Author Topic: Securing rope to horizontal bar  (Read 16981 times)

Bill Mann

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Securing rope to horizontal bar
« on: May 09, 2006, 08:01:25 AM »
Hello,
I was wondering what would be the most appropriate way to secure a rope to a horizontal chin-up bar. The rope is to support my bodyweight. Would a Bowline knot or some kind of Hitch be ideal?

squarerigger

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Re: Securing rope to horizontal bar
« Reply #1 on: May 09, 2006, 09:39:02 AM »
Hi Bill,

I was wondering why you need the rope to support your bodyweight?  Would it be attached to a harness or belt?  There are literally dozens of knots out there and it would be necessary to get a better handle on exactly how your body weight would be supported?  I do not feel comfortable giving advice of this sort without knowing the full declared use of the knot - I would not want to be responsible for recommending something that was later found to have failed (or perhaps succeeded?) to support you - more information please!

squarerigger

Bill

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Re: Securing rope to horizontal bar
« Reply #2 on: May 09, 2006, 09:53:26 AM »
Thanks for replying, squarerigger.

I was thinking of attaching 2 ropes for performing dips and chin-ups. I figure if each individual rope can handle my bodyweight, the set-up would be adequately strong.

Willeke

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Re: Securing rope to horizontal bar
« Reply #3 on: May 09, 2006, 10:28:03 AM »
Bill,
Can you give some more info?
Like what kind of rope do you want to use, and what kind of bar do you use?
And what is on the other end of the rope. (Is there one loop connecting the two ropes or do you hold one rope in each hand.
Do you want the rope to be able to move around and along the bar or do you want it fixed in one place.
And how do you expect to use the ropes, I get the impression you will hold the rope all the time and put your full weight on it (and take it off it again) many times each day.

It may seem unneccesary to give all these details, but it makes a lot of difference what kind of rope is used. Some kinds slip out of knots that are safe in others.
Also it is important to know if the bar is round or square.

Willeke
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Bill

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Re: Securing rope to horizontal bar
« Reply #4 on: May 09, 2006, 10:47:45 AM »
Hi Willeke,

I think the rope is made of cotton, it's white. It's 3-strand twisted and each strand is 3-strand in turn. I've made an eye-splice at the end of each rope to serve as a handle, for each hand, so each rope will be indepedent of the other. I've tested the rope before to hold my bodyweight.

The bar looks like the one shown here (I am attaching the ropes to the horizontal bar): http://fitness-onthe-run.com/circuit/images/615_200x.jpg
I intend to knot/hitch/maybe even splice each rope to the bar, interior side of each upright, so the position is to be fixed, not moved around and along bar. Hopefully, I will be able to vary the lengths though.

Yes, I will use it several times a day like basic olympic-style "rings".

roo

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Re: Securing rope to horizontal bar
« Reply #5 on: May 09, 2006, 08:33:09 PM »
Quote
The bar looks like the one shown here (I am attaching the ropes to the horizontal bar): http://fitness-onthe-run.com/circuit/images/615_200x.jpg
I intend to knot/hitch/maybe even splice each rope to the bar, interior side of each upright, so the position is to be fixed, not moved around and along bar. Hopefully, I will be able to vary the lengths though.

Yes, I will use it several times a day like basic olympic-style "rings".

I'd recommend using a hitch over a loop to prevent sliding.  It might also be a good idea to put rubber between the rope and the bar to further discourage movement.  Make sure you choose a hitch that will remain easy to untie when needed so you can re-tie or adjust things as required. 

With that in mind, here are some options:

http://notableknotindex.webs.com/sailorhitches.html

http://notableknotindex.webs.com/slippedbuntline.html

http://notableknotindex.webs.com/timberhitch.html

http://notableknotindex.webs.com/gnathitch.html
« Last Edit: February 26, 2012, 01:04:23 AM by roo »
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KC

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Re: Securing rope to horizontal bar
« Reply #6 on: May 09, 2006, 10:10:04 PM »
i'd think some kind of Transom at the cross members (like for kites) that was based on constrictor with extra 8 (Boa?).  i'd want Standing Part that hands pulled on to cross directly on Bitters to trap securely.  This should eliminate any creep or walk along either direction on the axis of either crossmember.  Then, secure tail.

For adjustability i'd Fig.8 stopper the Bitter Ends, then friction hitch another line to each line.; or each line back to self with Friction Hitch to form eye/ eye splice prussicked to self to form eye.

i'd consider rope handles to make it easier on hands.  Consider if ya fall thru, where head and bod might get banged up.

Tensile strength should be sonsider leveraged angle of rope if not perfectly straight from support to handgrip, % loss in lacing and any impacting, then X  >4; i think.  

It is good ya realize these will move, are not solid grips.  Butterflys etc. night start out with a truck inntertube sliced, that hands grip and placed under feets; so it tightens as you come down; until confident and trained to usher through movement right.

« Last Edit: May 09, 2006, 10:22:28 PM by KC »
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Bill

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Re: Securing rope to horizontal bar
« Reply #7 on: May 10, 2006, 04:50:52 AM »
KC,

I like the idea of making a Transom knot where the vertical upright and horizontal bar intersect. This should prevent creeping and undoing of the knot if the Standing Part is pulled along or at an angle parallel to the horizontal bar. This happens when the gymnast's hands in rings are pulled close together, forming a "V" with the two ropes. However, I'm afraid the rope might fray on the edges of the plastic square that's projecting at each intersection.

I have gloves to make it easy on the hands for holding the ropes. The whole idea is that the rope won't break and I don't fall through! But I'll have some padding on the ground.

At an angle pulled, the rope is weakened, but I'm not sure what you mean by %loss of lacing or X >4. Do you mean the lacing of the eye-splice? Are you saying the eye-splice handles are not solid grips?

This is how they look: http://www.peraltasquadron.org/images/CD_3_line_Splice.jpg

Bill

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Re: Securing rope to horizontal bar
« Reply #8 on: May 10, 2006, 11:27:47 AM »
Quote


I'd recommend using a hitch over a loop to prevent sliding.  It might also be a good idea to put rubber between the rope and the bar to further discourage movement.  Make sure you choose a hitch that will remain easy to untie when needed so you can re-tie or adjust things as required.  

With that in mind, here are some options:
http://www.geocities.com/roo_two/sailorhitches.html
http://www.geocities.com/roo_two/slippedbuntline.html
http://www.geocities.com/roo_two/timberhitch.html

Roo,
The Timber Hitch worked nicely. I tested each rope individually with my full bodyweight and it held. I haven't tried moving the ropes together horizontally under tension though.

Another thing, it seemed to stretch under the tension which I guess is only normal, considering flexibility of the material, otherwise it might just snap. This brings us to question the strength of the cotton rope. Do you think this material is fine or would you suggest getting something else like nylon rope?

Bill

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Re: Securing rope to horizontal bar
« Reply #9 on: May 10, 2006, 11:31:25 AM »
Quote

I haven't tried moving the ropes together horizontally under tension though.

By this I mean, bringing the two hands together like in this picture: http://singaporegymnastics.org/images/pix6.jpg

KC

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Re: Securing rope to horizontal bar
« Reply #10 on: May 10, 2006, 03:31:08 PM »
Quote

At an angle pulled, the rope is weakened, but I'm not sure what you mean by %loss of lacing or X >4. Do you mean the lacing of the eye-splice? Are you saying the eye-splice handles are not solid grips?



i rather think that at an angled pulled, the tension is leverged higher in the ropes.   Thereby, more tensile strength is needed or used for the same loading.  i imagine that as the line is pulled straight down with the flow of gravity force, then the force on line is equal to the load.  But as gravity as active force pulls down and rope goes at angle, it takes a longer route, to do the same work of carrying load so far from support as calculated by distance measured with flow of gravity.  So, for a 5' drop, it now takes 6' of line.  So, rope device is not inilne with pull force, but at more leverged angle, like turning wrench device with perpendicular rather than inline force.  

So, a crate on a pallet, being lifted by overhead hook has line bent over hook, then down sides and hooks to pallet.  But, high tension pressure at top of crate, where rope bends to come to point at hook; so to keep from crushing crate top, we place spanning bars across to reinforce.  Because the angled line raises the line tension to use more of the available tensile strength, to have less tensile strength left for other tasks/ forces/ headroom.   The loss of useable tensile by this model is not from strength loss of line, but rather more tension in line.


The strength loss, comes from the tight bight around support, around knot to self etc.  Then, we have an inner arc and an outer arc, of the tight bight.  The inner arc, would become compressed; which in a tension only device like rope, means the compressed inner bight isn't working, and only the outer arc of the tight bight is tensioned, and only it is working to carry the loading.

The stiffer the rope is, the more compressed area/ resistance to bending the inner arc of the bight has; the more weakened the rope is, as less of rope is working as tension support.  Also, the larger the diameter of the rope, becomes a multiplier of this (d)effect; for the larger arc the outer arc of bight has to make/ is more stretched/ tensioned.  Whereby the rope diameter on this tight bight/ bend becomes the leveraged axis/ multiplier.

Whereby, if we used flat rope/ webbing on same tight bight/ bend, there would be about Zer0 leverageable axis, given that the flat dimension was the one bent, thereby giving about Zer0 multiplier.  

So anyway, the leveraged/multiplying tension force of the angle(equal and opposites of pull and support not inline/ taking longer route for same work), leads to this dividing"% (of strength) loss of lacing(knot)".

The rope must be strong enough to accomodate the multiplied tension even though the rope strength is lessened!  If we constantly work the numbers to consume the available tensile of rope (after dividning it's strength under multiplied load) rope won't last long/ have less cycles to failure, and any impact or change could give failure also.  So, i'd recommend rope be at least 4x the strength needed after other calculations.


Orrrrrrrrrrr something like that. :P
« Last Edit: May 10, 2006, 03:32:10 PM by KC »
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roo

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Re: Securing rope to horizontal bar
« Reply #11 on: May 10, 2006, 07:31:04 PM »
Quote

Roo,
The Timber Hitch worked nicely. I tested each rope individually with my full bodyweight and it held. I haven't tried moving the ropes together horizontally under tension though.

Another thing, it seemed to stretch under the tension which I guess is only normal, considering flexibility of the material, otherwise it might just snap. This brings us to question the strength of the cotton rope. Do you think this material is fine or would you suggest getting something else like nylon rope?


I'd use nylon.  It's roughly 7 times stronger than cotton.  Let's say you expect the rope to see 400 lb at some point, just for a rough estimate.  Let's then multiply that number by two to account for reduction of strength due to knots or severe curvature.  

800 lb. (working load limit)

For a factor of safety of 5, we'd select  a rope with a minimum breaking strength of 4000 lb.

For nylon, that'd be about a 7/16" diameter rope.


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Dan_Lehman

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Re: Securing rope to horizontal bar
« Reply #12 on: May 11, 2006, 02:31:24 AM »
Quote
For nylon, that'd be about a 7/16" diameter rope.

And, for cotton, that'd be much thicker, and so much kinder to the hands.

--dl*
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Bill

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Re: Securing rope to horizontal bar
« Reply #13 on: May 11, 2006, 04:19:40 AM »
Thanks for all your help guys. I've uploaded a photo I took of the rope so you can further comment. It's about half an inch in diameter.

http://putfile.com/pic.php?pic=5/12920143370.jpg&s=f5

Can you confirm that it is cotton?

Jimbo

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Re: Securing rope to horizontal bar
« Reply #14 on: May 11, 2006, 06:58:22 PM »
Quote
http://putfile.com/pic.php?pic=5/12920143370.jpg&s=f5

Can you confirm that it is cotton?

Bill,

No one in his right mind would venture a guess as to the material of which your rope is constructed, just by a picture on a WWWeb page!!  As SquareRigger implied, any "advice" given is subject to litigious retribution.  Nevermind the ruling classes, to paraphrase SquareRigger: it would hurt my heart if I found my advice caused you pain!!!

But, in the spirit of traditional Individual Responsibility, I hope you may find this useful:

Fibres Guide - How to Identify the Synthetic Fibres Used In Rope Making

As to the problem at hand, if you put in eyes at either end of a rope of the "right" length, why not just drape the rope (with half-knots if you're not "smooooth", to keep it from slip-sliding away) across the "handles" (what look like handles in the wee pic anyway)?

Also, as I sometimes throw cordage over the roof beams for a fun workout (and Rings are my favorite workout "toy" -- though I'm too poor for the "real thing", so I just use eyes & fixed loops), could you hold forth on the details of your "rig" some more??  I'd like to know if you're using the thimbles as depicted in your Eye-Splice pic, and do you consider the Eyes as your "rings" or do you fasten traditional rings to these eyes?  Also, if you're hanging off the workout toy in the picture, where do your feet (or head) go when you get vertical??  You've given me some interesting ideas, which I appreciate very much.  Thank you!


I hope this helps!  And happy sweating!!!


Jimbo
Thank you all, for everything.  As of 6/6/6, I have changed my password to a random string (which I forgot), thereby assuring that anyone posting as "Jimbo" in the future will NOT be me.  Good luck!!!