The brake mechanism consists of a guide 2 (figure 83) pads, caliper 3, two brake shoes 4 and brake disc 1. The pads are driven by wheel cylinder 5.
Figure 83. Front wheel brake mechanism:
1 - brake disc; 2 - shoe guide; 3 - support; 4 - brake pads; 5 - cylinder; 6 - piston; 7 - sealing ring; 8 - sewn cover of the guide pin; 9 - guide pin; 10 - sewn casing; 11 - shoe spring.
Guide 8 (figure 84) the pad is made of high-strength cast iron in the form of a bracket, has four bosses. In two of them, threaded holes are made for fastening the pad guide to the steering knuckle, in the other two, holes are drilled for the pins 9 (see figure 83) caliper. The brake pad guide has a longitudinal groove through which the brake disc passes, and two openings for placing the brake pads. The configuration of the openings is made according to the shape of the brake pads. In addition, in the side openings there are two shelves to which the brake pads 4 are pressed by springs 11. All this ensures a tight fit of the brake pads in the guide and does not allow them to vibrate.
Figure 84. Front wheel brake mechanism (detailing):
1 - wheel cylinder; 2 - nipple for bleeding the brake drive; 3 - sealing ring; 4 - piston; 5 - protective cap; 6 - retaining ring; 7 - support; 8 - shoe guide; 9 - brake pads; 10 - protective cover; 11 - guide pin; 12 - guide pin mounting bolt; 13 - brake hose; 14 - bolt for fastening the cylinder to the caliper.
Support 7 (see figure 84) is cast from high-strength cast iron. At the bottom it has a groove for the brake shoes, and in the center of the casting there is a through inspection window into which the lugs of the brake shoes are pressed. The wear of the brake shoe linings is visually determined through this window. The springs of the shoes rest against the steps of the window. This ensures that the brake shoes are pressed against the guide and fixed relative to the caliper. Cylinder 1 is fastened with its flange by two bolts 14 to caliper 7, forming a "floating" bracket. In order to ensure joint mobility of the caliper and wheel cylinder relative to the guide, they are connected to the guide of the shoes not rigidly, but by means of pins 9 (see figure 83), which are installed in the guide holes. The guide pins are secured with 12 bolts (see figure 84) to the flange of the wheel cylinder. The mounting bolts are fixed with locking plates. During assembly, the pins are coated with grease, which protects this connection from corrosion, in order to ensure a constant force for moving the bracket, regardless of the service life of the car. To prevent air resistance from being created in the holes due to its compression when moving the pins, there are three chamfers on the pin shaft. A protective cover is put on the annular grooves of the pin and the guide 8 (see figure 83), protecting the fingertips from exposure to water and dirt.
The brake pads are steel and have a shape that ensures their tight fit to the pad guide. At the top of the pads are lugs that, as indicated above, fit into the caliper window.
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The spring 11 is attached to the shoe with the help of a finger. When installing the caliper, it presses on the spring, ensuring that the shoes are pressed against the guide. A friction lining is glued to the shoe.
The wheel cylinder is attached to the caliper and the shoe guide as described above. A hollow piston 6 is installed in the cavity of the cylinder 5 (see figure 83) diameter of 48 mm, which is sealed in the cylinder by a rubber ring 7. This ring has a trapezoidal shape. It is located in the groove of the cylinder and tightly covers the piston. When the piston moves, it carries the ring along with it, twisting it in the groove of the cylinder. Due to the elasticity of the sealing ring, the piston then returns to its original position. The cylinder cavity is protected by a rubber cap 5 (see figure 84), the edges of which are placed in the grooves of the piston and cylinder. Two holes are made in the cylinder. In one of them, a nipple 2 is screwed in for bleeding the brake mechanism drive, and in the other, a hose nipple 13 for supplying fluid to the cylinder.
Brake disc 1 (see figure 83) is cast from grey cast iron. Six holes are drilled in the disc hub, four of which are for the wheel disc mounting bolts and two are for the wheel disc guide pins. The working surface of the disc is made with great precision. The normal disc thickness is 12 mm, the maximum permissible is 10.8 mm. The brake disc is covered from the inside with a protective casing 10, which is attached to the steering knuckle.