Vehicle Dynamics Basics
Vehicle dynamics (two words often used in EVOC) is the application of the laws of physics to a vehicle in motion. That vehicle can be a fighter jet, train, or a horse drawn cart. In our case it is a vehicle with four rubber tires or two or as in some training I have done 18 rubber tires. The basic principals are the same no matter how many tires are attached to the vehicles. Hence when driving through cones, around corners, or trying not to hit something the vehicle / driver combination must operate within the laws of physics and specifically within Sir Isaac Newton's three laws of motion. Most people shy away from using the laws of motion as a training tool because of the math. For most people their only exposure to the laws of physics is what they were taught in high school. With all due respect to high schools the subject is mired in books and seems to have no practical value. For those who are math challenged, once the theory is explained in English versus engineer talk, and they turn a classroom discussion into hands on practical scenarios, it is amazing how all that math actually makes sense. All driving scenarios, no matter how simple or complex, are an exercise in the laws of physics. Integrating Vehicle dynamics into your program is one of those things that does not take up time or cost money.
Newton’s 3rd Law of Motion
Remember from high school for every action there is an opposite and equal reaction? So if there is a force pushing on the Center of Gravity (CG) of the vehicle, there has to be an equal and opposite force pushing back. That force pushing back is created by the friction the tires make with the road and it makes no difference if there is 2, 4 or 18 tires. When the student turns the steering wheel to maneuver through an exercise - any exercise - there is energy pushing on the CG of the vehicle. The amount of energy is determined by how much the student moves the steering wheel and how fast they are traveling. The more speed and the more steering the more energy pushing on the vehicle. Refer to the article YOUR CAR IS TALKING TO YOU - LISTEN for more in depth information. (linked below)
Vehicle Dynamics and the Slalom
If there is one exercise that appears in most all EVOC programs it would be the slalom, and it is a good starting point to talk about vehicle dynamics. The slalom is Newton's 3rd law of motion at work.
As mentioned above every time the student moves the steering wheel at a speed there is a force pushing on the CG of the vehicle. In a four cone slalom with the cones separated by 60 feet, if the student drives through correctly they are changing those forces acting on the vehicle 3 times, and doing it in a short period of time. At the higher speeds the force pushing on the vehicle is changing from side to side approximately every second.
Staying with the four cone slalom, at the 3rd and 4th cone, as the vehicle approaches the limit it will be either understeering or oversteering. This is Newton talking to the student; Sir Isaac is telling them what they have to do next, but since he has been dead for 280 years you should be telling the student they need to recognize the warning signs of under and over steer. They need to stay within their limits or the limits of the vehicle.
Weight transfer
As the speed increases there will be a great deal of weight transferred to the outside front tire. The car will exhibit body lean as it is driven through the slalom course. How much weight? This is a visual example of the 3rd law in action. At the 3rd and 4th cone the outside tires at the higher speeds may be stressed to the point where they're very nearly riding on their rims.
At higher speeds at the 3rd and 4th cone the 3rd law is working overtime. During the turns (and in the slalom there's virtually nothing but turns) the outside front tire is losing its adhesion to the point of becoming ineffective, while the other front tire is being lifted nearly off the ground making it close to useless. This scenario will cause a tremendous amount of understeer, this is the place in the program to have the students see and feel the laws of motion at work.
Some other slalom talking points
Explain to the student that the force on the vehicle is generated by a combination of speed and steering. If they apply too much speed or too much steering the result is under or over steer.
As speed increases, the students will notice a big difference in how the car reacts to their inputs. The steering wheel becomes very sensitive. When a student gets to the limit, small changes in steering or speed create big changes in the way the vehicle responds. Make the point that the steering wheel and the gas pedal are connected. How much you can turn the steering wheel depends on how much gas you have applied. Refer to the article USING THE VEHICLE - for more in depth information.
Focus on the path you want the car to take - don't focus on the cones. In the real world in an emergency you have to focus on where you want the car to go - not the object that is in our path. Look where you want to go. Your hands will follow where your eyes look. If you look at the cone you will hit it.
If the student makes a mistake at cone one they pay for it at cone three. Real world is that you don't pay for your mistake where you make the mistake, you pay for it later.
Any questions or comments please feel free to contact me
