9.10.11. Repair of the brake mechanism of a forward wheel
Dismantling of the case of a brake bracket is made when replacing pistons, fingers, sealing rubber details.
It is necessary for dismantling of the case:
- to disconnect a flexible hose from the case of a brake bracket;
- to remove brake shoes;
- to take brake shoes and to mark them that at the subsequent assembly to put on the former place;
- to remove a finger cover from the basis;
- to take the case with a finger from a basis opening;
- to establish wooden whetstone 20 — 25 mm thick (fig. 8.13) between the piston and the case;
- to push out the piston from the cylinder, having connected a hose with the low pressure of air to an inlet opening of the case;
- to remove a piston cover from a flute of the piston and to take the piston from the case, and a cover from a case flute;
- to take the dulled shovel a sealing ring from the case.
Having executed these operations, to wash out all details isopropyl alcohol or fresh brake fluid.
It is inadmissible to use for washing gasoline, solvents or other liquids on a mineral basis
To check all details for existence of wear, damages and corrosion, paying special attention to the working surfaces of the piston and an opening of the cylinder. Edges of a sealing ring have to be sharp, without curves, and a surface equal, without vyryv. In the presence of strong corrosion on the working surface of the piston it needs to be replaced.
Assembly of the case of a brake bracket.
After check and replacement of the failed details to assemble the case of a brake bracket taking into account the following recommendations:
- before assembly to be convinced that the working and sealing surfaces of the case pure; to grease with TU 38.10.1129-80 NG-213 liquid a sealing ring and to establish it in a case flute;
- to grease with NG-213 liquid the working surface of the piston and a cover and to install the last on the piston (fig. 8.14). Without displacing a cover since the end of the piston, to fill it in a case flute;
- carefully a hand to insert the piston with a cover into a case opening. To fill a cover in a piston flute;
- to install the case with fingers in basis openings;
- to establish blocks on the former place;
- to connect a flexible hose to the bracket case.
Replacement of the directing fingers needs to be made in the following order:
- to execute operations on removal of brake shoes. At the same time it is necessary to mark blocks that at the subsequent assembly to establish them on the former place;
- to turn out a bolt of fastening of the second directing finger (fig. 8.15);
- to remove covers of fingers from the basis;
- to take the directing fingers from basis openings;
- to replace the worn-out directing fingers, previously having greased them with UNITOL-1 lubricant and having put on them protective covers (covers should not have damages);
- to execute the operations done earlier in the return sequence.
Replacement of the basis.
It is necessary for replacement of the basis:
- to disconnect the case from the basis (see above);
— to take brake shoes from the basis and to mark them that at the subsequent assembly to put on the former place;
- to turn out two bolts of fastening of the basis to a rotary fist and to remove the basis;
- to establish the new basis on a rotary fist and to wrap bolts of fastening of the basis the moment of 100 — 125 N · m (10 — 12,5 kgfs · l), previously having cleared the carving surfaces of a fist and bolts of old sealant and to apply fresh Unigerm-6 sealant of TU 6-01-1285-84 on bolts.
To make further assembly (see. "Assembly of the case of a brake bracket").
Repair of a brake disk.
The disk is exposed to repair if its working surfaces have deep risks and an axial beating more than 0,1 mm. The axial beating of working surfaces of a disk is checked by the indicator at rotation of a disk on hug bearings.
It is necessary for repair of a disk:
- to remove the case and the basis from a rotary fist (see. "Replacement of the basis");
- to remove a disk from a nave for what to turn off bolts with spring washers;
- to proshlifovat working surfaces of a disk on the basis of its face surface adjacent to a nave.
When grinding it is necessary to provide the minimum difference on processing between disk walls. The size of the total admission of parallelism and planeness of a working surface of a disk of rather basic surface has to be no more than 0,05 mm (that corresponds to a difference in the indication of the indicator at its movement on the checked surface), and the size of the total admission of parallelism of working surfaces of a disk among themselves has to be not less than 0,03 mm. Disk thickness after regrinding has to be not less than 19 mm, and the roughness of its working surfaces has to be no more than 1,25 microns in accordance with GOST 2789-73.
At detection of cracks or deep рисок, and also at a thickness of disk less than 19 mm it is necessary to replace a disk new.
For this purpose it is necessary to establish a disk on a nave and to wrap bolts of fastening of a disk the moment of 44 — 56 N · m (4,4 — 5,6 kgfs · м). To install the case of a brake bracket on a rotary fist (see. "Replacement of the basis" and "Replacement of blocks of brake mechanisms of forward wheels").