Clock hitch

[Tom Dunlap]

Several years ago, when the original ISA forum was the only on-line arbo discussion, I met Glen Riggs. A variation on the "False crotch hitches" thread was going on. Glen described to me, in an email, how to tie a really useful anchoring hitch.

One of the best attributes of the Clock Hitch is that the description is simple enough to learn without a diagram. Glen told me that he has told groundies how to tie the hitch while he's in the tree even if the groundie has no knot tieing experience.

Her's how to tie it:

Start with the eye of the rope at a place on the tree opposite from where you plan on attaching your anchor. Wrap the rope around the tree and thread the tail through the eye. Move the rope up the tree into position and take up the slack before taking the tail back around in the opposite direction. Pull the rope tight as you wrap. When you get back to the eye, thread the rope through the eye again. Pull the rope snug and tie off with your favorite hitch. I generally make a slipped half hitch with the tail, back onto itself. Then I drop a half hitch over the bight formed by the slipped anchor. For more security, drop another half hitch over the bight.

Since most of the load is taken by the friction on the wraps, little is actually on the tucks through the eye. If I had any concern, it would be the secound tuck through the eye. This puts a load on the eye splice that is "odd". When I've had enough rope, I've made a third wrap to snug up the whole works. This lessens the load on the eye even more.
This works really well for anchoring pulleys. The biner/shackle can be mounted anywhere around the tree.Be sure to anchor around both wraps of the Clock Hitch. If the rigging point changes all you have to do is slip the biner/shackle around. Another plue is that multiple anchor points can be clipped onto the ropes.

Here is a discussion point. When using a block, would there be a concern about having the double wrap on the pin instead of an eye? I've only anchored a block like this a few times. When I have done that, the loads have been low. It seems like this would be acceptable but the practice does deserve time under the microscope.

Glen had been using the Clock Hitch for years in severe loading. If there were a security issue, Glen would have pushed this tie off by now. When I asked him where the name came from he said, with his best isn't-it-obvious "Philly attitude", "Well, it goes round and round like a clock!"

Tom

 

[TheTreeSpyder]

i think that pulling on anyother direction on a spliced or tied eye; than on the designed axis of pull from down the tail by anchoring to clamp eye shut and to the opposite end of the eye for the load pull; invites faults not fortified against in the system of the eye.

i think that a sheetbend is a cut open bowline, and lacks security in the different way that the formed joint is loaded. i think if you make a bowline and set pulls perpendicular across it from the standing end or actual knot /joint of the bowline , it would not have bowline security etc. i think if you loaded into the eye properly and put a hook on the other end of the bowline eye so that it covered the 'joint' that made the bowline eye, and pulled it wouldn't be as trysty either.

I think that the load pull coming from eye center and resisted from the pull of the line on splice or knot is the design, because other angles of pull attack weaker fortifications in strength, and don't load the not or splice properly to grip joint properly per load? I think pulling back in any way into the throat of the joint of (esp.) splice or knot; could serve to 'pry' it apart and odd angle and any pull from that direction negating pull from load's side of eye; thereby negating some of the load force that tightened the knot/splice to needed levels per the load?

i think a customary pull down the long axis of the eye is proper; it powers the knot or spice to hold the tail securely that makes the joint. Pulling at odd angles, or even some back into throat of eye can draw tail out of splice/knot, for it is not loaded right to maximum to maintain it's grip and faces an odd compromising angle of pull.

Orrrrrrrrr something like that!

 

[Mike_Maas]

Spyder asked me to link this old drawing:

 

[RescueMan]

I agree with Spyder that loading the eye into the throat of the splice is asking for trouble, but the drawing that Mike attached shows the second wrap secured through the bight made by the first wrap. This looks a little better but it could easily pull that bight into the throat of the splice as well.

Another potential problem is that loading a sling around a broad stem creates a vector force in each leg of the sling exponentially proportional to the width of the angle. The general rule of thumb in the rescue world is to keep any internal sling or multiple anchor angles to less than 90 degrees to avoid a significant multiplication of forces.

0.7 x load on each leg at 90 degrees
1.0 x load on each leg at 120 degrees
1.9 x load on each leg at 150 degrees
2.9 x load on each leg at 160 degrees
5.7 x load on each leg at 170 degrees
etc...

- Robert

 

[Tom Dunlap]

Robert,

In plain English, can you explain how, "Another potential problem is that loading a sling around a broad stem creates a vector force in each leg of the sling exponentially proportional to the width of the angle." applies here?


Like I said, The tuck through the eye hasn't set well with me. Depending on the diameter of the tree and how snug I pull the CH, the pull on the tucks might be close to parallel. Add the amount of friction from the wraps on the tree and I wonder how much of the actual load is on the tucks.

This would be a good experiment to play with. I think that some valuable insight could be gained using throwline for the CH. Of course, any results would have to be qualified and footnoted but it would be a start.

Any feedback about putting a block around the two wraps?

Tom

 

[Mike_Maas]

Does this help, Tom?

 

[frans]

The biggest challange I have with tying this knot through the eye is I cant seem to find an application for it!
Usually when I am tying off a line it is to suspend a block high up in a tree so I can rope off limbs and when I am done I can lower the block sos I dont have to climb back up to fetch the block.
I tie the end of the rope in a different manner:
I take a wrap around the trunk,then with the tail end I bring the rope up over the standing end and back around the trunk in the opposite direction. I do this several times and finish it off with a few half hitches.

 

[TheTreeSpyder]

i think i see what RescueRob is pointing at, not the eye question; but safety of loading of a line stretched around trunk almost flat by Port or pulley; the flatter the more leveraged. Because there is no choke positioning, to keep from sliding in pull direction (if not perpendicular to mount), must be set tight to keep from sliding etc.; so will be mounted on tight, flat line prolly.

So if the device of the Porty or Pulley etc. pulls on that flat angle, it would be like loading DWT (Thread and Calculator) to flat angle with high load.

Even though there are both lines going through Porty etc. eye; only the tightest (1st wrap?) carries most of the load of the leveraging proposed.

Seems Mike snuck in here sayig the same thing as i write! i think one of the advantages of the original style Porty is the long neck that can be slid inside of Cow Hitch etc. to loosen without untying.

 

[RescueMan]

Sorry. Attached is a drawing of a tight sling around a stem, showing the internal angle formed by pulling away from the tree.

Just as the anchor loads in a speedline will be dramatically multiplied the closer the line is to straight (which is why the chunks are never dropped onto the line and why the line isn't tightened until the load is on it), any anchor strands which oppose each other will cause a multiplication of the load as the reaction forces in the opposing strands become more significant than the load itself.

It is actually a hyperbolic function (if anyone is interested?), which approaches infinity the closer the angle gets to 180 degrees (e.g. at 179 degrees, there is 57.3 times the load on each anchor).

As far as the two strands going through the clevis of a block - I would think that if the block has room enough for a single rope, then there is going to be some compromise of the ropes where they crush against each other at that point.

- Robert

 

[RescueMan]

Wrap 3 Pull 2

In rescue, an increasingly popular anchor system made with 1" tubular webbing (could also be rope) is the Wrap-3-Pull-2 (see attached picture).

This takes 4,000 lbs test webbing and creates a 12,000 to 14,000 lbs anchor, if the internal angle is kept to less than 90 degrees, and it completely isolates the knot from the load (notice the knot is in front). It also has the advantage of cinching on the post/tree so it doesn't slide, and it self-equalizes as the load vector shifts.

If it is tied with rope, the knot could be any secure bend since there is virtually no load on it.

- Robert

 

[Tom Dunlap]

OK, I get what you'r talking about now.

Now I'd like to see if that makes any difference. Given that the eye sling is long enough to either tie a Clock or Cow. Same loads on both. Since the anchor for the Clock goes around two turns of rope and there is some sharing, but I agree, not completely equal, which anchor point would have the higher load?

This might be solved during daylight hours in the shop using a fish scale.

Tom

 

[RescueMan]

Re: Clock vs. Cow

Tom,

If what you're asking is: does the Clock Hitch or the Cow Hitch impose higher loads in the anchor rope?

Then the answer is: likely the Clock.

The Cow Hitch and the Timber Hitch are different ways of making a girth hitch from a single strand of anchor rope. A girth hitch can multiply the tension at the bight/eye by up to 2x, while pulling on two opposing anchor strands (like in the Clock) can multiply the load by much higher factors.

 

[TheTreeSpyder]

Re: Clock vs. Cow

On the Cow, TH etc. the single choked eye leg comes out to hold device.

While in the Clock it does ride one or both lines, it would only have doubling/basket strength if the legs of support came stright off device to anchor, parallel; any angle gives leveraging; almost flat; high leveraging.

The high leveraging, is the real sweating a purchase of power from the line magically IMLHO. The tighter the line, the less it will flex at loading, so as with solids that offer high magical leverge to make the impossible light; only if the lever is reinforced to take the immense leveraging; as same with the flexible line. Leveraging line when it is reinforced with stretching, can give high leverage with more input and output force values available by stiffening the line agianst bending like a board.

This can work for us or against us. We've only talked of it working agianst in speedline, DWT, anchoring devices etc.(all same number/science); but this high power can work for us; best in sahort distance needed just power situations IMLHO.

But a factor to realize in any guise in the rigs i think!

-KC

edit, great attatchment Rob thanx!

 

[knudeNoggin]

Re: Clock vs. Cow

Rescueman cites the Wrap3-Pull2 structure. What I suggested for a false
crotch in that so-named thread included what might be similarly named as
"Wrap2-Pull1"--or, from another perspective, a minimal VT.
The anchor rope from the block would have 2 equal-length legs. Tie off the ends,
before you (i.e., back on the block side of things) with a
Reverse Surgeon's knot,
or some other (looks like a simple start to the Reef/Square
with ends Slip-knotted would work!?)

Consider the anchor rope that you're using: does it NEED to be
doubled, or is it amply strong? (the latter, I believe)
The sort of VT structure I suggest would soften the angle of the
legs from the block in extension, and unlike the Cow/TimberH,
two legs would bear load, AND there'd be no rope-vs-rope point.

--knudeNoggin

 

[Tom Dunlap]

Re: Clock vs. Cow

Knudenoggin,

Actually what I have used is a Wrap 2 Pull 2 since I clipped the anchor around both round turns. I nver thought of this being a Wrap X pull X setup. Now that you mention it I'm going to pull out my rescue books and read up on it.

I have never really had a concern about the strength of my ropes or anchor slings. If I ever felt a limitation I pick a bigger rope or cut smaller pieces. When I look at rigging options I like to see a good reason to use one vrs another.

Tom

 

[Mark Chisholm]

Re: Clock vs. Cow

Rob,

Where is that "capacity adjustment" acting? On the stem? Or the sling itself?

Thanks for the input.

 

[RescueMan]

Re: Clock vs. Cow

</font><blockquote><font class="small">In reply to:</font><hr />
Where is that "capacity adjustment" acting? On the stem? Or the sling itself?

[/ QUOTE ]

Sorry, I don't like that particular chart, but it was the only one I had easily available. The "adjustment" is in the strength of the anchor sling (compared to the strength of a single strand of the rope) when chokered.

It would more clear if, like the upper (basket hitch) chart, it quantified the load multiplier factor for each choker angle (see attachment).

- Robert

 

[TheTreeSpyder]

Re: Clock vs. Cow

Thanx for the 2 charts Rob, they are now in my 'Stolen Goodies Room'!

i find the leverages fascinating, especially as they define and sort what happened in past experiences i remember; when magic of high leverage seemed to be helping or hurting!

And this lil'woodtick clinging to the side of a giant, find 5:1-14:1 + leverage in hands reach quite useful if i can tame it and forge against it placing that 'martial arts' against me or target.

If you take Dave's DWT chart and just read the weight "m", the primary angle "A" ("a" is secondary angle and not needed here; the line tension produced at each end is given in "t", and the multiplier of effort at the bend shown in "t Load%" (Once again the secondary angle info of Load Anchor 2 "L" and the multiplier % are not needed here). But anyway; you can input the weight, and the spreadsheet can calcualte force at any degree bend, even show the differance in loading force between 179 deg. loading and 179.001 deg.! etc. But any way comes up with the same numbers, calculates etc. everything to your testing numbers etc.

To sneak thru the download filter, knock off the trailing ".txt" i faked. to turn the last charachters of the filename to ".xls"; to run in Excel.

The numbers of leverage purchase run very high at near flat; this can stand against any rig it is allowed to and not sifted out by the craftsman/technician supposed to guard the door agianst such entrances of force into the equation; and to habitually set minimum loading in every easy way possible. Sometimes those same numbers can work for us, especially short, intenese; pulses of high power at the right time can make all of the differance like initiating movement, purchase to a captured sweat of line past friction point, force high strength hinge by high loading right at first flexxing etc. This, power that threatens laoding can be tamed and used IMLHO!

 

[RescueMan]

Re: Clock vs. Cow

</font><blockquote><font class="small">In reply to:</font><hr />
This, power that threatens laoding can be tamed and used

[/ QUOTE ]
Just as any mechanical advantage can become a disadvantage if applied in reverse, the same is true of a mechanical disadvantage, such as this vectoring principle of tensioned lines.

In river rescue, in which there are typically few resources available to, for instance, unpin a boat lodged against a rock by the force of the moving current, one might attach a rescue throwline to the boat and to a tree or rock along the shore, tighten it as much as possible, and then push at 90 degrees on the middle of the span. This will create a significant multiplication of force on both anchors and, if the tree or rock doesn't move, the boat might well break loose.

The same principle can be used to pull a slightly leaning tree if there is no winch or come-along available. It's called a vector pull.

- Robert

 

[Riggs]

Funny thing Tom is how close minded all the "experts" were just ten years ago. I'm not gonna start dropping names, that would be too much fun . Tom has always had an open mind and is not intimidated about being shown something he might have never seen before. I can't say that about some of the "experts" .I've always felt the need for a direct line to the anchor point , makes things a lot easier.Thanks Tom for running with it, we need more people like Tom D. I never tie the Clock for strength , just so it can be moved around the base of the tree , but it will hold whatever. About time we had a rope rescue poster , I get into all that jazz. It would be fun though to start talking about all the closeminded crap that happened just ten - eleven years ago . "Where's the waitrees at with my drink..."