FMVSS 121 Brake Performance and Stability Testing

FMVSS 121 Brake Performance and Stability Testing FINAL REPORT - Revision A SwRI Project No. 03-05190 Prepared for Mr. Bill Washington Air Brake Systems 4356 E. Valley Road Mount Pleasant, MI 48804-0293 April 22, 2002

FMVSS 121 Brake Performance and Stability Testing FINAL REPORT - Revision A SwRI Project No. 03-05190 Prepared for: Mr. Bill Washington Air Brake Systems 4356 E. Valley Road Mount Pleasant, MI 48804-02983 Prepared by: John Bishop, Group Leader Southwest Research Institute 6220 Culebra Road San Antonio, TX 78238 This report January must 31, be reproduced 2002 in full, unless SwRI approves a summary or abridgement. Reviewed by: Approved: Scott T. McBroom, Manager Gary L. Stecklein, Director Advanced Vehicle Technology Vehicle Systems Research Department

EXECUTIVE SUMMAR Southwest Research Institute (SwRI) contracted with Air Brake Systems to provide a performance comparison test of a truck equipped with the Air Brake Systems MSQR-5000 brake system device to a baseline vehicle without the MSQR-5000. The comparison was made using the dynamic stopping procedures taken from FMVSS 121 to determine stopping distance from 60 mph on a dry surface and stopping stability in a curve from 30 mph on a wetted surface. These tests were run with the vehicle loaded to GVWR and with the vehicle empty. Two different stopping techniques were used during the testing. The FMVSS 121 requirements state that the driver use full treadle brake application. This procedure was used and in addition, the wet stops were repeated using the manufacturer s recommended procedure consisting of modulated or best effort stopping procedures. For the straight-line test, results indicate that the vehicle is able to stop from 60 mph on dry pavement within FMVSS 121 required stopping distances with the OEM brake system and with the MSQR-5000 system installed. The stopping distances are generally very similar. The one significant exception is that the empty vehicle with the MSQR-5000 installed stopped from 60 mph on a dry surface in an average of 13% shorter distance than the OEM equipped vehicle. There was no such difference at GVWR. For the wetted curve test, the vehicle is required by FMVSS 121 to stop from 30 mph on a wetted surface while negotiating a 500-foot radius curve and maintaining itself within in a 12- foot wide lane. When using full treadle brake application per FMVSS 121, the vehicle did not stay in the 12-foot lane. This occurred for the vehicle with and without the MSQR-5000 brake valve at both vehicle weights. Based on the test results and discussions with the manufacturer, SwRI found that the MSQR-5000 system does not function in the same manner as an electronic anti-lock brake system (ABS). With full treadle application, it is possible to cause wheel lockup that results in the vehicle not staying within the 12-foot lane. When using the Air Brake System s MSQR-5000 recommended braking procedure for the wetted surface stops, the vehicle is able to stay in the 12-foot lane. During the stopping testing, the MSQR-5000 system did not significantly increase or decrease vehicle stopping performance. A more detailed discussion of the test procedure and the test results is contained in the body of this report. i

TABLE OF CONTENTS Page 1.0 INTRODUCTION...1 1.1 Vehicle Procurement and Break-in... 1 1.2 Vehicle Description... 1 1.3 Test Plan Development... 5 1.4 Vehicle Preparation and Instrumentation Installation... 5 1.5 Brake Burnishing... 5 1.6 Stopping Test Results Summary... 6 1.7 Stopping Distance Testing Loaded to GVWR... 7 1.8 Stopping Stability Testing Loaded to GVWR... 8 1.9 Stopping Distance Testing at Empty Vehicle Weight... 9 1.10 Stopping Stability Testing at Empty Vehicle Weight... 9 1.11 Conclusion... 9 ii

LIST OF ILLUSTRATIONS Figure Page 1 Air Brake Systems Test Vehicle, Left View...2 2 Air Brake Systems Test Vehicle, Right View...3 3 MSQR-5000 Diagram and Installation Schematic...4 4 Vehicle Entering 500-foot radius...8 5 Vehicle After Stop...8 iii

LIST OF TABLES Table Page 1 Test Configuration and Test Matrix...1 2 Vehicle Description...2 3 Air Brake Systems Truck Instrumentation...5 4 Stopping Results Summary...7 iv

1.0 INTRODUCTION Southwest Research Institute (SwRI) was contracted by Air Brake Systems to do brake performance testing of its tractor-trailer vehicle. The vehicle was supplied by Air Brake Systems for the testing. SwRI did not perform any modifications to the vehicle other than repairs that were absolutely necessary in order to complete the testing. A test plan was developed to evaluate the stopping capability of the vehicle compared to the dynamic stopping requirements specified by FMVSS 121. The stopping tests and evaluations performed are shown in Table 1. Table 1. Test Configuration and Test Matrix Testing Procedure for Air Brake Systems Test Vehicle Number Procedure Test Speed Braking Effort Operating Conditions Result Number of Stops Brake System Configuration Vehicle Weight Burnish 40-20 mph.31 g Stop Monitor Brake Temp Dry Stay below 500 F 500 With MSQR 5000 GVWR 1 Stability 30 mph Full 500 ft radius turn Wet 12 ft lane Stay in Lane (3 times) 4 With MSQR 5000 GVWR 2 Stability 30 mph Best Effort 500 ft radius turn Wet 12 ft lane Stay in Lane (3 times) 2 With MSQR 5000 GVWR 3 Stability 30 mph Full 500 ft radius turn Wet 12 ft lane Stay in Lane (3 times) 4 With MSQR 5000 Empty 4 Stability 30 mph Best Effort 500 ft radius turn Wet 12 ft lane Stay in Lane (3 times) 2 With MSQR 5000 Empty 5 Stability 30 mph Full 500 ft radius turn Wet 12 ft lane Stay in Lane (3 times) 4 Without MSQR 5000 GVWR 6 Stability 30 mph Best Effort 500 ft radius turn Wet 12 ft lane Stay in Lane (3 times) 2 Without MSQR 5000 GVWR 7 Stability 30 mph Full 500 ft radius turn Wet 12 ft lane Stay in Lane (3 times) 4 Without MSQR 5000 Empty 8 Stability 30 mph Best Effort 500 ft radius turn Wet 12 ft lane Stay in Lane (3 times) 2 Without MSQR 5000 Empty 9 Stopping Distance 60 mph Full Dry Stop in 355 ft 6 With MSQR 5000 GVWR 10 Stopping Distance 60 mph Best Effort Dry Stop in 355 ft 6 With MSQR 5000 Empty 11 Stopping Distance 60 mph Full Dry Stop in 355 ft 6 Without MSQR 5000 GVWR 12 Stopping Distance 60 mph Best Effort Dry Stop in 355 ft 6 Without MSQR 5000 Empty 1.1 Vehicle Procurement and Break-in SwRI obtained the 1990 Kenworth T600 tractor/trailer from Air Brake Systems. This vehicle had approximately 552,000 miles on the odometer at the start of the project. The test plan for the vehicle was to leave the tires and brakes in the as received condition to best simulate a typical in-service vehicle with used tires and brakes. Since the vehicle is a used vehicle, no vehicle break-in was required. However, burnishing of the brakes was performed prior to brake performance testing to insure that there was no glazing or other pre-existing conditions of the brake components. 1.2 Vehicle Description The test vehicle is a 1990 Kenworth T600 tractor with a 1984 Trailmobile dry van trailer as shown in Figures 1 and 2 and a description is shown in Table 2. The vehicle is equipped with Air Brake Systems MSQR-5000 brake valve. A diagram and schematic of the MSQR-5000 brake valve is shown in Figure 3. 1 The was converted to the OEM configuration by replacing the MSQR-5000 brake valve shown in Figure 3 with a pipe tee. 1 Information taken from Air Brake Systems web site: www.airbrakes.com 1

Figure 1. Air Brake Systems Test Vehicle, Left View Table 2. Vehicle Description Make Model S/N Trailer Mileage Engine Transmission Rear Axle Brakes Weight Tires 1990 Kenworth T600 Tandem conventional with sleeper 1XLADE9X7LS545471 Dry van/ tandem axle 551,896 (as received) Caterpiller 3176 ATAAC 350 hp Eaton/Fuller 9 speed RT014613 3.70 ratio F23105C Drum, not equipped with electronic anti-lock brakes 80,000 lbs GVWR 11R 24.5 Tractor various brands 11R 22.5 Trailer various brands 2

Figure 2. Air Brake Systems Test Vehicle, Right View 3

Figure 3. MSQR-5000 Diagram and Installation Schematic 4

1.3 Test Plan Development The test plan is based on the dynamic stopping requirements set in FMVSS 121 for vehicles with air system brakes. The dynamic portion of the tests done was done as closely as possible to FMVSS requirements. The stopping tests done are shown in Table 1. 1.4 Vehicle Preparation and Instrumentation Installation Prior to the performance of any testing, SwRI inspected the vehicle for any apparent mechanical problems. During inspection of the brake systems, SwRI found that two of the air hoses connecting the MSQR-5000 system to the rest of the brake system were in need of repair. DOT approved hoses and fittings were used to repair these components. A fifth wheel was installed on the vehicle to measure vehicle speed. A g- meter was installed to assist the driver during the process of burnishing the vehicle brakes. The brake temperatures were evaluated during the brake burnishing using an optical pyrometer rather than using a relatively time consuming and expensive method of installing thermocouples that requires removal of the brake shoes. This procedure was substituted based on SwRI s experience in brake burnishing of heavy vehicles that has historically found that a properly working heavy truck brake system generally maintain an adequate operating temperature throughout the burnishing procedure. SwRI installed 50,000 lbs ballast to the vehicle to bring the weight of the vehicle up to GVWR or 80,000 lbs. Table 3 shows a list of the instrumentation installed on the tractor-trailer. Table 3. Air Brake Systems Truck Instrumentation Instrumentation Measurement Accuracy Optical pyrometer Brake pad temperature Reference only Dayton microwave fifth wheel Speed/ Stopping distance +/-0.5 mph +/- 0.5 feet G-Tech Pro Stopping deceleration rate Reference only 1.5 Brake Burnishing Proper brake system testing requires burnishing of the vehicle brake system shoes. This process is equally critical to achieving accurate and consistent results for new brake systems as it is for brake systems that have been in service for some period of time. In the case of a new brake system, the burnishing procedure breaks in the new brakes and allows the components to properly seat themselves. In the case of vehicle with an older brake system, the shoes can become glazed during heavy or hard stopping which can result in significantly reduced brake performance. The brake burnishing procedure is designed to heat the brake components up and maintain a moderately high temperature during a series of 500 snubs. This process insures that good test results are obtained. The Air Brake Systems vehicle brakes were burnished by making 500 snubs from 40-20 mph at a deceleration rate of 10 ft/sec 2. After approximately 80 snubs were made, 5

one of the trailer brake drums cracked and came apart from the vehicle. Fortunately, there was no additional damage done to the vehicle. The vehicle was taken to a repair facility where SwRI explained the nature and purpose of the testing to the repair facility. SwRI asked for their recommendation as to the proper repair procedure to insure that the vehicle would finish the test. Their findings suggested that all of the drums had considerable heat cracking and could also fail at some unknown time. In addition, the trailer wheel seals were leaking which could damage the brake shoes on the trailer. SwRI contacted Air Brake Systems and obtained permission to repair the vehicle using the repair facilities recommendations. Once the repairs were complete, the burnishing process was restarted. After approximately 1/3 of the snubs had been performed, it became apparent that two of the trailer wheel brakes were not working as well as the rest of the wheel locations and that these brakes were likely out of adjustment. These brakes were readjusted which brought the operating temperatures of these brakes to a level more in line with the rest of the brake locations as allowed by FMVSS 121. In addition, the front wheel seal and or vent showed evidence of leakage. SwRI returned the vehicle to the repair facility where the leaking problem was repaired at no cost to Air Brake Systems. The burnishing procedure was then completed with no additional complications. 1.6 Stopping Test Results Summary The stopping tests were performed in accordance with both the FMVSS 121 recommendations and using the recommended stopping procedure agreed upon with the manufacturer prior to the testing. FMVSS 121 states that the test be performed with the driver applying maximum treadle valve pressure to the system for both the 30 mph wet surface stops and the 60 mph dry surface stops. The manufacture recommends that the driver operate the brake system using a modulated or best effort stop mode. During the wet stops, the tests were performed using both procedures. In the case of the unloaded vehicle stops from 60 mph on dry pavement, the stops were performed only using best effort procedure. The stopping results showed that the vehicle is able to stop from 60 mph within 355 feet on dry pavement per FMVSS 121 requirements for all stops except one. This longer stop occurred from 60 mph with the OEM brake system and with the vehicle empty. FMVSS 121 also requires that the vehicle be able to stop from 30 mph on a wetted surface while negotiating a 500-foot radius curve. FMVSS 121 requires that this stop be made with full treadle application and requires that the vehicle be able to stop within a 12-foot wide lane. Using full treadle application, the vehicle is not able to stay in a 12-foot lane for any of the brake applications. Using the MSQR-5000 manufacture s recommended stopping procedure, the vehicle is able to negotiate the 500-foot radius curve and stay in the 12-foot lane for all of the stops except one case with the OEM brake system. 6

Table 4 shows the stopping results. In most cases, the average stopping distances are within 5% for cases with the OEM brake system compared to the stops with the MSQR-5000 installed. This is within testing repeatability and does not indicate a significant difference between the OEM system and the vehicle with the MSQR-5000 system. The only case where a significant difference in stopping performance or stopping distance is noted was a dry stop from 60 mph with the vehicle empty. In this case, the vehicle with the MSQR-5000 installation stopped in an average distance approximately 13% shorter than the OEM configured vehicle. Table 4. Stopping Results Summary Stop Wet Loaded Full Treadle 30 MPH GVWR Brake Test 1/15/02 OEM Tests Results For Air Brake Systems MSQR-5000 SwRI Project 03.05190 Wet Loaded Best Effort 30 MPH Wet Loaded Full Treadle 30 MPH MSQR-5000 Wet Loaded Best Effort 30 MPH Percentage Difference (positive indicates improvement with MSQR-5000) Wet Loaded Full Wet Loaded Best Treadle Effort 30 30 MPH MPH Stayed In Lane Stayed In Lane Stayed In Lane Stayed In Lane 1.0 75.0 N 80.0 N 84.0 N 80.5-10.7% -0.6% 2.0 68.0 N 87.5 71.0 N 91.0-4.2% -3.8% 3.0 73.0 N 72.0 N 1.4% 4.0 71.5 N 74.0 N -3.4% Avg. 71.9 83.8 75.3 85.8-4.5% -2.3% OEM Highway Loaded 60 MPH Meets FMVSS 121 Stopping Distance Highway Loaded 60 MPH 1.0 288.0 284.4 2.0 305.6 317.5 3.0 339.6 304.0 4.0 325.7 303.0 5.0 331.9 343.7 6.0 290.2 317.2 Avg. 313.5 311.6 MSQR-5000 Meets FMVSS 121 Stopping Distance Highway Loaded Treadle 60 MPH 1.3% -3.7% 11.7% 7.5% -3.4% -8.5% 0.6% Full Wet Unloaded Full Treadle 30 MPH Unloaded Brake Test 1/16/02 OEM Wet Unloaded Best Effort 30 MPH Wet Unloaded Full Treadle 30 MPH MSQR-5000 Wet Unloaded Best Effort 30MPH Wet Unloaded Full Treadle 30 MPH Wet Unloaded Best Effort 30 MPH Stayed In Lane Stayed In Lane Stayed In Lane Stayed In Lane 1.0 152.3 N 155.8 152.0 N 169.3 0.2% -8.0% 2.0 144.6 N 160.5 159.9 N 144.1-9.6% 11.4% 3.0 144.2 N 147.5 N -2.2% 4.0 137.7 N 153.9 N -10.5% Avg. 144.7 158.2 153.3 156.7-5.6% 0.9% Highway Best Effort Unloaded 60 MPH OEM Highway Best Effort Unloaded 60 MPH Meets FMVSS 121 Stopping Distance 1.0 381.6 N 246.7 2.0 318.5 264.1 3.0 273.8 293.3 4.0 264.7 275.1 5.0 314.8 274.7 6.0 252.9 249.5 Avg. 301.1 267.2 MSQR-5000 Meets FMVSS 121 Stopping Distance Highway Best Effort Unloaded 60 MPH 54.7% 20.6% -6.6% -3.8% 14.6% 1.4% 12.7% 1.7 Stopping Distance Testing Loaded to GVWR The stopping distance testing was performed with the vehicle loaded to GVWR and the stop initiated from 60 mph. The test was performed with the MSQR-5000 system installed and with the MSQR-5000 system removed or what is called the OEM 7

configuration. The stopping distance tests were performed on Highway 90 west of San Antonio. This stretch of road has asphalt in good condition, is very flat, and has relatively low traffic volumes. The results showed very little difference in the average stopping distance with and without the MSQR-5000 system. The stopping test was done with full treadle application and met the FMVSS stopping distance requirements for all stops. 1.8 Stopping Stability Testing Loaded to GVWR The stopping stability was performed with the vehicle loaded to GVWR both with the MSQR-5000 installed and with the OEM brake system. The test was performed at an airport facility using the tarmac area of the facility. This is a concrete surface similar in appearance and roughness to an asphalt road. In order to achieve a thoroughly wetted surface, two fire trucks were used to soak the surface between each pass of the vehicle. The vehicle was driven into the 500-foot radius curve set up on the tarmac surface as shown in Figure 4. Once the vehicle entered the curve, the brakes were applied. The first set of stops used a full treadle application per FMVSS 121. These applications result in lockup of the steer axle tires and consequently, the vehicle is not able to negotiate the 500- foot radius curve within a 12-foot wide lane as shown in Figure 5. Figure 4. Vehicle Entering 500-foot radius The second set of stops was made using Air Brake Systems recommend stopping procedure. This procedure required best effort or modulated braking. Using this procedure, the vehicle is able to negotiate the curve for all but one stop with the OEM brake system. Figure 5. Vehicle After Stop 8

1.9 Stopping Distance Testing at Empty Vehicle Weight The stopping distance testing was performed with the vehicle empty and the stop initiated from 60 mph. The test was performed with the MSQR-5000 system installed and with the MSQR-5000 system removed or what is called the OEM configuration. The stopping distance tests performed are the same as those used during the GVWR testing. The stopping test was done with best effort treadle application and met the FMVSS stopping distance requirements for all stops except for one of the OEM brake system stops. These tests found the only significant difference in stopping distances with and without the MSQR-5000 system. In this case, the vehicle with the MSQR-5000 installation is able to stop in an average distance approximately 13% shorter than the OEM configured vehicle. 1.10 Stopping Stability Testing at Empty Vehicle Weight The stopping stability was performed with the vehicle empty both with the MSQR-5000 installed and with the OEM brake system. The test was done at the airport facility using the same test course and the same test procedures as the GVWR testing. The first set of stops used a full treadle application per FMVSS 121. These applications result in lockup of the steer axle tires and consequently, the vehicle is not able to negotiate the 500-foot radius curve within a 12-foot wide lane as shown in Figure 5. The second set of stops was made using Air Brake Systems recommend stopping procedure. This procedure required best effort or modulated braking. Using this procedure, the vehicle is able to negotiate the curve for all cases. 1.11 Conclusion For the straight-line test, results indicate that the vehicle is able to stop from 60 mph on dry pavement within FMVSS 121 required stopping distances with the OEM brake system and with the MSQR-5000 system installed. The stopping distances are generally very similar. The one significant exception is that the empty vehicle with the MSQR- 5000 installed stopped from 60 mph on a dry surface in an average of 13% shorter distance than the OEM equipped vehicle. There was no such difference at GVWR. For the wetted curve test, the vehicle is required by FMVSS 121 to stop from 30 mph on a wetted surface while negotiating a 500-foot radius curve and maintaining itself within in a 12-foot wide lane. When using full treadle brake application per FMVSS 121, the vehicle did not stay in the 12-foot lane. This occurred for the vehicle with and without the MSQR-5000 brake valve at both vehicle weights. 9

Based on the test results and discussions with the manufacturer, SwRI found that the MSQR-5000 system does not function in the same manner as an electronic anti-lock brake system (ABS). With full treadle application, it is possible to cause wheel lockup that results in the vehicle not staying within the 12-foot lane. When using the Air Brake System s MSQR-5000 recommended braking procedure for the wetted surface stops, the vehicle is able to stay in the 12-foot lane. During the stopping testing, the MSQR-5000 system did not significantly increase or decrease vehicle stopping performance. 10