ACTAR Vehicle Dynamics 3

Question 1

What is the 'center of gravity height' effect on rollover threshold?

Accepted Answer

Higher CG lowers the rollover threshold, making rollover more likely at lower lateral accelerations

Answer

A higher center of gravity increases the overturning moment relative to the stabilizing moment, reducing the lateral acceleration needed to initiate rollover.

Question 2

What is the significance of the 'static stability factor' (SSF) in rollover analysis?

Accepted Answer

SSF = track width / (2 × CG height); higher SSF means greater rollover resistance

Answer

The Static Stability Factor equals half the track width divided by the CG height; a higher ratio indicates the vehicle can sustain greater lateral acceleration before rolling over.

Question 3

How does 'load transfer ratio' (LTR) differ from static stability factor in rollover analysis?

Accepted Answer

LTR is a dynamic measure using actual wheel loads during a maneuver, while SSF is a static geometric ratio

Answer

LTR uses the actual difference in wheel normal forces during a dynamic event (LTR = (F_right - F_left)/F_total), making it a real-time dynamic measure versus SSF's static geometric estimate.

Question 4

What is 'dwell time' in steering input analysis and why is it relevant to crash reconstruction?

Accepted Answer

The duration a steering wheel is held at a particular angle before being returned or reversed

Answer

Dwell time is how long a driver maintains a steering angle, which affects the magnitude of lateral displacement achieved and can indicate intentional versus panic steering.

Question 5

A vehicle with a wheelbase of 110 inches has its CG located 48 inches behind the front axle. What percentage of vehicle weight is on the front axle (static)?

Accepted Answer

56.4%

Answer

Front axle load % = (distance from CG to rear axle / wheelbase) × 100 = (110−48)/110 × 100 = 62/110 × 100 ≈ 56.4%.

(ACTAR) Accreditation Commission for Traffic Accident Reconstructionist Practice Test

(ACTAR) Accreditation Commission for Traffic Accident Reconstructionist Practice Test

ACTAR Vehicle Dynamics 3