Preperation
TIE-DOWN CHAIN
In the demo a Grade 100, 3/8 chain that has been cut to 10′ long. This ensures that here is plenty of tail when the chain comes over the steering knuckle.
Begin by installing the tie-down chain in a choke, right around the steering axle and the spring. Then the tail of the chain will go underneath the axle, right between the engine and the frame rail. From there, the tail of the chain comes up over the top of the frame, and passes over the steering knuckle.
The sister chain is also secured to the tie-down chain on each side of the axle (one on one side of the steering knuckle), and the other side, on the top side of the axle (forward of the axle).
TIP FROM THE DITCH:
To protect your chain sling, and to reduce friction between the chain and the frame use and edge protector (like you would see on a flat bed). Install the edge protector between the chain sling and the frame.
LINE ANGLE & LINE LOAD
If you put a protractor on the line, you can actually measure the line angle. Currently the line angle is setting at 30 degrees.
The line angle is not vertical, nor is is horizontal. This means that there is some kind of tension factor. When consulting the rigging manual, that includes tension factors, you will find that at 30 degrees there is a tension factor of 2.
If we assume that the bus weighs 20,000 lbs, and we are upright half:
Multiply half of the static weight (10,000 lbs), by the tension factor (2). Therefore, to upright the bus with one line, the tension factor or the line load would be 20,000 lbs.
CRIBBING
In the survey, make sure that the parking brakes are on. You will still need to install a back up. The easiest and quickest way to do this is to grab some cribbing off your rig, and place it in a V-pattern down by the tires.
This way, when the casualty lands, it will land right into the cradle made by those blocks.
CHAIN BREAK
The chain brake utilizes the chain in a ratchet-binder so that we can marry the tire in one position by use of the chain.
In this demo, a 1/4″, grade 100 chain around the inside hub of the wheel. The chain is passed through the spring and up through the top-side spring. The chain binder is installed right in the middle of it. Therefore, when tension is applied, and the bus comes over to it’s wheels, the tire can only roll a couple of inches.
