The ratchet straps are just the assemblies of ratchet buckle and tie down webbing, if we use cam buckle instead of ratchet buckle then it’s cam buckle tie down, it’s pretty straight forward, isn’t it? Due the low strength of the cam buckle, we usually see these cam buckle tie downs being used on pick up trucks, 1” cams are all over the place while 2” cams are being used in box trucks. 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, with 3,333LBS, 5,400LBS working load and a design factor of 3:1, these ratchets have 10,000LBS and 16,2000LBS breaking strength respectively, which are pretty strong for most tie down applications.
So far we talked about tie down devices for flatbeds or similar commercial vehicles, we will see there are other kind of trucks, the typical one is box truck, and most of them have E Track installed inside the truck, for these rigs we use e track straps. In fact box truck has much bigger share than flatbed truck, the percentage maybe around 80%, of course this is only estimation but you get the idea, and the conclusion is that e tack straps are by far the most popular tie downs. The e track straps usually have working load limit of 1000lbs, which is only 30% of the 2” flatbed tie downs, and the breaking strength is only 3,000lbs based on design factor 3:1. 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.
As we mentioned in the first paragraph, the design factor of ratchet assembly is 3:1, that means the working load limit is 1/3 of the minimum breaking strength, 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 most common materials in making tie down webbing are nylon and polyester, which serve different tie down applications. Nylon webbing has better elongation than polyester, so for shock absorption wise nylon is ideal material while polyester usually is used to make tie downs for heavy equipment. 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.