Click here for large version (320kb) without labels Clockwork Gears
Overview When entering the lightroom at lighting-up time the dog clutch would be disengaged and the brake applied. Lifting the brake/clutch lever would allow the dog clutch to engage and the last movement of the lever lifted a brake pad applied to the worm drive spindle and the lens would turn When putting the light out in the morning,the reverse happened,brake applied,dog clutch disengaged which allowed the lens to be turned manually for cleaning,etc. Drive There is an endless chain with a 60 Lb. weight which goes over the main drive spindle,as the weight drops the main drive gear turns and power is transferred via spur gear to bevel gear Then through dog clutch to lens final gear drive. ______ Dog Clutch ________________________ Rotor Brake Speed Control Power transferrd by two spur gears to worm drive Final worm drive spindle turns an air rotor with adjustable blades which gives a rough speed control Final speed control achieved with adding or removing weights from main weight. Two further worm drives powered the clock You set the clock after rewinding,checked on next wind and adjusted as required. Rewind The endless chain also goes over the winding spindle which is held stationary via a ratchet,as the weight drops the lens is turned and the righthand side of chain extends,when the weight has nearly reached end of travel the keeper turns the winding handle against the ratchet and rewinds the lefthand side of chain (As the weight is still pulling the righthand side of chain down the lens continues to turn.) There are two positions for drive handle,one a direct drive the other a three to one reduction. If the weight dropped too far it would operate a switch and sound a horn.
Machine clock	Winding handle + Alternate spindle gave a 3-1 reduction
	Three bells on machine 1-gave a steady ding ding when machine was in operation 2-A rewind bell which sounded when weight was fully rewound 3-Bell which sounded every half-hour,when machine running.
60 pound weight with two sizes of timing weights	.
Lens Final Gear Drive Inside the cog wheel you can see part of the annular trough which holds the mercury. The lens support framework floats on the mercury,one reason for the layout,was to allow fuel supply lines to be routed via the central column.
Mercury Bath Diagram The mercury float system was invented in 1890 by Leonce Bourdeilles (1839-1899) the Inspector-General and Chief of the French Lighthouse Service. The lens floated on a mercury trough,the bearings you can see are purely to keep the lens centralised.

All photographs Copyright Fred Fox.