Workbook and Learning Aid for Complete Air Brake Systems

Transcription

1 Workbook and Learning Aid for Complete Air Brake Systems L20013 Rev. 4/04 AIR BRAKE SYSTEMS TRAINING MATERIALS

2 Inside Front Cover is Blank

3 INTRODUCTION The purpose of an air brake system on heavy duty vehicles is to convert air pressure to mechanical energy to activate the foundation brakes. FMVSS-121 dictates how this is to be done for over-the-road ve hi cles. The purpose of this workbook is to help you gain an understanding of how the complete air brake system operates. This will be accomplished by learning the function of each sub-system. Included in this workbook are: TRUCK SYSTEMS Air Supply Secondary Service Primary Service Parking Anti-Compounding Emergency (Prior to 3/1/98) Emergency (After 3/1/98) TRACTOR/TRAILER SYSTEMS Tractor Parking & Trailer Air Sup ply Trailer Control Trailer - Full Function Valve Trailer - FFABS FOUNDATION BRAKES NOTE: The systems described within are merely typical air brake systems

4 TRUCK - AIR SUPPLY SYSTEM - 2 -

5 TRUCK - AIR SUPPLY SYSTEM COMPONENTS COMPRESSOR AIR DRYER CONDENSER/SEPARATOR WET TANK (AIR RESERVOIR) PRESSURE RELIEF VALVE AUTOMATIC DRAIN VALVE LOW PRESSURE SWITCH GOVERNOR - 3 -

6 TRUCK - SECONDARY SERVICE SYSTEM - 4 -

7 TRUCK - SECONDARY SERVICE SYSTEM COMPONENTS ONE-WAY CHECK VALVE SECONDARY SERVICE TANK (RESERVOIR) PRESSURE CONTROLLED CHECK VALVE MANUAL DRAIN VALVE AIR GAUGE DUAL FOOT VALVE QUICK RELEASE VALVE ABS IN-LINE VALVE (MODULATOR VALVE) SERVICE CHAMBER AUTOMATIC BRAKE ADJUSTER - 5 -

8 TRUCK - PRIMARY SERVICE SYSTEM - 6 -

9 TRUCK - PRIMARY SERVICE SYSTEM COMPONENTS ONE-WAY CHECK VALVE PRIMARY SERVICE TANK (RESERVOIR) MANUAL DRAIN VALVE AIR GAUGE DUAL FOOT VALVE SERVICE RELAY VALVE ABS IN-LINE VALVE (MODULATOR VALVE) SPRING BRAKES AUTOMATIC BRAKE ADJUSTER TWO-WAY CHECK VALVE STOPLIGHT SWITCH - 7 -

10 TRUCK - PARKING SYSTEM - 8 -

11 TRUCK - PARKING SYSTEM COMPONENTS TWO-WAY CHECK VALVE DASH VALVE (YELLOW DIAMOND KNOB) QUICK RELEASE VALVE SPRING BRAKE - 9 -

12 TRUCK - ANTI-COMPOUNDING SYSTEM -10 -

13 TRUCK - ANTI-COMPOUNDING SYSTEM COMPONENTS QUICK RELEASE WITH TWO-WAY CHECK VALVE Inlet Check Valve Disc. Inlet Delivery Delivery Delivery Inlet or Control 1 Inlet or Control

14 TRUCK - EMERGENCY SYSTEM (Prior to March 1, 1998)

15 TRUCK - EMERGENCY SYSTEM COMPONENTS INVERSION VALVE (PRIOR TO MARCH 1, 1998) OEM#N20950AA - AM#KN28030 Control Inlet Dash Valve Supply Delivery To Spring Brake Primary Reservoir Supply NEW INVERSION VALVE (AFTER MARCH 1, 1998) OEM#N20950CA - AM#KN28032 Primary Balance Port Secondary Control Port Delivery Port Supply Port Exhaust Check Valve

16 TRUCK - EMERGENCY SYSTEM (Prior to March 1, 1998)

17 TRUCK - EMERGENCY SYSTEM (After March 1, 1998)

18 TRUCK - EMERGENCY SYSTEM COMPLETE (After March 1, 1998)

19 TRUCK - SELF-TEST (Prior to March 1, 1998)

20 TRUCK - SELF-TEST (After March 1, 1998)

21 NOTES

22 TRACTOR PARKING AND TRAILER AIR SUPPLY SYSTEM

23 (2 Line) (3 Line) TRACTOR PARKING AND TRAILER AIR SUPPLY SYSTEM COMPONENTS MANIFOLD DASH CONTROL (YELLOW DIAMOND KNOB & RED OCTAGON KNOB) QUICK RELEASE WITH TWO-WAY CHECK VALVE (2 LINE) TRACTOR PROTECTION VALVE -- OR -- (3 LINE) TRACTOR PROTECTION VALVE TRAILER SUPPLY GLADHAND (RED)

24 TRACTOR - TRAILER CONTROL SYSTEM -22 -

25 TRACTOR - TRAILER CONTROL SYSTEM COMPONENTS HAND CONTROL VALVE TWO-WAY CHECK VALVE STOPLIGHT SWITCH -23 -

26 TRACTOR - AIR SYSTEM COMPLETE

27 TRACTOR - SELF-TEST

28 TRAILER - FULL FUNCTION VALVE SYSTEMS (PRIOR TO MARCH 1, 1998) TWO TANK FFV JUMBO TANK FFV AXLE BY AXLE FFV SINGLE AXLE FFV

29 TRAILER - FULL FUNCTION VALVE SYSTEM COMPONENTS FULL FUNCTION VALVE STANDARD RESERVOIR JUMBO RESERVOIR SPRING BRAKE TRAILER SERVICE GLADHAND (BLUE)

30 TRAILER - FULL FUNCTION VALVE COMPLETE SYSTEMS TWO TANK FFV JUMBO TANK FFV AXLE BY AXLE FFV SINGLE AXLE FFV

31 TRAILER - FULL FUNCTION VALVE SELF TEST TWO TANK FFV JUMBO TANK FFV AXLE BY AXLE FFV SINGLE AXLE FFV

32 TRAILER - FULL FUNCTION ABS (AFTER MARCH 1, 1998) TWO TANK FFABS - AIR SUSPENSION JUMBO TANK FFABS - SPRING SUSPENSION AXLE BY AXLE - MOD II SYSTEM SINGLE AXLE FFABS

33 TRAILER - FULL FUNCTION ABS SYSTEM COMPONENTS FULL FUNCTION ABS TRAILER VALVE ABS RELAY VALVE STANDARD RESERVOIR JUMBO RESERVOIR SPRING BRAKE TRAILER SERVICE GLADHAND WITH QUICK RELEASE

34 TRAILER - FULL FUNCTION ABS COMPLETE SYSTEMS TWO TANK FFABS - AIR SUSPENSION JUMBO TANK FFABS - SPRING SUSPENSION AXLE BY AXLE - MOD II SYSTEM SINGLE AXLE FFABS

35 TRAILER - FULL FUNCTION ABS SELF TEST TWO TANK FFABS - AIR SUSPENSION JUMBO TANK FFABS - SPRING SUSPENSION AXLE BY AXLE - MOD II SYSTEM SINGLE AXLE FFABS

36 ABA - IDENTIFICATION Automatic Brake Adjuster Installation Instructions AA1 Model - S-ABA Model Two versions of brake adjusters are available from Haldex. The easiest way to identify each is by the shape of the cover plate assembly, as shown below in Figures 1 and 2. Figure 1. AA1 The control arm of the AA1 Model must be placed with the pointer in the notch, for proper initial setup. All AA1 Model setups must occur with air chambers fully released. Figure 2. S-ABA The control arm on the S-ABA Model can be located anywhere within the range of the mounting hardware. No installation pointer is required with the S-ABA Model due to the flexible positioning of the control arm. All other S-ABA Model installation procedures are the same as the AA1 Model. ABA - TYPICAL APPLICATIONS Figures 3 and 4 show typical brackets for automatic brake adjuster applications on trailer axle brake assemblies. Figure 3. Integral cam support anchor bracket for 12 1/4 and 16 1/2 brakes. Figure 4. Bolt-on cam support anchor bracket for 12 1/4 and 16 1/2 brakes. Slotted adjustment plate is mounted to the S cam bushing. Plate for Rockwell/Meritor, Dana and Fruehauf axle requires two bolts. Eaton requires one bolt (see inset). Position plate on adjuster side of the S cam support. Added plate thickness may require the use of longer mounting bolts. (Refer to torque chart included in these instructions.) -34 -

37 ABA - INSTALLATION INSTRUCTIONS STEP 1. Assure brake chamber push rods are fully retracted. Mount slotted adjustment plate, if needed, to cam support. Apply anti-seize type lubricant to camshaft splines. Torque anchor plate fasteners per torque chart included in these instructions. STEP 2. Place at least one inner cam washer on shaft then install adjuster with the 7/16 adjusting hex pointing away from the air chamber. STEP 3. Secure adjuster to shaft with snap ring. Install enough washers (per TMC recommended practice) to reduce end play to less than.060. STEP 4. Rotate the 7/16 hex clockwise to move adjuster into clevis. (Do not pull push rod out to meet clevis). STEP 5. Coat clevis pin with anti-seize type lubricant and install. Secure clevis pin with cotter pin. STEP 6A. With the S-ABA Model Brake Adjuster (shown in Figure 2), the control arm position can be set anywhere within the slotted area of the bracket and the adjuster will function properly. Haldex recommends a common position for all installations -- all the way towards the axle, until the control arm comes to the end of the slotted bracket. This common position should help to avoid confusion for the end user. STEP 6B. With the AA1 Model Brake Adjuster (Figure 1), rotate the control arm away from adjustment hex, toward the air chamber until it comes to an internal stop. The Installation Indicator must fall within the slotted area with the brake fully released. The view of the indicator varies from side to side. Haldex AA1 Trailer Adjusters are unhanded and are used on both axle sides

38 ABA - INSTALLATION INSTRUCTIONS (CONT D) STEP 7. Insert the flat end of the anchor stud through the control arm bushing. Push the threaded end into the anchor plate slot and loosely install flange nut. STEP 8. After positioning control arm and anchor pin to desired location, tighten the flange nut to Ft. Lbs. Note: S-ABA control arm position is all the way toward the axle. AA1 control arm position is such that the installation indicator falls within the control cover slot. These common positions work well for most applications. STEP 9. Adjust brakes by rotating the 7/16 adjustment hex clockwise until the lining just contacts the drum. Parts List /8 x 1 1/4 Long Bolt (Meritor) /16 x 1 Long Bolt (Fruehauf) /8 x 1 1/4 Long Bolt (Fruehauf) /4 x 1 1/4 Long Bolt (Dana) /4 Flat Washer (Dana) /4 x 1 1/4 Long Bolt (Eaton) Torque Chart STEP 10. Rotate adjustment hex counter clockwise 1/2 turn. A ratcheting sound will occur on backoff and is normal. Re-check all fasteners for proper installation. Note: Final push rod stroke may not be reached until trailer is put into service and the brakes are burnished. 3/ Ft. Lb. 5/ Ft. Lb. 1/ Ft. Lb

39 Recommended Procedure For Cutting Brake Chamber Push-Rod (Service Brake Chamber or Double Diaphragm Spring Brake Chamber) This procedure is applicable to Haldex Automatic and All Manual Brake Adjusters WARNING: Always chock wheels to prevent vehicle from moving. Vent vehicle system air pressure to zero psi.! A. When preparing to install a spring brake chamber, ensure that the unit is fully released (power spring caged) and the service brake push-rod is fully retracted to zero stroke position. Thread the clevis jam nut onto the push-rod. B. Place the brake chamber into the appropriate brake assembly bracket. Tighten the holding nuts to the bracket studs ( lb. ft.). C. Measure the distance from the centerline of the S-Cam to the centerline of the push-rod (See Figure 2 - Dimension A). This measurement should be equal to the length of the brake adjuster being used (See Figure 3 - Dimension A). Figure 1 NOTE: If Dimension A - Figure 2 and Dimension A - Figure 3 are not identical, the chamber mounting bracket is either bent and must be straightened or replaced, the chamber has been mounted improperly in the bracket or the length of the adjuster installed is incorrect. Make any necessary corrections before going to Step D. D. Measure and record the length of clevis to be used. This measurement should be taken from the center of the clevis pin hole, to the bottom of the yoke assembly (See Figure 1). Figure 2 E. Using a square, mark the push-rod at the 90 o setting (See Figure 2 - Mark #1). From this mark, subtract the measurement recorded in Step D and make a second mark on the push-rod (moving toward the brake chamber mounting surface). (See Figure 2 - Mark #2). Figure 3 F. From Mark #2, measure toward the brake chamber mounting surface the distance listed in Table 1 - Column D (See Reverse Side) for the brake chamber type being installed. Mark and cut the push-rod. BRAKE ADJUSTER

40 G. Install the clevis onto the push-rod and secure the jam nut (33-90 lb. ft.) Connect the clevis to the brake adjuster using the clevis pin and cotter pins (See Figure 1). Uncage the spring brake. H. Release spring brakes and adjust the brake adjuster to the manufacturers recommendation. Important Note: Some automatic brake adjusters require a slightly different rod length. Always refer to the original manufacturers installation guidelines. Column A Maximum Chamber Available Readjustable Set-Up Type Stroke Stroke Stroke /4 1 3/8 1 3/ /4 1 3/8 1 3/ /4 1 3/4 1 3/ /4 1 3/4 1 3/8 20LS* 2 1/ / /4 1 3/4 1 3/8 24LS* 2 1/ /2 24XLS** 3 2 1/2 1 3/ / /2 30LS* 3 2 1/2 1 3/ /4 1 3/4 * Long Stroke ** Extra-Long Stroke Column B Table 1 Stroke Values Column C Column D! DANGER A spring brake or combination service/spring brake must be disarmed before disposal, or forceful release of the compression spring may occur in the future without warning

41 Recommended Procedure For Cutting Brake Chamber Push-Rod (Service Brake Chamber or Double Diaphragm Spring Brake Chamber) This procedure is applicable to CSI Midland/Gunite and CSII Midland/Crewson Automatic Brake Adjusters WARNING: Always chock wheels to prevent vehicle from! moving. Vent vehicle system air pressure to zero psi. A. When preparing to install a spring brake chamber, ensure that the unit is fully released (power spring caged) and the service brake push-rod is fully retracted to zero stroke position. Thread the clevis jam nut onto the push-rod. B. Place the brake chamber into the appropriate brake assembly bracket. Tighten the holding nuts to the bracket studs ( lb. ft.). C. Measure the distance from the centerline of the S-Cam to the centerline of the push-rod (See Figure 1 - Dimension A). This measurement should be equal to the length of the brake adjuster being used (See Figure 2 - Dimension A). NOTE: If Dimension A - Figure 1 and Dimension A - Figure 2 are not identical, the chamber mounting bracket is either bent and must be straightened or replaced, the chamber has been mounted improperly in the bracket or the length of the adjuster installed is incorrect. Make any necessary corrections before going to Step D. D. Using a square, mark the push-rod at the 90 o setting (See Figure 1 - Mark #1). Figure 1 Figure 2 E. From Mark #1 measure back toward the brake chamber mounting surface in accordance with Chart A ( X Dimension), make a second mark and cut the push-rod at Mark #2 - See Figure 1). F. Install the clevis onto the push-rod and secure the jam nut. Connect the clevis to the brake adjuster. Uncage the spring brake. G. Release parking spring brakes and adjust the brake adjuster to the shortest possible stroke without the brakes dragging. Proper set-up stroke should now be established.! BRAKE ADJUSTER Chart A Brake X Adjuster Length Dimension 5-5 1/2 2 1/ /2 DANGER A spring brake or combination service/spring brake must be disarmed before disposal, or forceful release of the compression spring may occur in the future without warning

42 THE FUNDAMENTALS OF BRAKES All types of automotive brakes are mechanical de vic es for retarding the motion of a ve hi cle by means of fric tion, and per haps the most im por tant requisite in re spect to the fun da men tals of brakes is an un der stand ing of the laws of fric tion. WEIGHT 100 LBS. WEIGHT WEIGHT 100 LBS. WEIGHT 100 LBS. If Pull Re quired Is 60 Pounds C.O.F. 60% or.6 If Pull Re quired Is 50 Pounds C.O.F. 50% or.5 If Pull Re quired Is 35 Pounds C.O.F. 35% or.35 FIG. 1 Coefficient of Friction COEFFICIENT OF FRICTION Friction is the resistance to relative motion be tween any two bodies in contact, and it varies not only with different materials but also with the condition of the materials. The amount of fric tion developed by any two bod ies in contract is said to be their coefficient of friction, and this is expressed by stat ing the amount of force re quired to move the one body while it re mains in con tact with the other; the amount of force being expressed in relation to the weight of the mov ing body. Thus, if the moving body weighs 100 pounds, and a force of 60 pounds is required to keep it moving while it remains in contact with another body, the co ef fi cient of fric tion between the two bodies is said to be 60% or.6. If 50 pounds force is necessary to keep on moving, the co ef fi cient of friction is said to be 50% or.5. If only 35 pounds force is required, the coefficient of fric tion is 35% or.35. The coefficient of friction between any two sur fac es chang es with any variation in the con di tion of one or both surfaces. As an example, the introduction of oil and grease between two dry, flat metal surfaces will great ly reduce the friction be tween them, which proves that the con di tion of these surfaces plays a great part in the actual fric tion they develop. This pos si ble variation in the co ef fi cient of friction is always present when any factor con trib ut ing to the fric tion al value of any material is subject to change either permanent or temporary. Heat is always present where friction is being developed. For example, when a bearing is not properly lubricated, the lack of lubrication causes a rise in the coefficient of friction with a resultant rise in the heat that causes the bear ing to fail. ENERGY OF MOTION TO HEAT ENERGY Since friction is the resistance of relative motion between two bodies in contact and since fric tion results in heat, a more com plete def i ni tion of a brake would be that it is a mechanical device for retarding the motion of a vehicle by means of friction, thereby chang ing the energy of mo tion into heat energy. Thus, when the speed of a vehicle is reduced by ap ply ing the brakes, the energy of motion is actually changed into heat en er gy and the brakes must dissipate or ab sorb the heat developed. 100 HORSEPOWER 100 HORSEPOWER STOPPED - TO 60 M.P.H. - IN ONE MINUTE 100 HORSEPOWER 100 HORSEPOWER 60 M.P.H. - TO STOPPED - IN LESS THAN SIX SECONDS FIG. 2 Forces Involved In Braking FORCES INVOLVED IN BRAKING It is difficult to appreciate the tremendous forc es in volved in stop ping a modern commercial ve hi cle, par tic u lar ly from the higher speeds. A simple method of explaining this is to make a comparison between the horsepower required to accelerate a ve hi cle and the horsepower re quired to stop it. A truck with an engine ca pa ble of developing 100 horsepower will re quire about one minute to ac cel er ate to 60 miles per hour. The same ve hi cle should be ca pa ble of easily stop ping from 60 miles per hour in not more than six seconds. Ig nor ing the unknown quan ti ties, such as roll ing friction and wind resistance which play a part in all stops, the brakes must develop the same energy in six seconds; in other words, the brakes do the same amount of work as the engine in one-tenth the time and must develop approximately 1,000 horsepower during the stop

43 20 M.P.H. 40 M.P.H. 60 M.P.H. IF WEIGHT IS DOU BLED STOPPING POWER MUST BE DOU BLED IF SPEED IS DOU BLED STOPPING POWER MUST BE INCREASED 4 TIMES IF WEIGHT AND SPEED ARE DOU BLED STOPPING POWER MUST BE INCREASED 8 TIMES FIG. 3 Effect of Weight and Speed on Brakes EFFECT OF WEIGHT ON BRAKES Another factor to be considered is the effect on brak ing when the weight and speed of a vehicle are in creased. Brake sys tems are designed to properly con trol a vehicle loaded to its gross vehicle weight (GVW). If the GVW is exceeded, braking performance is af fect ed; if the weight of the vehicle is doubled, the energy of motion to be changed into heat energy is also dou bled. The brake cannot properly dissipate and absorb the increased heat and braking performance of the ve hi cle is less ened. EFFECT OF SPEED ON BRAKES The effect of higher speeds on braking is much more various. Not so many years ago the average speed of a commercial vehicle was only 20 miles per hour. To day, even con ser va tive estimates place the average speed of commercial ve hi cles at 40 miles per hour. Comparing stops from a speed of 20 miles per hour with stops from a speed of 40 miles per hour, en gi neer ing calculations show there is actually four times as much energy of motion to be changed to heat energy dur ing a stop from 40 miles per hour as there is during a stop from 20 miles per hour. Thus, if the speed is doubled, four times as much stopping power must be de vel oped, and the brakes must absorb or dissipate four times as much heat. It naturally follows that if both the weight and speed of a ve hi cle are doubled, the stopping power must be increased eight times and the brakes must absorb or dis si pate eight times as much heat. 30 FT. 120 FT. 270 FT. FIG. 4 Stopping Distances Another way of illustrating the effect of speed on stop ping ability is to compare the stopping distance if the speed is increased without the stopping power also being in creased. As shown in Fig. 4, a vehicle which will just stop in 30 feet from 20 miles per hour will require 120 feet to stop from 40 miles per hour and 270 feet to stop from 60 miles per hour. Introducing both weight and speed into the com par i son again, a 10,000 pound vehicle traveling 60 miles per hour has 18 times as much energy of motion as a 5,000 pound vehicle traveling at 20 miles per hour. If a stopping power is used on both vehicles which will only stop the 5,000 pound vehicle from 20 miles per hour in 30 feet, the 10,000 pound vehicle from 60 miles per hour will require 18 times as much distance or 540 feet to stop. 1 FT. 200 LBS. 1 FT. 200 LBS. 300 LBS. 3 FT. 3 FT. 300 LBS. 3 FT. 1 FT. 2 FT. 2 FT. 2 FT. FIG. 5 Leverage 100 LBS. 100 LBS. LEVERAGE Having reviewed the forces involved in braking a vehicle, con sid er ation must also be given to how these forces are developed and directed to do the braking work. It is difficult even to imagine a braking system which does not, in some way, make use of one of the oldest mechanical de vic es gov ern ing the trans mis sion and modification of force and motion; the lever. A lever is defined as an inflexible rod or beam capable of motion about a fixed point called a fulcrum. It is used to transmit and modify force and motion. Fig. 5 illustrates three simple types of levers; the only difference in them being the location of the fulcrum in relation to the applied force and the delivered force. All shapes and sizes of levers used in a brake system are one of these three types. The simple law of levers is that the applied force mul ti plied by the perpendicular distance between the line of force and the ful crum always equals the de liv ered force multiplied by the per pen dic u lar distance between the ful crum and the line of force. Thus, with a leverage A B C

44 ar range ment as shown in view 5A, an applied force of 100 pounds two feet from the fulcrum will give a de liv ered force of 200 pounds at a point one foot from the fulcrum. With a leverage ar range ment as shown in view 5B, an applied force of 100 pounds three feet from the fulcrum will lift 300 pounds at a point one foot from the fulcrum. Note that in both cases the delivered force exceeds the ap plied force because the applied force is farther from the ful crum than the delivered force. With a le ver age arrangement as shown in Fig. 5C, the de liv ered force is the farthest from the fulcrum; therefore, it is less than the applied force. If the applied force in this case is 300 pounds at a point two feet from the fulcrum, the delivered force at a point three feet from the fulcrum will be 200 pounds. The delivered force of any lever is determined by multiplying the applied force by the distance it is from the ful crum and then dividing this answer by the distance the delivered force is from the fulcrum. In determining the distance at which any force is act ing on a lever, the true length of the lever arm is the perpendicular distance from the force to the fulcrum, re gard less of the shape of the lever. The lever arm is al ways mea sured at right angles to the direction of the force. The product of the force acting on a lever, multiplied by the distance the force is from the fulcrum, is called the turning moment; when this relates to a shaft it is called torque. The turning moment or torque is usu al ly expressed in inch pounds, foot pounds, foot tons, etc., de pend ing upon whether the force is mea sured in pounds or tons and whether the distance is measured in inches or feet. As an example a force of 100 pounds acting on a lever arm five inches long would result in a turning moment or torque of 500 inch pounds. The most easily recognized lever in an air system is the brake adjuster. The length of the lever arm of a brake adjuster is always the perpendicular distance between the center line of the brake camshaft open ing and the center line of the clevis pin opening in the arm. Another form of lever not always recognized is the brake cam. All brake cams are levers and are used to transmit and modify the torque and turning motion of the brake camshaft in such a way that the brake shoes are spread and forced against the brake drum, not only in the proper direction but also with the proper force. Spreading the shoes in the proper direction, of course, depends on the proper location of the cam in respect to the location of the brake shoes. The transmission of the proper force is partially determined by the effective lever length of the cam. If the effective lever length of the cam is not considered and is too long or too short, the brake shoe force will be correspondingly too little or too much. Full consideration must therefore be given to the effective lever length of any brake came, if the final shoe pressure is to be correct. It is also important that the effective lever length of the cam remains constant as the lining wears and the shoes have to be spread further; otherwise, the brake performance will vary as the lining wears. Another form of lever found in all forms of braking systems is the brake shoe. This is one of the simpler forms because it is easily recognized as a beam, fulcrumed at one end on the hinge pin, which forces the brake lining against the drum when the brake cam force is applied to the other end. Perhaps the least easily recognized lever in a brake system is the relation of the brake drum diameter to the tire diameter. In order to understand this fully you must remember that although the brakes stop the brake drums and wheels, it is always the tires and road surface that stop the vehicle. This is clearly demonstrated when quick stops are attempted on wet or icy roads. Under these conditions the brake equipment may still be as efficient as ever in stopping the wheels, but its ability to stop the vehicle quickly disappears because there is not sufficient friction between the tire and road to develop the necessary retarding force. Returning to the principles of leverage involved in the relation of the tire and brake drum size, the retarding force developed by the brake shoes acting against the drum is working on an effective lever length of the brake drum radius. Counteracting this is the retarding force developed between the tire and the road, working on an effective lever length of the rolling radius of the tire. Since it is not practical to have brake drums as large as the tires, the principles of leverage require development of a greater retarding force between the brake shoes and the drums than between the tire and the road. Also, since a rubber tire on a good road surface has a higher coefficient of friction than brake lining against a brake drum, it is necessary to develop additional retarding force between the brake shoes and brake drum in order to overcome the difference in friction. DECELERATION In discussing brakes, the term deceleration is often used. This term expresses the actual rate at which a vehicle is losing speed and usually denotes the speed being lost each second, in terms of miles per hour or feet per second

45 BRAKES APPLIED 1ST SECOND 2ND SECOND 3RD SECOND SPEED 20 M.P.H. 18 M.P.H. 16 M.P.H. 14 M.P.H. DECELERATION RATE - 2 MILES PER HOUR PER SECOND SPEED 30 FEET 20 FEET 10 FEET 5 FEET PER SECOND PER SECOND PER SECOND PER SECOND FIG. 6 Deceleration For example, as shown in FIG. 6, if a vehicle is moving at the rate of 20 miles per hour, and one second later its speed is only 18 miles per hour, the vehicle has lost a speed of two miles per hour during one second. Its speed has dropped two miles per hour in one second, therefore, its deceleration rate is two miles per hour per second. second, it will be traveling ten feet per second, and at the end of the third second, it will be stopped. Thus, by losing speed at the rate of ten feet per second per second, it would lose its initial speed of 30 feet per second per three seconds. Similarly, if the initial speed is 20 miles per hour and the deceleration rate is two miles per hour per second, the stopping time will be ten seconds. One important thing to remember in respect to stopping vehicles is the fact that while the deceleration rate may be constant for each second during the stop, the distance the vehicle travels each second during the stop varies greatly as the speed decreases. This is illustrated in Fig. 7 which also shows a vehicle decelerating at the rate of ten feet per second per second from an initial speed of 30 feet per second, but the positions of the In the same way, if a vehicle is moving at a rate of 30 feet per second, and one second later its speed is only 20 feet per second, then it is decelerating at the rate of ten feet per second per second. BRAKES APPLIED 1ST SECOND 2ND SECOND 3RD SECOND 25 FEET 15 FEET 5 FEET Therefore, the change in the rate of speed of a vehicle during a slow-down or stop is expressed by first stating the rate of speed being lost, such as miles per hour or feet per second and then by stating the time required for this rate of speed to be lost. SPEED 30 FEET 20 FEET 10 FEET STOPPED PER SECOND PER SECOND PER SECOND FIG. 7 Deceleration Thus, in examining the expression covering a deceleration rate of say, ten feet per second per second the first part ten feet per second is the rate of speed being lost, and the second part per second is the time in which the loss of ten feet per second takes place. If a vehicle is moving at a known rate and is decelerating at a known rate, the stopping time will be the initial speed divided by the deceleration rate, provided both the rate of speed and the deceleration rate are expressed on the same basis. As an example if a vehicle is moving at the rate of 30 feet per second and is decelerating at the rate of ten feet per second, the stopping time will be the initial speed of 30 feet per second di vid ed by the deceleration rate of ten feet per sec ond per second or a stopping time of three seconds. This perhaps can be more easily understood if ex plained in the following manner; if a vehicle is moving at the rate of 30 feet per second and begins to decelerate at the rate of ten feet per second per second, at the end of the first second it will be traveling 20 feet per second; at the end of the second vehicles are shown in relation to the distance traveled each second during the stop. This shows that although the rate of deceleration remains constant throughout the stop, the ve hi cle actually travels 25 feet during the first second after the brakes were applied, 15 feet during the second second and only 5 feet during the third second. The distance being traveled each second during the stop is always greater at the beginning of the stop. To keep stop ping distance as short as possible, it is important that the brakes become fully effective when the pedal is depressed by the driver. Any time lost between the instant the brake pedal is de pressed and the instant actual deceleration begins is important because the vehicle continues to travel at close to its initial speed. In this case, the loss of only one second between the instant the driver depresses the brake pedal and the point where the brakes are really applied will result in lengthening the actual stopping distance by 30 feet. Thus, if four

46 It is this part of brake fundamentals which is not often considered in judging brake performance, particularly when dif fer ent forms of brakes are involved. A common method of testing brakes is by the use of a seconds instead of three elapse between the instant the driv er depresses the brake pedal and the instant the vehicle stops, the actual stop ping distance will be increased from 45 feet to 75 feet. In other words, by reducing the stopping time under these con di tions by only one second or 25%, the actual stopping dis tance is reduced by 30 feet or 40%. decelerometer a device that determines the maximum rate of deceleration developed during a stop and which shows a calculated stopping distance from a speed of 20 miles per hour based on the maximum rate of deceleration developed during a stop. Such instruments do not, however, make allowances for lost time before the braking system develops full power and therefore are not suitable for analyzing time lag factors in brake per for mance. The true performance of any type of brake system in terms of stopping time or stopping distance can only be determined by actually measuring the time and distance the vehicle travels from the instant the driver depresses the brake pedal to the point where the vehicle actually stops. Such tests can, of course, be made comparative only by using instruments to determine accurately the speed of the vehicle at the in stant the brake pedal is depressed. In so far as brakes are concerned, a driver is mainly interested in the amount of time and the distance required to bring his vehicle safely to a stop under emergency conditions as measured from the instant he depresses the brake pedal. Any lag in the time between the instant he does his part and the instant the brakes become effective affects stopping distance

47 Brake Calculations (Typical 20,000 lb. Rated Axle) Coefficients: ( ,000)--( ,000)--( ,000) Make Year Model Load:Pass Pay Axle - Front or Rear: Empty Weight on Axle % Load on Axle Lbs. Load on Axle % Load Transfer Lbs. Load Transfer Total Axle Load 20,000 lbs. Tire Size 11.00R24 Rolling Radius 21.4 Brake Drum Diameter 16 1/2 Lining Size: Width 7 Thickness 3/4T Long Arc. 8 7/8 A; 9 C Degrees of Segment Lining Part No. FMSI No. 4625A Cam B.C. Rad..5 Brake Chamber Type 30 Diameter 8 3/32 Effective Area 30 Brake Adjuster 5 1/2 Make of Axle Rockwell Axle Number Suggested Lining Type CP (531) WORK FACTOR = Total Weight on Wheel X Rolling Radius (in.) Timken Bus. Max. 85 Truck Max. 110 Drum Diameter 2 (in.) X Brake Width (in.) 10,000 X 21.4 = X 7 = = 112 GROSS WEIGHT: = Wheel Load (lbs.) LINING AREA, RATIO Lining Area (Per Wheel) 10,000 10,000 = 4 X 7 X = 40 lbs/in

48 K FACTOR = Road-Tire Adhesion (.6) X Weight on Wheel.6 X 10,000 = 6,000 lbs. The Retarding Force Per Wheel BRAKE FORCE = 2 X Line Pressure X Chamber Area X Lever Length X Lining F X Drum Radius PER WHEEL Cam Base Circle X Tire Rolling Radius 2 X 60 X 30 X 5.5 X.393 X 8.25 = X 21.4 = 10.7 = 6,000 lbs. DEC, FT/SEC. 2 = X Retarding Force on Axle Total Axle Load X 6000 X 2 = X 2 = = 19.3 Ft./Sec. 2 REQUIRED = Tire Rolling Radius X.6 X Weight on Wheel X Cam Radius AL FACTOR Drum Radius X Lining Friction X 2 X Air Pressure Westinghouse 21.4 X 6 X X.5 = X.393 X 2 X 60 = 389 = 165 REQUIRED = Tire Rolling Radius X.6 X Weight on Wheel X Cam Radius COEFFICIENT OF FRICTION Drum Radius X Chamber Area X Lever Length X 2 X Air Pressure 21.4 X 6 X X.5 = X 30 X 5.5 X 2 X 60 = =.393 This brake calculation sheet is required only when there is some doubt as to whether brake input is satisfactory. It is used to determine required brake input, lining coefficient of friction, etc

49 NOTES

50 NOTES

51 NOTES

52 NOTES

53 NOTES

54 NOTES

55 NOTES

56 NOTES

57 NOTES

58 NOTES

59 inside back cover is blank

60 Haldex ( headquartered in Stockholm, Sweden, is a provider of proprietary and innovative solutions to the global vehicle industry, with focus on products in vehicles that enhance safety, environment and vehicle dynamics. Haldex is listed on the Stockholm Stock Exchange. Haldex has a yearly turnover of close to 5.6 billion SEK and employs 4,300 people. Disclaimer: The products described within this literature, including without limitation, product features, specifications, designs, availability and pricing are subject to change by Haldex and its subsidiaries at any time without notice. This document and other information from Haldex, its subsidiaries and authorized distributors provide product and/or system options for further investigation by users having technical expertise. It is important that you analyze all aspects of your application and review the information concerning the product or system, in the current literature or catalog. Due to the variety of operating conditions and applications for these products or systems, the user, through their own analysis and testing, is solely responsible for making the final selection of the products and systems and assuring that all performance, safety and warning requirements are met. 2010, Haldex AB - This material may contain Haldex trademarks and third party trademarks, trade names, corporate logos, graphics and emblems which are the property of their respective companies. The contents of this document may not be copied, distributed, adapted or displayed for commercial purposes or otherwise without prior written consent from Haldex. Austria Haldex Wien Ges.m.b.H. Vienna Tel.: Fax: info.at@haldex.com Belgium Haldex N.V. Balegem Tel.: Fax: info.be@haldex.com Brazil Haldex do Brasil Ind. e Com. Ltda. São Paulo Tel.: Fax: info.br@haldex.com Canada Haldex Ltd. Cambridge, Ontario Tel.: Fax: info.ca@haldex.com China Haldex International Trading Co. Ltd. Shanghai Tel.: Fax: info.cn@haldex.com France Haldex Europe SAS Weyersheim (Strasbourg) Tel.: Fax: info.eur@haldex.com Germany Haldex Brake Products GmbH Heidelberg Tel.: Fax: info.de@haldex.com Hungary Haldex Hungary Kft. Szentlörinckáta Tel.: Fax: info.hu@haldex.com India Haldex India Limited Nasik Tel.: Fax: Italy Haldex Italia Srl. Biassono (Milan) Tel.: Fax: info.it@haldex.com Korea Haldex Korea Ltd. Seoul Tel.: Fax: info.hkr@haldex.com Mexico Haldex de Mexico S.A. De C.V. Monterrey Tel.: Fax: Poland Haldex Sp. z.o.o. Praszka Tel.: Fax: info.pl@haldex.com Russia OOO Haldex RUS Moscow Tel.: Fax: info.ru@haldex.com Spain Haldex España S.A. Granollers Tel.: Fax: info.es@haldex.com Sweden Haldex Brake Products AB Landskrona Tel.: Fax: info.se@haldex.com United Kingdom Haldex Ltd. Newton Aycliffe Tel.: Fax: info.gbay@haldex.com Haldex Brake Products Ltd. Redditch Tel.: Fax: info.gbre@haldex.com USA Haldex Brake Products Corp. Kansas City Tel.: Fax: info.us@haldex.com Commercial Vehicle Systems