Stevington Windmill

An Impossible task at Stevington Windmill

Stevington Windmill near Bedford was constructed in 1770 for a baker Richard Pool. It was still in use in 1921 but was derelict so was extensively repaired by P. W. P. Keech a local carpenter and millwright who raised the body of the Mill (the buck) off the main post, repaired the framing, reboarded it, and raised the trestle on piers. Local opinion was that the task was impossible, but Keech and his team of five or six men completed it in twelve weeks. 

At that time the millstones were replaced with those from Milton Ernest Mill, and the tentering gear was renewed. The Mill continued to work commercially until 1936 and in 1951 was acquired by Bedfordshire County Council who carried out further repairs to celebrate the Festival of Britain.  The sails were renewed by E. Hole & Sons of Burgess Hill in 1958, and further repaired in 1972.

As in most post mills, the rotating buck rests on a large post supported by four quarter-bars whose lower ends are tied together by crosstrees, making four strong triangles. Recently at Stevington the ends of these timbers were found to have decayed badly, the main post had also settled onto the crosstrees causing one to bend, death-watch beetle attack was severe, and rodents were nesting inside two of the cross-trees. In short, the Mill was in danger of collapsing. 

Dorothea Restorations was charged with repairing the trestle, but how could new ends be scarped on to the structural timbers whilst they support the Mill?  An apparently impossible task.

One option would be to prop the buck from the ground, but this would require extensive dismantling of the roundhouse roof and erection of heavy steel-work, difficult and costly in a field with no surfaced road access.

Calculation came to the rescue. It was demonstrated that the four lower-end spigots on the main-post would be capable of carrying the weight of the Mill, provided the load was shared equally between them, so a special steel frame was constructed and erected under the post, set on sand to spread loads.

A cable-stay system was designed to prevent the raised Mill from toppling over. Calculations were carried out assuming a ‘worst case scenario’ wind blowing on the side of the buck.  Eight steel ropes were fixed to a light-weight steel ladder-beam passing through the buck at high level and out through the weather and tail-hatches to avoid cutting into the mill’s sound weather boarding. The Ladder beam was propped and tied with webbing straps at numerous points to the buck’s main framing to avoid point-loads developing which could strain the timbers or damage their joints.  The cable-stays were fixed to ground-anchor augurs screwed in using an hydraulic driver, calculated to give a pull-out load of 5 Tonnes in the prevailing soil conditions. Pre-stretched cables were used which required very little tension, keeping loads on the buck to a minimum. Additional stability was provided by wedging up the tail ladder and securing it to steel stakes, and by a 3T Tirfor winch set behind the Mill, secured to a triple-ground anchor.

A plumb-bob and levels were set up to monitor the buck, and when all was ready one 20T bottle jack was used to lift the entire structure 40mm., taking the loads off the trestle.

Three quarter-bars and cross-trees were then repaired, one at a time. Their ends were replaced with new English Oak scarphed on with double ‘birds-mouth’ joints bolted or clamped together, and a secret steel flitch-plate was set into a slot inside the new end of each cross-tree to resist its tensile loading.  Each flitch carried an end plate to spread loads, and was retained by an oak wedge set into sound timber in the crosstree, bolted laterally and grouted with pourable resin.

The fourth quarter-bar was decayed on the exterior, but micro-drill tests revealed its interior to be in good condition, so it was retained and strengthened with a plate running down its upper face, anchored to the supporting stone pier, and clamped to the cross-tree.

Once all the repairs were completed the mill was lowered onto its trestle, resting an inch higher than at the outset to ensure that the main post was not resting on the crosstrees.

The whole operation lasted three months, about the same time Keech’s team of 5-6 men took to reconstruct the Mill one hundred years ago. Dorothea’s team was smaller in numbers but with better equipment at their disposal the level of safety was probably higher. Modern millwrights continue to carry out impossible tasks with the same ingenuity and craftsman-ship as their predecessors.



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