Moments provide a way to combine a number of components or items to calculate a CG for them as a group (Image F). One pound of force times 12 inches is 12 in.-lbs. "Moments" are a force or weight times a distance: One pound of force times one foot is 1 ft.-lb. Lateral centers of gravity (CGs) are measured from the vehicle centerline toward the right or passenger side as positive, left as negative. These are used to calculate individual wheel loadings and incompliance calculations. The horizontal and vertical centers of gravity for the entire sample truck is shown with the center of gravity (CG) symbol. Unless a lateral center of gravity is given for the chassis or a component, it is assumed to be on the centerline of the chassis. If individual wheel loadings are calculated, the lateral centers of gravity are also used. For example, the center of gravity of the truck chassis is shown at the top of the frame rail at the back of the cab and the body and cargo centers of gravity are shown with a single symbol at the center of the body about a third of the body height above the floor.įor the process of calculating weight distribution on the axles, the horizontal centers of gravity are used. The centers-of-gravity of the truck chassis is shown at the top of the frame rail at the cab and body and cargo centers-of-gravity are shown with a single symbol at the center of the body about a third of the body height above the floor.Įach truck component, including passengers and cargo, have a center of gravity. Most of the time, the center of gravity of a truck body is in the air, similar to the hollow ball example. If the center of gravity of a truck body is in the material of the body, it is coincidence. In the case of a hollow ball, the center of gravity is also at the center, but it is not in the material. When considering a solid ball, such as a billiard ball, it is obvious the center of gravity is the center of the ball and in the material that makes up the object. The center of gravity of an object does not have to be in the material of the object (Image C). While the concept of an object's center of gravity is something many of us feel confident in understanding, do you know how to figure out the center of gravity on an odd-shaped object? What about something like a truck, considering the weight of the engine, axles, and loaded or unloaded trailer?
What is the Impact of a Truck's Center of Gravity? The two rear axles on the tandem-drive truck are limited either by axle capacities or legal weight restrictions to 17,000 lbs. The rear axle on the single-drive truck is limited by the axle capacity or legal weight restrictions to 20,000 lbs. Both trucks in Image A have a front axle rated at 12,000 lbs., limiting the weight on those axles.
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