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Dismantling seems more difficult than it really is because there are few external clues to the rather simple construction.
Please use well fitting screwdrivers in good condition to avoid marring the original screw heads. A quality new (unworn) screwdriver will loosen the tightest screws almost effortlessly compared with a worn or badly "sharpened" screwdriver. Quality screwdrivers are no longer as expensive as they once were. Find one which fits BEFORE making the task much more difficult (or completely impossible) by damaging the original screw head with a crappy screwdriver or poorly fitting spanner. (wrench).
ISOLATE THE POWER TO THE DRIVE ELECTROMAGNETS BEFORE DOING ANYTHING ELSE!!
ONLY THEN REMOVE THE PENDULUM BOB:
The electromagnets are so powerful that they may easily trap a finger or push the pendulum about completely uncontrollably with your extremities trapped! The pendulum is so heavy and has such momentum that it can easily crush a finger when swinging or when being lowered from the WT movement.
Removing the driving power will avoid sudden, nasty surprises and quite possibly serious blood loss! Climbing back down in the darkness via the usually rickety ladders and tiny trapdoors from a high clock tower in agony is not an easy task. You may require skilled professional help from the emergency services.
Presuming, of course, that anybody knows you are actually up there. You did discuss your plans just prior to your climb with a responsible person, didn't you? Better still do not go alone. Still leave a message with a third and fourth person if you go up as a team.
Carry a mobile phone with a fully charged battery to summon emergency help if needed! Think very carefully about safety first! Nobody wants to find a mummified corpse slouched over the old clock movement when somebody finally realises they haven't seen you around for a few months.(Or years!) They may well join you in the hereafter if your dessicated body is still live with mains electricity! Do NOT assume that anybody will notice the clock is no longer running. You probably went up there because it wasn't running. Then what?
Most smaller WTs run of 20-24Volts DC. Use a volt meter (or multimeter) to confirm the voltage BEFORE touching the WT movement anywhere. There are live, bare metal components so take great care. Old electrical installations may have faults exposing high (dangerous) voltages on bare metal! YOU HAVE BEEN WARNED!
When removing the pendulum bob it is essential that the pendulum bob shaft retaining screws are completely removed. Many WTs will rest on a shelf with a narrow slot for the pendulum rod. Only the bare, stub pendulum rod will pass easily down through the narrow slot in the clock table or shelf.
Once the screws are removed the heavy bob can then be carefully lowered along with its stub rod. Preferably onto a strong and stable support placed just below the bob before you attacked the bob fixing screws. Otherwise it may be much too late and you find that you cannot support the heavy bob. Then what? Do you drop it onto the worm ridden floorboards of the clock chamber and then on down right through the intervening floors of the tower?
Take great care because the bob really is very heavy at 11kg (over 25lbs) even on the smallest C40A WT.
In fact the bob retaining screws can be very difficult to unscrew unless the bob is properly supported. Steady pins may or may not be present. (Note the small holes where the pins would normally fit) The steady pin holes do not quite match on the two halves of my pendulum rod. Presumably the original bob was lost, swapped or damaged before purchase. The steady pins would greatly aid the removal of the bob from the upper pendulum rod section by supporting the weight of the bob.
The lower part of the rod lies in front of the upper rod when they are screwed together. Avoid fitting longer replacement screws than necessary because they will strike, or rub on the main casting as the pendulum swings. Quite easily causing unsightly and permanent damage to the main casting on a single swing of the pendulum!
Once the pointed screws are loosened enough to clear the grooves, with any luck the rod will just pull out of the bearing case. Just by pulling and turning the brass knob back and forth. Unscrewing them by a couple of turns is probably all that is necessary. Complete removal of the locating screws risks their loss unless they are stored safely.
If the shaft doesn't pull out easily then it is strongly suggested that the upper pendulum rod and bearing case are removed as a separate assembly from the WT movement. The bearing case is secured by the two 2BA screws which hold down the bearing assembly onto the top of the WT's main casting. Set the screws safely aside in a suitable container to avoid loss.
It would be much safer to remove the upper pendulum rod and bearing case from the WT to a safer place before dismantling. BA screws are not readily available in many parts of the world so take great care not to lose any of them!
The small pointed locating screws are only supposed to be finger tight to allow the brass knob to turn the bearing support shaft easily. If you over-tighten the screws then the shaft cannot turn. Or damage will be caused to the points of the screws or pendulum bearing shaft. The locking nuts should be a clue to not over-tighten these screws. The nuts allow the screw to be locked without being fully screwed in tight. Tighten the screws finger tight and then try to turn the brass knob. The knob should turn easily after you have cleaned and re-greased the bearings.
It is fascinating to see how a good but gentle clean has turned these later components back into their original colours. Before cleaning the steel parts looked much like yellow brass thanks to the accumulation of old oil. The paint had also taken on a greenish hue reminiscent of the Gent's factory's earlier paint finish rather than the later grey with a hint of blue.
[I am indebted to Allan T. for sharing this excellent image taken during his restoration of the NOTL Waiting Train movement. There is little doubt as to Allan's remarkable skills, patience and care in returning the WT to active use without causing damage to the original finish. My deliberately patronising tone in this blog post certainly does not apply to Allan!]
The owner of a larger C40B model has kindly sent some images of his roller bearing, pendulum suspension. The details are quite similar to the smaller C40A, illustrated above. Except for the substitution of the much more robust and longer lasting, journal roller bearings in place of the ball bearings. The suspension pivot shaft is also much larger.
Note the same, small, pointed screws which hold the suspension shaft in place via grooves in the shaft.
These should only be finger tight with the small nut used for locking the screw in place.
Here there are three screws holding the protective cover instead of only two in the C40A.
The rollers are housed in brass or bronze cages.
A good coat of grease applied to the roller bearings should last for many years.
I am most grateful to Bart.S for sharing these images.
Please avoid excessive force when dismantling and rebuilding a WT! Screws must be started square onto the component and should always turn easily. If a screw won't turn then the screw is probably out of square. Back it off and try again. Damage is often irreparable and spares are NOT available.
Originality counts for a great deal in clocks. A clumsy or thoughtless moment can destroy a historical clock installation. If you lack the mechanical or electrical skills to work on a Gents' WT (or any other electrical clock system) then do seek help. Do it first. Not after you have caused permanent damage! Advice is only ever an email away. If I can't help with a specific problem myself then I know others, far more knowledgeable, who can.
chris.b at smilemail.dk