For decades our mantra has been, “When Stuff Happens, You Can’t Be Average.” This is the first in a series of articles that will cover that moment in time “When Stuff Happens.”
Former Vehicle Dynamics Institute (VDI) or (if you are up in age) Scotti School students know that the Scotti School was and VDI is anal about training our students to maximize the capability of their vehicles. To pass the VDI course or to be certified as an ISDA security driver, a driver must use a minimum of 80% of the vehicle’s capability. We ensure the 80% standard by measuring the amount of G’s a driver applies to the vehicle. We spend hours training students to use every tenth of a G the vehicle has to offer. Why? The simple scientific fact is that every tenth of a G that VDI can train a driver to use significantly adds to their survivability when stuff happens.
We are starting off the “When Stuff Happens” series by explaining the effect g-forces have on the driver, the principal, and the vehicle.
Safety/Security and the Concept of G’s
Anytime the steering wheel is moved while the car is in motion, a lateral or sideways force is created. This force is pushing in the direction opposite to the way the car is turning.
The unit used to measure that force is G’s. It is this force that determines whether a driver can stay in control of their vehicle. A tenth of a G can make the difference between hitting the car in front of you or driving around the car in front of you.
This is how it works. If the path of a 4,000-lb. car is altered in a way that produces a single G, that g-force is equivalent to 4,000 lbs. of force pushing the car away from its desired path. The equation for computing this force is simple. The amount of force pushing on the car is equal to the G’s times the weight of the vehicle. So a 4000-lb. car with 1 G applied would be 4000 lbs. x 1G = 4000 lbs. pushing on the vehicle’s center of gravity (CG).
If we turned the same 4,000-lb. car in such a way that .7G was created, then we would have 2,800 lbs. of force (4,000 x .7 G’s = 2,800 lbs.) pushing on the vehicle’s CG. If the car weighed 3,000 lbs. and was turned the same way, the equation would read 3,000 lbs. x .7 G’s = 2,100 lbs., and so forth. Understand that the lateral g-forces created in a turn are based upon both the vehicle’s weight and how much the steering wheel is moved or the degree, or sharpness, of the turn. When you think about it, it is common sense—the faster you go, and the more you turn the steering wheel, the more force is added to the car.
G’S x WEIGHT OF CAR = HOW MUCH WEIGHT IS PUSHING ON THE CAR
A CAR WEIGHS 4000 LBS.
1 G = 4000 LB. PUSHING ON THE CAR
.8 G’s = 3200 LBS. PUSHING ON THE CAR (4000 x .8 =3200)
.6 G’s = 2400 LBS. (4000 x .6 = 2400)
.4 G’s = 1600 LBS. (4000 x .4 = 1600)
We, and everybody else on the planet who is serious about their training, use G’s as a measure of driving skills and a method of testing.
As we mentioned, a tenth of a G could mean the difference between surviving and not surviving.
Here is an example:
Scenario 1 – If someone is traveling 40 mph in a driver/vehicle combination that can handle .875 G’s, they would need approximately 49 feet of distance to clear a barrier that is 10 feet wide.
Scenario 2 – With all the parameters the same as above, such as vehicle position and speed (40 mph) but now with a driver/vehicle combination that can handle only .4 G’s, they would need approximately 72 feet of distance to clear the same barrier, any distance less than 72 feet would create an event.
So, the driver/principal are moving at 40 mph, and there is a ten-foot-long vehicle blocking the road. You and the principal are 60 feet away from the blocking vehicle.
Scenario 1 No Problem
Scenario 2 Problem