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  • Graham Powis Member of the British Horological

'At the Bench'


It is very important that customers' know they're getting value for money and above all a GOOD JOB. When a Client brings their beloved clock in for repair very few will have any idea of what goes on with their clock once it's left in our care.

Pictured above is a Junghans A32 clock movement. This mechanism is normally fitted to a Westminster Chiming Clock. This clock mechanism has geared winding and auto correct on the chimes in case the chimes and time are out of synchronisation this is perhaps because the chimes have wound down, the auto correct mechanism will bring them back into sync. These are a beautifully engineered clock, Junghans must have put a lot of thought into the design of this mechanism because despite its complexity it is designed to be taken apart and reassembled with the repairer in mind.

Things don't get any easier around the rear of the clock either, there are hammers that strike gongs to play the Chimes that mimic the great clock of the Palace of Westminster {Big Ben}. I would like to show you in this blog post what takes place when a clock is brought to Cumbria Clocks for attention.

Most of the components of a clock movement are held captive and cannot be accessed without dismantling the clock.. If you're going to have your clock repaired pay to have it done properly. I get 2 or 3 clocks a month brought into the workshop where the customer paid a low price to get their clock repaired. It isn't their fault they paid for an inferior job they just weren't properly informed. The botcher just dabbed a bit of oil here and there and six months down the line its stopped again so we're back to square one.

O.K, lets go through the process of servicing this Junghans A32 mechanism, this clock comes under the category of a complicated clock repair. That mass of levers and gears you see above is going to be completely dismantled, here goes.

Right then! The levers have all been removed and the top plate removed to expose the gear trains {3 in all).. This is the point where you find the problems caused by wear, these problems could have been avoided but invariably clocks are not serviced as often as they should be. I will take a look at what's needed to repair this clock, read on.

Once the clock is dismantled I found that the 3rd wheel and escape wheel pivot holes {pinion end} had worn oval. As the wheels turn in the clock the force applied to them is the greatest at the point from which they are being turned {by the previous wheel}, Thus if the lubrication has become ineffective the hole will often wear oval due to the neighbouring force applied to drive the wheel. For details of how we bush a worn pivot hole please go to the main website and look on the 'workshop pages'.

The chances are that the pivot will have become quite roughened if it has worn the pivot hole oval. There is absolutely no point in just replacing it again as is, the pivot hole will wear oval again in double quick time. The pivot will need to be 'dressed' before it is allowed to run in the brass bush I have just fitted. The picture above shows our 'Rollimat Pivot Polisher' this is a pivot finishing lathe. Its tungsten planetary wheels give superb results. This is something you probably wouldn't even consider but burnishing the pivots properly will allow longer running times between servicing. Some shy away from polishing pivots for fear of snapping them or not keeping them round, you can be sure that wont happen at Cumbria Clocks. In a lot of cases I can do a better job than the original when I brass bush a plate and machine its pivot. More to follow!

So we have reached the point where the clock has had its wear issues addressed and has been cleaned so what we now have is a tray of parts that looks like this. Altogether a lot cleaner than when we started!

There are quite a few processes that I haven't described here, the description would otherwise become somewhat 'long winded'. My intention here is to outline what my customer is getting for their outlay and not give an over technical description of what is actually taking place. So to recap the clock has been completely taken apart, the working surfaces have been attended to and some brass bushes have been installed. The clock has the been ultrasonically cleaned {yes, I always get loads of muck off them}, The picture above shows the clock 'bits' having gone through the necessary processes to overhaul the clock..

I always push a peg dowel through the pivot holes to ensure that all the old oil and accumulated muck has been removed, a tell tale sign is muck on the dowel peg having removed it from the pivot hole. This is an important part of the repair process so a 'make haste slowly' approach will save me time in the long run. So now that I'm happy with all the procedures carried out so far it's time to start reassembling the mechanism,

Here the clock wheels and other items required such as the hammer arbor are 'planted' on to the bottom plate. absolute cleanliness is essential, a small speck of grit could easily go undetected during the assembly stage,

The front plate has now been fitted and the mechanism here is viewed from above. The wheels are now held captive between the clock plates. It is always a good idea to oil the wheel pivots before the clock's front work is assembled, oiling clocks is a precise affair. Most oils are designed to flow freely, premium clock oils* are designed to be globular and stay where it's put. The correct amount of oil has to be delivered in precise amounts, too much oil is actually worse than too little. An excess of oil will flow out of its oil sink all over the clock plates, absolutely no use at all! I used Moebius D5 on the slower high torque wheels and Moebius D3 higher up the gear train {including the escapement faces}. Correct oiling is a precise operation, the wheels and pinions of a clock mechanism run without oil but correct oiling is vital with all the pivots on which the train wheels rotate.

* £30 for a 10ml bottle.

Here is a side view of the clock movement showing the striking train. People say "My clock has a lovely chime at the hour", this isn't quite correct. remember, a clock chimes the quarter's and 'strikes the hour'. So! I have assembled the clock wheels in the plates, you could be forgiven for thinking that as long as they're in the right place then all is well? Well no not quite? Some of strike and chime train wheels have pins at 90 degrees to their teeth, these are intercepted by a myriad of detents and levers. Others carry rotating cams that we will see on the front plate later.Therefore they HAVE to be planted in the correct position or the clocks' chime and strike sequence will not work as it should. It's a bit like the valve or ignition timing in an internal combustion engine, they to have to be set up and assembled correctly for the engine to run. Now the fun can begin, assembling the levers and cams on the clocks front plate.

Here the striking and chiming levers and cams are being installed. Again, everything is a timed sequence so it's vital everything is located correctly. On Clockwork the strike is always discharged by the action of the chime at the hour. It must commence instantaneously as the fourth quarter finishes running with the correct number of blows to coincide with the hour!

Things are now taking shape. The chime and strike levers have now been fitted, the quarter chiming cam can be clearly seen near to the top right. The motion work gears are also in place, these gears work at a ratio of 12:1 hence the minute and hour hands will go around the dial and tell the correct time. The clock mechanisms auto correct also has to be correctly set up, at the quarter to the hour the chime mechanism locks into a deeper slot via a detent that rides on the edge of the chime cam. There are four lobed cams on the going train's minute wheel arbor, these unlock the chime train every 15 minutes, one of these four lobes has a higher lifting profile. Only the higher lobed cam can lift the detent out of its deeper slot so the trains can run at the hour. If it isn't lifted out it's slot it's because one of the lower lobes that discharge the quarters has attempted to lift it, but has failed to so do because of its lower lifting height. Only when the higher lifting cam lobe comes around again will the detent lift out of the deeper slot, thus the chime and strike trains will run and sound the hour correctly once more having been synchronised. The auto correct feature is invaluable on quarter chiming clocks and saves the owner a lot of fiddling!! On the Junghans A32 the auto correct mechanism is somewhat ingenious!

The next part of the repair is something most owners would not consider as a part of the clocks servicing regime, nonetheless it is very important that it is done.

SPRINGS!! The clock mainsprings are contained within the barrel wheels, on this clock we have three trains so therefore we need three springs to drive the gear trains. The clock will have been wound may times over the years and the coils will inevitably have been rubbing against each other. Over time the grease will need changing, the only way to do this is to remove the spring from the barrel. The spring is then washed in solvent and inspected, if a spring has lost its elasticity or is damaged it will have to be replaced. If all is well it can be replaced having been cleaned and greased. The picture above shows a spring having just been removed from its barrel. I have used a mainspring winder for this task {one I made myself}. If an attempt is made to remove or replace the springs without a mainspring winder the spring will be ruined. This does happen I've seen done in several clock workshops, rest assured, I would only ever use a mainspring winder when working on your clock.

In the picture above I have re-greased the spring with the correct clock mainspring grease and I have wound the coils of the spring tight on the mainspring winder so that it can be fitted into its barrel again. This process requires a knack to do it properly ideally the spring needs to seat in the bottom of the barrel first time!

All three springs have now been replaced into their respective barrels, once I've greased the winding arbors I can replace all three barrel covers.

Remember me telling you at the beginning that these clocks were designed with the repairer in mind? Well here's one of the reasons why, you can assemble the main clock mechanism and fit the barrels wheels later! Simply brilliant! This makes life so much easier, these things start to get heavy as you start to add the components to them. The other plus is if a spring should require replacement you don't have to disassemble the entire clock as you would have to do with most others. Above, all three barrels are in place, a sub plate is fitted over them to secure them into their working position.

The front plate is now fully assembled. This clock has geared winding on the going and chime trains, this really is a super feature making winding much easier. The geared winding is held behind the round discs you can see the winding squares protruding from each one. At this point I'll give the clock a wind and see that everything is behaving as it should. Everything seems to be fully operational so now I can concentrate on the next stage.

Lets now turn our attention to the rear of the clock. I have assembled the chime hammers and pin wheel, the whole assembly is collectively known as the 'gallery'. Around the back of the gallery is a gear that meshes with the bottom gear of the three shown on the clock. It then has to be set up so that when the respective quarter comes around the correct tune is played.

Having set the tune up here is the assembled gallery. You will notice a wire lifter attached to the arm at the top right, this is the strike lifting arm. It lifts three of the hammers simultaneously to play a chord when the hour is struck.

So we have got there in the end, here is a side view of the clock movement viewed from the striking train side. There is more to these clocks than it's owner realises, these are a complicated mechanism! The clock will now be tested for timekeeping and function for a week or more before being returned to its case.

This is the final part of the job. The clock has been returned to its case having made sure it functions properly first. The next stage is to take it back to the customer, because this is a pendulum controlled clock the pendulum will have to be put in the 'in beat position'. Imagine a metronome beating away evenly so that the tune can be played in time, it's not dissimilar to that. This old clock has been loved by its owner for many years, but in all that time they've never thought to have it serviced. For all that it is now back to working order again. These are truly a great clock, I think I will look for a clock with a Junghans A32 movement to add to my own collection! If you own one of these beauty's and haven't had it serviced since ?? consider taking it to your local clock expert for attention!


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