Backshot Water Wheel, 1844-1850

Model, (scale 1:24), of high breast waterwheel at Wheal Friendship near Tavistock, Devon, with transmission, rods and bell crank levers. Contemporary model of the 'Old Sump Wheel', exhibited at the Great Exhibition, 1851. Made by Nathaniel Smith of Mary Tavy, Devon, England, 1844-1850.

This arrangement was adopted at Wheal Friendship for mine drainage, with the waterwheel operating a set of pumps to drain away floodwater from deep in the mine. The power of the wheel was transmitted through cranks at 180°, and therefore counterbalanced, to two lengths of horizontal rods coupled to bell-crank levers at the pits, where six plunger pumps were worked. Balance bobs arranged in pits behind the wheel were used to compensate the weight of the pump rods. The wheel was 51 ft. diam. by 10 ft. face and had 180 buckets built of wrought iron. The axle was a hollow iron casting with flanged ends, but the arms were of wood. The wheel made 5 revs. per min. In 1841 it was reported to have given an overall efficiency of 69 per cent. (See Proc. Inst. Civ. Eng., 1842, ii, 97.)