Performance-based Brake Testers PDF Download
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Author: United States. Federal Highway Administration. Office of Motor Carriers
Publisher:
ISBN:
Category : Motor vehicles
Languages : en
Pages :
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Book Description
This report documents the results of a series of tests in which several different types of performance-based brake testers (PBBTs) were compared side-by-side (i.e. a round robin test) in their ability to accurately measure brake forces (BFs) and wheel loads (WLs) of commercial vehicles (CVs), and to then predict the vehicle deceleration capability for a 32.2 km/hr on-road stopping test. The PBBTs consisted of five roller dynamometers (RD), two flat plate (FP) testers, and one breakaway torque tester (BTT). A PBBT that can also meet a set of functional specifications could be used for law enforcement by safety inspectors once performance-based criteria are codified. In the test program, specific ratios of BF to WL were imposed on both a 5-axle combination tractor semi-trailer and a two-axle straight truck, in both the fully laden and unladen conditions. In each loading condition, the overall vehicle braking capability was set to achieve a proposed minimum requirement of 0.4g, where g is the acceleration due to gravity. In addition, the brakes on specific individual wheels were set to provide a BF/WL of 0.25 and 0.35, for a steer and a non-steer wheel, respectively. The vehicles were also instrumented to record stopping distances and decelerations from on-road stopping tests performed from 32.2 km/hr. In general, nearly all of the PBBTs were able to accurately measure the CVs' brake forces. Only one of the FP-type testers experienced erratic performance during the round robin. In contrast several of the PBBTs had difficulty in reporting the accurate gross vehicle weight. In some cases, particularly with the portable PBBTs the reported wheel loads for axles 2 and 4 (the lead axle on the tandem set) of the 5-axle vehicle were very high, leading to an under-prediction of the vehicle deceleration capability. Calibration checks of the PBBT weighing mechanisms indicated that all could meet the functional specifications. As such, it was concluded that accounting for the redistribution of axle loads due to the vehicle suspension and the geometry of the PBBT ramp would require special test procedures or remote entry of vehicle or axle weights for use in law enforcement. The repeatability of all the PBBTs was good, meeting the acceptability criteria in more than 93 percent of the test cases.
Author: United States. Federal Highway Administration. Office of Motor Carriers
Publisher:
ISBN:
Category : Motor vehicles
Languages : en
Pages :
Get Book Here
Book Description
This report documents the results of a series of tests in which several different types of performance-based brake testers (PBBTs) were compared side-by-side (i.e. a round robin test) in their ability to accurately measure brake forces (BFs) and wheel loads (WLs) of commercial vehicles (CVs), and to then predict the vehicle deceleration capability for a 32.2 km/hr on-road stopping test. The PBBTs consisted of five roller dynamometers (RD), two flat plate (FP) testers, and one breakaway torque tester (BTT). A PBBT that can also meet a set of functional specifications could be used for law enforcement by safety inspectors once performance-based criteria are codified. In the test program, specific ratios of BF to WL were imposed on both a 5-axle combination tractor semi-trailer and a two-axle straight truck, in both the fully laden and unladen conditions. In each loading condition, the overall vehicle braking capability was set to achieve a proposed minimum requirement of 0.4g, where g is the acceleration due to gravity. In addition, the brakes on specific individual wheels were set to provide a BF/WL of 0.25 and 0.35, for a steer and a non-steer wheel, respectively. The vehicles were also instrumented to record stopping distances and decelerations from on-road stopping tests performed from 32.2 km/hr. In general, nearly all of the PBBTs were able to accurately measure the CVs' brake forces. Only one of the FP-type testers experienced erratic performance during the round robin. In contrast several of the PBBTs had difficulty in reporting the accurate gross vehicle weight. In some cases, particularly with the portable PBBTs the reported wheel loads for axles 2 and 4 (the lead axle on the tandem set) of the 5-axle vehicle were very high, leading to an under-prediction of the vehicle deceleration capability. Calibration checks of the PBBT weighing mechanisms indicated that all could meet the functional specifications. As such, it was concluded that accounting for the redistribution of axle loads due to the vehicle suspension and the geometry of the PBBT ramp would require special test procedures or remote entry of vehicle or axle weights for use in law enforcement. The repeatability of all the PBBTs was good, meeting the acceptability criteria in more than 93 percent of the test cases.
Author: Steven J. Shaffer
Publisher:
ISBN:
Category :
Languages : en
Pages : 134
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Author:
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Category : Trucks
Languages : en
Pages : 4
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Author:
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Category : Administrative law
Languages : en
Pages : 1262
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Author:
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Category : Highway research
Languages : en
Pages : 904
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Author:
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ISBN:
Category : Technology & Engineering
Languages : en
Pages : 248
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ISBN:
Category : Traffic safety
Languages : en
Pages :
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Author: Richard W. Radlinski
Publisher:
ISBN:
Category : Air-brakes
Languages : en
Pages : 46
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Author:
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Category :
Languages : en
Pages :
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This proof-of-concept research was performed to explore the feasibility of using real-world braking data from commercial motor vehicles to make a diagnosis of brake condition similar to that of the performance-based brake tester (PBBT). This was done by determining the relationship between pressure and brake force (P-BF), compensating for the gross vehicle weight (GVW). The nature of this P-BF relationship (e.g., low braking force for a given brake application pressure) may indicate brake system problems. In order to determine the relationship between brake force and brake application pressure, a few key parameters of duty cycle information were collected. Because braking events are often brief, spanning only a few seconds, a sample rate of 10 Hz was needed. The algorithm under development required brake application pressure and speed (from which deceleration was calculated). Accurate weight estimation was also needed to properly derive the braking force from the deceleration. In order to ensure that braking force was the predominant factor in deceleration for the segments of data used in analysis, the data was screened for grade as well. Also, the analysis needed to be based on pressures above the crack pressure. The crack pressure is the pressure below which the individual brakes are not applied due the nature of the mechanical system. This value, which may vary somewhat from one wheel end to another, is approximately 10 psi. Therefore, only pressures 15 psi and above were used in the analysis. The Department of Energy s Medium Truck Duty Cycle research has indicated that under the real-world circumstances of the test vehicle brake pressures of up to approximately 30 psi can be expected. Several different types of data were collected during the testing task of this project. Constant-pressure stopping tests were conducted at several combinations of brake application pressure (15, 20, 25, and 30 psi), load conditions (moderately and fully laden), and speeds (20 and 30 mph). Data was collected at 10 Hz. Standard and stepped-pressure performance-based brake tests with brake pressure transducers were performed for each loading condition. The stepped-pressure test included the constant-pressure intervals of brake application at 15, 20, 25, and 30 psi. The PBBT data files included 10 Hz streaming data collected during the testing of each axle. Two weeks of real-world duty cycle (driving and braking) data was also collected at 10 Hz. Initial analysis of the data revealed that the data collected in the field (i.e., day-to-day operations) provided the same information as that obtained from the controlled tests. Analysis of the data collected revealed a strong linear relationship between brake application pressure and deceleration for given GVWs. As anticipated, initial speed was not found to be a significant factor in the deceleration-pressure relationship, unlike GVW. The positive results obtained from this proof of concept test point to the need for further research to expand this concept. A second phase should include testing over a wider range of speeds and include medium brake application pressures in addition to the low pressures tested in this research. Testing on multiple vehicles would also be of value. This future phase should involve testing to determine how degradation of braking performance affects the pressure-deceleration relationship.
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Category :
Languages : en
Pages :
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The Federal Motor Carrier Safety Administration, in coordination with the Federal Highway Administration, sponsored the Heavy and Overweight Vehicle Brake Testing (HOVBT) program in order to provide information about the effect of gross vehicle weight (GVW) on braking performance. Because the Federal Motor Carrier Safety Regulations limit the number of braking system defects that may exist for a vehicle to be allowed to operate on the roadways, the examination of the effect of brake defects on brake performance for increased loads is also relevant. The HOVBT program seeks to provide relevant information to policy makers responsible for establishing load limits, beginning with providing test data for a combination tractor/trailer. This testing was conducted on a five-axle combination vehicle with tractor brakes meeting the Reduced Stopping Distance requirement rulemaking. This report provides a summary of the testing activities, the results of various analyses of the data, and recommendations for future research. Following a complete brake rebuild, instrumentation, and brake burnish, stopping tests were performed from 20 and 40 mph with various brake application pressures (15 psi, 25 psi, 35 psi, 45 psi, 55 psi, and full system pressure). These tests were conducted for various brake conditions at the following GVWs: 60,000, 80,000, 91,000, 97,000, 106,000, and 116,000 lb. The 80,000-lb GVWs included both balanced and unbalanced loads. The condition of the braking system was also varied. To introduce these defects, brakes (none, forward drive axle, or rear trailer axle) were made inoperative. In addition to the stopping tests, performance-based brake tests were conducted for the various loading and brake conditions. Analysis of the stopping test data showed the stopping distance to increase with load (as expected) and also showed that more braking force was generated by the drive axle brakes than the trailer axle brakes. The constant-pressure stopping test data revealed a linear relationship between brake application pressure and was used to develop an algorithm to normalize stopping data for weight and initial speed.
