Case study: Wicken Fen Windmill

Client:

National Trust

Contract Type:

Damage Repairs

Duration of contract:

3 months

Works Undertaken:

The main wrought iron wind-shaft was found to be broken. The task presented the mill-wrights Dorothea Restorations with a number of challenges. The site is open to the public, and marshy with only board-walk access.  Restoration had to be planned to use only equipment that could be man-handled onto site. With no road access for a crane to hoist the sails a ‘sky hook’ was created inside the restricted cap-space comprising a steel beam and scaffold trestle secured by webbing straps. 

The tail was tied down to the concrete base of the tower to prevent the cap being pulled off. Access for the mill-wright inside the cap was via a very small gap between the curb and main frames called ‘shears’, requiring flexibility, good planning, and a minimal breakfast!

The new shaft was made of high-tensile steel with an iron journal cast on.  The bore of the central cross holding the sails had worn extensively so the new shaft was ‘blued’ and dressed by power-sander to fit the worn hole.

Remote greasing lines were added to facilitate future maintenance. New aluminium cap-front sheets were fitted, and all exposed surfaces liberally coated with traditional tar varnish. Before being hoisted into place the sails were placed on scaffold trestles and slinging-points adjusted to give the correct angle of lift.  After hoisting into position, ropes on the tips of each sail manned by NT staff pulled the sail-assembly onto its new shaft, where it was secured by a single large nut.

The work was finally inspected by Lee Fish, NT Senior Buildings Surveyor. The scoop-wheel is now working again, draining water from the fen on demonstration days, operated by volunteers when wind conditions allow.