Partial C40A on eBay

A middle period example of the most commonplace, smaller, C40A, Gents Pulsynetic Waiting Train is up for auction on eBay. It is numbered 567.


It is hoped that the lucky winner will not be too disappointed to discover the lack of the vital 120 tooth, drive wormwheel and its shaft.

Without it no clock dial, hand drive is possible. Though this will not affect the ability of the heavy pendulum to swing under power, is is very likely the ratchet wheel will spin around uselessly during part of the cycle. 

This occurs when the weight of the time setting hand crank and its ceramic knob reaches the top of its arc. Without some friction [from the missing wormwheel] there is nothing to restrain its sudden fall onwards to 6 o'clock. 

The seller has mentioned the lack of a drive so has covered himself from that point of view. An optimistic buyer might hope for more and bid in ignorance of the facts. 

The auction images are acceptable, with my usual advice that overcast daylight and a neutral background are much to be preferred for such technical subjects. Sunshine and flash photography against a  light [or dark] background are not ideal. I have tried to adjust the auction images for educational value for posting here on the blog.

 Other than the lack of the vital wormwheel drive system, this later example of the C40A seems almost complete. The sloping section of the main casting above the drive electromagnets is indicative that this is not an early example. As does turquoise paint and electroplated details. The very earliest WTs would be painted black with golden lacquered brass details. Later examples, than this one, were painted industrial, light grey. Again with plated details.

An optimistic idealist might also have hoped for a bevel wheel cluster and crown wheel but there would be little point without a wormwheel to drive them. Since no known spares are available for these old movements it falls to the new owner to arrange the manufacture of a wormwheel and shaft. A second, cast support bracket, for the worm shaft  is also missing and would need to be reproduced. Forked expansion [universal] joints for the lead off work would be desirable if a hand drive is needed for a clock dial. These are more readily made from channel section. Or can sometimes be found on eBay since they are almost universal in turret clock lead-off work to the dials.

There is a way to manufacture a wormwheel in aluminium by "hobbing" with a screw thread cutting tap in a lathe. Whether there is a screw thread which exactly matches the W's worm in all respects I really cannot say. Interestingly, the aluminium would not look too out of place. Bare, lightly brushed aluminium is not too dissimilar to the WT's original, matt plated components.

The original wormwheel would be a spoked casting in bronze. Perhaps a machining enthusiast can be found who would make a new wormwheel out of brass using a dividing head and hand-made, fly cutter. This would be much more difficult and require more equipment and skill than hobbing softer aluminium with a matching screw tap. [If one was available!] There is just a chance that Gents chose a standard thread for their WT worm so that it could be easily cut on a normal, screw-cutting lathe. So using a non-standard screw thread seems less likely. Gents were mechanical, turret clock makers so would have no problem producing wormwheels.

The original time setting crank is present on this WT. As is the Hipp toggle damper with dangling rubber hose. This has the effect of stopping the Hipp toggle from vibrating so wildly that it might seat in the Hipp V-block on the return swing. This would result in power being sent to the pendulum drive in opposition to its swing. Resulting in a stalled pendulum with the power running continuously through the contacts and drive electromagnets!

This is an unlikely, but not impossible, occurrence and rather depends on the lateral and vertical adjustment of the pendulum drive contacts. The simple toggle damper provides a high level of insurance against this happening. I ran my own similar WT without a damper for years without any problem during normal running. Only during manual contact adjustment was there ever a problem with the toggle rocking back and forth deep in the V-block.

The lower pendulum rod and heavy bob are present in matching colours to the main frame. No length adjustment is required with a WT movement since timekeeping is tightly controlled by the associated master clock.

The movement number was discovered and an image added to the auction details. This looks to be stamped into the main frame. My own WT has its number visible stamped on the relay electromagnet front support plate.

A view of the rear of the movement where the cast bracket for the bevel wheel cluster would have been mounted on the blank spot on the main casting. The toggle damper points down at the impulse pallet with nearby impulse roller on the tip of the drive electromagnets armature just visible.

 The WT section looks complete. The gathering pawl, masking pawl, ratchet wheel with D-shaped pin and relay electromagnet are all present and correct.

The original, ceramic knob on the time setting crank is a nice detail. For some reason these hand cranks often go missing. This crank allows the time on the [missing] time setting dial to be quickly corrected for Summer and Winter time setting of the driven clock dial. Or the hands to be quickly set to time after a pause for maintenance. The time setting dial would be mounted on one of the bevel wheels and fitted with a small pointer This was standard turret clock practice though njhand cranks would serve no purpose .

The massive, pendulum drive electromagnets are present. As is the armature with impulse roller. The bandaged coils are a slightly later iteration of a series of protective measures for the copper wire turns adopted by Gents. 

The drive impulse is not achieved by catching under the hooked section, as would seem likely at first sight. It is the rising of the roller against the sharply curved underside of the impulse pallet which provides a smooth but powerful push to the pendulum. The more gentle curve is actually the dead face of the impulse pallet.

This drive system can be most easily recognized as an inverted roller and pallet common to the gravity arm impulse of popular British master clocks like the Gents' Pulsynetic. The drive action can be repeated on demand from the Hipp amplitude switch up to 30 times normal during bad weather. Or when ice, birds or wind impede the hand movement on the exposed clock dial[s].

The pendulum support bearing was a complete break with centuries of tradition in the use of sturdy ball bearings. These were sealed from dirt in a closed case and replaced the fragile flat suspension spring found on countless clocks of all types.

To avoid asymmetric wear on the hidden ball races a knob was provided on the pendulum support shaft. The advice was given to turn the knob at random intervals and angles to avoid wear. The text varied over time. "REV" refers to revolutions rather than an abbreviation for the minister of the church housing the clock. The pendulum support bearings will likely need to be cleaned and repacked with grease.

The smart, Gents' cast nameplate of the WT's manufacturer. With the base of the damper screwed into the WT's mainframe to its right.

The lucky winner of the auction should take great care if it is intended to dismantle this WT movement for cleaning. The massive electromagnets are joined by rather fragile wires. The combination of great weight and thin wires could lead to a "tail" being broke off close to or inside the coils spool.

The only way to repair such a disaster could be to to unwind the entire coil to reach the broken wire. It goes without saying that such an event would destroy all originality in appearance of the affected coil. My own advice would be to leave the electromagnets in situ and wrap the coils with cling film[?] to protect them from gentle cleansing of the metalwork. I used odour free lamp oil to clean my own WT as a gentle solvent.  [GB paraffin. US Kerosene?] A "factory gate finish" is highly undesirable IMPO. The patina of age on the movement is part of its history. It should be respected as much as possible.

This image shows the missing wormwheel, its shaft, bushes and bearing components all held in place with tapered pins. The worm shaft components lie in the background but are normally above and at right angles to the wormwheel.

The pitch of the worm and its diameter do not seem typical of imperial threads. Though worms do often use an ACME thread form. The worm is 5/8 [0.625"ΓΈ]  and has 13 threads in 7/8" [22mm] Converting to the full inch makes 14.8 TPI. Perhaps it is a Metric thread? 1.69mm pitch?

The bevel wheel shown on the right is not always a standard feature on all WTs. The hands of a single dial may be driven straight off the wormwheel shaft via a universal, lead-off, expansion joint. Which is the plated forked device seen on the far end of the shaft.

Two dials in line on opposite ends of the WT movement may be driven by having another universal joint on the other end of the wormwheel shaft. Bevel gears are only necessary where there is a change of height or direction between the movement and dials. Or where three or four dials are driven from one movement. Or where two or more dials are at right angle to each other on a tower or building. WTs are incredibly powerful for their size and even this smaller C40A can drive the hands of four 6' dials.

Click on any image for an enlargement.

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