As may be easily imagined there were difficulties in arranging such a large reflector to turn steadily even at a slow 4 rpm through gale force winds. Two fifty horsepower three-phase motors were provided as standard, but four were fitted to the machines built in notoriously windy locations. As the reflector cut through the wind currents of a hundred amps per each of the three phases were common and this might reduce to thirty amps during an easier part of the rotation. Such wildly varying demand on the public mains system was not tolerable, and this was allieviated by provision of a 'buffer' in the form of a motor/alternator set equipped with a very heavy flywheel six feet in diameter. Some people claimed to be able to hear the flywheel 'sighing' due to the stress of imparting it's energy at moments of peak loads, but I never could because at those times the noise of the screaming gale drowned out everything else.
An elaborate servo mechanism controlled the speed of rotation of the aerial by automatically boosting the power at moments of need and reducing it as necessary to maintain a constant rate of rotation. 
The Emotrol cabinet contained a water-cooled ignitron ( a triggerable mercury arc rectifier ) for each phase of each of the two motors. This worked in similar fashion to the modern domestic light dimmer i.e. the output to the turning motor armatures could be controlled by choosing the point on successive slopes of the AC sine wave at which to fire the device, i.e. it fired fifty times per second, and a servo mechanism varied this choice in such a way as to maintain a steady speed of rotation regardless of wind pressure. Hence as the reflector turned through a strong wind these currents would vary, typically 20 to 80 amps per phase per motor, but perhaps peaking to 100. Meters on the cabinet allowed the currents to be monitored.
The actual speed to be maintained could be altered by buttons on the cabinet and a meter indicated that speed.
Because they were handling currents like these the ignitrons had to be water cooled. Here a very low tech device was employed and is shown on the left.
A glass tube containing a metal cone was the basis of a flow gauge for the vital ignitron cooling system and this was mounted very visibly on the wall near the workshop corner. The pumped flow lifted the cone against a graduated scale.
The turning motors were mounted radially on the upper gantry. One is shown in threequarter view and is the object pointing towards the near corner of the gantry railing.
Turning motors position.
And this is the massive turntable. The ball bearings are three inches in diameter.
Now can you imagine having to split this massive assembly to gain access to the balls for maintenance purposes? Well it had to be done at RAF Buchan and we have a few pictures available of that hair-raising event.
This last diagram shows the hand-turning device. I never saw it in use and I cannot imagine it being used for other than small movements for engineering purposes. It was mounted in the roof of the rotating cabin.
Pictures & diagrams sourced from the Neatishead museum and kindly supplied by Bob Jenner
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