Tread-wheel, an apparatus used in the prisons of Great Britain for enforcing a portion of the sentences of imprisonment with hard labour. Sir W. Cubitt about 1818 devised the construction by which this form of employment was first practically carried into effect. The Prison Act, 1865, requires that every male adult prisoner over sixteen years of age sentenced to hard labour shall during at least three months of his sentence be employed on labour of the first class, namely, crank, capstan, tread-wheel, stone-breaking, or other like kind of bodily labour. The minimum period was by the Prisons Act, 1877, reduced to one month.
The tread-wheel consists of a hollow cylinder of wood on an iron frame, and revolving on an iron axle. The cylinder is usually about 5 to 6 feet in diameter, and on its outer circumference are steps about 7½ inches apart. The weight of the prisoners coming on these steps in succession causes the wheel to revolve. By means of suitable gearing this power may be transferred and utilised for grinding corn, pumping water, and other purposes. The speed of the wheel must be regulated by some sort of brake which may be applied by means of a 'governor.' According to the present practice, the speed is such that the prisoner ascends at the rate of 32 feet per minute. They are kept at this work for 6 hours in each day, divided into two periods of three hours each; and during each of these periods they are on the wheel for spells of 15 minutes, and then resting for 5 minutes. A prisoner, therefore, ascends 8640 feet per diem. In order to prevent intercourse between prisoners, wooden partitions are placed so that each of them works in a separate compartment, and each compartment has a handrail by which the prisoner steadies and partly supports himself while the wheel is moving, and while mounting or getting off it.
The crank is sometimes substituted for the tread-wheel as a means of enforcing hard labour. It has the advantage that the prisoner can work it in his cell. The prisoner turns a handle as in raising a bucket from a well, the handle causes a wheel to revolve, and the resistance to be overcome may be derived from a brake fitted on the wheel, or from mill machinery applied to grinding corn, pumping water, turning saws, or other purposes. The crank, when applied to overcome the friction of a brake, is liable to the disadvantage that the pressure may vary excessively from the heat evolved in the friction, which causes the surfaces to swell and increase the friction, and various forms of crank have been devised to counterbalance this, the most successful being that of Mr Appold. The present practice is to limit the pressure to 12 lb.; and the prisoner is required to make in 6 hours 8000 or 10,000 revolutions, according to his strength, the number of revolutions being recorded on a dial. Before a prisoner is put to tread-wheel or crank labour, he is examined carefully by the medical officer to ensure his fitness for such employment.