What is the Static Margin?

'What Is' type questions related to highway safety, accident reconstruction and vehicle simulation
brian
Posts: 499
Joined: Tue Jul 14, 2009 10:52 am

What is the Static Margin?

Post by brian »

Q: What is the Static Margin?
A: The Static Margin is defined as the longitudinal distance from the center of gravity (CG) to the neutral steer point divided by the wheelbase.
staticMargin1.jpg
staticMargin1.jpg (19.96 KiB) Viewed 12063 times
It is positive if the CG is forward of the neutral steer point. The neutral steer point is the point at which an external lateral force will produce no steady-state yaw velocity (e.g., see References 1,2 below).
When the neutral steer point is behind the CG, the static margin is positive and the vehicle has understeer cornering characteristics. When the neutral steer point is forward of the CG, the static margin is negative and the vehicle has oversteer characteristics. A neutral steer point at the CG produces a zero static margin and neutral cornering characteristics.
It is defined by the following equation:
staticMargin2.jpg
staticMargin2.jpg (11.64 KiB) Viewed 12062 times
On typical vehicles, the static margin ranges between +0.03 and +0.07 (e.g., Reference 2 )Also see Static Margin in the McHenry Software Getting Started Manual.
The topic is also presented in our book McHenry Accident Reconstruction.
References:
1) Vehicle Dynamics Terminology, SAE J670e.
2) Gillespie, Thomas D., Fundamentals of Vehicle Dynamics, Society of Automotive Engineers, 1992.
Question? Comment? Please email us
MORE TOPICS see:Forum Index & McHenrySoftware.com
(c)McHenry Software, Inc ALL Rights Reserved.