The gear room has three purposes: to receive the material for grinding and move it through a trap door to the pan room above, to transmit the drive from the engine to the pans in the room above and to receive the ground material for settling. To take the weight of the pans in the room above the lower floor is constructed using iron framing and four course wide brick walls with jack vaulting. This make it extremely strong. The mill was built by the well known and respected firm of George Kirk who had a yard and foundry on the right hand side of the Trent and Mersey canal just before the next bridge travelling north. Approximately one third of the mile (500m) from the mill.
Line Shafts and Bevel Gears
Power is transmitted via the flywheel axle of the engine through a ratchet. This enables the engine to be barred backwards by hand without moving any of the machinery if it has stopped on a dead centre. Rim gears transmit the power to line shafts which run the length of the room. Along each line shaft are five bevel gears which drive vertical shafts taking the power to the pan room above. Most of the gears and the line shafts are original to the 1857 build. The gears on the window side are operated during steaming weekends, the other side being preserved. To disengage a vertical shaft to ‘stop’ the operation of a pan in the room above the bevel gear wheel on the vertical shaft is jacked up by a screw thread on each side. The line shafts are in sections connected by dog splines so it will run true.
Running off the Ground Material
After the material has been ground in the pans in the room above it is drained out through channels under the upper floor into wooden chutes called launders to a wash tub. This contains paddles which rotate to ‘blunge’ it through vertical bars and break up coagulated particles (lumps) to give a smooth homogeneous suspension locally know as a slop. The mix was then run into one of two rectangular tanks called settling arks. Much larger arks holding 25 tons (25.4 tonnes) of liquid were beyond the gear room wall and have been lost during site development. As the solid particles settled wooden bungs in a vertical plank were knocked out to run off the clear water. This left a thickened slop which could be put into barrels and delivered to customers or pumped to drying beds (which have been lost) where water was evaporated off and the solid product shipped as blocks.
Pulsometer Steam Pump
Above the settling arks is a rare working ‘Pulsometer’ steam pump. This may be the only working example of a Hall’s “pulsometer” pumping engine, which works without cylinder or piston and may be regarded as the modern representative of the engine of Savery. It was designed to have only one moving part (a ball) which made it very suitable for pumping abrasive liquids such as ground flint and bone in an aqueous suspension i.e. a slurry. It was manufactured by the Pulsometer Engineering Co. Ltd. founded in London in 1875 by a British engineer when he bought the patent rights from American, Thomas Hall. It has two chambers, steam pressure empties one side whilst a vacuum created from condensed steam draws fresh liquid into the other side. A steel ball then rocks over a knife edge to allow the process to be repeated.