I
thought readers might be interested in an elegant
mechanism I came across for moving a stone nut in
and out of mesh with the great spur wheel. Whilst
researching the different mechanisms available for
carrying out this process, Andy Selfe in South
Africa sent me the attached photograph of a hand
wheel arrangement he had come across at Elim Mill,
Western Cape, South Africa. The hand wheel above the
stone nut is turned to raise the pinion out of
engagement. However, when I sat down and tried to
produce a sketch of how this was actually achieved
the task was not as easy as I had anticipated.
Going
back to Andy, he provided me with a rough sketch,
which John Brandrick
has been kind enough to interpret and draw, see
below. Inside the gear a tapered cone is machined
with a keyway in it. On the stone spindle is a
corresponding cone with a key insert. The pinion
just has to move upwards far enough for the key to
clear the inside taper in the gear for it to
disengage.
Regarding the date and manufacture of the mill
machinery: James Walton in his book ‘Watermills,
Windmills and Horse-mill of South Africa’ on page
49, states that the original wooden machinery was
replaced with iron machinery manufactured by I.
Zimmermann of Danzig, Germany (now Gdańsk, Poland)
in 1881.
Picture and information supplied with thanks to Andy
Selfe, South Africa. Drawing with thanks to John
Brandrick.
This
article first appeared in the January 2014 edition
of the SPAB Mill News
