In the north west corner of the Forge, our third water wheel drives an air pump or blower.
John Cockshutt II took out a patent No.988 in 1771 for the manufacture of malleable iron – requiring several tuirons in the finery or bloomery.
After the Forge closed around 1910, much of the Forge equipment was sold for scrap. The Blowing engine was destroyed at that time. It became a project for the Forge volunteers to recreate this ancient device.
The first task was clearing the area around the Blower wheel. Debris from the demolished roof was cleared away and uncovered the bed-stones of the old blower which had been demolished. The scrap-man had left behind a few metal items of interest: the big end strap to hold the connecting rod to the crankshaft brasses (measuring this gives us the size of the crankshaft journals and the width of the brasses and the method – gib and cotter – of securing the con-rod to the crankshaft).
Fortunately these metal items were carefully saved at the time enabling new ones to be made following the old pattern.
Grooves in the stone bed show where the cotters have worn away the stone due to them being knocked down to tighten the brasses. A cylinder gland in cast iron gives the method of allowing the piston rod to slide through the cylinder cover, very similar to 19th C steam engine practice.
Many years ago, a brick column had been built on the old Blower bed straddling the west crank bearing with its housing and support casting. The column was put there in order to support a failing roof timber. When the scrap-man took away the rest of the Blower, this brickwork prevented the removal of the bearing support. This vital evidence shows us where the crankshaft actually was, also its height which allows the crank throws to be worked out which in turn give the stroke of the pistons in the cylinders.
The stone bed is built of varying pieces of stone – some 2 feet thick. These have hollows cut into them to receive the cylinders. Various other features could be seen – holding down bolts cut off level. Examination of the stone surfaces revealed parts of the face being ‘dressed down’ level in order to bed some parts of the mechanism.
Andrews gives the cylinder diameter at about 2’0”. We estimated the stroke at 20”. Add the piston thickness and room for the clacks at each end. A cylinder length of 2’6” was decided on. Stanton and Staveley Ironworks near Nottingham supplied, at no cost, two tubes of centrifugally cast iron.
Enough information now available for our volunteers to recreate a very acceptable replacement of the original air pump.
A water pump driven from the same wheel was successfully restored and now pumps water round a closed demonstration circuit.