Winch to operate self-acting sluices (flap valves) on a land reclamation scheme installed by Telford at Fleet Mound as part of his great north road project in 1816 enlarged in 1834. The winch which may originate from these early dates was only used when too much fresh water on the land side of the Mound was beginning to flood farm land. At most times the flaps operated automatically when the head of water on the land side was higher than the sea level at low tide.
Three rods for use with the winch were used to fasten off the chain to hold one sluice open so that the winch can be used in turn to open up two further sluices. This winch dealt with 3 of 6 sluices.
It is an example of a single-purchase winch. The winch consistes of a pair of lever handles fitted to the squared ends of a round shaftcarrying a pinion. This pinion gears with a spur-wheel keyed to a lower shaft, upon which is also fitted a drum or barrel. To a hook or eye on the inside neck of the left hand flange of this barrel the rope or chain (to be connected to the load) is attached. Therefore, the turning of the handles causes the barrel to rotate and wind the rope upon it, thereby elevating the load. Both shafts turn in bearings bored in the cast-ron end standards or A frames. These frames are bound tightly together and kept at a fixed distance apart by three wrought-iron collared stays, secured on the outside by screw nuts. For more see: Jamieson, A. Elementary Manual on Applied Mechanics. Charles Griffin, London, 1900. Machines like this were manufactured by Loudon Brothers, Glasgow.
Is is beleived – possibly apocryphally – that the winches were replaced only after an operator was injured when opening or closing a flap. An operation overlooked by Health & Safety at the time.
For more information the Fleet Mound see https://canmore.org.uk/site/14787/the-mound.