What Are Pound-Feet?
Understanding the Load Capacity of Your Cargo Accessory is Important
Overloading any system, be it as large as a train or as small as a cargo carrier, can lead to a failure of that system. For systems with two or more support points, like train cars, trucks, and autos, weight as represented by pounds can be a suitable measure of load-carrying capacity. For systems with a single support point, such as most bumper-mounted cargo accessories and the bumpers that support them, a more accurate measure of capacity is the pound-foot. A pound-foot is equal to one pound supported one foot away from the support point. Two pounds supported one foot away from the support point is two pound-feet while one pound supported two feet away from the support point is also two pound-feet. Put simply: Weight times distance equals load. A great example of this is a diving board; the further out on it you walk, the more it depresses. See also https://en.wikipedia.org/wiki/Pound-foot_(torque).
Because bumper-mounted cargo accessories and the bumpers that support them utilyze a single support point, pound-feet more accurately describe load capacity than do pounds. It is for this reason that we test and rate our products using pound-feet. To determine your cargo's load, multiply the number of feet the center of your cargo is from the bumper times the weight.
Using the example to the right, we see two 50 pound generators on a tray. The center of the left-most generator is 0.625 feet (7.5 in/12) from the bumper, giving us 31.25 pound-feet of load (0.625 ft. x 50 lbs.). The right-most is 1.67 feet (20 in/12) from the bumper, giving us 83.3 pound-feet (1.67 ft. x 50 lbs.). Adding the two loads together gives us a total load on the tray of 114.6 pound feet.
Should you have questions calculating pound-feet, please feel free to contact us.