Hobs - car parts that are responsible for the connection of certain nodes and elements of mechanisms. They are installed both in the front and rear suspension and are used to connect the suspension elements and mounting the levers, fixing the car engine and gearbox. There are several varieties of silent blocks, but floating bush is most often used.
The design of silent blocks
The silent block is a hinge, the design of which consists of metal bushings and gaskets located between them. Such an insert is made of polyurethane or rubber and dampens vibrations transmitted from one mechanism to another.
Floating silent blocks device
The floating silent block is a ball-type hinge. Together with other silent blocks and shock absorbers, he is responsible for providing high-speed advantages of the car, dynamics of acceleration and braking, controllability.
Unlike other similar parts, ball joints provide a movable and reliable connection of the levers, suspension bearings and wheels of the car, so that they can move in different directions in certain planes, including vertical. The floating silent block provides a movable connection of the wheel strut and suspension arms, which makes it possible to turn the front wheels and respond to vertical oscillations of the spring.
Types of design of silent blocks
Ball joints for cars are available in several variations. The first model consists of a body, in the hole of which a ball pin with a spherical head is installed, made of composite material of the liner and a spring that compresses the liner. The hole in the body is through, its walls consist of conical and cylindrical surfaces. On the outer surface of the liner at an equal distance from each other are conical sections. They interact with the annular compression spring and the equidistant surface of the housing. A cover is mounted in the housing, which presses the spring, and the spring element itself includes a spring and support sections.
The design of the silent block
The silent bush floating rear, having the design described above, has disadvantages - the high cost of the spring element and too complicated design. Given the most important characteristics for such a part, its closest analogue is a ball joint consisting of a housing, a ball pin, a compression sleeve and an insert. The sleeve, in contrast to the spring, is made of their polymeric material.
The disadvantage of this design is the complex and time-consuming production process. For the manufacture of hinges that can compress the entire body from the tail side of the finger, special equipment is required.
Analysis of all existing designs of ball joints allows us to draw the following conclusions:
- Features of such parts depend on the year of manufacture and manufacturer.
- Floating silent blocks develop as the material and design features of the bushings change - from elements made of metal to teflon parts covered with a plastic clip.
- The number of bushings parts in recent years has decreased from 12 to 6. This was achieved by eliminating the elements that were responsible for lubricating and adjusting the ball joint during operation of the car.
- All ball joints require reliable and high-quality protection of rubbing surfaces from contamination. Special covers for bearings - anthers - are characterized by a short service life due to rapid wear and tear. To reduce wear and friction, they try to use inserts with Teflon shirts in plastic cases. The reliability of the joints is also enhanced by increasing the surface roughness of the fingers.
The principle of operation of floating silent blocks
At normal and medium loads, the floating silent block behaves like a normal hinge, but with an increase in the degree of impact, its resistance to strong shocks increases, but does not harm the elastic. A similar result is achieved due to the fact that there is liquid inside the part, which is why the hinge was given the name floating.
During the movement of the car, all of its nodes connected by the silent blocks also come into motion. This causes the angular displacement of the ball pin relative to the housing. The force is transmitted from the hinge body to the finger through the liner, the wear of the head is compensated by the spring.
The inner surface of the liner has a large diameter, which reduces the load on the surface of the head and guarantees a high level of wear resistance of the structure as a whole. The polymer liner, before proceeding with the assembly of the hinge, is pressed onto the liner. The silent bush floating back, especially its metal parts, is covered with a special protective composition that protects against corrosion.
How silent blocks are attached
Hinges are installed in the suspension arms in several ways. The most common, which is used to mount the floating KIA Sid silent block, is to press the part together with the external sleeve into the lever eye. He fastens in it due to the force of friction. This design dampens vibrations and various loads. It is repaired trivially and easily: the old silent block is knocked out with a sledgehammer or a hammer, and a new one is installed in its place.
If the lever is loaded in one direction or plane, or it itself acts as a guide, then the silent block is dispensed with without an external sleeve. In such a situation, hinges are used, at the end of the elastic elements of which there are collars. With the help of the latter, he is pressed into the eye.
Recently, integrated silent blocks have become very popular, in which the role of the outer sleeve is played by the eye of the lever, inside which an elastic element is pressed in. Similar elements can be found in the latest Toyota cars - floating silent blocks on such vehicles are integrated. Such a design does not have a special engineering sense: its main task is to increase profits for the manufacturer, since it is almost impossible to press-fit new rubber into the lever outside the factory conditions. In this case, you will have to make a complete replacement of the lever, which costs a very large amount.
Rubber or polyurethane?
In almost all models of silent blocks, the elastic element is made of rubber. The higher the content of this material in the composition, the better the characteristics of the joints. Despite this, they have their own analogues, not inferior in quality.
Non-original silent blocks are most often made from synthetic polyurethane and are very popular with car owners who want to save on original parts for the car.
A huge advantage of this material is its long service life. Polyurethane bushings can be used for several years.
Despite this advantage, polyurethane silent bushings do not have special advantages. Many of them do not undergo a vulcanization reaction, respectively, it is impossible to securely attach their elastic part to the metal part, and it is impossible to compress such a material: it is too hard. Hinges made of low-quality polyurethane quickly fail - after 40-50 thousand kilometers. The reason for this is the detachment of the elastic material from the surface of the sleeve.
Even if the composition of the silent block is selected correctly, the main problem remains rigidity. After installing the polyurethane bushings, the car's ride is reduced, the suspension elastokinematics are violated - the nature of the arrangement of the wheels under the influence of lateral and longitudinal forces. Simply put, this can eliminate the thrusting effect of the rear suspension, which is typical for many modern car models.
The life of silent blocks
Correctly installed high-quality silent blocks even under adverse operating conditions are able to work for a long time. On average, their functioning period is from 70 to 150 thousand kilometers.
The service life and the difference in them directly depend on the quality of the product. Cheap models made of poor materials can not cope with serious loads and quickly fail. For example, the floating silent blocks "Mercedes" are of high quality and long life.
Active use of the car in bad road conditions - driving on off-road or dirt roads can contribute to the rapid wear of silent blocks.
Malfunctions of silent blocks
Active use of the car on bad roads, as mentioned above, can adversely affect the state of the suspension. Too high loads primarily affect the silent blocks.
The maximum load falls on the suspension rods and parts of levers. For preventive purposes, it is advisable to diagnose silent blocks every 50 thousand kilometers. This procedure will allow you to pre-determine the malfunction and understand whether replacement of floating silent blocks is required.
If the car has not been diagnosed for a long time, the wear of certain parts can adversely affect the handling and safety of the vehicle.
The main signs that the silent block floating is defective are:
- The machine wags from side to side or moves only in one direction.
- Lateral tire wear.
- When braking, the car loses directional stability.
- The body vibrates while driving.
- A visual inspection of the silent blocks reveals a violation of their integrity.
- Suspension creaks while driving.
- The stiffness of the suspension increases.
Each of these signs, as well as all together, indicates possible malfunctions in the operation of the hinges. In such a situation, it is advisable not to continue operating the vehicle. Replacing floating silent blocks will help to cope with malfunctions.
How to replace a floating silent block
Depending on the make and model of the car, the process of replacing the hinge may differ and have its own characteristics. However, for almost all vehicles, replacing rear floating silent blocks has common features.
Silent block replacement process
First, the handbrake on the car loosens and the wheel is removed. The pads are reduced, after which the brake caliper is unscrewed , and the pads themselves are removed. Fixing bolts are unscrewed: from the wishbone, brake caliper, stabilizer bar and shock absorber. The last moment - removing the brake disc and unscrewing the body bolts from the ABS sensor.
The cotter pin is pulled out, after which the nut of the breakup lever is unscrewed, the bolt of the hinge itself is loosened, and the bolts of the longitudinal arm are unscrewed. As a result, there is only a hub without attachments. Its mounting bolts are also removed, as are the handbrake mechanism bolts. Only the lever and the floating silent block ("Mark-2" or another car - it doesn’t matter) should remain, mounted on the wire from the sensor.
Anther is removed from the oil seal on the rear bumper side, behind which a separable clip is hidden. It is removed from the seat using a drill for 6-8 mm. After that, the lever turns over, and the ball of the silent block together with the sleeve is removed from it. Its holder is knocked out with a mallet or a special puller.
The new joint is carefully lubricated and then installed. You can press-in using the same mandrel that was used to remove the old part, or you can resort to a portable vice. After installing a new silent block, all parts are assembled in reverse order. After replacement, it is advisable to check the shock absorbers, breakup levers and other suspension elements for wear.
The final suspension elements are tightened only after the car is removed from the pit or jack and lowered to the ground.
Features of replacing silent blocks on different makes and models of cars
The process of replacing hinges can vary and have characteristic features depending on the specific make and model of the vehicle on which the entire procedure for installing the part is carried out. For example, a floating silent block "BMW" before replacing it will require the owner to visit a turner - the rear fists of such cars are aluminum, not cast iron, so they need a special puller. Original pullers are expensive, so it will be more profitable to make them with craftsmen.
Many car models require the installation of only original spare parts. Of course, you can install non-original silent blocks, but this is fraught with their rapid wear and tear and loss of warranty.