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Restoration of the boulter (flour sifting machine)

During 2015, the Wheatley Windmill Preservation Society raised funds for the restoration of the Boulter, which was in a very sorry state in the mill. David Empringham, millwright, was commissioned to restore the boulter, and here is his description of the boulter and how it worked.

The boulter was restored in 2016 by David Empringham Millwrights. In the condition it was found at the outset, it was difficult to understand its use or how it worked. When the tower was restored, little thought was given to its integrity with the building, the result being that it was literally cut free from the mill structure and it became completely divorced from its chutes.

The restoration sought to retain as much of the original as possible, hence the splices to the tops of the legs, which would have previously been joined into the floor beams. The legs at the left hand end had been deliberately shortened, quite possibly to improve the flow of meal through the rotating sieve. Blocks have been added in such a way that this stage in its history is still evident.

Boulters, before they went out of use, were finished with woven cloth, particularly silk in later times. Since these cloths are no longer available, and to make the process clear, the restoration has used polyester mesh in two grades. The fine mesh has openings of 250 microns - equivalent to 70 grit for fine flour. The coarser mesh has openings of 375 microns - equivalent to 50 grit, producing wholemeal flour. The sieve, rotating at about 40 r.p.m. billows out and strikes against the beater bars, thus forcing the flour through the mesh.

The foremost beater bar is removable, which allows the bulkhead over the tail end to be removed: this was necessary for removal of the rotor when the cloths became worn. The feed into the top end of the boulter would originally have been from a meal hopper from the floor above. Likewise the flour produced would have passed down chutes to bins or sacks on the floor below. These are indicated by the dummy top ends of the three chutes in the floor.

David Empringham. April 2016.

When the restoration was complete, the boulter was returned to the mill and re-installed. Here is a slide show of the photos taken during the process.