A C40B

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The new owner of this C40B has very kindly shared some fine images of this interesting turret slave movement. I recommend you click on the images below to enjoy a larger, high resolution enlargement. The incredible improvement in appearance, from the auction images, should be readily apparent.

While the C40B shown here may have a slightly different appearance to other WTs illustrated on this blog it follows exactly the same design principles.

The 'B' simply denotes a larger, more powerful  movement for driving the hands of larger dials than the smaller C40A. Even larger models followed the same alphabetic convention as they increased in size: C, D and E.

In reality the WT movement is an incredibly powerful slave clock designed to drive the hands of large, exposed clock dials. A slave clock cannot keep accurate time without a separate master clock. The genius of the Gents' WT's designers was in harnessing low voltage DC electricity to provide a very powerful and very accurate turret clock.




Overall view of the Gents' C40B Pulsynetic Waiting Train movement. This is a later movement recognisable by the hex, socket head screws, uniform grey paint and plated components. The electromagnets have also been bandaged for protection. The lower half of the heavy pendulum has been separated from the movement in this image. The two fixing screws and locating pin are visible at the bottom of the upper pendulum rod section just above the table. The large, bronze, reduction wormwheel is clearly visible on the horizontal (clock hand) drive shaft. The larger the wormwheel the greater the control over the exposed clock hands. Though the reduction ratio of worm to wormwheel 1:120 cannot change. Otherwise the WT would not run to time. The final drive speed of 1 rph  (rev per hour)  being required for the minute hands.

Here the freely pivoted Hipp toggle is resting against the V-block. Normally the toggle rattles freely back and forth over the V-block without consequence. Only when the WT's pendulum begins to lose its large arc will the toggle drop into the V of the block. On the return swing (to the right) the toggle depresses the V-block and closes the contacts just beneath. Electricity then flows to the large electromagnets. Strongly attracting the armature. Which lifts the impulse roller against the impulse ramp. Giving the pendulum a very strong push.

A captioned image showing the details of the Waiting Train mechanism. The constantly swinging pendulum draws the ratchet wheel around by one tooth on every swing to the right. Fixed to the face of the ratchet wheel is a D-shaped pin. As the pin reaches the top of its circular travel it lifts the L-shaped arm. Which in turn lifts the driving pawl out of the teeth of the ratchet wheel. The driving pawl is on the left of the rectangular frame pivoted near the top of the pendulum rod. When the L-shaped arm is raised far enough by the D-shaped pin the arm is temporarily locked by a counterbalanced, stepped latch. The latch sits just above the core of the small electromagnet. The pendulum continues to swing but the clock hands remain stationary. Remaining safely locked against rotation by the reduction worm and wormwheel.

An oblique view of the WT components.  The  rectangular frame carries the gathering pallet which pulls the ratchet wheel around one tooth a time.

The reverse view of the movement. Note the deep, reinforcing ribbing to the cast mainframe. The frame has to resist the powerful drive of the electromagnets and the reaction forces of the massive swinging pendulum. The bifurcated top of the pendulum rod can be seen at the top. The WT was a break with the convention of using a flexible spring steel strip to support the pendulum. The roller bearings, enclosed in a cast box, ensure a very long life without the risk of a suspension spring breaking very far from spares.

The cylindrical green object is a coiled wire wound choke to suppress sparking at the main contacts. There are secondary contacts between the contact blades and their steady bars.These contacts connect the choke to quench any sparking at the main drive contacts.

A closer view of the pendulum drive electromagnets from the rear. Note how the (normally lowered) armature is pivoted between its support plates at either end. When the armature is attracted to the cores of the electromagnets the roller is forced to rise with considerable power.

The pendulum weighs 18kg and the movement 25kg. 
The approximate dimension are: Height  15”  Depth  6.5”  Width  19”






WT maintenance notes: Should the impulsing of the pendulum drive electromagnets become unreliable then the contacts should be checked and cleaned of oil residues if necessary. Easy access to the movement might well have invited over-oiling of the Hipp toggle pivots and V-block over time. The oil would run down and flood the contacts situated just below the V-block. This will almost inevitably increase the resistance at the contact points. Even drawing a rag through the closed contacts will often help. Avoid using coarse abrasive materials (like sandpaper!) or the contact life will be greatly shortened. Nor is this remotely necessary.

All the electrical connection tags, particularly at the main Drive contact blades, should also be checked for tightness. The WT C40B needs a 0.4 Amps, low voltage, DC power supply. This is achieved with 20 Volts through the 51 Ohms total resistance of the twin electromagnets.

The small WT mechanism 'relay' electromagnet needs only 0.22 Amp. The WT should be inserted in series in the timekeeping system from the masterclock. Just like any other slave.

Above all: Avoid trapping your fingers in the working WT movement! The possible crushing forces are easily underestimated. The mass of the very heavy pendulum bob is not easily resisted by puny flesh. Nor should the enormous power of the drive electromagnets ever be underestimated!

Such is the power of the WT movement, to overcome mechanical  resistance, that it can easily destroy weak components. Particularly if a lock-up occurs anywhere in the leading off work, hand motionwork or hand supporting arbors. Take no chances with temporary or unsupervised lash-ups! They could be very costly indeed!


Note that I have resized and adjusted the original images to better suit the unique blog format.

Click on any image for an enlargement.