On 7th May 1873 Charles Edwin Hammond took out a patent on
a novel centrifugal governing mechanism designed to control
the speed of a windmill. [Patent No. 1654].
The first of these was fitted into the cap of Jack Windmill at Clayton, and the
second in the rear of the bin floor at Windmill Hill Windmill at Herstmonceux, a post
mill in which the Hammonds had an interest. This is
basically a large centrifugal governor similar in action to
the type used to control the tentering of millstones. A belt from the
windshaft drove a cone friction clutch system which
conveyed its action to the existing striking gear.
This could only be applied to Cubitt's patent sweep control
and was intended as an additional refinement to be readily
incorporated. Cubitt's method controlled the sweeps by
relying on a counterweight load operating the shutters in
response to a change in wind pressure via a series of
levers and rods. The drawback with this was that power was
lost unnecessarily when a sudden gust of wind occurred
causing the sweep speed to vary, or if the work load within
the mill changed. In this latter case the miller would be
required to alter the weight setting to compensate.
Hammond's governor was intended to override the Cubitt gear
whenever the sweep speed varied from a predetermined norm,
whatever the wind or load conditions. Two opposed iron
cones were fitted to a keyed sleeve. These were, according
to sweep speed, raised or lowered by centrifugal weight
levers . In turn the small cones drove a larger iron cone
backwards or forwards which, via a light shackle chain and
pulley, immediately pulled the Cubitt's weight wheel into
the 'open' or 'closed' shutter position. The existing
weight and chain were retained, acting in a second groove
in the rim of the weight wheel. This was used to provide
the initial setting and controlled the mill entirely at the
idle position in the governor's action. A torque limiter
was provided to prevent the existing striking gear being
strained as the sweep speed increased.
Mr. Hammond's unique mechanism was used in both mills for a
considerable time and was in working order at Herstmonceux
mill when milling by wind ceased there in 1892. The concept
seems very sound as the speed at which the windmill worked
was quite critical especially if, as in the case of Jack,
rolling equipment was installed. The wind however, never
blows to order and the sort of conditions required to keep
the sweep governor usefully employed would only have occurred for
limited times. Periods of near still air often prevail even
on the Downs.
Extracted from the publication "Clayton Windmills" compiled by Simon Potter and published by the Jack and Jill Windmills Society for the preservation of Jill Mill.
In the early 1980s this Governor was renovated and installed in a working configuration in Jill Windmill at Clayton by volunteers from the Jack And Jill Windmills Society. It was loaned by Mr R. Buckmaster on the understanding that it would be returned to Herstmonceux post mill when the restoration of that mill reached an appropriate juncture.
Paul Frost (left) from Windmill Hill Windmill and Michael Peat (right) from Jill Windmill lowering Hammond's Patent Sweep Governor
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appeared in the Argus on Tuesday 24th May 2005
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In May 2005 the Governor was returned to Herstmonceux.