Use this knot when you need to tighten a rope to hold something down like a tarpaulin or to secure items in the back of a truck. I used three to hitch up and tether down my rain gutter. Click on images for larger images.
This knot can also be used as a crude pulley system with a 3:1 advantage if you ignore the massive amount of friction. I did this when I hitched up the HPS light in my growroom.
There are a few versions of the trucker's hitch, all of which are concerned with how the loop in pic. #3 is formed. One version uses a figure-of-eight loop, another uses a slipknot. I prefer this version because it's easier to untie. There's no knot to jam, the twist simply untwists when you untie it.
If you ignore the massive amount of friction (which it has, yes!),
ReplyDeletethe structure is 3:1. From the formed eye in the line, each of the
down->up->backdown lines bears tension against the one line
going away from the eye. (But in rope-through-rope, the actual
mechanical advantage might be about 1.5:1.)
Yes, you're right. It is 3:1. The advantage of a trucker's hitch was a bit of a brain-twister for me for a while. Seems obvious now. Will edit.
ReplyDeleteFor securing heavy loads the mechanical advantage may be of secondary benefit to the additional friction afforded by the load sharing arrangement. The real tension is achieved by a process called 'swigging', well known to sailors when tightening a sail halyard:-
ReplyDeleteIncreased tension can be put in the system by pulling outwards in a horizontal direction, taking in the slack, then repeating until taut and tying off. This results in a much tighter rope than simply pulling down to the hitching point.