In essence, Yarloop Workshops had its own foundry. The first stage in the production of metal castings is the design and manufacture of the patterns. Following last month’s article on pattern-making it is logical to proceed to the next aspect in the production of replacement steel objects, that is moulding.
This foundry existed in the large area on the south-west corner of the Main Workshop. That area had a steel furnace and a bronze furnace on the west side and a covered area to the south. This covered area had a brick enclosure where the moulding material was stored.
The moulder takes the wooden pattern and produces a mould from it using moulding clay in a container called a flask. At Yarloop these appeared to be mostly metal trays, a number of which were on the site before the Fire. They consisted of separate top and bottom trays hinged together. The moulder, after placing the pattern into the flasks, uses the moulding clay to form the mould around it. They would then fire the clay in a kiln creating a cast in preparation for the molten metal to be poured into it.
The pattern maker had to allow for shrinkage as the moulded metal cooled. The moulder had other complexities such as the effect of the moulding material on the cast’s surface. A mixture of graphite and water was used to form a smooth surface and stop the metal adhering to the mould. The moulder also had to consider the effect of the rate of cooling and the added complexity of moulds for objects that had internal cavities.
The coke-fed furnaces heated up the steel or bronze to a suitable liquidity that could be poured into the mould. The steel furnace at Yarloop contained a cupola (container) within it in which the metal melted and could then be released from a gate that consisted of a clay plug at the base of the furnaces, into a ladle. The ladle could be supported by a gantry crane as it was moved to the mould for the pouring. According to Geoff Fortune, who, as a boy was allowed to observe from a distance, the pouring of the several moulds was usually done on a Wednesday. The much smaller bronze furnace appeared to melt the metal in a crucible that could then be removed for pouring.
All of the equipment mentioned was still in the Workshops before the Fire, but we have yet to find any of it.[1]
The moulding area with the clay store through the end doors.
Looking back to the Pattern Maker’s Shop. Note the gantry crane overhead.
The bronze furnace looking from above.
The opening from the steel furnace with a small ladle below
The moulder’s trays. Note the patterns behind. This cat often occupied the Workshops Museum.
Photos are believed to be from a Shire safety audit in 2015, a year before the Fire.
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[1] From ‘The Phoenix Rises Very Slowly’ Part 17, by Allan Ward.