Section 5.—BRAKES AND RETARDING APPLIANCES.
To retard or arrest motion (revolving or rectilinear).
[35]. Strap and lever brake. The strap is usually faced with wood or leather, but sometimes is used without either. Wood is liable to become noisy. Leather gives the best grip. Iron upon iron, or wood upon iron is not safe if liable to become oily or wet.
[36]. Block and lever brake. Wood or cast-iron blocks are used.
[37]. Compound block and lever brake; avoids putting cross strain on the shaft—used on winding engines, &c.
[38]. Internal toggle brake, employed for friction clutches. See [Section 15]. The inner ring is turned to fit loosely inside the outer ring and split, the toggles being arranged as shown to expand the ring till it is locked to the outer ring.
[39] & [40]. Double block and lever brake on wheel rim grips the wheel rim between the lever stocks or jaws. The strains are self-contained.
[41]. Disc brake; considerable end pressure is required with this form, and must be arranged for in the bearings of the shaft.
[42]. Compound disc brake. Several discs may be employed, sliding on feathers on the shaft.
[43]. Fan brake; may be run openly in air, or enclosed in a drum with water, oil, or other liquid. (See Allen’s patent Governor, &c.)
[44]. Spring brake, acting on a small grooved pulley; for light purposes.
[45]. Rope brake or grip, with toggle motion, and screw for relieving.
[46]. Rope brake: grips by the angular distance between the jaw centres becoming less as the lever end falls.
[47]. Rope brake; with cam lever gripping motion.
[48]. Eccentric action lever and block brake. The eccentric is fixed to the brake lever. This plan also avoids cross strain on the shaft.
[49]. Strap and screw brake.
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[50], [51], & [52]. Three forms of car brakes. See also the common “skid” or cart brake.
[53]. Combined strap and lever brake. (Fielden’s.)
[54]. Shaft grip, or brake.
[55]. Centrifugal brake, or clutch. The weight segments are driven into contact with the ring by centrifugal force. Springs may be used to return them out of action.
[56]. Three-segment compound brake: grips the wheel all round.
[57]. Compound bar brake, with right and left hand screw grip levers, used for heavy gun compressors.
[58]. Compound ring brake, on similar principle to [No. 57]. See remarks to [No. 41].
[59]. Wedge and split ring, used for internal brake ring or clutch, in a similar way to [No. 38].
[60]. Hollow drums, with radial pockets, half filled with loose material, or water, mercury, &c., which retard the motion of the drum by the weight and friction of the loose material.
An hydraulic cylinder and piston is frequently used as a brake or retarding device for reciprocating motion, the water passing from one side of the piston to the other, through an adjustable valve. Friction brakes are employed as dynamometers to indicate the power given off or absorbed by any piece of machinery. Automatic brakes (see [Sections 15] and [69]) are used for hoisting machinery, &c.
Brushes, formed of stiff bristles or wire, are used as a retarding device for circular or rectilinear motion.