The ratchet straps are just the assemblies of ratchet buckle and tie down webbing, but if we use cam buckle in place of ratchet buckle in the assembly we have cam buckle tie down, it’s as simple as that. 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. Unlike cam buckle, ratchet buckle are much stronger, and 2”,3” and 4” ratchet buckles are used in industrial grade applications, such as heavy duty transportation, the typical working load limit for 2” tie downs is 3,333lbs, for 3” and 4” which is 5,400lbs, since these tie downs have design factor of 3:1, the minimum breaking strength is 10,000lbs and 16,200lbs.
Of course what we discussed above is mainly for flatbed trucks and some other kind of 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 box trucks have E Track installed and use logistic tie downs . It is estimated that 80% trucks are box trucks, and the e track tie down system is just for semi trailers , so e track straps are most popular tie down straps. And these straps are not as strong as the one we use on flatbed truck, the working load limit of typical e track straps is 1,000lbs, with minimum breaking strength of 3,000lbs. 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. You also have e track cargo bar, shoring beam, e track tie off, etc. at your disposal, with e track tie down straps you will be able to secure any kind of cargo , make the transportation experience as it should be , but remember that you can never be more careful when it comes to your precious truck and load , make sure your cargo are tied down properly all the time.
We already discussed the design factor of ratchet straps, it is 3:1 and for the record all this says is that safe load limit of tie down straps is 1/3 of it’s 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 downs 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.