Ore Processing Sites

Tuckingmill Valley Calciner

This early calciner is identified by the extensive use of granite in construction. The pyramidal roof is also typical and seems to be original. The site's proximity to several iron foundries is shown by the use of cast iron straps to connect the two grids of wrought iron cross-ties. These were necessary to hold together the two internal brick vaults, both under and over the combustion chamber, as these had very shallow vaults, which could have cracked or deformed easily if even slight outward movement occurred.

The lower vault with a large diameter gear, driven by a worm gear on a drive shaft. This made the driveshaft rotate very slowly, as it was important to ensure even combustion on the revolving table above and prevent ore being thrown off by centrifugal force. The power source is unknown in this case, though small water wheels were popular.

The mouth of the combustion chamber, with two furnace holes and a pair ofcentral rodding holes in a splayed and arched embrasure. Additional tiebars using old rails as connecting straps have been added. The original cover building has gone - although the current one may retain elements of the original's roof structure.

Detail of furace door, with ashpit beneath. Distortion of the structure is evident from the shapes of the rails flanking the furnace door, while the arch above has burnt out and been crudely patched. Constant running repairs were always necessary on calciners.

View into combustion chamber through upper rodding hole, with large circular domed revolving table, fixed to vertical drive shaft. This had an iron frame, into which were fixed refractory bricks, held together with fire cement. Rakes fixed to the ceiling vault can be seen in the distance - these kept the ore on the move during a burn. The ore was tipped in through a hole in the ceiling (not visible here).

View along side of revolving table, showing smooth surface. Burnt leavings from the process fell into the void beneath the table and were raked out via the lower rodding holes. Again, the fixed rake can be seen, bolted to the brick ceiling vault.