Close look of Ratchet Straps: Material and Making
The ratchet tie downs are the assembly of tie down strap and ratchet buckle , it’s a well known fact, if we use cam buckle instead of ratchet buckle then it’s cam buckle tie down, it’s pretty straight forward, isn’t it? 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. 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, 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.
Until now all we discussed about is the tie downs for flatbed or similar commercial vehicles, there are another kind of ratchet straps for semi trailers, ratchet e track accessories , these tie down equipment will be used with E Tracks installed inside the semi trailer. 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.
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 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. When making the webbing, we have to take following characteristics in to consideration, the breaking strength, elongation, abrasion and the environment. There are mandated criteria for breaking strength and elongation of the tie down strap , 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.