What is the reasoning behind WLL requirements?

Six one half dozen the other. Different way of saying the same thing

 

Why is it adequate? Because based on experience, empirical testing and/or modelling, it has been determined that it is sufficient securement so long as it is applied correctly.

The WLL is the safe limit within which a securement or lifting device can be used and reused. In the case of securement devices it is generally between 1/4 - 1/6 of the minimum breaking strength/load (MBS/L). In the case of lifting and hoisting devices it is generally 1/10 of the MBS.

 

YES I completely agree with this and with the more is not always better .
For me it's all piece of mind .

 

straight from the FMCSA handbook:

Performance Criteria
FMCSA has adopted new performance requirements concerning deceleration in the forward direction, and acceleration in the rearward and lateral directions, that cargo securement systems must withstand. Deceleration is the rate at which the speed of the vehicle decreases when the brakes are applied, and acceleration is the rate at which the speed of the vehicle increases in the lateral direction or sideways (while the vehicle is turning), or in the rearward direction (when the vehicle is being driven in reverse and makes contact with a loading dock). Acceleration and deceleration values are commonly reported as a proportion of the acceleration due to gravity (g). This acceleration is about 9.8 meters/second/second (32.2 feet/second/second), which means that the velocity of an object dropped from a high elevation increases by approximately 9.8 meters/second (32.2 feet/second) each second it falls. FMCSA requires that cargo securement systems be capable of withstanding the forces associated with following three deceleration/accelerations, applied separately:

1. 0.8 g deceleration in the forward direction;
2. 0.5 g acceleration in the rearward direction; and
3. 0.5 g acceleration in a lateral direction.

These values were chosen based on researchers' analysis of studies concerning commercial motor vehicle performance. The analysis indicated that the highest deceleration likely for an empty or lightly loaded vehicle with an antilock brake system, all brakes properly adjusted, and warmed to provide optimal braking performance, is in the range of 0.8-0.85 g. However, a typical loaded vehicle would not be expected to achieve a deceleration greater than 0.6 g on a dry road. The typical lateral acceleration while driving in a curve or on a ramp at the posted advisory speed is in the range 0.05-0.17 g. Loaded vehicles with a high center of gravity roll over at a lateral acceleration above 0.35 g. Lightly loaded vehicles, or heavily loaded vehicles with a lower center of gravity, may withstand lateral acceleration forces greater than 0.5 g.
Generally, motor carriers are not required to conduct testing of cargo securement systems to determine compliance with the performance requirements. The new rules explicitly state that cargo immobilized or secured in accordance with the general securement rules, or the commodity-specific rules, are considered to meet the performance criteria.

 

They go into all that detail about G forces then the last sentence basically says ignore all that if meet the general securement rules you are good.

 

So they let you know WHY the rules are as they are? Waste of space. Nobody ever wants reasons for what they do.

 

Ive never officially hauled equipment on the open road... But I have hauled a few pieces of farm equipment short distances... I always prefered 1/2" Grade 70 chain over 3/8"... And lots of them!!!

 

##### heavy though. Got a 20' 1/2" binder chain for getting pulled. I don't look forward to dragging that thing out.

 

F'n A Rights they're heavy!... And you best have an 8 foot cheater to snap them big binders shut too.

 

But still .8 times 26k is 20.8k which 13.2k doesn't meet.
I don't think forward facing chains at a ~45 help much in pulling down adding friction to prevent forward motion. I do have a physics degree and could calculate it out but I am too lazy.