Range Clock
A ==Range Clock== is an instrument that can indicate a hypothetical range to a target and continuously adjust the presently indicated range by applying a range rate set upon it. It is not unlike a clock that can be set not only for the time of day, but also the rate at which time passes.
Evolution from Clockwork to Electric
The first clock to be developed was the Vickers Range Clock, which were windup devices with a clock-like face to indicate the present range. Knobs permitted the operator to
- set the present range
- set the range rate
- wind up the spring if it ran low (a little telltale warned when this was needed)
With such a device offering only a visual display of the range, the model of use was for the operator to verbally or otherwise relay the present range onward to the guns, where others would keep their sights set according.
Later clocks such as those embedded within Fire Control Tables such as the Dreyer, Argo or Ford Rangekeeper needed to have more torque in the shafts expressing the range output than were needed to move hands around a small dial as in the Vickers. To meet this requirement, they usually replaced the clockwork power source with a human turning a large crank at a speed governe by watching a stop-watch, or by electric motors (although it was a common practice even then to retain the hand-crank in case of loss of electrical powerCite error: Closing </ref> missing for <ref> tag
The caveats to this would, of course, be if the disc-and-wheel variable speed drives somehow slipped under general conditions of use and not merely when being adjusted. There were two primary worries that could cause this to occur: oil finding its way onto the drive discs, or ad hoc custom appurtenances being added to the Dreyer table that would increase the load upon the range clock's output shaft. Both these threats were identified and addressed by explicit warnings to fire control personnel. Don't oil the range clock drive discs (use petrol)[1], and don't get all clever and add doo-dads to the Dreyer table[2].
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