We all know that when assemble tie down strap and ratchets together we get ratchet strap, when the ratchet buckle is replaced by cam buckle then you get the cam buckle straps. Cam buckle tie downs are only for light duty use, and 2” cam buckles are the biggest size we will see in the real world use, and it’s still light duty. Compare to cam buckle the ratchets are stronger and more widely used, the available sizes of ratchets are 1”,2”,3” and 4”, and the ratchet buckle generally has higher working load limit than the cam buckle, they have working load limit of 3,333lbs, 5,400lbs and 5,400lbs respectively, these assemblies have design factor of 3:1, thus the minimum breaking strength is 10,000lbs, 16,200lbs and 16,200lbs respectively.
So far we talked about tie down devices for flatbed trucks or similar commercial vehicles, in reality semi trailers are much more than flatbeds in numbers, since they are box trucks the tie down needs are different, you will see most semi trailers have E Track installed and use logistic strap . It is estimated that 80% trucks are box trucks, and the e track tie down system is just for box trucks , so logistic straps are most popular tie down straps. With 1,000lbs safe load limit and 3,000lbs minimum breaking strength, e track tie downs are not as strong as flatbed tie down straps, It’s understandable that e track straps have lower working load limit, because the box truck wall will provide strong support for the loads inside, and the truck wall will prevent the loads from falling off, rolling over, tilting and some other dangerous movements. With the help of e track cargo bar, rope tie off and some other e track tie downs and accessories, it’s pretty easy to secure loads inside the box trucks, but easy doesn’t mean not important, you still have to look out for any risks may present in the process of transportation, so secure your loads as reliable as you can, use the right tie down equipment for your job.
In first paragraph we talked about design factor of ratchet tie downs, which is 3:1, so the working load limit is 1/3 of maximum breaking strength for ratchet straps, in the mean time the design factor of grade 70 tie down chains is 4:1, so the chains can support heavier load, and are more resistance to abuse, such as high/low temperature, moisture, while tie down straps usually only work well under normal condition. The standard material of which tie down webbing is made is nylon webbing or polyester webbing, depends on different tie down applications. The typical application for nylon webbing is motorcycle tie down, while polyester webbing is ideal for tying down concrete pipes. Elongation, tensile strength, abrasion and environment, these have to be taken into consideration when making tie down strap. There are mandated criteria for breaking strength and elongation of the tie down straps , while the abrasion and environment are mostly estimation and subjective sometimes, different area may have different requirements. Therefore the manufacturer may have to make these tie downs to different standards.