. 

Below left the suspension post can be seen to have been broken in the past. It has been repaired at some point, crudely, with a piece of brass having been soldered against one of the posts arms. The other arm had a small stress fracture. I decided the best form of repair, to keep as much of the original part as possible, was to fit a donor piece of brass and fabricate new arms on the existing suspension post. A female dovetail was cut into the suspension post, and a male dovetail in the donor brass. The dovetail was sweat soldered, and the donor piece was milled, filed and finished to shape, and a slit cut to make the suspension arms. 

   

The suspension spring assembly was in a sorry state. The  spring was bent and creased, and the suspension block that fits in the pendulum crutch had been repaired with solder before now. It was not usable. These suspension assemblies can be bought as a complete part, however, it doesn't take long to make a bespoke one from brass stock with the required suspension spring length and block.

The pivot holes were extensively worn throughout the movement plates. The blue marks showing the direction of wear. Re-bushing was required throughout, though due to the extensive wear all the pivot holes, their centres were carefully found through depth gauging the engagement between wheels and pinions. Below, the pivot holes have been re-bushed and fresh oil sinks cut. the main wheel pivot holes have also been re-bushed and finished.

Here is a picture of a few of the repaired pinions, seen earlier above, that have had the wear in the pinion leafs filled by micro welding. This was completed by Geoffrey Walker FBHI, as I don't have a micro welder, but would quite to have one. Geoffrey has done a good job and is a very nice chap, a pleasure to deal with.

Below the repaired anchor arbour, complete with two new pivots, new collet and crutch. Below right, the impulse pallets have been finished and polished to a mirror finish. The impulse faces are polished to a mirror finish, and the entry drop has been reduced.

Now all the repairs to the components have been completed, they have been cleaned and double given another look over before assembly.

During assembly, the strike train requires synchronising. This type of movement is ordinarily quite straight forward in this regard, however, it required detective work, to find that the count lever end was slightly out of shape, and hence it was difficult to time it falling into the count wheel at the same time as the stop lever, falling into the hoop wheel indent. 

Below are pictures of the assembled movement, which is now running very well on a test stand.