How Tie Down Straps Keep Flatbed Cargo from Moving

Have you ever seen a flatbed truck loaded with pallets secured by tie down straps running over the top? I see it all the time where I live. I know how the straps keep the cargo from moving around, but only because I studied physics in school. I would imagine that most people don’t understand the science behind it. The science can be described in one word: friction.

Whether you call them truck tie down straps, ratchet straps, or even buckle straps, they all work on the principle of friction. If you have ever noticed, the straps don’t do anything other than apply downward force on the top of the load. But that force is powerful enough to create the friction that holds everything in place.

More About Friction

Within the realm of physics, friction is defined by the Miriam-Webster online dictionary as “the force that resists relative motion between two bodies in contact.” In simple English, two objects making contact create a certain amount of energy as their surfaces rub against each other. That energy is what we call friction.

Friction prevents movement thanks to opposite forces working against one another. The greater the friction, the less likely an object will move across the surface of whatever object it is making contact with. So in a trucking scenario, greater friction between cargo and trailer bed reduces movement.

By now, you might be wondering what tie down straps have to do with all of this. Tie downs are where force and fraction meet. The amount of downward force applied by a tie down determines the friction between load and trailer bed.

Think of It as Weight

We can avoid a lengthy scientific explanation by thinking of force as weight. In the case of securing down cargo with a tie down strap, tightening the strap is very similar to putting extra weight on top of the load. The greater the weight, the harder the load presses into the trailer bed below. This increases friction.

If it helps, think in terms of a piece of paper on the kitchen counter. If you placed a feather on top of the paper, the feather would not prevent you from sliding the paper back and forth. But what if you put a paperweight on top? Sliding it back and forth would be harder. Replace the paperweight with a concrete block and you won’t be able to slide the paper at all.

Tie down straps work much the same way except that, rather than applying dead weight, they apply an equivalent force through tightening. The tighter the strap, the more force generated. The greater the force, the greater the friction.

Different Types of Straps

According to the makers of the Rollercam brand of tie down straps, there are different types of straps identified by their buckles. A truck driver will always use ratchet straps simply because they are the only option capable of handling the heavy loads commercial trucks carry.

Rollercam makes a cam strap that works well for personal applications. Their strap features a cam buckle through which the open end of the strap is threaded. The buckle has a spring-loaded plate with teeth that clamp down on the strap. Cam straps are more than adequate for securing smaller loads to pickup trucks, trailers, and vehicle tops.

Regardless of the tie down strap used, friction is that which keeps cargo from moving around. Friction is created by the force generated when tie down straps are tightened. Get a strap as tight as possible and cargo should stay in place.

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