RADS Theoretical Ratio

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...The drt can be called a 2:1 in a sense, but I don’t agree in a traditional rigging sense at least...

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Hey, Reg, good to hear from you. Glad you joined in.

The sentence I quoted you on exemplifies where most of the confusion comes from; i.e., rigging vs climbing. It would be nice if there was just one nice easy answer. Everybody wants this, but as in so many things we do, the answer is "it depends...".

In rigging the load moves from point A to point B. Those points as portrayed in almost all charts, are stationary.

In a climbing scenario, point A and point B are constantly in flux. This has to be figured into the equation.

Reg, please don't wait three years to post again.
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Dave

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Yeah it’s a difficult one word Dave, even though we can all feel the difference. But the 3:1 line travel concept is clearly wrong as shown again in Taylors Vid....but if he’d shown an anchor reversal you would witness the 3:1 line travel.

Yet at the same time we all know that it would take more effort to haul our identical twin brother off the ground than what it would ourselves being part of the system, same 3 line configuration for both i.e. your Rads thing. The difference being that you (the climber) are actually climbing/travelling up the 3 rd line on the rads, not just pulling from the ground to haul something else up....hence the MA, 3:1, 3 part load distribution or whatever you want to call it. Again, there is no 3:1 line travel but still remains a 3 way load share, unlike a 2:1-redi hauling system, hence the advantage. So you are both right.
 
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. Again, there is no 3:1 line travel but still remains a 3 way load share, unlike a 2:1-redi hauling system, hence the advantage. So you are both right.

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How is there not three feet of line travel. all three legs of rope get used up when advancing. It requires 3 feet of rope to pull yourself up one foot. I think Moss had the best reason why RADS could be considered a 2:1 being that it is both a 1;1 system AND a 3:1 hence the average could be considered a 2:1.
 
Taking my own stab here, but the simplest way I think about MA was told me by a rope rescue instructor that I met while natural rock climbing in high school.

The number of legs of line in a system directly correlates to the amount of mechanical advantage in a system.

IE, take for instance the standard fiddle block. Four pulleys, but five legs of line in the system, therefore a 5:1 MA. If you take the tail leg and go out sideways from the blocks, it now becomes a 4:1 MA with a change of direction redirect.

Same thing in the RADS setup, there are three legs of line, one coming down from TIP, one going up from climber to "ascender", and one tail leg coming back down past climber. True, like Taylor said, you only need the two feet of rope to travel one foot, but there are definitely THREE legs of line involved in the system, therefore a 3:1 MA.

If you were to take the tail leg and go 90 degrees sideways, or horizontally from the ascender, you would then have a 2:1 MA with a change of direction redirect.

Anyways, thats my take on MA, as told me many years back, and if you ask any rock rescue, mountain rescue or firefighter, they will tell it the same way. Legs of line in system = amount of MA in system.
 
Or, alternatively, RADS could be described as a 2:1 for 1/3 of your body. It takes 2 feet of rope and 1/2 the effort for one third of your body to pick up the other 2/3rds of your body. I think that would be an exceptable proof of RADS being a 2;1.

Thanks for starting this discussion. It has been interesting to try and explain something that I know more from feel rather than words. I think that being part of this discussion has helped me grasp the concept better myself and hopefully able to articulate it better. It has also made much more confident that RADS is indeed a 3:1. You had me doubting myself for a minute there Taylor.
 
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. Again, there is no 3:1 line travel but still remains a 3 way load share, unlike a 2:1-redi hauling system, hence the advantage. So you are both right.

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How is there not three feet of line travel. all three legs of rope get used up when advancing. It requires 3 feet of rope to pull yourself up one foot. I think Moss had the best reason why RADS could be considered a 2:1 being that it is both a 1;1 system AND a 3:1 hence the average could be considered a 2:1.

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Taylor pulls down 2 feet of line to haul the object 1 foot. Not how much rope gets used up altogether. That is a 2:1.

If Taylor were to reverse the anchors he would have to pull 3 feet to move the object 1 ft (3:1), exact same configuration just reversal of the anchors. Anyone can try it.

You are only getting a 2:1 with the Rads, but as the 3rd line is actually carrying part of your weight (unlike to a hauling system) its becomes a 3 part load share. It is right there, no mystery. You've just put me out till 2020 now Kevin, did you do that on purpose?
 
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...You are only getting a 2:1 with the Rads, but as the 3rd line is actually carrying part of your weight (unlike to a hauling system) its becomes a 3 part load share. It is right there, no mystery...

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Right there, no mystery huh?
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Even after Kevin's video with a scale showing actual weight transfer? Reggie, are you saying that you think the RADS is a 2:1 or a 3:1? Your previous posts stated you agreed that it was a 3:1.
It is the fixed over head pulley that causes most of the misunderstanding in the RADS configuration. It is most easily understood in use, not graphs. When climbing on a fixed overhead pulley, you gain one foot for every two feet of rope pulled. You are pulling half your body weight. This constitutes a 2:1 system. I hope everyone can at least agree on this.
The exact same pulley setting when used by a ground person to lift a load is a 1:1; i.e., no mechanical advantage.
When using the RADS configuration AS A CLIMBER, that same overhead pulley is in place. By itself this already is a 2:1. With the addition of a lower, moving pulley, it becomes a 3:1. Think about this.
If this is sill confusing, please, just go out and try it. It is quite obvious when using a RADS that the pull is much easier than a 2:1 and you are going no place in a hurry because you are using more rope than the 2:1.
If you doubt that this RADS system fully utilizes three times the rope, trying descending from your tie in point with just two times your rope. Trust me, you will not make it.

Dave
 
Taylor -

This has been quite an interesting discussion, hasn't it? I appreciate your participation and wish express my respect for your opinions. Your exceptionally creative and professional videos are highly regarded by many -- <u>certainly by me.</u>

There have been some important points made by the participants and some errors, too. But, for the most part, the errors have been minor. However, I <u>think</u> I've found the one central point of confusion that may be the cause of the diverging opinions about the 'RADS Ratio'.

FWIW … here's some additional thoughts … so, hopefully we'll all get 'on-the-same-page' … maybe

I'm thinking the confusion has to do with which block is being moved relative to the person doing the pulling. That is, the direction of the pull related to the direction of the moving block.

First, allow me to propose some definitions. Since "Rigged to disadvantage" was mentioned in one video, it would be appropriate to agree on the definitions of 'Advantage' and 'Disadvantage' in 'Simple-Tackle' rigging. This may lead to the heart of the controversy.

Simple-tackle (as opposed to complex) is any rope and block arrangement used to pull two points together where one block (or set) is stationary and the other block (or set) is moving. Then, Rigged To Advantage is where the direction of pull is in the same direction as the moving block. And, Rigged To Disadvantage is where the direction of pull is opposite the direction of the moving block.

Below is yet another simplistic diagram of a RADS. In the diagram point-D goes to the climber's saddle. Point-C goes to the climber's hand. Point-E goes to the TIP.

As seen by an outside <u>stationary</u> observer; point-D &amp; block-B move together toward point-E &amp; block-A which are stationary and point-C moves opposite block-B. However, as seen (and felt) by the climber; point-D &amp; block-B appear stationary, point-E &amp; block-A move together towards the climber and point-C moves in same direction as block-A.

This is where I believe the confusion exists. Relative to the climber who pulls at point-C, the climber sees point-E &amp; block-A move towards the climber. Therefore, because the pull is in the same relative direction as the moving block, I claim a RADS is a 'Gun Tackle', Rigged To <u>Advantage</u> … NOT Disadvantage.

Without immediately putting a ratio a 'Gun Tackle', Rigged To Advantage, please take another hard look at the diagram. Now, imagine the following: Point-D goes to a ground anchor point. Point-E goes to rigging point (like a tree top). And point-C goes to the hands of a rigger. So, exactly like in the above paragraph, point-D &amp; block-B are stationary and point-E &amp; block-A move together towards the rigger and point-C moves in same direction as block-A.

Question: Does the diagram look familiar?
Answer: It is a Z-Rig with a well-known 3:1 MA.

Yes, RADS is just a Z-Rig as seen from a from the climber's viewpoint.



Well, that's all I got! If that's not enough to get consensus, then like Dave and Kevin, I think I'll give up, too.


Best regards,
Jack


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The number of legs of line in a system directly correlates to the amount of mechanical advantage in a system.


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You have to be careful with this line of thinking. Here is a basic double line system with a pulley piggy backed on my down line of a basic ddrt 2:1. This would be a common way to lift a wounded climber out of a crotch and it could also be used as a very very slow way to haul oneself up the tree. Quiz.


what do you guess the weight on scale to be given that I way 175 lbs, more or less? explain. what would the weight be if I hand the pull end to a groundsman or a rescuer?

http://www.youtube.com/watch?v=oJ8Fsg17pCM
 
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...You are only getting a 2:1 with the Rads, but as the 3rd line is actually carrying part of your weight (unlike to a hauling system) its becomes a 3 part load share. It is right there, no mystery...

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crazy.gif
Right there, no mystery huh?
confused.gif
Even after Kevin's video with a scale showing actual weight transfer? Reggie, are you saying that you think the RADS is a 2:1 or a 3:1? Your previous posts stated you agreed that it was a 3:1.
It is the fixed over head pulley that causes most of the misunderstanding in the RADS configuration. It is most easily understood in use, not graphs. When climbing on a fixed overhead pulley, you gain one foot for every two feet of rope pulled. You are pulling half your body weight. This constitutes a 2:1 system. I hope everyone can at least agree on this.
The exact same pulley setting when used by a ground person to lift a load is a 1:1; i.e., no mechanical advantage.
When using the RADS configuration AS A CLIMBER, that same overhead pulley is in place. By itself this already is a 2:1. With the addition of a lower, moving pulley, it becomes a 3:1. Think about this.
If this is sill confusing, please, just go out and try it. It is quite obvious when using a RADS that the pull is much easier than a 2:1 and you are going no place in a hurry because you are using more rope than the 2:1.
If you doubt that this RADS system fully utilizes three times the rope, trying descending from your tie in point with just two times your rope. Trust me, you will not make it.

Dave

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Dave, if you read my post again you'll realise we almost on the same page (different terms). Please read it again.
 
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Right, Taylor used 2 feet to haul another object 1 foot but The object used three feet to pull itself one foot.

Yeah Reg Im trying to suck you in to the mundane semantics discussions on tree buzz. you may become trapped.

again, here is my rope wrench clearly eating up 3 feet of line in its Rads system to climb 1 foot.

http://www.youtube.com/watch?v=dvIoKOHusDU&amp;feature=related

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Kevin, the 3rd part of Taylors line in the video/confiuration is just a re-direct, not an MA.
 
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Dave, if you read my post again you'll realise we almost on the same page (different terms). Please read it again.

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Reg, it is the almost part, (different terms) that prompted the question. As you can see I am starting to flinch over this. I can see now that you were merely trying to be descriptive of why it is a 3:1 system.

Dave
 
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Dave, if you read my post again you'll realise we almost on the same page (different terms). Please read it again.

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Reg, it is the almost part, (different terms) that prompted the question. As you can see I am starting to flinch over this. I can see now that you were merely trying to be descriptive of why it is a 3:1 system.

Dave

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Deep breaths Dave. I still, personally wouldn't label it a 3:1 in a true sense, but I'll call it one for arguments sake in appreciating the advantage of the climber climbing up the 3rd leg to further his MA on the already 2:1.

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When climbing on a fixed overhead pulley, you gain one foot for every two feet of rope pulled. You are pulling half your body weight. This constitutes a 2:1 system. I hope everyone can at least agree on this.

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Assumiing you refer to DRT....again, I know what you mean, but your wording is misleading to my understanding. Corresponding with one foot measurements on a tree or ruler even, you pull one foot of rope down to gain one foot of lift. Do we agree on that also?
 
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When climbing on a fixed overhead pulley, you gain one foot for every two feet of rope pulled. You are pulling half your body weight. This constitutes a 2:1 system. I hope everyone can at least agree on this.

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Assumiing you refer to DRT....again, I know what you mean, but your wording is misleading to my understanding. Corresponding with one foot measurements on a tree or ruler even, you pull one foot of rope down to gain one foot of lift. Do we agree on that also?

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No we do not. What you just described is the 1:1 a ground man would experience when hauling up a load. What I described is what a climber will experience. This misunderstanding is why so many discount the top fixed pulley from the equation.

Dave
 
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When climbing on a fixed overhead pulley, you gain one foot for every two feet of rope pulled. You are pulling half your body weight. This constitutes a 2:1 system. I hope everyone can at least agree on this.

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Assumiing you refer to DRT....again, I know what you mean, but your wording is misleading to my understanding. Corresponding with one foot measurements on a tree or ruler even, you pull one foot of rope down to gain one foot of lift. Do we agree on that also?

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No we do not. What you just described is the 1:1 a ground man would experience when hauling up a load. What I described is what a climber will experience. This misunderstanding is why so many discount the top fixed pulley from the equation.

Dave

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Doesn't matter whos pulling the rope Dave. I'm talking about travel between marked points on the tree, not the climber hands an body passing each other as one moves down and the other up....but either way there is still equal movement on either end of the line. How could there not be?
 
As Jack stated, the RADS is a Z-rig. If a person on the ground pulls the climber up it is a 2:1 to the person on the ground.

If the person on the ground hands the pull rope off to the climber, it becomes a 3:1 to the climber.

Unless a pulley system falls in the 'simple' pulley category, counting lines supporting the load will not give the correct MA. I demonstrated this in my 15 segment pulley series.

http://www.youtube.com/watch?v=zX48pyWO7Pc

But the RADS is a simple pulley system and the MA can be accurately assessed by counting the lines supporting the load.

If we have a single pulley anchored overhead with a 150 lb climber on one end of the rope and a person(s) pulls the other end of the rope, how much force will the person(s) have to exert? 150 lbs. Now hand the rope to the climber, how much force does he have to exert to pull himself up? 75 lbs - this is exactly what a DdRT is except we don't use frictionless pulleys.

If you want proof that a DdRT is 2:1 to the climber and 1:1 to a ground person, then see if one person can pull up the climber on a DdRT setting. Then see if the climber can pull himself up.

The same principle holds for the RADS. It's a 2:1 to a person on the ground and a 3:1 to the climber.
 
the only ratio that matters is the one relative to the person doing the pulling. The only measurement that matters is in relation to the person doing the pulling. RADS is a climbing system and so the ratio would be relative to the climber. I dont see how RADS can be called anything but a 3:1.

Did anyone have any guesses on what my weight read when I piggybacked the pulley on my dDrt line?
 
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the only ratio that matters is the one relative to the person doing the pulling. The only measurement that matters is in relation to the person doing the pulling. RADS is a climbing system and so the ratio would be relative to the climber. I dont see how RADS can be called anything but a 3:1.

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But it's only a 2:1 to a person pulling from the ground, i.e. someone other than the climber.

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...did anyone have any guesses on what my weight read when I piggybacked the pulley on my dDrt line?

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Your weight would be your weight. If you mean how much force was in the pull line, It read one-sixth of your weight if everything was frictionless - well if you as the climber was doing the pulling.

But if you handed the pull line off to a ground person, he would experience 1/5 your weight.
 
Correct, the scale read 26 pounds.

I realized while doing this that one way to calculate a piggyback is to take the piggybacked pulley and bring it up and back over the limb and imagine it attached to the climbers harness, then count the lines involved. = 6
 
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Correct, the scale read 26 pounds.

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Whew - I like it when theory and 'real' agree!

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...I realized while doing this that one way to calculate a piggyback is to take the piggybacked pulley and bring it up and back over the limb and imagine it attached to the climbers harness, then count the lines involved. = 6

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Not sure how you got the right answer counting lines. Counting lines only works for simple pulley systems. What you described is a compound pulley system, i.e. a simple system acting on another simple system.

http://www.youtube.com/watch?v=zX48pyWO7Pc

When I sketch out the system you described I only see three or four lines supporting the load, depending on how you count them.

But the 'T' method will give the MA accurately and surely for any pulley system - simple, compound, and complex.
 
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