Wednesday

'WT' Dimensions and electrical requirements.

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My C40A Waiting Train movement dimensions:

Approximately 425mm (16.75") wide across the feet.

387mm (15.25") high from the underside of the feet to the top of the pendulum suspension casing. The suspension bearing hand wheel is very slightly taller.

Approximately 190mm (7.5") deep. The feet themselves are 150mm or 6" deep. (front to back)

The flat bottom of the pendulum bob extends a further 42 cm (16.5") below the underside of the feet/surface on which the movement rests.

The total overall height from the top of the movement to the flat bottom of the bob is 80cm. (or 31.5")

Later models of the C40A may vary from these dimensions. The main casting took at least two distinct forms over time. Larger models at least three forms.

The A-sized movement alone weighs approximately 18 kg. The pendulum bob an extra 11 kg. A total of 29 kg or 64 pounds. This is just manageable by a fit adult if a small WT needs to be moved manually.

Removal of the bob is essential if the WT is to be moved and placed down again. Do not rest the WT movement on the attached pendulum bob or damage is almost certain! Always remove the bob for safe transport and handling of the WT. Care should be exercised when undoing the two screws which hold the bob and lower half of the pendulum rod. The bob is quite heavy and could cause injury or damage.

I loosen both screws. Then remove one screw completely before undoing the second screw carefully by hand. Meanwhile, the bob is supported with the other hand. Or a solid object placed under the bob to take its weight.

Note that the top half of the pendulum rod extends beyond the surface on which the feet rest. The rod must be allowed to enter the slot provided in the bench top before the weight is taken on the cast feet of the WT movement. Or two battens provided to allow the rod to clear the supporting surface.

Larger models: B, C, D and E were also manufactured by Gents with a capacity of up to four dials of 28 feet in diameter in the case of the very largest models. These heavy duty movements are often of completely different form to this smallest C40A model. They used much the the same techniques but with greater sophistication.

The pendulum drive electromagnets together have a DC resistance of 46.8 Ohms.

The relay (timekeeping) electromagnet has a resistance of 15.2 Ohms.

The spark suppression choke measures 228 Ohms.

There seems to be some variation in resistance between WT movements so there is no need to worry about matching the above figures exactly.

A close-up of the support bracket for the relay electromagnet armature showing the movement number 309 stamped into the brass. This is the usual place to look for a WT movement number. Completely coincidentally No 309 was made in about 1939. Do not try to date a movement from its number in this simplistic way.

Note the heavy wax coating to protect the many turns of insulated copper wire of the electromagnets. The wax was partially dissolved by the cleaning fluids I used on the movement: Odourless paraffin lamp oil followed by a warm bath in washing up liquid and water. The coil had to be plunged into clean cold water to quickly halt the melting of the wax. The coils had appeared almost black at the time of purchase but the green dye of the typical Gents' insulating silk/cotton on the underlying copper wire was exposed by the cleaning. Since the movement will not be used in a harsh environment the loss of a little wax is unimportant. The wax could of course be tidied up a little to improve the overall appearance as a display item in a domestic setting.

The terminal block on the left side end of the movement frame. 

The top two terminal screws connect the relay electromagnet of the Waiting Train section of the movement. This time circuit connects to a remote and highly accurate, electric master clock which performs the timekeeping duties for the WT movement. Without the 1/2 minute impulse the WT runs too fast.

The DC voltage supplied will depend on the power required to run all the dials in the half-minute series time circuit operated by the master clock. Though the time circuit is designed to run on 0.22 Amps the voltage will vary greatly depending on the number of electromagnets in series with the master clock.

Each slave clock dial will have its own electromagnet. As will all the other apparatus connected into the time circuit. Including the WT's relay electromagnet coil. As many as 100 dials could be operated by one master clock. Though Gents' did offer relay switching devices to reduce the number of dials in any particular time circuit. Just to keep voltages to manageable levels. In original installations batteries were often used. Higher time circuit voltages would require a great many more batteries in series.

The bottom two terminal screws connect to the large pair of pendulum drive electromagnets via the contacts operated by the Hipp Toggle and V-block. This movement requires only 20 Volts DC. The 20 Volts DC drive supply will be connected to these two screws. This voltage is easily supplied today by an inexpensive plug-in "mains adaptor".

Warning!

Never connect a WT movement directly to the Mains electricity!
 

There would be a very high risk of death by electrocution! 

250 Volts AC will quickly destroy a WT movement! 

There would be a lethal voltage on many exposed metal parts only ever intended for 1A (maximum) 20 Volts DC. 

A fire hazard would also exist from violent overheating of the large electromagnets!

20 Volts DC is the recommended voltage for the drive electromagnets of this smallest C40A WT movement. A small, 20-24 Volts DC, plug-in "Mains Adaptor" is ideal.
Do not use higher voltages! Do not use AC! 

If you must use large batteries fit a suitable fuse in series with the movement to avoid damage in short circuits. Even a small battery has so much power that it can easily cause a fire in a dead short!



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