WT Pendulum suspension bearing maintenance.

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I have been asked for information about dismantling and cleaning hardened old grease from the enclosed pendulum suspension bearings. After a few years (or decades) the original grease in the bearing case may dry into solid mass. You can usually tell this has happened by trying to turn the large brass knob. If it is too stiff to turn easily then the lubricant may well have become rock hard.

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!

The secret to dismantling the silver coloured bearing case is to slacken off the small (arrowed) screws in the bifurcated top of the pendulum rod. These screws each have a pointed nose which locates in a groove in the pendulum support shaft.

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.

The screws and grooves are clearly marked with red arrows in these images. Once the small, pointed screws are slackened off the rod can be pushed forwards in the direction of the large brass knob. 

I found it easier to support the bearing case on the plywood jaws of a folding workbench. A tap with plastic headed hammer pushed the rod far enough to become flush with the rear of the pendulum rod.. Then the  rod was pushed completely out with light taps using a suitable punch or drift. Don't use anything which will mark or damage the shaft end! 

Hammering hard is completely unnecessary unless the bearing assembly is very badly corroded. Though this seems very unlikely with stainless steel components. Excessive force is very likely to permanently damage the bearing assembly. Try backing off the locating screws a little more then try removing the shaft again. The shaft is just a friction fit in the forked pendulum rod, the spacer sleeves and the bearings themselves. 

As the shaft is pushed free of the bearings the two spacer sleeves will probably fall free. If you are working in cramped or difficult conditions in a clock chamber you should be fully prepared for their fall.

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! 

Here the other surfaces of the bearing case and cover are seen. Again I have marked the grooves and pointed screws with arrows. After cleaning and re-greasing reassembly can proceed.  

Reassembly requires the shaft is pushed back through the front of the bifurcated pendulum rod, the first spacer sleeve, then the bearings in their cast metal case. The front cover should already be screwed in place before the first sleeve is slid over the bearing shaft. Finally the shaft can pass through the back of the forked pendulum rod top. The pointed screws can then be screwed home finger tight. The locking nuts can be pinched tight to ensure the locating screws do not unscrew over time. A small spanner (or wrench) is kindest. Don't mar the nuts with a pair of pliers! Nor is there any need to over-tighten ANY of the screws on a WT.

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.

If the grease has really hardened it might be sensible to soak the bearing case (complete with the journal bearings) in engine cleaner. Or other suitable (and safe) grease solvent. Hopefully it will not be necessary to remove the journal bearing races themselves from the bearing case. The bearings are not heavily loaded and rotation of the shaft should find a free spot once the bearings are properly cleaned and re-greased.  

Here is a later pendulum suspension bearing assembly from the Niagara-on-the-Lake Cenotaph WT. The loose sleeves design has been replaced by threaded, external bushes. These should be replaced the same way round as they were when removed. The pointed, grooved shaft, locating screws are still present in this later design. The journal bearings were apparently quite easy to remove from the casing for cleaning. 

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. 

Very old grease from the original installation may need to be removed first.

Dried, old grease can turn to hard wax and may be able to be detected by turning the knob provided.  

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

Click on any image for an enlargement.