Friday, July 08, 2011
A double leverage trucker's hitch that comes completely undone once the tension is off of it
That part is plenty fast. The slow part is undoing it. After releasing the half-hitches, the rope has to be pulled back through the slip-knot-loop. Then the loop itself, which can cinch up pretty tight, has to be untied.
Another version, the version I learned decades ago when I drove a lumber truck, gets its mechanical advantage from a loop that remains in place only so long as there is tension on it. Once you undo your half-hitches and release the tension on the rope, you just give the rope a shake and the loop comes undone. The whole shebang just pulls out straight.
Below are some written instructions that I left as a comment on the original truckers-hitch post. I'll add pictures if I can get around to it, but I think the verbiage here is actually followable:
With the far end of your rope secured to one of the downward pointing tie-off hooks or rope-hooks on the far side of your truck, pull your rope over your load and towards one of your near-side rope-hooks.As the author of the slip-knot version wrote, it takes a bit of practice get a feel for where to place the first loop with these kinds of knots. The more give there is in your load and in your rope, the further you have to start from your destination rope-hook.
Using your left thumb and forefinger, hold the rope at a point about 3 feet above or before the hook. Now with your right hand, come about a foot further down the rope and lift that spot on the rope up to your left thumb and forefinger so that you form a loop hanging off to the right of your left hand. Don't cross the rope over itself or twist it. Just bring it up and hold it next to the first passing of the rope.
Now go down a foot again, lift that point of the rope up, and wind it twice around the loop that you have hanging from your left hand. The wind should go over the top (or clockwise as seen from the right). Very important: the second wind should be TO THE LEFT of the first wind (further up the loop). This is where the knot's holding power comes from. The pull down on the second wind sucks it in tight behind the first wind so that it can't pop out.
Depending on the thickness of your rope, this double wind will use up somewhere between an eighth and a half of that last foot of rope you grabbed. The rest of that foot of rope will be hanging down, forming another little loop, while the continuing part of the rope hangs down from your right hand.
From here, take the index finger or the ring finger of your right hand and push a loop of the continuing part of the rope towards yourself and to the left, through the loop that is left over from the winding action. Now reach around and grab this loop that you just pushed through the previous loop and pull it down over (under?) your rope-hook.
Pull down on the free end of the rope it will pull this last loop upwards, snugging it up onto the rope-hook with the same two-times-mechanical-advantage as with the slip-knot-based truckers-hitch. To finish off either version of the truckers' hitch just pull down hard on the free end of the rope and secure it to your rope-hook with a couple of half-hitches.
To undo, just undo the half-hitches and let out enough slack to take the last loop off of the tie-off hook. Then shake and tug the free end of the rope and the whole shebang comes out. This is the advantage of the wind-it-over-twice method. When you are done, you don't have to pull the free end of your rope back through the slip-knot-loop or undo any slip-knot.
Also, you can create 4 times mechanical advantage by repeating this knot, in which case you have to start WAY back from your tie-off hook. I have used the quadruple leverage method a couple of on items that can't be gripped firmly without substantial squishing--like cushioned furniture.
The shake-out or double-wind version of the truckers-hitch doesn't LOOK reliable, and indeed, from the front of the knot, it is actually pretty easy to push the inner winding over the outer winding so that the whole thing comes undone, even when there is substantial load on it. But if nobody is standing there pushing the front of the inner winding out over the outer winding then there is no pressure in that direction.
All the pressure that the knot itself creates is at the BACK of the inner winding, where downward force is pulling the inner winding hard to the inside of the outer winding. Thus the knot should be secure, and in practice it seems to be. I have used this hitch thousands of times, including on plenty of heavy loads, and it has NEVER come undone on me.
Very fast, very easy to learn, and very reliable in my long experience. Highly recommended.