Lens Machinery

Stevenson Clockwork Machinery In use at Point of Ayre Lighthouse 1890 - 1991 Diagrams and drawings not to scale When entering the lightroom at lighting-up time the dog clutch would be disengaged and the brake applied as per the diagram 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. Clockwork Drive mechanism Description of clockwork mechanism in three parts Drive Speed control Rewind
Drive Cable drum ,rewind and primary gears One side of bevel gear Dog clutch and other half of bevel gear removed from final drive shaft when the light was automated	Showing clockwork drive to turn lens Cable wrapped around drum with a 90 pound (42 Kilo) weight turned cable drum and primary gears when brake released. Power transferred via spur gear to bevel gear Then through dog clutch to lens final gear drive spindle. When entering the lightroom at lighting up time the dog clutch would be disengaged and a brake pad on the lever would bear upon the air rotor spindle. 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.
Dog Clutch Brake/Clutch lever and Brake pad	Final gear drive to lens

Speed Control Spur gear drive to worm gear Little brass flap on the right hand side operated a bell striker,sounded a ding ding ding as lens turned	Another small spur gear from primary gear,on left side drives clock and through large gear on right via spur gear 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. You set the clock after rewinding,checked on next wind and adjusted as required.
Worm/Air rotor drive	Clock,bell (Removed on automation to allow room for motor mount) used to strike every hour
Weight 90 lbs (42 Kilo)	Clock Drive
Bevel Gear	Worm Gear
Clock Drive Spur gear from maindrive gear,worm gear to spindle,bevel gear to clock pointer
Rewind One of the "Crimes" for a lightkeeper to commit was to allow the light to become stationary or run at the wrong speed.Showing a false character? So a way had to be found to allow the lens to contnue rotating as the weight was rewound. Winding handle on swinging frame

Rewind Mechanism

Swinging frame diagram 2007 In normal operation ratchet lever engages ratchet teeth on cable drum and transfers drive to primary drive gear.

The gear wheel turning the rewind gear on the cable drum was mounted on a swinging frame which could be locked to the primary gear,as the weight was rewound the primary gear with swinging frame continued to rotate and turn the lens.
Ratchet operates when cable drum is rewound which allowed the primary gear to continue revolving in normal direction.

One thing was to note how far the swinging frame had rotated,if allowed to rotate too far it would lock the mechanism against the main frame and everything would stop,so it was rewind so far then release the gear lock, reset the swinging frame and gear lock and carry on winding
We had some white tape on the cable,so when that reached the drum we knew when to stop winding

Swinging frame showing rewind gear and counter balance arms (after rewinding and releasing gear lock counterbalance returns frame to start position)

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In normal operation as weight turns cable drum the ratchet lever on primary gear engages ratchet teeth on cable drum and they both turn in same direction.
During rewind operation as cable drum is rewound the ratchet lever on primary gear goes Click Click Click and gears turn in opposite direction.

Ratchet teeth cut into side of cable drum

Two ratchet levers

Ratchet lever pivots mounted 180 degrees apart on primary gear,spring tension applied by flat steel strip under tension

In normal operation ratchet lever engages ratchet teeth on cable drum and transfers drive to primary drive gear

Ratchet operates when cable drum is rewound,primary gear continues to revolve in normal direction.

Ratchet lever and pivot with spring tension applied ---- Showing spring lever strip

Swinging arm gear lock - free ------------ Swinging arm gear lock - locked

Some lighthouses had the weight dropping in a channel cut into tower wall,which gave more room,especially in towers used for accommodation.

The pulley below cable drum was free to slide on shaft which allowed cable to freely wind on and off drum.

Jack 2007 ________ Jack Diagram 2007

This was the type of lifting jack used when chariot wheels were fitted
Used to raise lens and service roller wheels