Clock hitch

[Mike_Maas]

I too am glad for the contributions Tom has made over the years, and for the those made by Robert recently.
The point he made about the forces generated on a rope with angles approching 180 degrees was something I was aware of in general terms (forces on a speedline) but never applied to the clock hitch.
I'll still use the clock hitch for attaching a port-a-wrap to the base of a tree but now I'll pay attention to the angles.

 

[Sawdust]

I'm working on getting some pics of the clock now. will post asap. From what I'm reading I think the clock is being tied wrong. I work with Riggsy from time to time and he showed me this quite a few years ago and have been using it ever since. The clock was showed to me to use as an anchor hitch for your friction brake, not for main anchor for block use. Again, I'll post pics. asap so I don't have to explain it and someone gets it all wacked.
Later

 

[TheTreeSpyder]

i kinda must agree with MM again (darn'it); about Tom; and Rob has been quite an addition here and around, bringing in polished science of the same mechanichs from a different perspective, giving fresh light to many things. Heck, i've even learnded from Mike's posts across some boards and years now.

i think that a clock hitch that is not dogged by deformity on the mount or pulled perpendicular to the mount, has a chance of sliding up or down, so would be tighter set to prevent that, but that makes line load at a leveraged angle. i think that, though a Porty/device grabs both lines only 1 will be tight enough generally to carry most of the load.

i think RescueRob's pic of the common anchor wrap from his world would be worth exploring as alternative. It only grabs one of the lines, allowing the other to seat to the anchor, giving some choke to prevent sliding up or down; wihtout forcing line to such a leveraged angle. Also, the joint of the knot in the line (or flat rope), in his version is in the most protected point from loading possible in the configuration. Yet, would easily be moved around and relocated even on a limbless run.

i think that anytime something incurs a pull or push, not on it's solid axis, it becomes leveraged; whether flexible line or stiff board or carabiner. Even a carabiner is leveraged if pulled correctly, it is just leveraged on it's short axis and not long one. If both long rails of the carabiner were as one, the device would be stronger IMLHO, for the spread that seperates them is leverageable, so is kept small, but the wider apart the spread is, the more leverageable. Less leverage on the small axis, so is maximum usage point. Just patterns to train eye to look for while scanning a rig i think.

-KC

 

[Mark Chisholm]

I like the pic that Rescue Rob showed us, but don't think that it is a good choice for the Port-A-Wrap. Yes the load factor is good, but it is far too loose for this application. You would have a tough time removing slack from the line each time. Maybe for an overhead or horizontal anchor, but not here.

The problem that we are seeing here is that a tightly attached sling proves to see more force than a looser one (theoretically). However, our applications require us to use a snug sling for both block attachment and anchor at the base. I see little that can be done to change this?

I feel that the clock hitch isn't much of a threat when tied properly and with adequate rope (strength that is). After all, it is seeing half of the force that the block is seeing (potentially), or less. And, if Riggs says it holds, then I would have to agree. I know his work.

The science behind the technique is always a good lesson!

 

[TheTreeSpyder]

Purty fair thar'Mark;

i'd kinda still go with Cow or locked TH, for more non- leveraged numbers and grip of choke hold; in all fairness to the 'RescueWrap'(?) of RoudTurn/Double Basket base (more protected from impacting knot 'joint'); it can be set tight as a Clock, leveragaing the same angle, securing more i would think. Or, then RescueRap could be set just a few degrees looser (for lots less loading near flat line), and make up for the 'loosenes' with it's full wrap gripping on the mount. Thereby present solutions of better grip, less loading if set right?

 

[Tom Dunlap]

Thanks for the chuck on the shoulder guys [He says while poking the chips around with his toe...] Glenn was the first person I met online, then emailed off line, then met in person. I know that I could have connected with a lot worse people

As others have said, the exacting math is important to consider. This gives a better knowledge of the whole picture. When I set up any rigging I follow an axiom that I heard Don Blair use. If the efficiency loss of a knot is the deciding factor in your rigging, get a bigger rope or cut smaller pieces. I think that most people who have even a casual understanding of the forces in rigging follow this axiom.

Like Mark, I know what Glen has done. If there were a shortcoming of the CH, Glen would have found it.

I'm giving some thought to the Wrap/Pick combo. I think that the Pick could be snugged up and still work for us. Snugging, though, still increases the angle though.

Tom

 

[Mark Chisholm]

Funny thing to me is how the clock hitch pictured here looks so much like a cow hitch. The only real difference is the use of the eye for tightening rather than slipping it through the bight. Hmmm.

 

[TheTreeSpyder]

i think that a non-leveraged basket type lacing gives 2.5x as much strength as the same line in a standard choke.

If the legs of the basket become spread/leveraged for more than 120% of load (~130 degrees); i think the choke mount (cow)would maintain higher strength in the same line as opposed to the leveraged basket option (clock with one leg).

 

[Mark Chisholm]

I'd like to test both of these knots and see which one breaks first (using them as intended). It would be a good reference point to know.

 

[NickfromWI]

Maybe that could be accomplished with some 3/8ths line and the winch.

 

[Tom Dunlap]

I wnoder if some relative degrees of magnitude could be gotten from using some thow line. Setting up some fish scales would be easy and cheap.

The proper way to do this though is in a test lab. Does anyone want to apply for a grant from the TREE Fund to research the efficiencies of various anchor hitches? There is money to be used, this might be the place to start.

Tom

 

[Mike_Maas]

</font><blockquote><font class="small">In reply to:</font><hr />
Funny thing to me is how the clock hitch pictured here looks so much like a cow hitch. The only real difference is the use of the eye for tightening rather than slipping it through the bight. Hmmm.

[/ QUOTE ]

The big difference is how it's loaded, tying is very similar.
From what I can figure from Robert's posts, if the clock hitch has angles of about 120 degrees, it would be about the same strength as a cow hitch (properly terminated cow, none of that single half hitch stuff).

 

[TheTreeSpyder]

Cow would lend a choke at ~80% tensile;

Clock at 120 would give ~100%loading,

So could squeak the loading percent to about 120% ; to approximate the weaker percentage of tensile in choke. That is where i got 130(+)deg.

So 1000# tensile loaded with 800# in a choke positioned mount (80%tensile) breaks. 1000 x 80% = 800

Also, 800# leveraged to 120% on a single leg of 1000#tensile (just about) breaks. 800# x 120% = 960#

 

[Sawdust]

here

 

[Sawdust]

Re: Clock hitch *DELETED*

Post deleted by Sawdust

 

[Sawdust]

try this

Nice...that worked...couple more comin

 

[Sawdust]

Tie hitch loosely at first so you can tuck all your rope in and your clevis. then start from beginning again and tighten each leg to it's fullest.

 

[Sawdust]

another

 

[Sawdust]

blah

 

[Sawdust]

blah blah