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RESEARCH - Vehicle Performance

Acceleration Testing of a 2016 Freightliner Cascadia with Automated Manual Transmission in Auto Mode
SAE Paper Number 2017-01-1418 Authors: Wesley D. Grimes, Thomas H. Vadnais, and Gregory A. Wilcoxson

The time/distance relationship for a heavy truck accelerating from a stop is often needed to accurately assess the events leading up to a collision. Several series of tests were conducted to document the low speed acceleration performance of a 2016 Freightliner Cascadia truck tractor equipped with an automated manual transmission in Auto Mode. Unlike the tests in previous papers, the driver never manually shifted gears. These tests included three trailer load configurations and two different acceleration rates. Data were gathered with both a VBOX and with the Detroit Diesel Diagnostic Link (DDDL) software. Results from both data acquisition systems were compared.

Acceleration Testing of a 2016 Kenworth T680 with Automated Manual Transmission in Auto Mode
SAE Paper Number 2017-01-1418 Authors: Wesley D. Grimes, Thomas H. Vadnais, and Gregory A. Wilcoxson

The time/distance relationship for a heavy truck accelerating from a stop is often needed to accurately assess the events leading up to a collision. Several series of tests were conducted to document the low speed acceleration performance of a 2016 Kenworth T680 truck tractor equipped with an automated manual transmission in Auto Mode. Unlike the tests in previous papers, the driver never manually shifted gears. These tests included three trailer load configurations and two different acceleration rates. Data were gathered with both a VBOX and with the Cummins Insite software. Results from both data acquisition systems were compared.

Updated Heavy Truck Air Chamber Force Data Charts
Accident Reconstruction Journal,  Nov/Dec 2016 Authors: Wesley D. Grimes, P.E. and Ronald B. Heusser

In the early 1990s Heusser published a paper describing the calculation methodology which would yield the approximate deceleration rate  for a heavy truck or tractor-trailer equipped with an air-brake system.  The equations and work-flow published required the analyst to utilize the pushrod force for the specific air chamber, based on the pushrod stroke and air pressure applied.  The pressure/stroke/pushrod force charts were published and were used in several spreadsheet solutions and computer programs publicly available.  These charts were an average set of data obtained from several air chamber manufacturers.  The manufacturers agreed to provide the data and allow it to be published as long as all the data was averaged and could not be associated with any particular manufacturer.

In the early 2000s air chamber manufacturers produced updated pressure/stroke/pushrod force data, which was again averaged between the different manufacturers. The data were assembled in a manner similar to the original data produced in the 1990s. At a later time a group of individuals also produced data for the Type-18 chambers which are commonly used with air-disc brake systems(2). Many analysts have had access to this data for several years, but it has come to our attention that the updated charts may not be known to some reconstructionists. That is the purpose of this article. Charts and tables for all of the updated data are included. When comparing this data to the earlier data it is clear that data around the ‘knee’ of the charts have slightly changed. It is unknown why this data has changed, whether from an update in the design, materials, manufacturing process, updated testing devices, or for some other reason. The authors feel that this updated data is the most accurate data for the majority of the vehicles on the road today.

Heavy Truck Brake Designer Validation Testing
EDC WP #2005-2 Authors: Thomas H. Vadnais, P.E. and Wesley D. Grimes, P.E.

In late August 2004, a week-long series of well-documented heavy truck braking tests was conducted at Transportation Research Center (TRC) in East Liberty, OH. Using the same tractor and flatbed semi-trailer, tests were performed with and without ABS, on wet and dry surfaces, loaded and unloaded, and at both 30 and 60 mph. Additional tests were done with the semi-trailer's ABS disabled, with only the tractor's ABS system cross-wired, with some of the tractor and trailer brakes out of adjustment, and with the bobtail tractor alone. Both the tractor and semi-trailer were documented to allow creation of an accurate HVE vehicle model, including all brake components. For this initial paper, SIMON runs, using the Brake Designer, were made of several actual test runs to validate the software against the actual test data. These were compared to similar simulations using generic vehicles. For this paper, only loaded, non-ABS, 60 mph tests were modeled, with all brakes in adjustment, and some out of adjustment.

Low-Speed Acceleration of a Kenworth T2000 Tractor-Truck with Autoshift Transmission
SAE Paper No. 2000-01-0470 Authors: Wesley D. Grimes and Charles P. Dickerson

The time/distance relationship for a heavy truck starting from a stopped position is often needed to accurately assess the events leading up to a collision. A series of tests were conducted to document the low speed acceleration performance of a Kenworth T2000 tractor- truck equipped with an auto-shift transmission. The tests included several load configurations and acceleration rates. The vehicle was instrumented with a DATRON speed sensor to measure time, distance and speed. This paper presents data from these tests and discusses low speed acceleration profiles of heavy trucks.

Vehicle Handling with Tire Tread Separation
SAE Paper No. 1999-01-0120 and 1999-01-0450 Authors: Charles P. Dickerson, Mark W. Arndt, and Stephen M. Arndt

Catastrophic and sudden tire tread separation is an event that drivers of motor vehicles may encounter and, in some instances, is implicated as the cause of motor vehicle crashes and related injury or property damage. In an effort to understand how tire tread separation affects vehicle handling, a series of tread separation handling test programs were conducted. In each tread separation test program a sport utility vehicle was instrumented and equipped with steel belted radial tires that were modified to emulate tread separation between the inner and outer steel belts. The test vehicle was then subjected to a variety of open and closed loop handling test maneuvers. This paper presents the data and analysis from these tests. The research demonstrates through controlled experiments that a tire tread separation has an effect on the vehicle's fundamental handling characteristics. It also demonstrates that the effect depends on the position of the compromised tire on the vehicle.

Low Speed Acceleration of the Freightliner FLD-120 Tractor Truck
SAE Paper No. 1999-01-0092 Authors: Wesley D. Grimes and Charles P. Dickerson

The time/distance relationship for a heavy truck starting from a stopped position is often needed to accurately assess the events leading up to a collision. A series of tests were conducted to document the low speed acceleration performance of a Freightliner FLD-120 tractor- truck. The tests including several load configurations and acceleration rates. The vehicle was instrumented with a DATRON speed sensor and the engine RPM was also documented. This paper presents data from these tests and discusses low speed acceleration profiles of heavy trucks.

Low Speed Acceleration of the Kenworth T600 Tractor Truck
SAE Paper No. 980366 Authors: Wesley Grimes and Charles Dickerson

The time/distance relationship for heavy trucks starting from a stopped position is often needed to accurately assess the events leading up to a collision. A series of tests were conducted to document tractor/trailer low speed acceleration performance. The vehicles were instrumented with a DATRON speed sensor and engine RPM was also documented. This paper presents the data from these tests and discusses the acceleration profile of heavy trucks in general.

Effects of Passenger and Cargo Loading on a Motor Vehicle's Mass Properties
SAE Paper No. 952676 Authors: Mark W. Arndt, Charles P. Dickerson, Stephen M. Arndt, Gregory A. Mowry, and Steven C. Shapiro

Vehicles may be loaded with passengers and cargo in varying configurations that affect its mass properties during normal use. Mass properties include CG location, weight, and mass moments of inertia. The objective of this paper is to develop an approach identifying possible passenger and cargo load configurations and accurately calculate and display their effect on a motor vehicle's mass properties. An approach is presented and discussed. The calculation method accounts for suspension compliance due to passenger and cargo loading. Overall, the approach provides more accurate and useful estimates of a motor vehicle's CG location and other mass properties. The approach may be of use to vehicle designers, operators, and regulators, providing enhanced access to vehicle parameters which are relevant to motor vehicle safety.

Motor Vehicle Mass Property Envelopes
SAE Paper No. 951065 Authors: Mark W. Arndt, Charles P. Dickerson, Gregory A. Mowry, Stephen M. Arndt, and Steven C. Shapiro

A vehicle may be loaded in varying configurations that affect its mass properties during normal use. These properties include total mass, center-of-gravity (Cg) location, and moments of inertia. The ranges of these parameters, which are determined by the varied load configurations, define the vehicle's mass property envelopes. These envelopes are useful for evaluating the effect of any load configuration relative to vehicle performance/design specifications. Mass property envelopes provide a clear visual representation of a range of key parameters that significantly affect motor vehicle control. Examples are provided in this paper that illustrate the usefulness of the vehicle mass property envelopes.

Analysis of Acceleration in Passenger Cars and Heavy Trucks
SAE Paper No. 950136 Authors: Charles L. Proctor, II, Wesley D. Grimes, Donald J. Fournier, Jr., John Rigol, Jr. and Michael G. Sunseri

When analyzing the time/distance performance of vehicles accelerating from a stopped position, a constant acceleration rate is often assumed. Acceleration profiles as a function of time are examined in this paper in order to identify errors associated with the constant acceleration assumption for a passenger car and a large truck. The paper also includes acceleration data collected from 219 large trucks measured over distances of 50 and 100 feet. For passenger cars, the assumption of constant acceleration is appropriate when evaluating velocity/distance scenarios with displacements of interest greater than 10 ft. For 5 ft or less, variable acceleration is recommended. When time factors are of special interest, attention must be given to the lag times associated with variable acceleration. The lag time does little to affect the velocity/distance relationship; however, it alters time/distance/velocity relationship by as much as 2 seconds. For heavy trucks, a speed surge is seen immediately before shifting from 2nd to 3rd gear, but due to the low acceleration values, little impact is seen in the time/distance profile. The constant acceleration assumption for heavy trucks appears valid for situations where the driver is shifting. In these tests the approximate constant acceleration was 0.07 g's. When the driver of a heavy truck does not shift, the transmission gearing as well as the weight of the load is important in determining the acceleration of the vehicle. When a heavy truck is not shifted, using constant acceleration 0.05 g's usually under-estimates the distance traveled in the 4-8 second range and over-estimates the distance traveled after 8 seconds. Based on the time and distance measurements for the 219 trucks, calculated average accelerations were 0.085, 0.106, and 0.138 g's over the first 50 ft for the flatbed, box, and bobtail configurations, respectively. Over a distance of 100 ft, the average accelerations were somewhat lower: 0.064, 0.073, and 0.118 g's for the flatbed, box, and bobtail configurations, respectively.

 

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