Help with Pulley System

Well lets's not be too encouraged by our politician's lackluster performance. Let's be contrary to our government and get something done by looking at all the angles on this topic and talk more. So who is going to be specific on this research? How about some reports based on true to life situations. That means outdoors with ropes and rigging and off the drafting table. I am assuming we have been operating off of theory witout solid real life testing out in the trees. Correct me if my memory fails me on this long thread.

You are absolutely correct, Treeman.

I first described the problem on 5 May. A few posts later (5-5-2007 at 08:58 PM), I suggested that people actually try the bare-bones system so that my “drafting table” analysis could be tested. I have tested it and it fails (the system causes the climber to descend while simply hanging there).

Since then, I have requested (maybe a half-dozen times) that others test the “three-pulley” system. Now, almost three weeks later, apparently no one has done that. I still am awaiting in-situ test results from someone else, rather than their just saying that I must be wrong.

I appreciate your call to action.

That being said, I logged in to post the following, but saw Treeman’s suggestion and wanted to respond to it first. Here is what I was going to post:

We have seen several people here who have presented their *opinions* (or the opinions of others) that the “Super System” is “safe.” I think it is worth noting, though, that no one has presented any engineering analysis to support those opinions, or to refute my analysis. Why do you suppose that might be?

Some people continue to cling to their belief that this system is without flaw when an engineering analysis shows that it is flawed. It’s an interesting comment on human nature that it’s quite difficult for some to give up their cherished beliefs. For some people, it’s impossible.

Many years ago, I ran across the cute comment, “Don’t confuse me with facts---my mind’s made up.” So, despite being fully aware that there are some of you out there who will not permit your mind to be “confused by facts,” I will, yet again, offer facts:

Fact 1 --- The system under discussion here---the “Super System”---has a serious design flaw.

This is not a spurious thought, not a hunch, not a guess, not a conjecture, not a hypothesis, not “just a theory.”

It’s a fact.

The system does have a serious design flaw. (Maybe it really should be renamed to the “Superflaw System.”)

Fact 2 --- Regardless of how many times it has been employed without incident, and regardless of how many times it is claimed that mythical “OSHA certified” people have approved it, and regardless of how many times someone desperately wishes it to be without flaw, Fact 1 still is true---it's still a fact.

Originally posted by Treeman
...I am assuming we have been operating off of theory witout solid real life testing out in the trees. Correct me if my memory fails me on this long thread.

I've been testing the real thing in trees. My photos are included earlier in the thread and here:
Super System photos

I can tell you exactly what will happen if a pulley is substituted for a cambium saver going over a branch. The top pulley (in the original system) will move down as the climber ascends.

What prevents the pulley from moving down in the original system is the effect of the rope bending around the branch inside the cambium saver and then changing direction as it chokes through the screwlink. Because the cambium saver has very low friction it is not a factor in preventing the pulley from moving down. It is the bend in the rope at the screwlink which is countering the unbalanced MA.

The pulley test suggested will be irrelevant if it doesn't simulate the bend in the rope I describe. The very low amount of friction inside the cambium saver is a total non issue. It is easily overcome by the movement of the climber on the rope. It is the bend at the screwlink which creating an equilibrium. However if the equilibrium is overcome by dynamic loading or a "jerky" climbing style, there is no negative effect for the climber.

I have tested this by not choking the system to the branch. In this case the top pulley merely moves down as the climber ascends.

Jim, I know you've done a small scale indoor simulation, how about some testing with the actual components of the system, rigged as originally designed (see photo link above), with a climber on the system. Once you've observed the baseline behavior of the system you may get additional ideas about testing variants.

I would like to see what I've described above confirmed or not by another tester. We need to establish baselines with the original system.

I am positioning myself as the observational empirical scientist in this discussion. I'm hoping that Jim on the theoretical engineering side can start to quantify some of what I'm observing through practical testing.
-moss

I know that moss and I could have resolved all this a long time ago if we had been able to meet, draw pictures, wave arms, and rig systems. But alas, we are geographically distant.

I thought about what we might say if we were together. This is a transcript of that imagined conversation. The names have not been changed to protect anyone.

Moss, if I have inaccurately represented your views, please speak up!

Announcer’s voice: . . . and now, CBS---Climbing Big Sycamores---brings you the latest episode of “Moss and Jim,” the popular, long-running, and ongoing story of a disagreement about . . . well, stay tuned and find out.

We join moss and Jim in moss’s secluded palatial mansion somewhere in the beautiful northeastern United States.

M: Jim, thanks for coming up here. I’m really glad we finally got together! I’ve read many of your posts and I like your ideas. You know, I have to say that you look a *lot* younger than I expected: You don’t look much over 55 or 60.

J: Gee; thanks, Andrew. And as I’ve said before, I really respect your ideas, your knowledge, and your experience. And you look even more handsome than I had imagined: I thought maybe you’d look like Brad Pitt or Leonardo DiCaprio or a young Robert Redford. You certainly have them all beat!!

M: Well . . . yes; I really do. It’s truly a problem sometimes: You probably noticed all those beautiful women hanging around outside the estate gates.

(moss shrugs resignedly)

(Jim nods.)

(M and J hug (briefly, of course).)

J: Let’s get started. One thing that has concerned me for a week or two is that maybe we have not been using the same setup. After all, we do seem to be getting different results. I’ve been using what Geof originally posted, minus the additional knots---just a bare-bones version of his picture.

By the way, that guy is a heck of an artist, huh?! I guess you, as a truly accomplished and published artist, can appreciate his work.

M: Yes, he really is good. I think if I get more work than I can handle---and that looks likely---I’ll pass some on to him. As for the climbing configuration, yes, I used the same thing. I agree: I don’t know why our results are different.

J: Well, let’s compare where we stand just now. . . .

(Phone rings.)

M: Oops . . . excuse me just a second, Jim.

Hello? ---- Yes---hi, Angelina; how are you? ---- Yes, I’m fine, too. Hey---I can’t talk just now; I’m in a very important meeting with one of my heroes. Can you call back this evening? ---- Yes, I have just a minute. ---- Saturday night? What did you have in mind? ---- Well . . . but wouldn’t your main squeeze mind our doing that? ---- Well, look; the truth is that my standards really won’t let me do that with you. ---- Oh! No no no!!! I didn’t mean that at all! It’s not that you’re not *beautiful* enough for me!! I meant my *moral* standards. ---- What? *Morals*---you know . . .morals . . .like . . . well, like that “thou shalt not” stuff. ---- Yes, yes. Look; I really have to go. Call back this evening; okay?

(Andrew hangs up phone and grimaces.)

See what I mean. It’s really a burden at times.

(In sympathy, Jim slowly shakes his head and wipes a tear from his eye, but does so with absolutely zero comprehension of what moss’s burden must be.)

M: So we agree that the Super System is unbalanced, to the tune of one-third of the supported weight. And you see that as a problem.

J: Yes, and much more than just a “problem.” As I’ve said, it’s a serious design flaw.

M: Well, that’s a point of disagreement. You say it’s a flaw; I say it’s just the way the system was designed. I don’t know for sure, of course, but I just can’t help but believe that the SS’s designers knew what they were doing. They certainly must have known that when it’s in use, that the friction at the branch would prevent any problems.

J: And you agree with that line of thinking? That the naturally occurring friction, any time the system is used---under any conditions---will render the system safe?

M: Yes. This system reportedly has been in use for a very log time, and probably by thousands of climbers, and I have never heard of an accident or incident.

J: So, then, you believe that it is absolutely safe to use---at least as safe as any of the commonly accepted climbing configurations?

M: Yes. As long as it is used with the link choking the branch, it is safe. I am fully convinced of that.

J: But you have to admit that the position of the link, the diameter of the supporting branch, the coefficient of friction between the rope and the branch, whether there is any foreign matter on the branch, whether the rope is damp . . . all that and much more are quite variable from tree to tree . . . even from hour to hour. They are total unknowns.

Those factors never can be depended on to provide reliability and consistency like, for example, the knots we use. Truly everything that counters the force imbalance is an unknown. We would *never* allow such a thing with any of our ropes, knots, or any other equipment!

M: I hear you. All I can say is that I think it is enough to adequately support my case to point out that there have been no reported accidents from this system.

J: Do you know that to be a fact?

M: No, but I have talked with many climbers who have used it, and they all say that.

J: Okay. I can’t argue with success.

I know it would be an unusual occurrence, but how about the situation that Mark and I have mentioned---where the friction between the branch and the rope is very low---low enough that it is not enough to counter that force imbalance? In that case, the climber will descend uncontrollably.

M: Well, Jim, here again, we have a disagreement. You say the climber will descend; I say he will not; he’ll just hang there.

J: But Moss, I have proved theoretically---incontrovertibly so---that the climber will, in fact, descend. I then proved it logically. And then I demonstrated it by modeling the system. How can you disagree with all that?!

M: I don’t for a moment doubt that you’ve done all that. I can’t at all argue with your extremely high intellect---I truly do bow to you in awe of it. In fact, I feel so incredibly inferior just being in your presence.

(a moment of uncomfortable and poignant silence as moss regains his composure)

M: We both know of your many scholarly publications, and that you are a well respected and in-demand consultant by some brilliant minds worldwide. I can only say that I set up the system myself, hung from it, and I stayed put. I did not descend even a millimeter.

By the way, you didn’t say that you actually tried it in the trees. Have you done that?

J: No, I haven’t been able to do that yet. But as I said, I did model it. I used the very same configuration. How could doing it in my den be any different from doing it outside?

M: I don’t know. But I do ask that you do it. Please just try it.

J: I’ll do that as soon as I get back home.

Back to the test you did---it was on the bare-bones configuration we just talked about? And you did it with all pulleys, to simulate low friction at the branch?

M: Absolutely. And I just hung there.

J: Moss, I just don’t get it. Could we run a test now? Do you have the time? You have some really nice trees out there. By the way, how big is your estate, anyway?

M: Oh, I only have about 80 acres on this one. The larger ones have better trees, too. Some of the trees here are even less than a hundred years old. But yes; I do have time. Let’s do it now.

(Phone rings.)

M: #!@*%!! Not again! Hold on---I have to hear who it is---it might be one of my brokers---I’ll let the machine answer it.

(little-girl voice from answering machine): Hello? ---- Andrew? ---- Are you there? ---- Andrew, this is Britney. Please pick up.

M: Oh ^$#^%#---not her again! I have NO idea how she ever got my number. She’s been calling ever since one of the tree-book advertisements showed my picture.

B: (whiny, whimpering voice from answering machine) Andrew, please call me. I so VERY much want to meet you!! I just don’t think I can go on living without having . . . . (Moss turns off answering machine)

J: (suppressing gag reflex; looks at wristwatch) Oh, rats!! I just realized the time!! I have to get to the airport and head back home!

M: Oh, Jim, I’m sorry. My Lear is in for its annual inspection right now, and the field where my other planes are based is too far from here, or I’d have one of my pilots fly you home.

J: Thanks for that, moss---I do appreciate it. Look---we have to continue this some time. I’m sure we can reach a resolution. I would stay, but Clint Eastwood read my paper “The Uses of Polymorphic Nonlinear Algebraic Set Theory as Applied to Biconical Non-Impedance-Matched Over-the-Horizon-RADAR Antenna Systems”---that’s a hobby of his, you know . . . .

M: (interrupting, and with a slight smirk) Yes, I read that treatise; it was very good. Did you consider using Descartes’ principle of regular tetrahedrons as part of the solution?

J: (with a huge burst of laughter) Ah, Andrew, you rascal, you! That’s too cool! Do you know that Stephen Hawking made the same joke when he stopped by last month to have me explain some things to him?! You guys are just too much!

Anyway, Clint is stopping by my house again today to talk with me about doing the screenplay for a book he wants to make a film of---some book about trees by . . . I dunno . . . Presley or Parson or Purston, or something like that.

M: Is it Preston? Richard Preston?!

J: Hmm . . .yeah . . . it might be . . . .

(voices fade out; theme music fades in)

CBS invites you to join us again soon on your favorite RTC forum for . . . .

I am reading up on how to write pieces that is non--non fiction. Setting, theme, viewpoint, dialog---all that stuff I should have gotten in school before I dropped out of college to become....well....who I was to become.

JimW- now that was a long piece of work you just did. I have just got to ask two questions.

1:
How many words was in that piece? Uhhhh....maybe I should do a cut and paste and let the software answer that.

2:
How long did it take to compose that piece? I can do 1000 or so words on a good day. I have little experience in script writing however: It would take me days to figure out how to do a scene of the last posting's length. (Treeman feels the shadow of inferiority descending like a cloud of locusts intent on defoliation). I'm impressed! (Treeman tries to hide the last remaining leaf of certainty as he hears the chomping of mandibles....or is it man-nibbles, nearing the nasal veins in the lobes).

So at this juncture, I think it is time to take a pause for the cause. Take a deep breath and let the smoke clear around the fusebox.

I have got to hand it to everybody- this has been one heck of a thread! Quite civil but hot as well as we express our feelings in the most literary way. One thing I know beyond a doubt- tree climbers are well above normal intelligence. What a community of folks we have here!! I rest my case.