SAE-J1505-2004.pdf

SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefrom, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions. Copyright © 2004 SAE International All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER:Tel: 877-606-7323 (inside USA and Canada) Tel: 724-776-4970 (outside USA) Fax: 724-776-0790 Email: custsvcsae.org SAE WEB ADDRESS:http:/www.sae.org SURFACE VEHICLE RECOMMENDED PRACTICE J1505 REV. APR2004 Issued1985-05 Revised2004-04 Superseding J1505 APR1995 Brake Force Distribution Test ProcedureTrucks and Buses ForewordThis Document has been changed to reflect a 5-year review and update. 1.ScopeThis SAE Recommended Practice provides the test procedure and instructions for air braked single unit trucks, buses, and combination vehicles. It also provides recommendations for: a.Instrumentation and equipment b.Vehicle preparation c.Calculating distribution of brake force 1.1PurposeThis procedure provides a method to determine the brake force distribution and threshold pressures for trucks and buses with a GVWR greater than 4536 kg (10 000 lb). 2.References 2.1Applicable PublicationsThe following publications form a part of the specification to the extent specified herein. Unless otherwise indicated, the latest revision of SAE publications shall apply. 2.1.1SAE PUBLICATIONSAvailable from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001. SAE J1854Brake Force/Distribution Performance GuideTrucks and Buses SAE J2115Brake Performance and Wear Test Code Commercial Vehicle Inertia Dynamometer SAE J1626Braking, Stability, and Control Performance Test Procedures for Air- and Hydraulic-Brake Equipped Trucks, Truck-Tractors and Buses 2.2Related PublicationThe following publication is provided for information purposes only and is not a required part of this specification. 2.2.1FMVSS PUBLICATIONAvailable from The Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402. FMVSS 121Air Brake Systems SAE J1505 Revised APR2004 -2- 3.Instrumentation, Equipment, and Facilities 3.1Each vehicle should be equipped with: 3.1.1A speed measuring device capable of measuring vehicle speed to within ±0.32 km/h (±0.2 mph). 3.1.2A means of measuring time to within ±0.1 s between two speeds such as a strip chart recorder or digital timer that receives a signal from the speed measuring device. 3.1.3Two pressure transducers and a recording device accurate to within 3.5 kPa (±0.5 psi). 3.1.4Brake lining thermocouples as per SAE J2115 and a suitable temperature readout device accurate to within ±11 °C (±20 °F). If brake lining thermocouples are not used, a contact pyrometer or other method may be used to ensure that adequate cooling time is provided between tests to ensure that brake heating and fade do not contaminate results. 3.1.5Valving to allow brakes on each axle or axle set to be operated, controlled, and evaluated independently. Valving must not disturb the inherent pressure differentials in the vehicle brake system and provide driver override capability. 3.1.6An external application system (see Figure 1) that can apply the braking system with a constant input is recommended. (Use of the driver's foot to apply the brakes may increase variation in the test results). This system must be designed, installed, and utilized in such a way as to take into account the inherent pressure differentials in the vehicle brake system. FIGURE 1EXTERNAL SYSTEM FOR BRAKE APPLICATION SAE J1505 Revised APR2004 -3- 3.1.7A system such as a treadle stop may be used provided that the brakes are applied at a controlled rate so as to minimize pressure overshoot during the brake application. Caution must be exercised when applying the brakes on individual axles during partial system testing. The stopping ability of the vehicle will be reduced. 3.1.8Measure and record ambient temperature and wind conditions, including wind speed and direction. 3.1.9Test should be run on a straight 3.6 m (12-ft) wide roadway with a dry Portland cement concrete or equivalent surface to reduce the likelihood of wheel lock-up. The vehicle shall be aligned with the center of the roadway at the beginning of each stop. The roadway should be dry and flat with no more than a 1% grade in all directions, including crown. 4.Vehicle Information and Data 4.1Vehicle information sheet (Figure 2) to be filled in prior to starting test. 4.2Test data sheet (Figure 3) to be used as a work sheet during testing. 4.3Vehicle information and test data sheets may be used for or extended to single unit trucks, buses, or multiple combination vehicles. 5.Vehicle ConditionBrake force distribution may be determined for any lining condition new or in service; however, to ensure the accuracy and validity of results, the following conditions should be met: 5.1Inspect the brake lining and mating surface. Replace if abnormal conditions exist or worn beyond manufacturers recommended limits. Adjust brakes to manufacturers specifications. 5.2Lining to drum or disc contact should be at least 90% of contact area. If contact area is not at least 90%, burnish procedure may be continued as specified in 5.6 until contact area is at least 90%. 5.3Inspect tires and replace if worn beyond manufacturers recommended limits or abnormal tire condition. Adjust tire pressure per vehicle manufacturers load recommendations. 5.4All components between the air compressor and each of the brake chambers must be functioning properly. 5.5Initial testing each day should be preceded by a series of brake snubs which will warm the brakes to 93 to 149 °C (200 to 300 °F). 5.6In order to satisfy SAE J1854 guidelines, the vehicle brakes shall be burnished prior to testing with the procedure as specified in SAE J1626 Section 11 or FMVSS 121 Section 6.1.8. 6.Braking Distribution Tests 6.1Install and secure instrumentation and test equipment in the test vehicle. One of the pressure transducers should be installed at the axle under test, down stream of any relay or proportioning valves; the other should be installed at the tractor to trailer or truck to trailer control glad-hand as the reference transducer. The axle transducer is moved from axle-to-axle as necessary and is used to ensure that brakes are fully activated (i.e., at steady-state) before data collection occurs. The reference transducer at the glad-hand is used to ensure that the desired input level is achieved. All data is related back to the reference level for braking force distribution calculations. The axle transducer may be omitted if the relationship between the reference pressure and the brake pressure is known and it is certain that the brakes are fully applied when the data collection is initiated. SAE J1505 Revised APR2004 -4- FIGURE 2VEHICLE INFORMATION SHEET SAE J1505 Revised APR2004 -5- FIGURE 3BRAKE FORCE DISTRIBUTION TEST DATA SHEET SAE J1505 Revised APR2004 -6- 6.2Weigh the test vehicle in the as-tested configuration on an axle-by-axle or axle-set basis. Weight should be distributed approximately in accordance with GAWRs and be sufficient to prevent wheel lock-up of one axle with respect to the others. 6.3Determine the glad-hand (reference) pressure level at which braking starts to occur at each brake by raising the vehicle and rotating the wheel by hand while gradually increasing input to the brake system. Record the glad-hand (reference) pressure level at which the brake torque is first evident on Figure 3. Continue to increase pressure to approximately 276 kPa (40 psi) and then slowly decrease it until the point at which the brake is fully released is determined. Record the glad-hand (reference) pressure level at brake release on Figure 3. The average of these two recorded values is defined as the brake threshold pressure. Calculate the threshold pressure for each brake and average these values for each axle or tandem set. 6.4Test the braking on each axle (or axle set) of the combination vehicle independently using the following procedure. 6.4.1Bring the brakes to the desired initial temperature (93 to 149 °C 200 to 300 °F hottest brake is recommended) by making snubs. Record temperature of all brakes. On subsequent snubs, control the hottest brake of the axle or axle set being tested to the same temperature as initially recorded on that brake by making snubs or cooling as necessary. 6.4.2Accelerate the vehicle to 73 km/h (45 mph), shift to neutral or de-clutch and immediately apply the brakes to the desired glad-hand (reference) pressure level. Pressure overshoot is not permitted. Ensure that a constant pressure is achieved at the test brakes before the vehicle decelerates to 64.4 km/h (40.0 mph). Continue to decelerate until the vehicle reaches 56.3 km/h (35.0 mph) and immediately release the brakes. Measure the time between 64.4 and 56.3 km/h (40.0 and 35.0 mph), i.e., delta V = 8 km/h (5 mph), average V = 60.4 km/h (37.5 mph) and record on Figure 3. Lower speed levels can be used if desired; however, the speed change measured should be maintained at 8 km/h (5 mph). Speeds above those shown should not be used as significant in-stop fade can occur due to high energy input to the brakes. NOTE The speeds indicated have been determined to work well on vehicles up to 36 300 kg (80 000 lb) GCW. For vehicles greater than 36 300 kg (80 000 lb) GCW, speeds should be reduced to limit energy input to the braking system in accordance with Table 1: 6.4.3Repeat 6.4.1 and 6.4.2 at the same input level (at the control glad-hand) for a total of 4 runs, 2 in each direction on the same area of the roadway to allow grade effects to be averaged out. If an external application system is not used, variation resulting from use of the driver's foot may require additional runs to be made. TABLE 1TEST SPEEDS FOR VEHICLES GREATER THAN 36 300 kg (80 000 lb) GCW GCW kg GCW lb Test Starting Speed km/h Test Starting Speed mph Timed Speeds Initial km/h Timed Speeds Initial mph Timed Speeds Final km/h Timed Speeds Final mph 45 400100 000603751.53243.527 54 400120 000533345.12837.123 63 500140 000472938.62430.619 -,-,- SAE J1505 Revised APR2004 -7- 6.4.4Repeat 6.4.1 to 6.4.3 for a range of glad-hand (69, 103, 138, 207 and 276 kPa or 10, 15, 20, 30, and 40 psi) pressure levels to cover desired operating spectrum. As a minimum, pressure levels of 103, 138, and 276 kPa (15, 20, and 40 psi) are recommended. Terminate test run if wheel lock occurs. Because all axles must be run over the same range to calculate distribution, it is desirable to test the axle which is expected to lock at the lowest pressure first to establish the range for the other axles. 6.4.5Repeat steps 6.4.1 through 6.4.4 for each axle (or axle set). 6.4.6Repeat steps 6.4.1 through 6.4.4 with all brakes operational (to serve as a data check). 6.4.7Repeat steps 6.4.2 and 6.4.3 with no braking (coastdown test) to determine parasitic drag. 7.Analysis of Data (Figure 4) FIGURE 4CALCULATION SHEET -,-,- SAE J1505 Revised APR2004 -8- 7.1Definition of Terms t = time in seconds d = deceleration in m/s2 (ft/s2) di = average deceleration of an individual axle or axle set (corrected for drag) 1 = vehicle front axle 2 = vehicle rear axle or axle set 3 = trailer axle or axle set ds = deceleration with all brakes operational (correct for drag) dc = average deceleration with no brakes appliedcoastdown deceleration davg = the average of the individual deceleration runs for each test condition dn = the sum of the individual average decelerations for each axle or axle set % Error = the sum of the individual axle average decelerations compared to the average deceleration with all brakes applied %Bi = the percentage braking contributed by each axle or axle set of brakes Fi = the braking force contributed by each axle or axle set of brakes w = total vehicle and/or combination weight in kilograms (pounds) g = 9.8 m/s2 (32.2 ft/s2) FA = the sum of all axle or axle set brake forces 7.2Calculate the deceleration for each of the coastdown runs using Equation 1: (Eq. 1) Average the four coastdown decelerations to obtain dc. NOTE Do not average time first, or grade effects will not be removed from the data correctly. 7.3Use Equation 1 to calculate deceleration for each of the runs with braking. Average the four decelerations for each axle or axle set at each pressure level. Subtract the average coastdown deceleration (dc) from the average braking deceleration (davg) to obtain di. 7.4At each reference pressure evaluated, add the individual axle average braking decelerations together and perform a data check by comparing this sum (dn) to the deceleration with all brakes operational (da) using Equation 2: (Eq. 2) A negative error (greater than 20%) at all input levels indicates possible brake fade due to the greater energy inputs per brake during the individual axle tests. This is not usually a problem at the test speeds specified in this procedure. If it is, lower test speeds may be necessary. A large random error indicates lack of repeatability in the brake application pressure level and more than four runs should be made. 7.5Calculate brake force for each axle or axle set using Equation 3: (Eq. 3) Calculate total brake force (Fa) by adding the individual axle or axle set of brake forces. d SI 2.234 t - d English 7.33 · t - -= = % Error dnda da - -100×= Fi w g - -di×= -,-,- SAE J1505 Revised APR2004 -9- Plot brake force (Fi) for each axle versus glad-hand reference pressure level on a common plot to show actual braking force distribution (see example, Figure 5). Each curve has its origin (Fi=0) at the average threshold pressure determined in 6.3. Straight line segments should be used to connect the individual data points. Plot total vehicle brake force for each data point. The origin of the curve will be at the lowest average vehicle threshold pressure determined in 6.3. Note that variation in threshold pressure for individual axles will change the slope of the curve as each axle begins braking. FIGURE 5BRAKE FORCE VERSUS REFERENCE PRESSURE, EXAMPLE 7.6Calculate the percent of total vehicle braking at each glad-hand reference pressure for each axle by using the braking forces from the force dis