Results 1 to 11 of 11
Thread: Tensionless Hitch
-
04-29-2014, 09:03 PM #1
Tensionless Hitch
I recently got an email asking for some elaboration on how the tensionless hitch works. I understood the concept, but I didn't fully understand the mathematics behind the setup. So after some research and thumbing through my old calculus textbook, I am happy to report this simplified load table that I calculated out.
Number of Wraps T1/T2 μ = 0.2 μ = 0.25 μ = 0.3 μ = 0.5 1 3 3 4 11 2 9 16 27 244 3 32 75 178 5,650 4 111 362 1,174 130,741 5 391 1739 7,735 3,025,434 6 1,374 8367 50,945 70,010,638 7 4,829 40,250 335,524 1,620,094,652
T1/T2 is the ratio of the force on the rappel strand to the force on the knot.
μ is the coefficient of friction.
When would you ever use this? I don't know. Get creative. Maybe at the bottom end of a guided rappel? Search and rescue situation? Thoughts?
-
04-29-2014 09:03 PM # ADS
-
04-30-2014, 08:29 PM #2
<>
-
05-01-2014, 09:37 AM #3
I know you might think this is a "simple" table. but for the non-math nerds out there, can you explain this in kindergarten terms that I can understand haha
CanyoneeringUtah.blogspot.com
My YouTube Channel
"As you journey through life, choose your destination well, but do not hurry there. You will arrive soon enough. Wander the back roads and forgotten path[s] ... Such things are riches for the soul. And if upon arrival, you find that your destination is not exactly as you had dreamed, ... know that the true worth of your travels lies not in where you come to be at journey
-
05-01-2014, 09:03 PM #4
In simplest terms: If you wrap the rope around the anchor(tree) once and have low friction, there will be nearly equal force on the knot and the load strand. If you wrap it seven times and have high friction, there will be practically no force on the knot and all of it on the load strand.
If interested in why this matters or in the concept of the tensionless hitch, I will explain further.
-
05-02-2014, 04:21 AM #5
I usually rig a tensionless at the top of Yankee Doodle with a 200' rope.
It allows you to get in the first 2 raps off this.
Although, I did have someone tie our rope to a tree at the bottom of the first rappel once.
Tensionless is non-retrievable, you are leaving a rope at a particular spot.
I usually go 8-10' down the rope(depends on diameter of tree)and tie a figure 8.
Then wrap the tail end around the tree however many times you wish and then re-thread the figure 8.I'm not Spartacus
It'll come back.
Professional Mangler of Grammar
Guns don't kill people--Static Ropes Do!!
Who Is John Galt?
-
05-02-2014, 06:27 AM #6
What is the advantage of something line this over say a stone knot
Sent from my iPhone using Tapatalk
-
05-02-2014, 06:59 AM #7
In rescue terms, a high strength tie-off is used to maintain the integrity of "full strength" in a system. If a system is to be built to an inherent strength of 30kn, assuming that carabiners, rope, anchor and any other components in the system are 30kn. If the rope is rated at 30kn, and a knot is introduced into the rope then the rope strength at the knot is reduced by roughly 30%. By using a "high strength wrap (friction) " or prusik bypass to eliminate force at the knot, the rope then maintains its 30kn integrity and isn't a weak link in the overall system. Commonly, if not always this type of rigging is used when setting up "Highlines". The introduction of the "MPD" has sort of changed thinking in the rigging of highlines to a degree though, but the use of overall system integrity for maximum strength hasn't. A couple photos of prusik bypass, high strength tie-off, and highlines that require full strength integrity.
-
Post Thanks / Like - 1 LikesTaylor liked this post
-
05-02-2014, 08:35 AM #8
Using a tensionless hitch is fast and easy, and does not require untying a tensioned knot when breaking down the rig.
That said, it depends upon the rope/object friction. There are things out there with very low friction such as steel pipes and very smooth logs. More wraps will make this less of a problem.
Tom
-
05-02-2014, 12:19 PM #9
A stone knot is not really a knot, but a hitch.
Would it not serve the same purpose and is easier to tie?
Does that type of hitch reduce the strength of the rope as knots do?
Just curious if anyone has any info on that. Not that it matters very much. Thanks
-
05-02-2014, 12:29 PM #10
-
05-02-2014, 03:07 PM #11
Similar Threads
-
[How To] Is the Clove Hitch Safe?
By craigskiles in forum CanyoneeringReplies: 51Last Post: 11-06-2013, 10:13 PM -
Hitch Carrier Compatibility
By DesertDuke in forum Mountain Biking & CyclingReplies: 24Last Post: 02-13-2013, 07:34 PM -
hitch up the moose grandpa....
By greyhair biker in forum General DiscussionReplies: 8Last Post: 03-16-2007, 03:30 PM -
HITCH CARRIER?
By nelsonccc in forum MotorcyclingReplies: 5Last Post: 08-29-2006, 08:01 PM -
How good is your trailer hitch?
By derstuka in forum JokesReplies: 1Last Post: 08-16-2005, 07:52 PM