EDR DeltaV - The Effects of Tire Friction
Posted: Wed Jun 08, 2022 3:28 pm
In the most recent Collision Magazine, Volume 16, Issue 1,
- in which we have an article on 109 MPH crash analysis with 3d Simulation
- Event Data Recorder DeltaV: The effect of Tire Friction
- which includes
- "In many EDR reports, the pre-crash deceleration from the bullet vehicle's braking is evident in its pre-crash data. For frontal impacts, the occupant kinematics would only produce greater driver braking, so it is fur co expect similar or greater braking during the impact. For a typical collision duration of 1110th of a second, and with a coefficient of friction or drag factor of 0.75, the /J.V from tire friction is the same as the speed change from skidding over a tenth of second which can be calculated as, 0. 75 * 32.2 fr/sec2* 0.1 sec * 3600 sec/hour/(5280 feet/mile) = 12/2 mph.
While a I½ mph DeltaV might seem insignificant for the analysis of many collisions, in low speed impacts, and situations where there is a large weight difference between the vehicles."
- "In many EDR reports, the pre-crash deceleration from the bullet vehicle's braking is evident in its pre-crash data. For frontal impacts, the occupant kinematics would only produce greater driver braking, so it is fur co expect similar or greater braking during the impact. For a typical collision duration of 1110th of a second, and with a coefficient of friction or drag factor of 0.75, the /J.V from tire friction is the same as the speed change from skidding over a tenth of second which can be calculated as, 0. 75 * 32.2 fr/sec2* 0.1 sec * 3600 sec/hour/(5280 feet/mile) = 12/2 mph.
- In collisions why does Mass1DeltaV1 not always equal Mass2DeltaV2?
which includes:
In A Hurry Executive Summary:- Q: So why do we not always get M1*DeltaV1 = M2*DeltaV2 with msmac3D (and/or comparing EDR data for two collision partners)?
- A: Why? Because of External Forces!
- aka tire forces and other external forces (structures scraping)!
- We have often said
- "The collision between two vehicles is not the same as a collision between two pool balls. More like two crushable rectangular boxes with wheels", with wheels/tires/rims/undercarriage produce external forces with or without braking
- April 2021: We also need to mention "Effective Mass" as another possible explanation for M1DeltaV1 Not Equal M2DeltaV2
- Please see What is the "Effective Mass"?
- April 2021: We also need to mention "Effective Mass" as another possible explanation for M1DeltaV1 Not Equal M2DeltaV2
- See Some Momentum Misconceptions which includes that statement and more issues to consider
- See our SMAC paper from 1973 where we note the importance of including consideration of external forces
- "The collision between two vehicles is not the same as a collision between two pool balls. More like two crushable rectangular boxes with wheels", with wheels/tires/rims/undercarriage produce external forces with or without braking
- A: Why? Because of External Forces!
- Q: So why do we not always get M1*DeltaV1 = M2*DeltaV2 with msmac3D (and/or comparing EDR data for two collision partners)?