Variations in Dynamic Weight Transfer (Nose-Dive)

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Variations in Dynamic Weight Transfer (Nose-Dive)

Postby brian » Mon Oct 25, 2010 4:52 pm

Q: Papers/research on Variations in Dynamic Weight Transfer (Nose-Dive) Between Wet & Dry Conditions?

The following is dry braking only and for only 3 vehicles, but can add to yourinformation database.
SAE paper 2006-01-1563 "Quantifying the Change in Ride Height Due to Braking: Brake Dive Test Data", Shawn P. Ray, Trevor M. Newbery and John A. Koziol
ABSTRACT
    The concept of brake dive is not new and most drivers are aware of this phenomenon. However, no known data is available to quantify the amount of change in vehicle height during braking. Often investigators involved in under-ride/over-ride collisions or relatively low speed collisions are faced with questions such as, "How much does the front bumper dip during braking?" or, "Is it likely that the relative bumper height mismatch is due to preimpact braking?" This paper will provide the results of field testing aimed at providing answers to these and associated questions. The study will also review the factors that affect brake dive and the parameters under which these factors can be determined or be reasonably estimated. We consider how these factors can be used to predict the amount of change in bumper height.
VEHICLES TESTED
    COMPACT CAR
    2005 Toyota Matrix XR, front wheel drive, 4-door hatchback, 4-cylinder, 1.8 liter engine, automatic transmission. This vehicle was not equipped with antilock (ABS) braking.
    MID-SIZE CAR
    2005 Chrysler Sebring LX, front wheel drive, 4-door sedan, 4-cylinder, 2.4 liter engine and automatic transmission. This vehicle was not equipped with antilock (ABS) braking.
    SUV
    2005 Ford Explorer XLT, four wheel drive, 4-door, sport utility, 6-cylinder, 4.0 liter engine and automatic transmission. This vehicle was equipped with 4-wheel anti-lock (ABS) braking.

SUMMARY
    The Toyota Matrix brake dive plateau is approximately 2 inches and the average maximum is approximately 2.8 inches.
    The Chrysler Sebring brake dive plateau is approximately 2.3 inches and the average maximum is approximately 3.9 inches.
    The Ford Explorer brake dive plateau is approximately 2.5 inches (variable with ABS active) and the average maximum is approximately 3.8 inches.
CONCLUSION
    The maximum brake dive of the selected vehicles varied from 2.3 inches (5.8 cm) to 4.3 inches (10.9 cm). The tests also indicate that the amount of brake dive is relatively independent of the initial speed.
    In non-ABS equipped vehicles, during the latter stages of braking, after the car enters a skid, the change in bumper height leveled off to a brake dive plateau of constant value. This value was less than the initial peak brake dive
PLEASE NOTE: In the following charts, The total time of each plot is different. The actual shape of the response is similar, the non-ABS has a flatter plateau
brake dive time histories.jpg
brake dive time histories.jpg (29.54 KiB) Viewed 1066 times
brake dive TH 2.jpg
brake dive TH 2.jpg (29.87 KiB) Viewed 1066 times
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brian
 
Posts: 498
Joined: Tue Jul 14, 2009 10:52 am

Re: Variations in Dynamic Weight Transfer (Nose-Dive)

Postby brian » Mon Oct 25, 2010 5:12 pm

From [url=http://www.aafs.org/proceedings[AAFS Annual Meeting Proceedings[/url] in 2008 in Washington, DC/Volume 14 Paper C9 Motor Vehicle Pitch Associated With Hard Brake Application by Anderson

    The purpose of this study is to provide empirical data regarding vehicle pitch and the resultant change in bumper height during hard braking. Seven vehicles representing most passenger vehicle types were selected for this study.
    Data was collected while each vehicle underwent hard acceleration to at least 40 mph, maintaining that speed for a few seconds, and then hard braking to a stop. A Racelogic VBOX III, a GPS based system, was used to collect longitudinal acceleration data. In addition, the VBOX III was used to collect data from external sensors for brake pedal force, vehicle pitch rate and bumper height.
    The front bumper dip ranged between 2.2 and 3.9 inches for all the vehicles, with the exception of the Toyota Sequoia whose front bumper dipped down 4.4 inches.
    The rise in rear bumper height for most vehicles ranged between 3.9 and 4.3 inches. However, the Toyota Sequoia, a large SUV, exhibited a rise in rear bumper height of 6.1 inches, and the Honda Civic, a small passenger vehicle, exhibited a rise in rear bumper height of only 2.1 inches. Data loss precluded collection of rear bumper height data during testing of the Dodge Caravan and the Toyota Tacoma.
See 2008 SATAI proceedings Paper number C9 Motor Vehicle Pitch Associated With Hard Brake Application
bumper dive.jpg
bumper dive.jpg (29.26 KiB) Viewed 1072 times
av decel for dive tests.jpg
av decel for dive tests.jpg (37.36 KiB) Viewed 1072 times
Question? Comment? Please email forum@mchenrysoftware.com. Also see the McHenry Forum Index
Visit McHenrySoftware.com for technical information & software. McHenryConsultants.com for litigation consulting.
(c) McHenry Software, Inc ALL Rights Reserved.
brian
 
Posts: 498
Joined: Tue Jul 14, 2009 10:52 am


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