A: Your question brings up a topic which has made the rounds over the years:
Why doesn’t someone write a program that uses negative friction?
So it backs up from rest to impact?
Well that hasn’t been done yet. That would be a separate discussion.
But
what you ask about is a Trajectory Solutions Procedure. And as part of our research we have used two different approaches: A Trajectory Analysis Approximation and Simulation.
- Trajectory Analysis Approximation:
- One uses the vehicle properties, drag, impact/separation position and rest positions and approximates the speed required for a vehicle to travel the distance and direction from separation to rest.
In the CRASH program you will find work my father, Ray McHenry, did on refinement of the Marquard relationships included clarification and generalization to include partially locked vehicles, to accommodate curved paths and accommodating residual linear velocity at the end of rotation, etc. for approximating vehicle separation speeds in a collision.
- A write up of the work he performed is contained in the NHTSA CRASH3 Manual (see section 2 page 55 etc.).
- We also include some pages on Trajectory Analysis from our book McHenry Accident Reconstruction.
- We include the conclusions from our 1981 study:
National Crash Severity Study--Quality Control, Task 5. Analysis to Refine Spinout Aspects of CRASH", NTIS Publication No. PB-81-180507 as part of the thread discussion of SPIN.- "To achieve a general improvement in the reliability and accuracy of approximations of the angular and linear velocities at separation, a step-by-step time history form of trajectory solution should be implemented."
- 1997 research CRASH-97 - Refinement of the Trajectory Solution Procedure, SAE Paper No. 97-0949 and our
- 2003 research SMAC2003- The Automatic Iteration of SMAC.
- One uses the vehicle properties, drag, impact/separation position and rest positions and approximates the speed required for a vehicle to travel the distance and direction from separation to rest.