Rudy,

I have a copy of the second edition of your book "Motor Vehicle Accident Reconstruction and Cause Analysis". On page 352, there is an equation for calculating the lateral acceleration of a tractor trailer at rollover. In this equation, the constant 0.1 is used in two places. I am unable to determine where this value comes from and whether it is an empirical value or not. I understand that the same equation is present in the 3rd and 4th editions. Can you provide me with any insight regarding the derivation of this equation?

Also, I attempted to work my way through example 22.6, but when I substituted the values into equation 22.58, I could not get the same results as you published. I understand that this example was dropped from the 4th edition. Can you tell me if there is a typographical error in either the equation or the example?

Thank you for your assistance.

Jonathan,

the equation on page 352 of the 2nd edition does not include the effects of the tractor trying to keep the trailer from rolling over. In the 4th edition the equation was changed to include the tractor. Hence, example 22.6 was dropped. The 5th edition was published in 1999. A complete explanation of the constant 0.1 may be too difficult to accompish via the discussion forum. In short, it takes care of the change of the center-of-gravity location reducing the rollover moment, and also reducing the stabilizing moment. Please, e-mail me your address so that I can mail the derivation and the complete equation.

PCB 11-2006 will discuss, among other subjects, tractor/trailer rollover with MARC1 application.
Please, down load it. It should be up on our website
by September 11, 2006. If you want to call, please do so on my cell phone 801-201-2532.

Thanks, Rudy Limpert