The wheel brakes have two brake pads with friction linings attached to them
The pads are mounted on axles with eccentric necks that allow the pads to be centered with the brake drums.
When braking, the pads move apart with a fist 4 and are pressed against the inner surface of the drum 11.
Wheel brake adjustment can be full or partial.
Before a complete or partial adjustment, it is necessary to check the correct tightening of the wheel bearings.
The brakes must be cold when adjusting.
Full adjustment is made only after dismantling and repairing the brakes or violation of the concentricity of the working surfaces of the brake pads and drums as a result of loosening the fastening of the axes of the pads.
Full adjustment should be done in the following order:
- 1. Loosen the nuts for fastening the axles of the pads and bring the eccentrics closer by turning the axles with the marks one to the other.
The marks are placed on the outer ends of the axles protruding above the nuts. Loosen the nuts of the expansion knuckle bracket bolts.
- 2. Apply compressed air to the brake chamber at a pressure of 1-1.5 kg / cm2 (by pressing the brake pedal with air in the system or use compressed air from a garage installation).
In the absence of compressed air, remove the pin of the brake chamber rod and, pressing the adjusting lever in the direction of the stroke of the brake chamber rod during braking, press the shoes against the brake drum.
Turning the eccentrics in one direction and the other, center the pads, ensuring that they fit snugly against the brake drum.
Check the fit of the pads to the drum with a feeler gauge through a window in the brake drum at a distance of 20-30 mm from the outer ends of the linings. The 0.1 mm probe must not run along the entire width of the lining.
- 3. Without stopping the supply of compressed air to the brake chamber, and in the absence of compressed air, without releasing the adjusting lever and holding the axles of the shoes from turning, securely tighten the nuts of the axles and the nuts of the bolts securing the expander bracket to the brake disc.
- 4. Stop the compressed air supply, and in the absence of compressed air, release the adjusting lever and attach the brake chamber rod.
- 5. Rotate the worm shaft of the adjusting lever so that the stroke of the brake chamber rod is within 15-25 mm.
- Make sure that when turning the air supply on and off, the brake chamber rods move quickly, without jamming.
- 6. Check how the drums rotate in the braked state. They should rotate evenly and freely without touching the pads.
With the specified adjustment between the brake drum and the shoes, there may be approximately the following gaps: at the expanding fist 0.4 mm, at the axes of the shoes 0.2 mm.
Partial adjustment is done to reduce the gap between the pads and the drum, which increases due to lining wear.
The presence of large gaps, which require partial adjustment, is detected by an increase in the stroke of the brake chamber rods, which should not exceed 40 mm.
Partial adjustment is performed only by rotating the axes of the worms of the adjusting levers, as well as with full adjustment.
With partial adjustment, do not loosen the nuts of the axles of the shoes and change the installation of the axles, as this may lead to a violation of the snug fit of the shoes to the drum during braking.
In the event of a change in the setting of the axles, a full adjustment must be made.
When carrying out both full and partial adjustment, it is necessary to set the smallest stroke of the brake chamber rods (about 15 mm).
To obtain the same braking efficiency of the right and left wheels, one should strive to ensure that the strokes of the rods of the right and left chambers on each axle differ little.
Caring for wheel brakes consists in adjusting the gaps between the shoes and drums, as well as periodic inspection, cleaning the brakes and checking the fasteners.
When inspecting, check the following:
- 1. Reliability of fastening of brake discs to axle pins.
- 2. Tightening the nuts of the axes of the pads and the nuts of the bolts for fastening the brackets of the expanding knuckles.
- 3. Friction lining condition:
- a) if the distance from the lining surface to the rivet heads is less than 0.5 mm, then the brake linings must be changed;
- b) it is necessary to protect the linings from getting oil on them, since the frictional properties of oiled linings cannot be completely restored by numerical weaving and washing;
- c) if one of the linings of the left or right brake needs to be replaced, then all the linings of both brakes (both left and right) should be replaced.
- 4. The state of the axles of the pads. If the pads do not rotate freely on the axles, then it is necessary, without disturbing the installation of the axles, to remove the pads, clean the working surfaces from rust and lubricate them with a thin layer of grease.
After installing the pads, remove excess grease.
- 5. Expander shafts. The shafts must rotate freely in the bracket without jamming. Lubricate the shafts in accordance with the lubrication map.
Please note that the amount of lubricant should be moderate, as excess lubricant can get into the brake.
- 6. Pedal action. The pedal after pressing should easily return to its original position; if this does not happen, then you need to check the action of the retracting spring and the movement of the parts of the brake valve drive, which should be free.
In fig. 2 given the installation size by which it is necessary to process the block after installing new friction linings.
The size of the pad radius (210-0.4mm) is given in relation to new drums. After the repair boring of the drum, the shoe radius should be equal to the drum radius, respectively.
