Specific braking force is normal. Checking the service brake system. The parking brake system does not provide a stationary position
Standards for braking efficiency of service and emergency brake systems, corresponding to STB 1641-2006, are given in the table:
|
Table. Standards for the braking efficiency of vehicles with working and emergency braking systems during testing on stands
* Not equipped with ABS or received type approval before 01.10.1991. ** Type approved after 1988. Note. The values in parentheses are for vehicles with a manually controlled emergency braking system. |
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The specific braking force Yt is calculated based on the results of checking the braking forces Pt on the wheels of a vehicle separately for a car, a tractor (truck tractor) and a trailer (semi-trailer) 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 - free fall acceleration, m/s2.
When checking the braking efficiency of the service and emergency brake systems on stands, the relative difference F of the braking forces of the axle wheels (as a percentage of the highest value) is allowed to be no more than 30%. In this case, the relative difference is calculated based on the results of checking the braking forces Рт on the wheels of the vehicle using the formula:
where Rt.pr, Rt.left are the maximum braking forces, respectively, on the right and left wheels of the vehicle axle being tested, N; Ртмах - the greatest of the indicated braking forces, N.
The parking brake system for vehicles with a technically permissible maximum weight 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 parking brake system control to activate it must be no more than 500 N for vehicles of category M1 and 700 N for other categories. For vehicles with a manually controlled parking brake system, the specified values should be no more than 400 and 600 N, respectively.
For the parking brake system, the relative difference F of the braking forces of the axle wheels is allowed to be no more than 50%.
Determining the conformity of brake systems of vehicles with wet tires on stands is permitted only by the indicators of wheel locking on the stand; in this case, the tires located on both sides of the vehicle must be evenly wet over the entire surface. The stand must be blocked when the difference between the linear speeds of the running surfaces of the tire and the stand rollers at the point of their direct contact reaches at least 10%. When the wheels of an axle are blocked on the stand, the maximum braking forces are taken to be their values reached at the moment of blocking.
Braking- the process of creating and changing artificial resistance to the movement of a car in order to reduce its speed or keep it stationary relative to the road.
Braking properties- a set of properties that determine the maximum deceleration of a car when it moves on various roads in braking mode, the limiting values of external forces under the action of which a braked car is reliably held in place or has the required minimum steady speeds when moving downhill.
Braking mode- a mode in which braking torques are applied to all or several wheels.
Braking properties are among the most important operational properties that determine the active safety of a car, which is understood as a set of special design measures that reduce the likelihood of an accident.
Due to the great importance of the properties that determine the safety of a car, their regulation is the subject of a number of international documents.
The effectiveness of the action is checked by measuring the braking forces developed on the wheels (the value of the total specific braking force of the working and parking brake systems; the coefficient of unevenness of the braking forces of the axle wheels; the force applied to the brake pedal), as well as by inspecting and testing individual components of the systems.
Meaning coefficient of axial unevenness of braking forces Kn determined separately for each vehicle axle using the formula:
where are the maximum forces developed by the brakes on the right and left wheels of each vehicle axle, respectively. Kn values for passenger cars should be no more than 0.09.
The value of the total braking force γт is determined by the formula:
γт = ΣРт/М
where – ΣРт is the sum of the maximum braking forces on the wheels of the vehicle kg.
M – total mass of the vehicle, kg.
The magnitude of the braking forces is adjusted taking into account the cost of turning the wheels, i.e. data obtained before checking the braking forces.
Brake response time is defined as the time interval from the start of braking to the moment at which the deceleration becomes constant, that is, the braking force reaches its maximum value and then remains constant.
Force on the control (brake pedal): for single vehicles of categories M1 – 490 N, M2, M3, N1, N2, N3 – 686 N; road trains M1 – 490N, M2, M3, N1, N2, N3 – 686 N.
The total specific braking force of single vehicles is not less than M1 – 0.64; M2, M3 – 0.55; N1, N2, N3 – 0.46; M1 road trains – 0.47; M2 –0.42; M3 – 0.51; N1 – 0.38; N2, N3 – 0.46.
The braking system response time is no more than s M1 – 0.5; M2,M3 – 0.8; N1 – 0.7; N2, N3 – 0.8; road trains from M1 – 0.5; M2 – 0.8; M3 – 0.9; N1 – 0.9; N2 – 0.7; N3 – 0.9.
The coefficient of unevenness of the braking forces of the axle wheels is not more than M1; M2 – 0.09; M3,N1, N2, N3 – 0.11; road trains – from M1, M2 – 0.09; M3 – 1st axis – 0.09, subsequent axes 0.13; N1 – 0.11; N2, N3 – 1st axis – 0.09, subsequent axes 0.13.
The value of the total specific braking force must be at least 16% relative to the permissible maximum weight of a single vehicle and not less than 12% relative to the maximum permissible weight of a combined vehicle.
During operation, it is possible to evaluate braking performance based on the braking distance and vehicle deceleration.
Braking distances- this is the distance that the car travels from the start of braking to a complete stop and is determined by the formula:
S=kv2/ 254φ
Where:
k – braking efficiency coefficient. It takes into account the disproportion of the braking forces on the wheels to the loads placed on them, as well as wear, adjustment and contamination of the brakes. This coefficient shows how many times the actual deceleration of the rolling stock is less than the theoretical maximum possible on a given road. Value k for trucks and buses 1.4…1.6, for cars 1.2
v – speed in km/h
φ – coefficient of wheel adhesion to the road.
Deceleration is the amount by which the vehicle's speed decreases per unit time.
Table Efficiency standards for braking performance and deceleration (SDA)
|
Name of vehicles |
Braking distance (m, no more) |
Slowdown (m/s 2, no more) |
|
Passenger cars and their modifications for transporting goods |
12,2 (14,6) |
6,8 (6,1) |
|
up to 5 t inclusive over 5 t |
13,6 (18,7) 16,8 (19,9) |
5,7 (5,0) 5,7 (5,0) |
|
up to 3.5 t inclusive from 3.5 to 12 t inclusive over 12 t |
15,1 (19,0) 17,3 (18,4) 16,0 (17,7) |
5,7 (5,4) 5,7 (5,7) 6,2 (6,1) |
|
Two-wheeled motorcycles and mopeds |
7,5 (7,5) |
5,5 (5,5) |
|
Motorcycles with trailer |
8,2 (8,2) |
5,0 (5,0) |
|
Road trains, the tractors of which are passenger cars and their modifications for the transportation of goods |
13,6 (14,5) |
5,9 (6,1) |
|
Buses with maximum weight: up to 5 t inclusive over 5 t |
15,2 (18,7) 18,4 (19,9( |
5,7 (5,5) 5,5 (5,0) |
|
Trucks with maximum weight: up to 3.5 t inclusive from 3.5 t to 12 t inclusive over 12 t |
17,7 (22,7) 18,8 (22,1) 18,4 (21,9) |
4,6 (4,7) 5,5 (4,9) 5,5 (5,0) |
- The stopping distance and steady-state deceleration values given in brackets apply to vehicles whose production began before January 1, 1981.
- Tests are carried out on a horizontal section of road with a flat, dry, clean cement or asphalt concrete surface at an initial braking speed of 40 km/h for cars, buses and road trains and 30 km/h for motorcycles and mopeds. Vehicles are tested in loaded condition with the driver by applying a single impact to the control of the service brake system.
- The effectiveness of the service braking system of vehicles can be assessed by other indicators in accordance with GOST 25478-91.
The parking brake system does not provide a stationary position:
- vehicles with full load - on a slope of up to 16% inclusive
- passenger cars and buses in running order - on a slope of up to 23% inclusive
- trucks and road trains in equipped condition - on a slope of up to 31% inclusive
The parking brake system control lever (handle) is not held by the locking device.
B t of the train is determined by the sum of the forces generated by all the brake pads of the rolling stock according to the formulaWhere Κ o is the actual pressing force of the brake pads on the wheelset (on the axle), kN;
n o is the number of brake axles on the train;
φ k - pads. If we take the average value of the friction coefficient for all pads to be the same, then formula (1) will take the expression
, N. (2)
Specific braking force of a passenger train
, N/kN. (3)
For freight train
, N/kN. (4)
The ratio of the sum of the forces applied by the brake pads to the weight of the train is called actual braking coefficient
, kN/kN (5)
then equation (3) takes the form, N/kN:
, N/kN. (6)
In the case when the train has cars with different pressure of the brake pads on the wheel, brake calculations using formula (6) become cumbersome, since the quantities φ to and K must be determined for each pad separately. In these cases, a simpler method is usually used - casting method. It is based on replacing the actual friction coefficient of the pads on the wheels, which depends on the pressing force TO, another meaning - calculated friction coefficient φ kr, independent of force TO.
Actual friction coefficient φ k for standard cast iron pads is determined by the empirical formula
, (7)
a is determined by the empirical formula
, (8)
Actual friction coefficient φ k for composite pads is determined by the formula
, (9)
For determining φ kr are accepted conditional average forces pressing pads on the wheelset: cast iron - K h= 26.5 kN (2.7 tf), composite - K k= 15.7 kN (1.6 tf). Substituting the values K h And K k into formulas (7), (8) and (9), we get:
for cast iron pads
; (10)
for cast iron pads with high phosphorus content
; (11)
for composite pads
. (12)
The values of the calculated friction coefficients of the pads on the wheels, calculated using formulas 10, 11 and 12, are given in Table 1.
In order to maintain the same braking force when braking, it is necessary valid replace the pressing force of the pads on the wheel pair calculated pressing force. The calculated pressing force is determined from the condition of equality of braking forces:
, (13)
where 
, kN. (14)
After substituting values φ to and φ kr into equation (14), the following expressions are obtained: for standard cast iron blocks
, kN; (15)
for cast iron pads with high phosphorus content
, kN; (16)
Calculated friction coefficient value φ brake pads
Table 1
| Speed v, km/h | Cast iron standard | Cast iron with phosphorus | Compositional |
| 0,270 0,198 0,162 0,140 0,126 0,116 0,108 0,102 0,097 0,093 | 0,3 0,218 0,178 0,154 0,138 0,127 0,119 0,112 0,107 0,102 | 0,360 0,339 0,332 0,309 0,297 0,288 0,280 0,273 0,267 0,262 |
for composite pads
, kN. (17)
The calculated forces of pressing the pads on the wheels are calculated for each type of rolling stock and are given in the form of standards established in the operating instructions for auto brakes, tables 2 and 3.
Calculated pressing forces on one cast iron brake pad of locomotives
table 2
Estimated pressing forces on one brake pad of freight and passenger cars
Table 3
| Car type | Brake pads | Pressure force on the block, kN | |||
| Material | Number | Laden | Average | Empty | |
| Freight Four-axle gondola cars Four-axle platforms, covered cars, tanks Six-axle gondola cars Eight-axle gondola cars Eight-axle tank cars Refrigerated Passenger All-metal weight, kN 530-620 480-520 With disc brake With speed regulator | Cast Iron Composite Cast Iron Composite Cast Iron Composite Cast Iron Composite Cast Iron Composite Cast Iron Composite Cast Iron Composite Cast Iron Composite Overlays Cast Iron | 38,2 11,6 23,5 10,3 18,5 8,8 7,5 52,0 | 14,8 23,4 15,4 21,8 13,5 7,4 - - - - - - | 12,6 8,2 12,8 8,5 12,4 7,5 8,6 7,5 4,3 - - - - - - |
If there are cars with cast iron and composite pads on the same train, then the pressing force of the pads on the axle is recalculated for one type of pad (usually cast iron), taking into account the equal efficiency of the brakes, Table 4.
Calculated pressing forces of car brake pads in terms of cast iron ones
Table 4
| Car type | Calculated brake pad pressure TO p, kN/axis |
| All-metal passenger cars with tare weight: q = 520 kN (53 tf) q = 470 kN (48 tf), but? 520 kN q = 412 kN (42 tf), but? 470 kN All-metal passenger cars VL-RIC with KE brake and cast iron brake pads: in passenger mode in high-speed mode All-metal passenger cars of RIC size on TVZ-TsNII “M” bogies with KE brake and composite brake pads (in terms of cast iron pads): in passenger mode in high-speed mode Passenger cars with a length of 20.2 m or less The rest of the passenger fleet Freight cars equipped with cast iron blocks in the mode: loaded medium empty Freight cars equipped with composite blocks (in terms of cast iron blocks) in the mode: loaded medium empty Four-axle isothermal and all-metal luggage cars with one-way braking Refrigerated rolling stock cars with cast iron brake pads in the mode: loaded medium empty Refrigerated rolling stock cars with composite brake pads (in terms of cast iron pads) in the mode: medium empty |
The total calculated pressure of the brake pads is calculated by the number of cars of each type ( n 4 ,n 6 ,n 8), included in the train, the number of locomotive axles of a given series ( n l) and the calculated pressure on one brake axle for each type of carriage and locomotive
If not all axles are brake axles, then this should be taken into account when calculating the total pressure of the brake pads. For this purpose, the total brake pressure for the train (4 n 4 TOр4 + 6 n 6 TOр6 + 8 n 8 TO p8) is multiplied by a coefficient equal to the proportion of brake axles in the composition. If the proportion of brake axles is specified for each type of car, then the corresponding coefficients are multiplied by each of the terms in expression (18).
After calculating the total calculated pressure of the train brake pads, the value is determined calculated braking coefficient
. (19)
The calculated braking coefficient characterizes the degree to which the train is provided with braking means. The more ϑ p, the greater the braking effect the braking forces create, the faster the train will stop and at a shorter distance. In order to ensure the safety of trains of JSC Russian Railways, the minimum values of the calculated braking coefficients have been established:
for freight trains at speeds up to 90 km/h - 0.33;
for refrigerated and diesel trains at speeds up to 120 km/h - 0.6;
for passenger trains:
at speeds up to 120 km/h - 0.6;
at speeds up to 140 km/h - 0.78;
at speeds up to 160 km/h - 0.8.
The full value of the calculated braking coefficient and the corresponding specific braking force are realized only during emergency braking.
In braking calculations for stopping at stations and separate points provided for by the train schedule, as well as in the case of a decrease in speed in front of a previously known place, service braking is used with the calculated braking coefficient:
for freight trains - 0.5 J R,
for passenger, electric and diesel trains - 0.6 J R,
in case of applying full service braking, take 0.8 J R.
When using braking calculations to determine the minimum distance between standing floor signals, the value of the calculated braking coefficient is taken to be 0.8 J R.
The rules for traction calculations recommend not taking into account the pneumatic brakes of the locomotive and its weight when determining the braking force. cargo trains moving on sections with descents down to -20 ‰. That is, in formula (5.19) we can exclude P, and in formula (18) exclude the term n l TO rl.
Example. Determine the total and specific braking force of a freight train weighing 40,000 kN, formed from 60 four-axle gondola cars equipped with composite blocks. The speed of the train at the beginning of braking is 60 km/h, the number of brake axles is 80%.
1. Estimated force of pressing on one brake axle of four-axle gondola cars when loaded (see Table 3)
Where n k - number of brake pads per axle.
2. Number of brake axles in the train
Where a T- number of brake axles in the train, a T = 80% = 0,8.
3. The total pressing force of the brake pads on the axle of the train
4. Friction coefficient of composite pads
5. Total braking force of the train (according to formula 5.2)
6. Specific braking force b t, N/kN, with train weight P+Q
N/kN.
Measuring instruments used to check braking efficiency and stability of braking systems must be operational and verified according to STB 8003.
Standards for braking efficiency of service and emergency brake systems during bench tests, corresponding to STB 1641-2006, are given in Table. 4.3.
The specific braking force ut is calculated based on the results of checking the braking forces RT on the wheels of the vehicle separately for the car and the trailer (semi-trailer) according to the formula
Chg=^G-> (4L>
Where £PT is the sum of the braking forces Pt on the wheels of the vehicle, N; M is the mass of the vehicle, kg; £ - free fall acceleration, m/s2.
|
Table 4.3 Standards for the braking efficiency of vehicles with working and emergency braking systems during testing on stands
* Those not equipped with ABS or those that received type approval before 01.10.1991. ** Type approved after 1988. Note. The values in parentheses are for vehicles with a manually controlled emergency braking system. |
When checking the braking efficiency of the service and emergency braking systems, the relative difference ^ in the braking forces of the axle wheels is allowed to be no more than 30% (as a percentage of the highest value). In this case, the relative difference is calculated based on the results of checking the braking forces Рт on the wheels of the vehicle according to the formula
|
|
|
|
|||
Where RT right, RT left are the maximum braking forces, respectively, on the right and left wheels of the vehicle axle being tested, N; Rtmax is the greatest of the indicated braking forces, N.
10 Kariashsvich
The parking brake system for vehicles with a technically permissible maximum weight must provide a specific braking force m of at least 0.16; combined vehicles - not less than 0.12. In this case, the force applied to the parking brake system control to activate it must be no more than 500 N for vehicles of category M1 and 700 N for other categories. For vehicles with a manually controlled parking brake system, the specified values should be no more than 400 and 600 N, respectively.
For the parking brake system, the relative difference in the braking forces of the wheels of the axle is allowed to be no more than 50%.
The tires of vehicles tested at the stand must be clean, dry, and the pressure in them must correspond to the standard pressure established by the manufacturer in the operational cementation. The pressure is checked in completely cooled tires using pressure gauges (GOST 9921-81).
It is allowed to determine the conformity of vehicle brake systems on stands with wet tires, but only based on wheel blocking indicators on the stand. In this case, the tires must be evenly wet over the entire surface on both sides of the vehicle. The stand must be blocked when the difference between the linear speeds of the running surfaces of the tire and the stand rollers at the point of their direct contact reaches at least 10%. When the wheels of an axle are blocked on the stand, the maximum braking forces are taken to be their values reached at the moment of blocking.
Checks on stands and in road conditions are carried out with the engine running and disconnected from the transmission, as well as the drives of additional drive axles and unlocked center differentials (if the specified units are present in the vehicle design).
Vehicles with a rigid axle linkage or a self-locking non-disconnectable differential are tested only in road conditions.
Standards for braking efficiency of the service and emergency brake systems during tests in road conditions are presented in Table. 4.4 and 4.5.
|
Table 4.4 Standards for braking efficiency of the service brake system during tests in road conditions |
Note. The response time of the braking system should not exceed 0.2 s.
|
Table 4.5 Standards for braking efficiency of the emergency braking system during road tests |
Note. The values in parentheses are for vehicles with a manually controlled emergency braking system.
The requirements for the appearance and technical condition of the brake system are as follows.
□ Brake pipelines of the vehicle braking system must be sealed, without damage, traces of corrosion, securely fastened and not have contacts with elements of the transmission and exhaust system that are not provided for by the design.
□ The location and length of flexible hoses of the brake system must ensure tight connections and prevent their damage, taking into account maximum deformations of the suspension, steering angles of the vehicle wheels and mutual movements of the tractor and trailer (semi-trailer). Swelling of hoses under pressure and damage to the outer layer of hoses reaching the reinforcement layer are not allowed.
□ The brake pedal must have an anti-slip surface, return freely to its original position and must not move laterally when pressed. The free play of the brake pedal must be adjusted in accordance with the vehicle's operating manual.
□ The parking brake lever must not be deformed or skewed. It must ensure installation in the fixed positions provided for by the design; The parking brake system control locking device must be in good working order.
□ The mechanical brake drive rods of the parking brake system must not be damaged or deformed, and the drive control cables must not have knots, abrasions or damage to the braid.
□ In hydraulic brake drives, leakage of brake fluid in the brake system elements and their connections, as well as a decrease in its level in the brake fluid reservoir below the established minimum value, including when pressing the brake pedal to the maximum, is not allowed.
The working surfaces of brake drums and discs must be clean, free from cracks or damage, and have uniform wear. Wear of brake drums (discs) and brake pad linings in excess of the limit values established by the manufacturer in the operational documentation is not allowed.
Topic: checking the brake system of a car.
Purpose: to study the methodology and modern technical means of checking the brake system of a car.
Equipment: roller brake tester MANA IW2 Euro - Profi.
1. Study the methodology for checking the brake system of cars.
2. Study the procedure for preparing for work and the technical parameters of the brake tester.
3. Preparation for measurements.
□ Check the air pressure in the vehicle tires and, if necessary, adjust it to normal.
□ Check the tires for damage and tread separation (they can lead to tire destruction when braking on the stand).
□ Inspect the wheels of the vehicle and make sure that they are securely fastened and that there are no foreign objects between the dual wheels.
□ If necessary, load the vehicle so as to ensure the weight of its axles is at least 90% of the maximum permissible (indicated in the operating instructions or on a special plate installed on the vehicle). Since loading is generally required only for the rear axles of vehicles (with the exception of category O), it can be carried out after checking the front axle brakes.
When loading the axles of a vehicle of category Mj, you can use specially prepared tared ballast, placing it in the rear of the passenger compartment on the seats or on the floor or in the luggage compartment (if equipped).
□ Assess the degree of heating of the brake components of the tested axle using an organoleptic method. The temperature of the elements of the brake mechanisms should not exceed 100 ° C. Optimal conditions are considered to be those under which a person’s unprotected hand can be kept in direct contact with heated brake drums (discs) for a long time. When making such an assessment, precautions should be taken.
□ Install a device (pressure force sensor) on the brake pedal to monitor the parameters of the braking systems when the specified force for actuating the control is reached.
□ Select the vehicle to be tested in the corresponding menu of the brake tester control program and display it on the screen as the current measurement. In this case, it is necessary to verify that the number of axles, type, category and year of manufacture of the vehicle are entered correctly into the initial data.
4. The procedure for measuring parameters of brake systems.
□ Drive the axle being tested onto the roller units, then move the gear shift lever to the neutral position. Unlock inter-axle drives if the vehicle has drives on more than one axle. Disable the forced locking of the cross-axle differential (if equipped).
□ Turn on the stand roller drive. In this case, the monitor will display the current value of the resistance of the rotating wheels in an unbraked state.
□ Brake with the service brake system by smoothly pressing the brake pedal all the way. After the stand rollers stop, stop braking. If the rollers do not stop, press the pedal all the way and after waiting for 3...5 s, release the pedal. When measuring the steered axle, it is necessary to monitor its lateral drift and compensate for it by turning the steering wheel accordingly.
□ Record the measurement results.
□ Re-measure. If the measurement result differs slightly from the previous one, you do not need to register it. If the difference is significant, it should be recorded and the measurement repeated. Stop measurements when reaching
affecting the stability of the results obtained. Take the result of the last measurement as the final result.
□ Turn off the drive of the roller units (if this did not happen automatically during the measurement process).
□ Measure the parameters of the parking and service brake systems. Enter the result in the table. 4.6.
Table 4.6
Table of registration of measurement results
|
Parking lot |
Indicators of specific braking force and braking stability are calculated based on braking forces measured at the moment the stand automatically turns off or the maximum permissible force on the brake system control is reached.
1. Draw a diagram and describe the operating principle of the brake tester.
2. Write down the diagnostic data in the table. 4.6.
3. Using formulas (4.1) and (4.2), make calculations and fill out the table. 4.7.
4. Draw a conclusion about the technical condition of the vehicle being tested.
1. What is the brake system used for?
2. What are the requirements for brake systems?
3. Why are roller force testers mostly used to test the brake system?
4. Tell us about the procedure for checking the brake system on the MANA IW2 Euro-Profi stand.
5. What are the regulatory requirements for brake systems?
An 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 brake system must provide a design specific braking force equal to 0.6 of the ratio of the curb weight on the axles affected by the parking brake system in the curb weight.
Test Methods
Checks on benches and in road conditions must be carried out with the engine running and disconnected from the transmission, as well as the drives of additional drive axles and unlocked transmission differentials. The total weight of diagnostic equipment placed on the vehicle should not exceed 25 kg.
Tests must be carried out under safe conditions.
The measurement error must be within the following limits for:
· braking distance - ±5%;
· initial braking speed - ±1 km/h;
steady deceleration - ±4
· longitudinal slope of the braking area - ±1%;
· braking force - ±3%;
· effort on the control - ±7%;
· braking system response time - ±0.03 s;
· braking system delay time - ±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 following requirements:
Initial speed – 40 km/h;
Correction of the vehicle's trajectory is not allowed (the steering is in an intact state);
Emergency, single, full braking.
When testing the stability of a vehicle, three stripes must be applied to the site, indicating the axis of movement, the right and left boundaries of the corridor. The car must move straight at the set speed along the axis of the corridor. The position of the vehicle after braking is completed is determined visually by its projection onto the supporting surface. In the event of the formation of two or more points of intersection of the resulting projection of the car and the boundaries of the corridor, the value of the stability parameter cannot be considered satisfactory.
Road tests can be carried out using universal means of measuring linear-angular quantities and a decelerometer - a mechanical device for measuring steady-state deceleration. In addition, there are now specialized electronic devices. These may include the “Effect” device. This device can comprehensively determine a number of parameters (Table 3.4).
Bench tests
brake systems on roller stands are carried out when there is a driver and passenger in the front seat of cars of categories M1 and N1. During testing, the condition of the stand rollers is important. They are not allowed to wear until the corrugated surface is completely worn out 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, you must be guided by the technical characteristics of the vehicle being tested.
The STS-2 model brake tester is designed to monitor the effectiveness of braking systems and braking stability of passenger cars, small buses, mini-trucks with an axle load not exceeding 19600 N, with a track width of 1200...1820 mm. Its technical data is 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 width of 1500...2160 mm, a vehicle wheel diameter of 968...1300 mm. Its technical data is given in table. 3.6.
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