The stand has two modes of operation: automated and non-automated.
The automated operating mode is used to quickly check the braking systems of vehicles.
For more in-depth diagnostics of brake systems, a non-automated mode is used.
3.1. Automated mode
3.1.1. Turn on the stand and let it warm up for 30 minutes.
3.1.2. Switching on the "Automatic" switch on the automated mode of operation, while one of the signal lamps of the mode display will light up.
3.1.3. Click the "Normal" button.
By repeatedly pressing the "Start" button, set the measurement modes for the front, rear axles and handbrake in sequence, guided by the mode display:
using the knob for the "Front axle" measurement mode, set the standard value of the braking force for the front axle of the tested vehicle on the right device;
for the measurement mode "Rear axle" - for the rear axle;
for measuring mode "Handbrake" - for the parking brake.
Press the button "Norm".
The standard values of the tested vehicles are given in the Appendix.
3.1.4. Place the car on the rollers of the stand with the wheels of the front axle. Switch on the roller drives by pressing the "Start" button. Set the measurement modes "Front axle". Read the readings from digital devices, rounding the least significant digit, and enter the result into the diagnostic card.
The rolling effort of unbraked wheels in serviceable vehicles should be no more than 0.5 kN.
Large values indicate wheel braking.
3.1.5. Step on the brake pedal quickly but without impact and hold it down.
If the brake system of the tested axle is normal, the "Pass" light board will be displayed, and the roller drives should be switched off automatically in 1-1.5 s after the start of braking.
Read the readings of digital devices, enter them into the diagnostic card.
If the roller drives do not turn off after the above time, then the brake system of the wheels of the tested axle is not normal.
If the board "Unevenness" is highlighted, then the coefficient of axial unevenness of the tested axis may be greater than the standard value. In this case, there are defects in the brake system of the wheel on the side of which the display is displayed.
Read off the values of the braking forces of the tested axle from digital devices and calculate the coefficient of axial unevenness using the formula:
where Rt.pr, Rt.lev - readings of digital devices.
Enter the axial unevenness coefficient in the diagnostic card.
If the coefficient values are more than the limit of 0.09-0.13, the braking system of the tested axle is not normal.
Switch on the lift by pressing the "Lift" button.
Set the measuring mode "Rear axle".
Check the condition of the rear axle brake system in the same way.
Set the measuring mode "Handbrake".
Pull the parking brake lever. The state of the parking brake system is determined in the same way.
3.1.6. If the test of the vehicle's braking system is negative, repeat the test in manual mode for the axle, the braking force of the wheels is not normal.
3.1.7. Non-automated operating mode.
Set the non-automated operation mode by pressing the "Automatic" switch, while the signal lamp of the mode display will go out.
Place the car on a stand with the front axle. Install a force-measuring device on the brake pedal, turn on the roller drives by pressing the "Start" button.
Press the brake pedal through a force-measuring device with a force of 0.4 kN no more than two or three times at intervals of 5-10 s to warm up the brakes.
Press the brake pedal with a force of no more than 0.5 kN, read the steady-state value of the braking forces from digital devices and enter them into the diagnostic card.
Switch on the roller drives by pressing the "Stop" button.
Click on the "Lift" button.
Place the car on casters with the wheels of the rear axle.
Check the condition of the rear axle brake system in the same way (including parking brake control).
3.2. Vehicle brake system assessment
3.2.1. The value of the total specific braking force is equal to:
where is the sum of the maximum values of the braking forces developed by all wheels, kN;
G a is the mass of the vehicle in running order, kN.
Enter the value of the total specific braking force in the diagnostic card.
The total specific braking force for the service braking system of the car must be at least 0.53, for the parking brake - at least 0.16.
3.2.2. Determination of axial unevenness of braking forces is carried out separately for each axle of the car according to the formula
p. 3.1.5.
where P t pr, P t lev are the maximum efforts developed by the braking mechanisms of the working brake system, respectively, on the right and left wheels of each axle of the car, kN.
Enter the value of the axial unevenness coefficient in the diagnostic card.
The coefficient of axial unevenness of braking forces for cars should be no more than 0.09-0.13.
3.2.3. Determination of the serviceability of the brake drive.
Smoothly press the pedal and at the moment the braking force begins to build up on each wheel, determine the pedal force at which the car's brake pads are pressed against the drum. With a good brake drive, the force should not exceed 0.1 kN.
3.2.4. Determination of the smoothness of the action of the brake systems and the completeness of the release.
To determine the smoothness of the brakes and the completeness of the release, slowly press the brake pedal while the wheels are rotating and follow the indications of the instruments - the indicators of the values of the braking forces. If the brakes are in good condition, the braking force should increase in proportion to the force on the pedals. After pressing the pedal, release it abruptly and observe the amount of braking force. Its rapid drop to the value of the force expended on the rotation of an unbraked wheel indicates a complete release of the brake mechanism. Press the pedal again at a fast pace and follow the readings of the instruments. If, when the pedal is pressed slowly, the braking forces of both wheels are approximately the same, and with a fast braking force of one of the wheels lags behind the other, then the resistance in the drive of this wheel is increased.
3.2.5. Evaluation of the ellipticity of pollution, oiling, wetting of brake drums.
Check the ellipticity of the brake drums with a pedal force of 0.15-0.20 kN. Fluctuations in the braking force readings by 0.2-0.4 kN and the pulsation of the pedal synchronous with the rotation of the wheels indicates the ellipseness of the brake drums. Checking each wheel separately, determine which brake drum has the indicated defect. The lack of proportionality between the values of the pedal force and the braking force (especially at low and medium forces) indicates that the brake linings are heavily soiled, oily or wet. Humidification can be easily distinguished from oiling by the increase in braking force during braking due to moisture evaporation due to heating of the brakes.
3.2.6. Evaluation of the operation of the braking system of a car with a hydraulic vacuum booster.
Check the brake system with a hydraulic vacuum booster by comparing the developed braking force with and without the booster. First, determine the braking force on the wheels of the front (rear) axle with a pedal force of 0.2 kN. Then start the engine and with the same effort on the pedals, take the readings of the braking force. The braking force with a working amplifier and a running engine should be 2.0-2.5 times more than with the engine off. If necessary, adjust the brakes on the bench.
Press and release the Elevator button. Take the car off the stand.
For testing at the stands, the vehicles are sequentially installed with the wheels of each of the axles on the stand rollers. The engine, additional drive axles are disconnected from the transmission and the transmission differentials are unlocked, the engine is started and the minimum stable crankshaft speed is set. Measurements are carried out in accordance with the manual (instructions) for the operation of the roller stand. For roller stands that do not measure the mass of the vehicle wheels, use weighing devices or reference data on the vehicle mass. Measurements and registration of indicators on the stand are performed for each vehicle axle and the indicators of the specific braking force and the relative difference in the braking forces of the axle wheels are calculated.
For road trains, when checking on stands, the values of the specific braking force must be determined separately for the tractor and the trailer (semitrailer) equipped with braking control. The obtained values are compared with the standards.
When checking the vehicle braking efficiency in road conditions without measuring the braking distance, it is allowed to directly measure the indicators of steady-state deceleration and the response time of the braking system or calculate the stopping distance based on the results of measuring the steady-state deceleration, the brake system lag time and the deceleration rise time at a given initial braking speed.
Methodology for calculating braking efficiency and vehicle stability indicators during braking
The specific braking force y t is calculated from the results of checks of the braking forces Pt on the wheels of the vehicle separately for the tractor and the trailer (semitrailer) according to the formula
where ΣP T is the sum of the braking forces P t on the wheels of the tractor or trailer (semitrailer), N;
M - the mass of the tractor or trailer (semitrailer) when performing the check, equal to the quotient of the sum of all reactions of the supporting surface to the vehicle wheels in a stationary state to the acceleration of gravity, kg;
g - free fall acceleration, m / s 2.
Relative difference F(percentage) of the braking forces of the axle wheels are calculated from the results of the brake force tests P t on ATS wheels according to the formula:
[G1] 
where P T pr, P t lev - braking forces on the right and left wheels of the tested vehicle axle, respectively, N;
R t max is the largest of the indicated braking forces.
The resulting F value is compared with the maximum permissible values. Measurements and calculations are repeated for the wheels of each axle of the vehicle.
Calculation of the braking distance is allowed S t(in meters) for the initial braking speed v 0 according to the results of checks of the vehicle deceleration indicators during braking (see Appendix E) according to the formula:
[G1] 
t is the time lag of the brake system, s;
t n - deceleration rise time, s;
j mouth ~ steady-state deceleration, m / s 2.
The stability of the vehicle when braking in road conditions is checked by performing braking within the standard traffic corridor. The axis, right and left boundaries of the traffic corridor are preliminarily designated by parallel markings on the road surface. Before braking, the vehicle must move in a straight line with the set initial speed along the axis of the corridor. The exit of the vehicle by any of its parts outside the standard traffic corridor is established visually by the position of the vehicle projection on the supporting surface or by the device for testing brake systems in road conditions when the measured value of the vehicle displacement in the transverse direction exceeds half the difference between the width of the standard traffic corridor and the maximum width of the vehicle ...
When checking in road conditions the braking efficiency of the working brake system and the stability of the vehicle during braking, deviations of the initial braking speed from the set value (40 km / h) not more than ± 4 km / h are allowed. In this case, the braking distance standards must be recalculated according to the following method:
Methodology for recalculating the braking distance standards depending on the initial braking speed of the vehicle
The braking distance standards (in meters) for vehicle braking with an initial speed V0 different from the normative one can be calculated by the formula:
where v 0 is the initial braking speed of the vehicle, km / h;
j mouth ~ steady-state deceleration, m / s 2;
A - coefficient characterizing the response time of the braking system.
When recalculating braking distance standards S, - the values of the coefficient should be used A and steady-state deceleration at the mouth for different categories of vehicles, shown in Table 7.
Table 7
The vehicle is considered to have passed the test of braking efficiency and stability when braking with the service braking system if the calculated values of these indicators correspond to the given standards. For vehicles that are not equipped with ABS, instead of complying with the specific braking force to the standards, it is allowed to block all the wheels of the vehicle on the stand rollers.
Table 3 shows the limiting values of the coefficient of unevenness of the braking forces for the wheels of one axle of cars and trailers K N. %, and for vehicles in running order, on a road with a slope - at least 23% for cars (category M) and at least 31% for trucks (category N).
With such a check, the force applied to the parking brake control should be no more than 40 kgf for cars and no more than 60 kgf for other cars. For freight road trains, the value of the compatibility coefficient of road train links K c for a two-link trailer road train is also determined, which is determined by the formula
where is the total specific braking force of the trailer link and the tractor, respectively (numerical values are given in Table 4).
The value of the compatibility coefficient of the links of the road train K c for a three-link trailed road train, which is determined separately for each pair of connected links according to the formulas
K c1 =, K c2 =,
where K c1, K c2 are the compatibility coefficients of the links of the road train, which characterize the ratio of the total specific braking force between the tractor and the first hitch.
The value of the compatibility coefficient of the links of the road train, according to the requirements of GOST, should not be lower than 0.9. In addition, for trucks and buses with pneumatic brakes, the tightness of the system is checked, which, when the engine is not running, should not allow a pressure drop of more than 0.5 kgf / cm within 30 minutes - with a free brake system. Asynchronous operation of brakes along the axles of road trains should not exceed 0.3 s. The values of the braking distance S t, setting the deceleration j set, the response time of the braking system t cf and the initial braking speed V 0 are given in table. 3, 4. These standards are used to assess the effectiveness of the vehicle braking system when testing them not on roller stands, but on horizontal, flat, dry areas.
Bench tests have a number of advantages over road tests: due to the use of stationary measuring instruments, the accuracy of test results is increased; separate check of each brake mechanism is possible; Standard test conditions ensure repeatability of results and comparability of data obtained at different times.
The values of braking forces on the wheels of trucks and buses are given in RD-200RSFSR15-0150-81 "Guidelines for diagnosing the technical condition of the rolling stock of road transport", and on wheels of cars - in RD-37.009.010-85 ". Guidelines for the organization of diagnostics of passenger cars at service stations of the "Autotechsluzhivanie" system.
Bench tests are carried out using brake testers of various models, the nomenclature of which is quite diverse (for example, the STS-2 model stand for monitoring the brake systems of passenger cars, small buses, mini-trucks with an axle load of no more than 19600N; STS-10 stand is designed for tests of brake systems of trucks, trolleybuses and buses; stands of the model SD-2M, SD-3K, SD-4, produced by the Chelyabinsk ARZ, KI-8901, produced by the Beregovsky SEZ, etc.).
The indicators of the effectiveness of braking by the working brake system during road tests of cars are the values of the braking distance and the effort on the control. During the tests, braking by the working brake system is carried out in the emergency, full braking mode with a single action on the control body (correction of the vehicle trajectory is not allowed). The initial braking speed is 40 km / h, the time for activating the brake system control is no more than 0.2 s.
Road tests are carried out on a straight, horizontal, level and dry road with cement or asphalt concrete pavement.
Bench and road tests must be carried out in a safe environment.
The measurement error should be within:
braking distance - 5%;
initial braking speed - 1 km / h;
steady-state deceleration - 4%;
limiting slope of the platform for braking - 1%;
braking force - 3%;
efforts at the governing body - 7%;
brake system response time - 0.03 s;
brake system lag time - 0.03 s;
deceleration rise time - 0.03 s;
air pressure in pneumatic or pneumohydraulic brake drive - 5%.
The vehicle's braking system is considered to have passed the test if the diagnostic parameters correspond to the normative ones. In order for the braking systems of the car to be able to successfully withstand the test, it is necessary to carry out qualified maintenance or repair of the main components.
Replacement of brake linings, disc pads and drums must be carried out on both wheels of the axle. After replacing these parts, it is necessary to let them run in for a run of 300-400 km.
When checking cars in wet weather or after washing, it is advisable to dry the brakes, especially of the drum type, by several braking or short driving with the vehicle braked. It is also not recommended to check the brakes of a car with studded tires on roller areal stands, because the coefficient of adhesion of the steel stud to the steel surface of the drum or pad can be significantly lower.
3.11.2.2. Steering control and testing
The technical condition of the vehicle's steering has a direct impact on driving safety. Therefore, increased requirements are imposed on its condition, which are contained in GOST R 51709-2001 and in the guidance documents RD200 RSFSR 15-0150-81, RD 37.009.010-85 and RD200 RSFSR 0086-79. Steering requirements are also contained in the technological documentation for the repair and maintenance of cars and in the operating instructions for specific car models. As a result of long-term operation without the necessary adjustments, the play of the steering wheel increases.
The numerical indicator of GOST, normalizing the operation of the elements of the steering mechanism, is the total backlash of the steering wheel, which during tests should not exceed the following permissible values:
for cars and trucks and buses created on the basis of their aggregates …………….… .10 о;
buses ………………………… ..20 о;
trucks …………… 25 o.
The total backlash of a car's steering can be measured by several instruments. The most common are the K-526 electronic backlash meter, the K-524 mechanical backlash meter, the K-402 model, etc.
The tests of cars equipped with power steering are carried out with the engine running. The range of relevant test equipment is varied. One of them is the K-465M installation.
The car is considered to have passed the test if the obtained values of the total backlash do not exceed the permissible values.
When preparing the vehicle for the inspection stage, it is necessary to carry out the next maintenance of the assemblies and parts of the steering mechanism, check the level of the working fluid and the tension of the pump drive belt in the power steering system, check the tightening and fixation of the threaded connections of the parts and assemblies, the condition of the anthers and protective covers.
Standards for the braking efficiency of the working and emergency braking systems, corresponding to STB 1641-2006, are shown in the table:
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Table. Standards for the efficiency of braking of vehicles of the working and emergency braking systems during tests at the stands
* Not equipped with ABS or having received type approval before 01.10.1991. ** Type approved after 1988 Note. The values in brackets are for vehicles with a manually operated emergency braking system. |
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The specific braking force Yt is calculated based on the results of checks of the braking forces Pt on the wheels of a vehicle separately for a car, a tractor vehicle (truck tractor) and a trailer (semitrailer) according to the formula:
where EPt is the sum of the braking forces Pt on the wheels of the vehicle, N; M is the mass of the vehicle, kg; g - acceleration of gravity, m / s2.
When checking the braking efficiency of the working and emergency braking systems at the stands, the relative difference F of the braking forces of the axle wheels (as a percentage of the maximum value) is not more than 30%. In this case, the relative difference is calculated from the results of checks of the braking forces Pm on the wheels of the vehicle according to the formula:
where Рт.пр, Рт.lev - the maximum braking forces, respectively, on the right and left wheel of the tested axle of the vehicle, N; Ртmах - the largest of the indicated braking forces, N.
The parking braking system for vehicles with a technically permissible maximum mass must provide a specific braking force Yt of at least 0.16, for combined vehicles - at least 0.12. In this case, the force applied to the control of the parking brake system to activate it should be no more than 500 N for vehicles of category M1 and 700 N for other categories. For vehicles with a manual parking brake system, the indicated values should not exceed 400 and 600 N, respectively.
For the parking brake system, the relative difference F of the braking forces of the axle wheels is not more than 50%.
Determination of the conformity of the braking systems of vehicles with wet tires at the stands is allowed only by the indicators of wheel blocking at the stand; in this case, the tires located on both sides of the vehicle must be evenly wet over the entire surface. The blocking of the stand should occur when at least 10% of the difference between the linear velocities of the running surfaces of the tire and the stand rollers in the place of their direct contact is reached. When blocking the axle wheels on the stand, the values achieved at the moment of blocking are taken as the maximum braking forces.
The indicator of the effectiveness of the parking brake system is the value of the specific braking force. When testing a vehicle with a permissible maximum mass, the specific braking force must be at least 0.16. for vehicles in running order, the parking braking system must provide a design specific braking force equal to 0.6 of the ratio of the unladen weight on the axles, which are affected by the parking braking system, in the unladen weight.
Test methods
Inspections on stands and on the road should be carried out with the engine running and disconnected from the transmission, as well as the disengaged drives of the additional driving axles and unlocked transmission differentials. The total weight of the diagnostic tools installed on the vehicle should not exceed 25 kg.
The tests must be carried out in a safe environment.
The measurement uncertainty should be within the following limits for:
Braking distance - ± 5%;
· Initial braking speed - ± 1 km / h;
Steady deceleration - ± 4
· Longitudinal slope of the platform for braking - ± 1%;
· Braking force - ± 3%;
· Efforts on the control body - ± 7%;
· Response time of the brake system - ± 0.03 s;
· Time lag of the brake system - ± 0.03 s;
Deceleration rise time - ± 0.03 s;
· Air pressure in the pneumatic or pneumohydraulic brake drive - ± 5%.
Checking the service brake system when road tests
must be carried out in accordance with the requirements below:
Initial speed - 40 km / h;
Correction of the trajectory of the vehicle is not allowed (the steering is in an inviolable state);
Emergency, single, full braking.
When testing the stability of the vehicle, three stripes must be drawn on the site, indicating the axis of movement, the right and left boundaries of the corridor. The car must move in a straight line with the set speed along the axis of the corridor. The position of the vehicle after the end of braking is determined visually by its projection onto the supporting surface. In the case of the formation of two or more points of intersection of the obtained projection of the vehicle and the boundaries of the corridor, the value of the stability parameter cannot be considered satisfactory.
Road tests can be carried out using universal linear-angular measurements and a decelerometer - a mechanical device for measuring steady-state deceleration. In addition, there are now specialized electronic devices. The “Effect” device can be referred to them. This device can comprehensively determine a number of parameters (Table 3.4).
Bench tests
brake systems on roller stands are carried out if there is a driver and a passenger on the front seat of cars of categories M1 and Ν1. When testing, the condition of the stand rollers is important. Their wear is not allowed until the corrugated surface is completely abraded or the abrasive coating is destroyed. Bench tests are carried out using brake testers of various models. The range of these devices is quite diverse. Therefore, when choosing a brake tester, it is necessary to be guided by the technical characteristics of the test vehicle.
The STS-2 brake tester is designed to control the effectiveness of braking systems and stability when braking passenger cars, small buses, minivans with an axle load not exceeding 19600 N, with a track gauge of 1200 ... 1820 mm. Its technical data are given in table. 3.5.
The STS-10 brake tester is designed for diagnosing the brake systems of trucks, buses, trolleybuses, trailers as part of road trains with a track gauge of 1500 ... 2160 mm, a car wheel diameter of 968 ... 1300 mm. Its technical data are given in table. 3.6.
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