The wheels, erank-shaft, and pedals are fitted with adjustable ball-bearings. and the wheels have rubber tires cemented into the felloes, and direct spokes headed at the felloe and screwed into the forged steel hub-Ilanges.
For steering, a lever-arm at the bottom of each steering-head is connected by a high rod to a lever pivoted below the main-frame bracket, and taking its motion through a connecting-rod attached to the lower end of the handle-bar up right. The brake is similar to that of a bicycle.
Band-Power _Tricycles have been introduced from time to time, notably the Oarsman and Velociman, In both of these driving-power is exerted by the arms instead of the legs. Their use, however, is very limited, being only of service in particular instances.
,Sociable Tricycles.—This type is merely an enlargement of the single form of tricycle. so as to permit two riders to sit side by side. S011il! Sociables " are capable of being converted into single machines.
Tandem Tricycles are constructed so that the riders sit one behind the other. The tandem principle is applied to most of the principal forms of tricycle. notably to those differentially geared the front-stcering type, by using an auxiliary trailing-frame with transverse and vertical joints between it and the front frame: and to the rotary machine by the addition of a light frame fixed in the rear of the front seat, to carry the hind seat and pedal crank-axle for the rear rider. Tandems of several classes are made convertible into single machines.
Carrier Tricycles.—The last kind of tricycles is one capable of being put to practical use for carrying a burden. There is one form known in England as the Coventry Chair," where a passenger is (tarried in a comfortable eludr constructed in the front part of the machine. and the driver's seat :mot driving mechanism, similar to that of the ordinary tricycle, are located between the driving-wheels in rear.
(See Cycling Art, Energy and Locomotion, by R. P. Scott ; and Construction of _Modern Cycles, by R. E. Phillips.) Damper Regulator: see Regulators.
Derrick : see Crane.
Diamond Drill : see Drills, Pock and Quarrying Machinery.
(lies: see Brick-Making Machinery, Milling Machines and Pipe Cutting and Threading Machines.