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, 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 flatbed trucks or similar transportation vehicles, we will see there are other kind of trucks, the typical one is box truck, and most of them have E Tracks 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 easy to understand that why e track straps are not as strong as regular ratchet tie down straps, inside the box truck the loads already have strong support, at least there is no risk of falling off, all the e track straps will do is to fixate the loads more than tie them down.

As we discussed in the first paragraph, the design factor of ratchet straps is 3:1, that means the working load limit is 1/3 of the minimum breaking strength, while grade 70 transport chains which have a design factor of 4:1, that means the transport chains will work in more tough environment than tie down straps, which usually are chose for regular loads. The standard material of which tie down webbing is made is nylon webbing or polyester webbing, depends on 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. Breaking strength has to reach the recommendation level no matter what, and elongation has to meet the requirement, abrasion and environment sometimes are not that clear cut, when designing tie down we may have to consider the most extreme conditions these tie down straps may be in, or we may just consider the normal transportation environment.