Stevenson Clockwork Machinery
In use at Maughold Head Lighthouse
1913 - 1992
Prior to Automation in 1992

Final gear drive

Clockwork Labeled
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Clockwork Gears


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.

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.

Bevel gear 2013

Chain for weight compensation,as the weight fell more chain would have been added to total weight and speed would have varied,the compensation chain varies weight distribution so effective drive weight remains the same and allows the adding and removing of timing drive weights to vary speed

Weight 2002 ________________________ Chain tensioner 2011
60 pound main weight with two sizes of timing weights _________ Part of chain weight compensation system

Dog Clutch 2007 ______ Rotor Brake 2007
Dog Clutch ________________________ Rotor Brake

Speed Control

spur gear to worm gear 2011
Power transferrd by two spur gears to worm drive

worm drive to air rotor 2011
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.

Also shows brake pad bearing on rotor spindle

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.

Winding handle 2002
Winding handle + Alternate spindle gave a 3-1 reduction

Machine clock
Machine Clock
Ignore cable/sockets/motors they were installed as part of automation drive

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.

Lens Final Drive 2002

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.

Mercury Bath Diagram
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.

General View 2002
The lens floated on a mercury trough,the bearings you can see are purely to keep the lens centralised.

All photographs Copyright Fred Fox.