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Replies: 42
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Oculus Spirit [85323]
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Lungineers, please help!
Nov 28, 2018, 12:08 PM
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Mcjr is getting this swing or similar from his grandparents:
https://www.amazon.com/b4Adventure-B4A-108S-Dreamcatcher-Swing-Royal/dp/B01FBA7RVS
I just helped FIL install one at his house. We bolted a 14 ft 4X6 into two oaks to hold the swing. It works, but 200 lbs is a decent load on it.
Anyways, I pretty much only have pines. What if I installed 5/16 galvanized aircraft cable (zip line cable) between two pines? Worried it might sag or slip but seems like a good idea in my head.
Is there a better or cheaper solution to hanging that swing without a nice oak branch?
thx
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Hall of Famer [20571]
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I beam***
Nov 28, 2018, 12:10 PM
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CU Medallion [54758]
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Skyhooks
Nov 28, 2018, 12:11 PM
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actually, you'd only need one, so that's good
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Oculus Spirit [85323]
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BRB, going to find one***
Nov 28, 2018, 12:19 PM
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Oculus Spirit [79201]
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What kind of hippie dream catcher swing is that?***
Nov 28, 2018, 12:12 PM
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Oculus Spirit [85323]
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Bend over and I'll show ya***
Nov 28, 2018, 12:20 PM
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Oculus Spirit [79201]
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OK, now what?***
Nov 28, 2018, 12:22 PM
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Oculus Spirit [85323]
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Just stay there***
Nov 28, 2018, 12:23 PM
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Lot o points [155901]
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My daughter has one of those. They're great.
Nov 28, 2018, 12:16 PM
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Then week two comes and they never use it again.
I think you're going the correct route with this elaborate rigging system you're devising.
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CU Medallion [54758]
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Cheapest & easiest on the tree(s) is a Tetherball setup
Nov 28, 2018, 12:17 PM
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just gotta invest in a decent helmet or two, too...possibly with facemasks
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All-In [47795]
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what happened to an old tire and piece of rope?***
Nov 28, 2018, 12:20 PM
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Oculus Spirit [79429]
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Kayden has sensitive skin and a rubber allergy
Nov 28, 2018, 12:23 PM
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Please try to be more Woke and empathetic towards others.
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All-In [47795]
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LMAO. one of my friends from Clemson said today that she is
Nov 28, 2018, 12:28 PM
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repulsed by gender reveal parties because they "conflate anatomy with gender" and "force binary boxes" which are harmful to a child.
These people vote.
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Lot o points [155901]
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I'm repulsed by gender reveal parties too, but
Nov 28, 2018, 12:30 PM
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only because they weren't a thing for gen X and earlier, and I never thought it possible that those expecting could find a way to monopolize and monetize even more attention than they were already getting by having a kid.
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All-In [47795]
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agreed***
Nov 28, 2018, 12:32 PM
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Oculus Spirit [97716]
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All-In [47795]
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^^^^your cisgendered white male privilege is showing^^^^^***
Nov 28, 2018, 12:39 PM
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CU Medallion [54758]
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Oculus Spirit [97716]
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The presence or absence of a Y chromosome
Nov 28, 2018, 12:50 PM
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Which results in the presence of a ##### or ######.
Which results in one gender making sperm and one making eggs. Which results in one gender giving birth to another human with or without a Y chromosome. Which results in a set of unique internal organs.
That results in having testosterone or estrogen hormones present, and a deep voice, breasts after puberty, and a host of other natural ####. Side note - the absence of a Y chromosome makes it extremely difficult to be an effective defensive lineman in football. The presence of a Y chromosome makes it impossible to breast feed an infant.
I mean, seriously, how do these people believe this stuff, then pass BIOL 1010?
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Oculus Spirit [79201]
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Whale you see when a man loves a woman
Nov 28, 2018, 12:43 PM
[ in reply to ### is a gender reveal party anyway? ] |
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he makes ##### to her. If she really loves him, she lets him make ##### to her without a rubber. Sometimes a woman is in heat and when the man ejaculates into her while making #####, this causes a baby reaction in her lower intestines. It grows and grows for 9 weeks before being born. But at about the 1.5 week mark the medicine man can rub KY jellies on her stomack and get a magic picture of the unborn baby body to see if it has a case of the peanuses or not. Some people want to know right away whether their baby to be will have a case of the peanuses, or if it's gonna be a non-boy. Others want to wait and gather round all their jealous hoefriends who aren't knocked up and are babyhongry to reveal to them just how much peanus their baby will have. They reveal this based on their social class. Rednecks shoot shotguns that have peanus colored smoke that comes out. Obeds make up a mystery batch of KoolAid and the color it turns after 15 seconds reveals wether it' s a boy or non-boy. So on and so forth.
And that's how it works.
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CU Medallion [54758]
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Hall of Famer [23693]
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Oculus Spirit [79201]
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Oculus Spirit [85323]
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Oculus Spirit [75717]
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That thing looks weird and I wouldn't have it.
Nov 28, 2018, 12:25 PM
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I also don't reckon I'd be bolting into trees too much.
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Hall of Famer [23994]
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Re: Lungineers, please help!
Nov 28, 2018, 12:35 PM
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rigging cable would be good, you just gotta make sure you get enough tension on the line so it doesn't sag and make sure the ends are clamped down good
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Oculus Spirit [79201]
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What if he doesn't like McJr? How loose should the
Nov 28, 2018, 12:37 PM
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clamps be then?
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Hall of Famer [23994]
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Tighter than Ms Lovin's neeple clamps
Nov 28, 2018, 12:43 PM
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but not too tight where the nips start bleeding
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CU Medallion [54758]
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pines move a good bit - doesn't seem like a great idea
Nov 28, 2018, 12:42 PM
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so, take vid please!
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CU Medallion [64837]
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how far apart are your trees?
Nov 28, 2018, 12:47 PM
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McLovin
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Oculus Spirit [85323]
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I don't know yet.....I'm going to put it here though
Nov 28, 2018, 12:50 PM
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Will prob buy 100 ft and expect to use 50-60
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CU Medallion [64837]
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Nevermind. You're on your own: use this calculator
Nov 28, 2018, 12:53 PM
[ in reply to how far apart are your trees? ] |
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https://www.ropelab.com.au/two-point-anchor-calculator/
This is all considering a static load, but if you're swinging, and REALLY swinging, then the dynamic load will be significant. I don't feel like doing the math, but just play it super conservative.
Play around with the allowable sag, and load numbers and keep an eye on the tension number. You'll notice how that tension climbs SIGNIFICANTLY as you decrease the allowable sag (it's all about the angles, bruther). I would go big on the cable. Definitely bigger than 5/16".
I also have some thoughts on anchoring the cable:
If you use eyebolts, be sure to check their rating. Bent eye bolts won't nearly be as strong as forged ones. Also, keep an eye on the thread size. It'll take a decent diameter to have enough "bite" in the tree to keep it from pulling out.
If you use cable clamps to secure the cable, NEVER SADDLE A DEAD HORSE!
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Oculus Spirit [85323]
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Something not right here
Nov 28, 2018, 12:59 PM
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Currently have a 90 ft zip line....pt to pt is prolly 80 ft.
I put my 205 lbs on the line and it sags 2 ftish?
According to this that would put a tension of 1877? What are the UOMs here? 1877 lbs? Cuz that def ain't right.
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CU Medallion [64837]
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Re: Something not right here
Nov 28, 2018, 1:10 PM
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The units should be whatever you entered. If you put pounds, then pounds would be the units of tension.
I didn't double check the math, but I would expect that 2000 pounds-ish would be pretty close.
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Oculus Spirit [85323]
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Thought I used a 500 lb tensile strength ratchet strap to
Nov 28, 2018, 1:14 PM
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tighten up the zip line.
I see now "units are not required" so if I used lbs for my weight, the tension should also be lbs.
Just doesn't seem right that I put 2000 lbs tension on it during install, maybe sag is actually 3 ft and I got 1400, idk?
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Oculus Spirit [85323]
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1500 tension, 500 load still tho***
Nov 28, 2018, 1:18 PM
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Oculus Spirit [79429]
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he’s posting a bunch of academic nonsense
Nov 28, 2018, 1:13 PM
[ in reply to Something not right here ] |
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The real world way is to just eyeball it, get everything anchored in a way that your gut says is right, and tug on it a few good times to make sure she holds. Most men will instinctively know that all is secure and ready to go.
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Lot o points [155901]
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HEAR HEAR. I love these fancy boys and their book learnin.
Nov 28, 2018, 1:16 PM
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You get the best rope you have lying around, give it a couple double knots, and send the kids out for fun.
Do you think they had all this math crap when they built the Hoover ###? If they didn't need it, I don't either.
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Lot o points [155901]
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Oh, and McLovin, just to give you a quick real answer.
Nov 28, 2018, 1:18 PM
[ in reply to Something not right here ] |
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Just my quick thoughts after giving it a once-over.
The deviation anchor force calculator assumes a stationary load and 100% efficiency, breaking with the assumption of a 0.2 friction coefficient from the Redirection Forces article.
To reproduce the equations used in the deviation anchor force calculator, we set exp(-mu*theta) equal to 1 for 100% efficiency. Theta is the deviation angle, and mu is the friction coefficient. The friction coefficient is therefore zero. The resultant subtends an angle of alpha = atan[(exp(mu*theta) – cos(theta)) / sin(theta)] measured counterclockwise from the horizontal.
Using theta = 75 degrees as an example, we get alpha = 37.5 degrees. Then the magnitude of the resultant is r = [(exp(-mu*theta)*sin(theta)) / cos(alpha)] = 122 % of the load, as reflected by the calculator. The force on the anchor = exp(-mu*theta) = 100% of the load.
If we instead assume a high efficiency pulley (95%), then mu = ln(1/0.95) / pi = 0.016.
alpha = atan[(exp(mu*theta) – cos(theta)) / sin(theta)] = 38.3 degrees.
r = [(exp(-mu*theta)*sin(theta)) / cos(alpha)] = 121% of load
force on anchor = exp(-mu*theta) = 98% of the load
Suppose an 85% efficient pulley. Then mu = 0.052, alpha = 40 degrees, r = 118% of the load and force on anchor = 93% of the load.
If the rope runs through an aluminum biner for 50% efficiency, then mu = 0.221, which is reasonably close to the 0.2 assumed in the Redirection Forces article.
alpha = 48.1 degrees,
r = 108% of the load,
force on the anchor = 75% of the load.
So the calculator is conservative in that it predicts higher forces than we would expect to see in actuality. The force on the anchor is not shown as an output because it is always equal to 100% of the load if we have 100% efficiency, being that mu = 0 and exp(0) = 1. For more information, see Paul Stovall’s article, Calculating Deviation Forces with Friction
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Oculus Spirit [85323]
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Absolutely correct Obed.
Nov 28, 2018, 1:20 PM
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I guess one of the most common roped applications of this is in rope access and the rope does not move through the deviation – other than with stretch.
I am happy for the results to be conservative and that those who understand what is truly going on with the physics can do more if they choose.
-Mclovin
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CU Medallion [64837]
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CU Medallion [54758]
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CU Medallion [64837]
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Best answer: It just be like that.
Nov 28, 2018, 1:20 PM
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Alternative answer: That's the way I was taught.
Alternative answer: The saddle side has more surface area than the U-bolt side, so it is less likely to crimp or weaken the cable. Also, it probably has something to do with the "live" aka "load" side of the cable being more important, but my brain is fried from all of this academic talk.
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Replies: 42
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