The ratchet tie downs are the assembly of tie down strap and ratchet buckle , it’s a well known fact, by this logic the cam buckle strap is just the cam buckle with tie down strap, why I am not surprised? Most likely these cam buckle straps are used on pick up trucks or passenger cars for luggage tie down, and small cam buckle(1”) are more popular than big ones(2”). Ratchet buckles are different, there are 1” to 4” ratchets, and they can be quite heavy duty and can stand all kinds of abuse, the most commonly used on commercial trucks are 2”, 3” and 4” ratchet tie downs, 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.
As of now what we talked about is the tie downs for flatbed 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 Track installed inside the truck, for these rigs we use e track straps. By estimation, there are almost 80% trucks on the road are box trucks, so these e track straps are supposed to the most popular ones by volume. 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. the low working load limit of e track straps stems from box truck wall provides support for the loads inside the truck, come to think of it, the loads won’t fall off the bed, not going to roll over, it’s much safer than the loads out there on the flatbeds, therefore low strength tie downs can be used to secure the loads.
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, for comparison purpose we know that the binder chain has a design factor of 4:1, which basically says that for the chains the working load limit will be 1/4 of their breaking strength, which indicates that tie down chains are designed for tougher environment than tie down straps are in. Nylon and polyester webbing are used in making tie down webbing, for different applications people will choose different material accordingly. Polyester webbing is almost perfect for tying down logs while nylon webbing is for small and light cargo. When making the webbing, we have to take following characteristics in to consideration, the breaking strength, elongation, abrasion and the environment. When making tie down straps , manufacturer has to follow the recommendation of breaking strength and elongation requirements, when it comes to abrasion and environment, there are much more variations to be considered.