A Gents Bell Striker. Part1: Switching Lever:

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A fellow enthusiast, who wishes to remain anonymous, has very kindly forwarded some really excellent images of his Gents' Pulsynetic bell striker. This device allowed master clock controlled, impulse clock systems to strike the number of hours on a large bell.  As can be seen in these fine images there is a very large wormwheel and hammer lifting cam. These lift the hammer away from the bell and drop it a suitable number of times to match the hour.

Due to the complexity and the number of images available I shall split discussion of the mechanism into several parts. The first will discuss and illustrate the switching involved in starting and ending the striking sequence:

Rather than repeat the sequence of actions, word for word, here is an earlier post describing an earlier bell striker.

http://waitingtrain.blogspot.dk/2012/12/gents-pulsynetic-bell-striker-c54.html

A general view is seen here of the bell striker from the front. The drive motor is on the far left. The main worm, its wormwheel and snail-shaped, hammer lifting cam are raised high on a sturdy bracket in the centre rear of the mechanism. The round, count plate, with slots in its periphery, limits the number of strikes each hour and is seen in the centre foreground. I will discuss its drive and how it functions in a later part.

The linkage on the extreme right would be connected to a bell hammer pull wire or rope. Note that the long, black, hammer lifting lever is quite separate from the white switching lever in the foreground. The black, bell striking lever is pushed down and released by the large, snail-shaped cam in the centre when the motor runs. The black striking lever is hinged just in front of the drive motor.

The long white arm in the foreground [which I shall call the switching lever] is counterbalanced by the lump of metal cast onto it on the left. This lever is hinged like a see-saw. The lever is made of aluminium and is the switching actuator for initiating and stopping the strike. It does so by means of several switches, or electrical contacts. Which are either open or closed depending on the lever's precise condition. [Either up or down]

The actual switches or contacts used varied over the history of Gents' bell striker mechanisms. Their purpose remains the same. A microswitch was used in some bell strikers to turn the drive motor on and off. There appears to be a box above the switching arm's pivot. Which may contain the switch for the drive motor.

Note the two large electromagnets hiding under the switching arm just to the right of its pivot. The switching lever normally rests with the counterweight down and the far end lifted upwards against the brass, height stop. An electrical contact can be seen supported by an L-shaped bracket fixed just above the counterweight. This contact would be closed only when the arm is lowered [at the far end] during striking.

This image shows the far end of the switching lever furthest away from the counterweight. Note the brass height adjusting screw and its large lock nut. This screw fixes the maximum height to which the switching arm may rise when free to do so. This is its normal or rest position.

Note also the shiny, steel, stepped latch on the right and the strangely twisted arm just to the left of the height adjusting screw. At rest, between striking sequences, the switching lever is normally raised and unlatched. The latch is connected [in a continuous U-shape] to the twisted metal arm. A brass leaf spring presses upwards against the base of the U-shaped lever/latch. Ensuring that the lever will latch itself via its long pin when it falls far enough.

When the contacts just above the counterweight close they pass electricity to the motor shaft brake release electromagnet. The shaft brake is released for as long as the arm is latched down.

Rotation of the main wormwheel and cam shaft also rotates a trip vane clamped to the same shaft. When this long metal arm strikes the top of the U-shaped arm the switching lever is unlatched. Due to the counterweight the switching lever can now rise again. The contacts above the counterweight open and the motor shaft brake is instantly re-applied.

Usually a separate timing device [known as a bell ringer] is driven by the controlling master clock of the entire clock system. The bell ringer sends out an electrical signal every hour on the hour.


The terminals for the low voltage, timing signal and brake solenoid are fixed on two insulated blocks at the front of the massive, cast iron, bed plate.

N.B. There is no connection between the low voltage wiring and the 250V mains electricity which drives the electric motor.

WARNING: Connecting these low voltage terminals to the mains electricity would immediately destroy the electromagnets. Very probably causing a dangerous fire! Exposed, bare metal parts would be very likely to carry a lethal mains voltage! Even if you survived, the bell striking mechanism and its entire clock system would probably be completely destroyed! Fires might even occur throughout the building! You have been warned! Low voltages only to be connected to these bare terminals.

Click on any image for an enlargement.

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C40C WT in ClockDoc archives

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There are a number of fine images of a C40C Waiting Train installation in the ClockDoc archives. The larger 'C' movement is most easily recognizable by the greater size of the hand setting dial/bevel wheel cluster [on the right] and matching 'shoulders' at the top of the mainframe. The far more common, smaller C40A frame was usually asymmetric. With a curve or indented straight section in the casting just above the power electromagnets. This symmetry only applies to the earlier C40C movements. Later WTs have a distinctly stepped frame with an open platform for the bevel wheel cluster.

I have borrowed an overall image from ClockDoc to whet the viewer's appetite.
The copyright for the image remains with the author and ClockDoc.
The image here has been reduced in both size and contrast in PhotoFiltre to maximize the detail in a smaller format.

Visit the ClockDoc Electric Clock Archives for some excellent closeups of this quite early mechanism. Enlargements of each image are available if you click on the magnifying glass above the images on ClockDoc.

http://www.electricclockarchive.org/ClockGallery.aspx?aid=2306

The many lacquered, brass/bronze parts are quite early in appearance. The contact assembly support post has a fixed, oval base plate. Only seen on early movements. Later WT movements have a taller base plate with slots for lateral contact adjustment. The masking pawl is of an early shape. As are the cast, brass contact steady bars with sharp angles. The coils of the power electromagnets are simply wound cotton or silk covered. Another early sign. Later coils had varying degrees of overall protection which his the individual strands of the windings.

Black paint on the mainframe and pendulum rod is usually an early sign but one can never be certain if it is original. This colour should not be taken as the sole indicator of an early movement. Though the sheer effort involved in stripping a later WT movement down just to paint every nook and cranny black will usually give the game away. One would never expect to see [later] plated parts on an original, black painted, WT movement.

Dismantling the massive power electromagnets from the cast main frame is fraught with very real danger of damage to the fragile coil leads. If a coil tail should be broken accidentally it could easily lead to a complete rewind of the coil! A very difficult task indeed and it is almost impossible to duplicate the coil's original appearance. It might be worth checking the paint below the coils as these do not allow easy access for a paint brush. The underside of the feet of the cast main frame might also show up any colour changes over the life of the movement.

The master clock in the same system is dated October 1925. So this WT may well be of a similar date. Though it should be remembered that Gents may have updated certain features over the lifetime of the clock under routine maintenance. The protective, galvanized steel enclosure may account for the fine condition of this movement. This C40C Waiting Train movement may have been working almost continuously for nearly 90 years. A tribute to the remarkable skills in design and manufacture by Gents.

The Gents WT was both a unique and a remarkably successful turret clock design. It's availability made the familiar weight-driven clocks completely obsolete. Requiring no winding and little in the way of maintenance, the WT kept time as accurately as its controlling master clock. Which usually meant mere seconds per month. Rather than the minutes per day variations of older, weight-driven movements. Many of which would lose time badly, or even stop, in a storm or icy conditions. The WT answered the need for far more accurate public clocks to match the modern requirements of the railways, commerce and industry right around the world.

The WT design also allowed very much larger dials at much lower expense than purely mechanical clock movements. Quickly setting a race in progress to achieve new records in huge dials quite incapable of being driven by weights. It also ensured matching accuracy for each dial in any clock system. Removing the need for the vertical weight shafts and access no longer important to the clock movement's winding and care made architects' lives very much easier. The compact size of a WT movement allowed towers, chimneys, war memorials and other architectural features to be fitted with large clock dials. Often in situations which would have been all but impossible with the older, mechanical movements.

Click on any image for an enlargement-

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