What is the Loading?
- Thread starter TheTreeSpyder
- Start date
Help Support Arborist Forum:
MasterBlaster
TreeHouse Elder
I'm under the bridge smoking a doob. 
You left out the best answer, number 9: <b>Impertinent</b>
Ken, is this your new design for a rope pre-stretcher? Or are you testing the anchors? Maybe the integrity of the stem or the pulley clevises?
Let's analyze what you've got.
The left-most rope sees a load of 100# and the total load is hanging from the lowest sheave, so that sling's got at least 100# on it. Now, since that's all the actual work that's being performed by this exercise, anything you do to increase the load on that sling assembly is unsafe and senseless. Seeing as how you've opted to perform the pointless stress test, however, let's continue with the additional loading.
Since the left-most line sees 100#, the right-most line must as well, so that's 200# hanging from the uppermost pulley. It looks like each leg is going to be another 100#, so the third pulley is up to 300#. We're now up to 400# of tension on the innermost end of the rope to support 100# of weight. In summary, the lower pulleys are carrying 100# and 300# respectively, so the total would be 400#. Is that the answer you're looking for?
So, after all this; is there a point you're trying to make? If so, what is it exactly?
Glen
Ken, is this your new design for a rope pre-stretcher? Or are you testing the anchors? Maybe the integrity of the stem or the pulley clevises?
Let's analyze what you've got.
The left-most rope sees a load of 100# and the total load is hanging from the lowest sheave, so that sling's got at least 100# on it. Now, since that's all the actual work that's being performed by this exercise, anything you do to increase the load on that sling assembly is unsafe and senseless. Seeing as how you've opted to perform the pointless stress test, however, let's continue with the additional loading.
Since the left-most line sees 100#, the right-most line must as well, so that's 200# hanging from the uppermost pulley. It looks like each leg is going to be another 100#, so the third pulley is up to 300#. We're now up to 400# of tension on the innermost end of the rope to support 100# of weight. In summary, the lower pulleys are carrying 100# and 300# respectively, so the total would be 400#. Is that the answer you're looking for?
So, after all this; is there a point you're trying to make? If so, what is it exactly?
Glen
For simplicity i tried to referance the whole load with pulleys etc. as the 100#; really meaning just one unit of the whole system/load's weight. The system being part of the load, might not need all of the considerations of the system weight seperate from the load.
Glens, i just wasn't sure who saw thru the puzzle deal etc.; just to show the extra force loaded, before thinking of what to do with it; verify the acknowledgement of it's existance, been a long week! Isn't force just loaded on the axis of fall stabilizing etc. alone? Aside from rigging, just throwing pull line over top seemed to make a surer, more focussed fall, but some power at the right time too. i've been noticing, using this for years before describing some of it (over the top, self torquing turn ) on ISA board when it was only one. Things i speak of i've been noticing someing different about and talking about for years, though most side with you, i have thought it well out and tested it best i could. Mayhem is best explanation, with common binding elements.
:alien:
Glens, i just wasn't sure who saw thru the puzzle deal etc.; just to show the extra force loaded, before thinking of what to do with it; verify the acknowledgement of it's existance, been a long week! Isn't force just loaded on the axis of fall stabilizing etc. alone? Aside from rigging, just throwing pull line over top seemed to make a surer, more focussed fall, but some power at the right time too. i've been noticing, using this for years before describing some of it (over the top, self torquing turn ) on ISA board when it was only one. Things i speak of i've been noticing someing different about and talking about for years, though most side with you, i have thought it well out and tested it best i could. Mayhem is best explanation, with common binding elements.
:alien:
Kneejerk Bombas
ArboristSite King
- Joined
- Oct 7, 2001
- Messages
- 36,971
- Reaction score
- 9,983
Glens,
You guessed 400#s?
How much pull is at the bottom sling of my similar drawing?
http://www.arboristsite.com/attach/13201.jpg
You guessed 400#s?
How much pull is at the bottom sling of my similar drawing?
http://www.arboristsite.com/attach/13201.jpg
Kneejerk Bombas
ArboristSite King
- Joined
- Oct 7, 2001
- Messages
- 36,971
- Reaction score
- 9,983
Looks like Glens went to bed, so I'll respond to my own question.
If the pullies are fixed to a system that won't allow them to expand or contract, they don't give any mechanical advantage. The load on Spider's puzzle sling is 100 pounds.
The load is 100 pounds, the sling takes 100 pounds. Each of the four legs take 25 pounds.
Otherwise you could create a perpetual motion machine!
If the pullies are fixed to a system that won't allow them to expand or contract, they don't give any mechanical advantage. The load on Spider's puzzle sling is 100 pounds.
The load is 100 pounds, the sling takes 100 pounds. Each of the four legs take 25 pounds.
Otherwise you could create a perpetual motion machine!
Kneejerk Bombas
ArboristSite King
- Joined
- Oct 7, 2001
- Messages
- 36,971
- Reaction score
- 9,983
I forgot to add, Glens, stop taking my work and claiming it as your own. I'll send it by legal tomorrow, but let's just say, cease and decist.
Tire Bait; this thread is about the self tightening, torquing load stuff.
Lumberjack
Banned
Mr. Mikey, your incorrect.
The reason your idea of perpetual motion wont work is this, take the sling off, does the bottom pulley move? Methinks so, thereby making a MA, just the log is holding it.
Answer: 400 pounds= 4 legs x 100 pounds each
The reason your idea of perpetual motion wont work is this, take the sling off, does the bottom pulley move? Methinks so, thereby making a MA, just the log is holding it.
Answer: 400 pounds= 4 legs x 100 pounds each
Mike,
I agree with you that ultimately the only thing that will be accomplished is some sort of mental exercise. These are levers, however, and just because you'll never be able to lift the USS Ronald Reagan with a 101 foot lever over a fulcrum 1 foot away from the keel using your 200# of manliness doesn't mean you won't put 10 tons of pressure on the fulcrum while trying.
I reckon you'd be pulling the lower pulley upward to the tune of at least 100#. I admit, this is all a little confusing... Or should I say "mayhemic"?
Glen
Lumberjack
Banned
And that aint countin the levers weight, which would be very substantial!!
Just to stir the pot, the 100' lever is only 100' when it is perpindicular to the fulcrum, but the arc on 100' aint that much
considering the 1' on the other side.All our gear is weightless and frictionless. Nothing but the best, and all that...
Normally my brain doesn't hurt, but I have to confess all this hypothetical pulley stuff is taking its toll on me. There's something about the pseudo block and tackles being dead-headed against themselves that's really hard to visualize and process. What I <i>really</i> want to figure out is <img src="http://www.mathacademy.com/pr/minitext/escher/penrose_triangle.gif" align="top">
Glen
Kneejerk Bombas
ArboristSite King
- Joined
- Oct 7, 2001
- Messages
- 36,971
- Reaction score
- 9,983
Dan (and Carl),
Maybe I am misunderstanding the drawing.
Do you perceive the pullies as able to move, or are they stationary and attached to one object?
I am thinking they cannot move. If a pully cannot move, it is only a redirect. There is no mechanical advantage in a redirect.
A pulley on an anchor as a redirect does not move (compared to link pulling it!)by definition? Pulling the line at support and lower pulley moves closer, non anchor. But the upper pulley maintains it's distance from that which pulls on it.
Here the upper pulley would carry 200#, if it were a drop eye/becket and end of line terminated there rather than to the spar at X; there would be 300#. For, even if pulley is on an anchor, still it will inherit the sum of the forces to the position at zero degrees line deflection.
So the 100# freee hanging load has 400# pushing up on it! Like i said a good attention getter for HS talk about climbing and rope sense, the ways you can use it, what to watch out for etc.
Or something like that
:alien:
Here the upper pulley would carry 200#, if it were a drop eye/becket and end of line terminated there rather than to the spar at X; there would be 300#. For, even if pulley is on an anchor, still it will inherit the sum of the forces to the position at zero degrees line deflection.
So the 100# freee hanging load has 400# pushing up on it! Like i said a good attention getter for HS talk about climbing and rope sense, the ways you can use it, what to watch out for etc.
Or something like that
:alien:
Lumberjack
Banned
It can move, take out the sling. The bottom pulley can move. Think if the log failed, the only thing holding them apart is the log.
About the redirect, anything less than 180* goin through it is MA. Look in "On Rope", it has the various loads on an easy to understand picture.
Lumberjack
Banned
Another way to look at it, what is holding back the 4:1 MA? The sling, thus making it 4:1 or 400 pounds. Even if you had it mounted on a 1/2" sheet of steel, and the pulleys axles welded to it, there would still be a 4:1 MA, the fact that it cant move is because you aint pullin hard enought
Kneejerk Bombas
ArboristSite King
- Joined
- Oct 7, 2001
- Messages
- 36,971
- Reaction score
- 9,983
OK, I get it now, each line has 100 pounds. So it's compressing the log with 400 pounds of force. The fact that the log doesn't compress means that all this force is just sitting there and it doesn't go in reverse, I mean the number of pullies doesn't change the output. It just changes how the rope is attached to the log.
This is why Spiders lacing doesn't help the pulling power of various configurations.
This is why Spiders lacing doesn't help the pulling power of various configurations.
Originally posted by MasterBlaster
I'm under the bridge smoking a doob.
with the troll?
http://www.zverina.com/z981116.htm
Nature wishes to take the easy way, the path of least resistance; the line loading higher at the bends and slants will want to straighten out IMLHO to relieve this leveraged force from within the line.
Also, on the hanging load, we have placed more stabilizing force at the pivot of the rigging point to the load i think. Also have extended a loaded leg to place another dose of pull on the load, at a leveraged distance from the pivot. i think somehow this gives more ballast to the heavier green end.
i think even self canceling pulls on an axis that are in the direction of movement is somehow more stabilizing, and some other things already mentioned elsewhere.
We are still pioneers into what lays right before us i think, Nature is an amazing creature, once the force is there; there might be a use for it.
Or something like that
:alien: :alien:
