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St Torpid's Bay lighthouse



 
The inspiration for the reversing loop at St Torpid's Bay
– a Rowland Emett illustration from the 1940s.


The Whittlecreek and Eaton St Torpid Heritage Railway will modernise this for twenty-first century tourism by installing a signal box (on stilts) by the turnout and converting it to a fast food takeaway specialising in oysters and other shellfish.

Construction of the lighthouse has commenced. This will be the world's first
wind-powered lighthouse, using windmill-type wooden gearing powered by a Leonardo di ser Piero da Vinci helical sail to rotate the parabolic reflector.
Just because the management happen to have a Pathfinders Leonardo da Vinci Aerial Screw Wood Kit.



 
The Lenny the Vinch's helical sail looks something like this when configured for lighthouse-powering purposes.


In a moment of impulse buying the management bought a cheap teaspoon while in Hunstanton, specifically to use as the reflector for this lighthouse. This was before being aware that the former lighthouse a kilometre to the north had the world's first parabolic lighthouse reflector back in 1776. Good scriptwriting by whoever was in charge of coincidences that day…



 
Key parts of the wooden kit repurposed, along with an LED tealight and a teaspoon. The sails have yet to be fitted.


The wooden cogs from the Pathfinders kit were assembled. The shafts were bushed with some suitable metal tube so they fitted into skateboard bearings. Four lengths of 2 x 1" wood were bored to take the bearings then screwed together. Only one of the bearings needed to be retained – some offcuts of polystrene sheet sufficed. Castrol LM grease was brushed on to the wooden cogs to improve the tribology.



 
The workshop's early 1980s can of Castrol LM grease.
In case you didn't know, the LM stands for 'lithium'. As in 'lithium soap'.


The wooden dowel which links to the sail was reinforced with the same metal tube. To improve the strength of the even-thinner wooden dowels which support the sail they were reinforced with lengths of ABS tube which happened to be a snug fit – no glue needed!

The rotating light was assembled around a short length of broom handle. The aluminium 'pot' from a wax tealight was repurposed to take a flickering LED tealight. The parabolic reflector is the aforementioned teaspoon with most of the handle sawn off and two wee holes drilled to take 2.5 mm self-tapping screws. The lens had been a long-time resident of the bits box (it may have come from a Box Brownie camera) and was glued into a purpose-made 'frame' made from black polystyrene sheet; again 2.5 mm self-tapping screws hold it in place. This frame was subsequently modified to fit on a brass bracket.



 
The final lantern assembly.


The faun/beige/ecru/pale taupe/light tan/whatever-colour-name-is-on-trend-this-week fabric sail supplied with the kit was used as a template for a replacement sail cut from reddish-orange kite fabric. This was mounted with hot-melt adhesive to provide maximum strength.



 
The helical sail 'set'. With authentic workshop clutter.


As this lighthouse is more like a windmill than a conventional lighthouse then not only does the light, lens and reflector need to rotate but also the whole housing needs to keep its 'tailfeather' to leeward. So yet another couple of skateboard bearings were set into the top of the lighthouse column – the bearings come in sets of eight, so there's still two left. A metal tube just sufficiently tight in the bore of the inner bearings acts as the shaft.



 
Initial stages of the assembly of the 'housing'.
 

 
The 'housing' almost complete.


The exterior of the housing is 3.5 mm ply 'scribed' to look like planking. The joints are strengthened on the inside with small wooden 'fillets' glued with hot melt adhesive (although initially small screws were used to get everything lined up).

Strips of bamboo were added to the vertical sides to improve the fit and appearance. A set of doors was added to allow maintenance of the mechanism. These are hinged using lengths of welding rod glued to the outside edges of the doors and then covered with bamboo strips. The rods rotate in holes drilled in the 'lintel' and 'doorstep' quadrants above and below the doorway.

After some deliberations about how best to make an octagonal Gothic lantern housing to surround the rotating parabolic reflector a chance conversation with a neighbour revealed that his son, David, had just purchased a small 3-D printer. Seems David would be quite happy to print eight windows. So a suitable SLT file was downloaded.

Seems 3-D printers are happiest when printing a polymer called PLA. This is an acronym for 'poly lactic acid'. However it is a misnomer it is the monomer which is lactic acid while the polymer is polylactide. Whatever, it has useful mechanical properties (somewhere between ploystyrene and polycarbonate) which is nifty as the monomer is made from fermented starch, using sugar beet trimmings and other plant waste as the starting point.


   
 
The lantern housing under construction.


One of the windows was modified to make a doorway, and the other seven glued to a wooden plinth using hot-melt adhesive. The whole subassembly was sprayed with grey primer then silver paint. But it then looked too silver… So a coating of pewter-coloured paint was brushed on the exterior. Hopefully this is enough to slow down the biodegradation which PLA is susceptible to.

After this eight strips of bamboo were cut to form the main roof timbers and eight kebab skewers cut to form the timbers in the 'valleys' of the roof. They are joined at the centre to a short length of ABS tube (this was initially supported on a simple jig to ensure it was central and at the correct height).

Eight pieces of thickish aluminium foil were hot-melt glued to the roof timbers. Another piece of foil made the central 'cap'. A weather vane inspired by the 'weather cod' on the church tower at Seagrave in Leicestershire was constructed from thin copper. The rest of the weathervane is from assorted pieces of polystyene (including Slater moulded letters) painted with brass-effect paint. The weathervane itself rotates within the ABS tube at the centre of the roof.



 
Awaiting the weathervane.
 



 
Many churches have a weather cock. The church tower at Seagrave in Leicestershire instead has a 'weather cod' (more likely intended to respresent a carp), thought to have been erected in the 1930s. Curiously the village's name derives from Old English seath graf ('pit or pool grove') which refers to a pre-Christian sacred pool in which, presumably, large fish might have abounded. The remains of later medieval fishponds survive not far from the church.
 



 
The St Torpid's Bay lighthouse weather cod


The main column of the lighthouse was envisaged to be based around 150 mm diameter uPVC pipe. But none was to hand. Sometime in the future this may come about.

So in the meantime a quick-and-dirty column was constructed from a part-sheet of 3 mm ply which had been kicking around for over a decade and had become slightly warped. This was marked out with four rhomboids which used as much of the sheet as possible. Two 'floors' and some corner fillets were cut from scraps and the whole lot combined with small screws assisted by hot-melt adhesive.

Two bearings for the upper housing were assembled from off-cuts of wood drilled to take a pair of skateboard bearings. These were screwed to each of the floors (with a hole in the top 'floor' to allow the shaft to pass through).



 


'Quoins' were added to the external corners from some right-angle beading which had never been used for its intended purpose four years ago. These were fixed with exterior-grade 'No More Nails'. The same adhesive was used to fix the 'string courses' cut from bamboo strips. These handily cover up the screws which fix the sides to the 'floors'.

A Romanesque-style doorway and two windows were fabricated from offcuts of strip wood and dowel. The arches were done 'the proper way' – from wedge-shaped voussoirs of stripwood, which were fixed together with hot-melt adhesive. Steps up to the doorway were from another offcut of wood.



 


The whole assembly was painted with some old exterior undercoat which had started to get gloopy – just what was needed to hide a multitude of minor sins in the fitting together! A top coat of masonry paint was then applied.

But it didn't look quite 'masonry' enough. So mixed in some 'gritty' molochite with the masonry paint and trowelled it on the lower part. Yes it would have made more sense to have used render mix on the plywood before painting with unadulterated white masonry paint. 20:20 hindsight is a wonderful concept but doesn't help in practice.

    note for the nerds and the otherwise unduly curious
    Molicite is a made-made granular material produced from calcined kaolin (a.k.a. China clay) and used in specialist ceramics.

Lengths of welding rod were fitted into holes drilled in the steps, and strips of bamboo glued to the top to form a handrail. These strips were stained dark oak. Finally a door made from lollipop sticks glued to thin ply then stained dark oak was glued inside the doorway. But not before small brass pins were nailed into the door to simulate the fixing bolts for a pair of hinges on the inside. And, somewhat as an afterthought, a keyhole drilled through.



 


Apart from the exterior-grade 'No More Nails' (which cost 7 and wasn't all used) the main column was constructed from left-overs.


costings

The management don't normally bother with costings. But out of interest here they are:

    Leonardo da Vinci Aerial Screw Helicopter Working Wood Model Kit: 15

    part-sheet of ply for the upper housing: say 7

    8 x skateboard bearings: 5.40

    1 teaspoon: under 1

    8 x 3-D printed Gothic windows: four bottles of beer (about 10)
    [yes, they were a bargain!]

Everything else was in stock or a left-over. OK the supply of hot-melt adhesive went down rapidly, but there wasn't any need to restock.

In total about 40. More than offset by the amount of fun designing and constructing.


St Torpid's Bay lighthouse keeper

Maintenance of the St Torpid's Bay lighthouse is supervised by a retired lighthouse keeper, Eddie Stone, assisted by his wife, Rosetta (who is also an ancient languages research assistant).

Thanks to Ian for help with their recruitment.


lighthouse-themed gifts

The Whittlecreek and Eaton St Torpid Heritage Railway gift shop will shortly have an attractive range of lighthouse-themed teatowels and other gifts.

     
 
Mama Mia says 'Neva forgetti Faro spaghetti'
 

 


acknowledgements

Thanks to Alexey Zernov (a.k.a. Njorn) for creating the Gothic window STL file, David for printing the windows, and Alby for 'stoner' surname puns. Ian, as ever, made frequent admiring and encouraging remarks as this project manifested.



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Images and text copyright Bob Trubshaw 2018–2021