General requirements for car repair

The main part of mechanical faults of components and assemblies is caused by friction processes, deformation elements, the aging of the parts, etc. These and other processes are vpekut for wear and damage to components. How to wear can be divided into three periods: the running-in, normal wear and alert. In the process of running an intensive wear of friction parts, resulting in unevenness of the mating surfaces are reduced, increasing the contact area, the specific load is reduced, the rate of deterioration is slowing and a period of normal wear and tear. It is characterized by relatively low growth rate of the gap in conjugation, but by a certain gap wear rate increases sharply, indicating the beginning of the period of emergency wear. Operating the machine with an emergency wear leads to breakdowns. During operation it is important to subject node before the emergency repair wear, while maintenance costs are considerably lower than in the repair unit from accidental wear.

Before deciding to repair it is necessary to diagnose the state of aggregates. Generally, diagnosis is carried out by circumstantial evidence, such as increased noise, vibration, oil consumption, a breakthrough crankcase gases and others. For better diagnostics unit must be disassembled, parts wash, inspect and carry out the necessary measurements. As a result of the inspection and measurement of a decision on the continuation of the operation or the need of repair. It should be guided by the following considerations: if the actual dimensions of parts are within tolerance zones, permitted this manual, the continued operation of the unit without repair possible; if the size exceeded the permitted tolerances, it requires repair. Extensions of fields tolerances given in this guide should be understood as the use of a residual resource of host interfaces without recovery. In case of repair of the unit in the reduction of interfaces field extension over the nominal tolerances are not allowed. Repair technologies can be divided into four main stages:

- Dismantling and cleaning;

- Control and sorting;

- The actual repair: restoration of micro and macro geometry of surfaces of details and physical and mechanical properties;

- Assembly with prior control of parts, entering the assembly.

Disassembly and washing operation is carried out in several stages: the outer washing machine, pre-demolition unit nodes, sink nodes, nodes on the dismantling of parts, washing and cleaning of parts. All items are to control and sorting should be thoroughly cleaned of dirt and varnish, degrease, rinse and dry.

The oil channels and holes in parts must be cleaned, rinse under pressure and blow compressed air. Details of aluminum and zinc alloys are not allowed to wash in alkaline solution used for cleaning steel and cast iron parts, as aluminum and zinc are soluble in alkalis.

In the process control of parts chips, cracks, dents and other damage to the shell detect by visual inspection. At critical parts checked for cracks using a flaw. Dimensions of parts must be monitored in the most exposed areas. Gear teeth wear unevenly, and when the control should measure at least three teeth arranged at an angle of 120 ?�. Given the need to ensure continued gears during the turnaround chipped teeth and nature of fatigue spalling on the working surface of the teeth are not allowed. Assembly units, such as a rod with a cap, engine block to the crankshaft bearing caps, gear transmission and final drive, you can not razukomplektovyvat. The rest of the assembly units can be razukomplektovyvat; but if you decide to continue the operation of mating components without repair, they razukomplektovyvat inappropriate. In all cases, parts repair welding and surfacing weld must not have slag inclusions, undercooked areas, undercuts and other defects. After welding, the weld must be clean and eliminate spatter, so they do not interfere with the installation of mating parts.

Threaded holes worn or damaged threads reduced threading the increased size of the repair, welding holes, followed by threading of nominal size, installation of spiral thread inserts. The use of threaded inserts is preferable for reasons of quality and recovery effort. Inserting a spiral, resembling a spring made of a wire of a rhombic cross section. At one end of the helix is folded the process leash with which the insert is wrapped in pre-prepared hole. The technological process of repair of the threaded holes using a helical insert includes the steps of:

- Reaming holes to repair the defect size;

- Tapping the thread in it, corresponding to the size of the helical insert;

- Screwing the helical insert and breaking of technological notch on a leash.

Table. 1.5 the dimensions of the holes and thread a spiral inserts are used in the repair of automotive parts.

To repair the threaded holes spiral inserts produced special kits that include inserts, drills, taps, special keys to screw insertion, the barbs for srubaniya technological lead.

Details supplied to the assembly, must be clean and dry. Threaded connections must not be damaged. Disposable self-locking threaded fasteners during assembly must be replaced with new ones. If you are unable to use new self-locking parts when they need to be using the old stopper from further loosening.

When assembling be sure to replace with new gaskets and seals. Rubbing the surface of the parts during assembly lubricate clean oil. When installing rubber cuffs lubricate working surfaces to prevent damage during installation. When installing cuffs with metal housing put into the groove to set the cuff thin layer of sealant.

The assembly of components and assemblies made in accordance with this guidance.

Table 1.5 Dimensions of holes and thread under reconstruction spiral insert

With the help of a measuring instrument to check up the size of the assembly of mating parts. When assembling the parts in conjunction with a movable landing should be provided free of relative movement without jamming. Sleeves, rings ball and roller bearings install using mandrels. When pressing the bearing force should not be transmitted via balls or rollers. Press tool should rest on the press-fit ring. Joining Effort should be directed parallel to the axis of the bearing to prevent misalignment. If the terms of the build installation of critical parts is carried out with a hammer, it is necessary to use a mandrel and hammer from soft metal, plastic, rubber, as well as accessories for fitting parts.

The keys must be firmly planted in the shaft keyways with a hammer or a soft metal mandrel. Backlash dowels in slots shafts is allowed.

Studs should be wrapped tightly into the threaded holes without backlash. Items must fit over the stud bolts. Podgibaniem studs when installing them is not permitted parts, fastening assembly or parts of several nuts or bolts should be conducted evenly around the perimeter - first preliminary and then final. All the same nuts and bolts of the connection must be tightened one point.

In all cases, the guidance provided, you must use a torque wrench, allowing to adjust the torque. Tightening torques, unless specifically stipulated in the technical conditions are determined depending on the diameter of the thread in accordance with the Table. 16.

When mounting parts bolts protrude from the nut by at least two or three of the thread, unless otherwise specified.

Table 1.6 Recommended tightening torque of threaded connections

Pins must not protrude from the slots nuts. The ends of the pins should be diluted and bent - a bolt and a nut on the other.

Tubes fuel and brake drive before assembly to blow compressed air.