TRICYCLE (from prefix tri, three, and Gr. 1cbaos, circle,

See also:

• WHEEL (0. Eng. hweol, hweohl, &c., cognate with Icel. hjol, Dan. hiul, the Indo-European root is seen in Sanskrit chakra, Gr. r in Aos, circle, whence " cycle ")
• WHEEL, BREAKING ON THE

wheel)  . The tricycle, as a machine for pleasure riding, has steadily diminished in relative importance since the advent of the safety bicycle (see CYCLING) . In its modern form it is a chain-driven rear-driver . The driving axle is provided with a differential gear, which allows of both wheels being driven whether the tricycle is moving in a straight or in a curved path . There are four rows of balls, two near the middle resisting the pull of the driving chain and two near the road wheels supporting the vertical load . Two types of driving axle are in use . In one the axle is supported from a parallel frame tube by four short brackets . In the other type, the Starley-Abingdon axle, the frame tube is concentric with the axle, and the middle portion is enlarged to form a casing for the chain-wheel, with two apertures for the chain to pass through . The other mechanical details are nearly all similar to those on a bicycle . Carrier tricycles, for tradesmen's delivery purposes, are made in two types, one with an extended wheel base and the carrier behind the rider, the other with a single rear driving wheel, the two steering wheels and the carrier being mounted in front on a transverse tube or frame which is jointed to the rear frame at the steering head . The second arrangement gives the simplest possible form of tricycle, but it is unsuited for touring purposes . Tricars.—The tricar or motor tricycle was first made by removing the front wheel of a motor bicycle and replacing it by a frame carrying two side steering wheels and a seat .

With a powerful

engine this arrangement gives a light vehicle from which good performances are obtained on roads with easy gradients . On steeper gradients the power must be increased, and the belt drive with only one speed is inadequate . The modern tricar is on different lines, resembling a small motor car on three wheels . The engine is 6 to 10 h.p., preferably with two cylinders, air or water cooled, with clutch and gear-box giving two or three speeds, sometimes also a " c reverse " speed . The transmission is usually by a chain from the engine shaft to the gear-box, thence by another chain to the rear road wheel . The frame or chassis is supported on the three road wheels by springs . The steering gear is on the same general lines as that of a motor car . The weight of a tricar of 7 to 10 h.p. is between 700 and Iwo lb . It is a much faster vehicle, especially uphill, than a small car of equal price . The rear tire, however, is subject to severer working conditions than the two driving wheel tires of a small car, and must be of adequate strength, or trouble will be frequent . The tricar cannot be said to have attained to the same degree of trustworthiness and freedom from breakdown as the motor bicycle or motor car . The rear tire is difficult to remove, in case of puncture .

The chain drive,

direct from a small chain-wheel on the engine shaft, is faulty in principle . The engine shaft running often at 2000 revolutions per minute, the chain is necessarily noisy, and is subject to continual gradual stretching, necessitating frequent readjustment . In all respects, except speed, the tricar is inferior to the small car . (A .