Pulleys and GRCS

Been using GRCS to "crane" logs off house roofs due to storm damage in the area, however I have been quite limited in my rigging work as I have only been using one pulley attached high in the tree. Knowing the forces at work here, I seem to be at a loss as to how to increase the lifting power of the GRCS using additional pulleys. After all, the GRCS only lifts so much and then the wraps slide.
Anyone care to share their setups/info/ideas?

The wraps don't seem to slide when the self tailer is used.

Also, you could use 2-1 mechanical advantage by attaching a block in the fallen tree and tying the rigging line end off near the gin pole block.

We've done some mighty huge trees even without resorting to MA-+-

Be careful you don't overload your attachment point in the tree.

attachment point using 1 pulley = twice the weight of the load
2 pulleys = 4 x's

Load the entire spool with wraps, use the self-tailer and the rope shouldn't slip (sometimes new ropes have a coating and they don't grab).

The re-direct on support will give ~2x increase on force of lift. A little less for more open angle than pairallell lines; and also change the angle of pull(to a median line between the 2 legs of line to pulley). The friction of the pulley will reduce this some more in hold and lower operations, but increase the loading in lifting operations.

If more power is needed, and don't want to hoist more pulleys to support; can rig a pulley just above GRCS; then the line would go up to a prussik grabbing mainline, and then return line down to GRCS. For a Z-Rig; powered by GRCS. The pulley just above GRCS could be a prussik minding pulley, with a prussik on mainline; or just prussik and other tender. Now system can lift, until upper prussik position compresses down to GRCS. Then tended prussik on mainline can hold load; while pole extends upper prussik position upwards for another pull.

Longer pulls could be had; by mounting a pulley at base of host tree; GRCS on another low anchor, and Z-Rig horizontally (or just 2:1 with seperate line)between the 2 positions. Then finishing the 3x pull into the the pull of the GRCS. This would also place a tensed line horizontal at ground level; this could be a risk; and bent for a high leveraged pull to initiate movement, quick adjust etc. perhaps.

This is a lot of lifting power; lots of line tension. Perhaps different leveraged position of rope hitch on load; easier moving hinge pivot could be used instead or as tandem strategy; less rope stretch to fight, lower friction bearing pulley(s) if no shocks to planned for lifting phases.

Xtra said:

Be careful you don't overload your attachment point in the tree.

attachment point using 1 pulley = twice the weight of the load
2 pulleys = 4 x's

Click to expand...

Truth, be carefull yarding logs with an unguyed tree as a spar. I have removed logs from houses with cranes, if no crane and it aint a good sawlog, just buck it in chunks and throw them down.

Very good point on guying back supports that load force is not inline with support column. Gin pole guying needed if support was'nit anchored well

Here is another idea, that gives 2x GRCS and only loads pulley redirect 1xLoad (+PulleyFriction on lift; -PulleyFriction on hold or lower).

The retrievable bowline goes on weaker/more leveraged support; green line hangs free and is only for placing/ retreiving bowline; this keeps load at this position to 1/2 X Load. If; line on this support is not bowline on support, but rather just redirected to tie back down to trunk; would be 1 X Load (-Friction).

Bearing pulley on lift gives less loading and effort; on hold/lower bushing gives less loading and effort. Bearing pulleys aren't for any shock loading though.

Another consideration is how the pulley is suspended. We are assuming it is just hung by a choker to float above load; so that it has a 2x potential. But, if it is suspended by another rope tied off at ground(for easier placemeant and retrieval); then it has a 4x Load potential(in FrictionLess Universe); for one 2x system is nested within the other.

For, this stacks another multiplier of 2:1 on top of the other 2:1. The amount of friction on the branch will decrease the loading below that; but the multiplier must be recognized to be above 1x the previous multiplier. This new multiplier(line holding pulley; tied off at ground); remains the same whether lifting/holding or lowering. While the original multiplier directly holding load; varies it's effect still. So that friction of the pulley reduces loading on lowering and holding, while increasing loading on lifting.

So, the 2nd rig in this picture for lifting gives:
Support Load = Load X (2+PulleyFriction) X (2-BranchFriction)

For lowering or holding gives:
Support Load = Load X (2-PulleyFriction) X (2-BranchFriction)

or 4xLoad if ruling out/ignoring friction in test case;
assuming Zer0 degrees angle spread on each line.

Sailor Theory: You must keep calculating until the force flow stops. Each force must have an equal/opposite to be satiated; or wanders from port to port until it finds/is exhausted/satiated by it's equal/opposite! All points from the beginning of this journey until the end , become loaded points.

Orrrrrrrrrr something like that

spyder,, i think you have some bad numbers on your rigging figures... you have 1/2x, 2x, 4x, on your charts..they're wrong...your redirect pulley,,is just that,,it redirects the line... it gives you no mechanical advantage....as for the pulley choked to the limb vs. a pulley on a line over a limb, tied off to the tree.. there is no difference.. the forces are the same,, there is no 2x's to 4x's advantage...it's a common misconception....check out this link,, it's fairly basic,,,but it explains a lot....




http://science.howstuffworks.com/pulley.htm

juststumps, you're confusing MA with the load multiplier factor that the anchors are subjected to. Different animals. TS is spot on.

Ummmmmmmmm; yeah; i seem to h'ear that a lot:bang: ; thanx fer at least being polight about it....

But in my imagery/wierld; a redirect pulley holding 100# on 1 leg of line(thereby line tension); must have an equal 100# tension on the other leg of line to same pulley; or the load falls. The culmination of 2 legs of 100# tension on the support gives 200# pull/loading on said support. Just as if the pulley was on a load, 1 end of line tied off, the other pulled at 100# tension; places 200# pull on said load at pulley. The laws working for ye for 2x pull on load; or the inverse- against ye for 2x load on support without prejudice; as any of the laws can work for or against with change of pivot etc.



edit; guess ol'RB beat me to it!
Perhaps; my Mayhem Puzzle design that tests the limiting borders would clear thangs up!:taped:

rbtree said:

The wraps don't seem to slide when the self tailer is used.

Also, you could use 2-1 mechanical advantage by attaching a block in the fallen tree and tying the rigging line end off near the gin pole block.

We've done some mighty huge trees even without resorting to MA-+-

Click to expand...

rbtree,, has it down....

gin pole block 0 advantage

gin pole block to load, thru pulley, back to gin pole,, 2 to 1

gin pole block to load, thru pulley, back to gin pole,, another pulley,, back to load,,,3 to 1

gin pole block to load, thru pulley, back to gin pole,, another pulley,, back to load,,,another pulley,, back to gin pole,,, 4 to 1

and so on

fiddle blocks will increase mechanical advantage. When a line is redirected it still takes 100 pounds of force to lift 100 pounds. Run a line through a block in the tree then to a block at the base of the tree, now move back up the line and attach a third block(use a rope grab device or a bowline on a bite) this will give you 3 to 1 mechanical advantage. fiddle blocks can increase this even more.

TheTreeSpyder said:

Ummmmmmmmm; yeah; i seem to h'ear that a lot:bang: ; thanx fer at least being polight about it....

But in my imagery/wierld; a redirect pulley holding 100# on 1 leg of line(thereby line tension); must have an equal 100# tension on the other leg of line to same pulley; or the load falls. The culmination of 2 legs of 100# tension on the support gives 200# pull/loading on said support. Just as if the pulley was on a load, 1 end of line tied off, the other pulled at 100# tension; places 200# pull on said load at pulley. The laws working for ye for 2x pull on load; or the inverse- against ye for 2x load on support without prejudice; as any of the laws can work for or against with change of pivot etc.



edit; guess ol'RB beat me to it!
Perhaps; my Mayhem Puzzle design that tests the limiting borders would clear thangs up!:taped:

Click to expand...

tree , thanks for the polite thing,,i try to be...

but your still wrong,, i guess you didn't view the link....if you tied 100 lbs to a tree limb,, you would have 100lbs at the knot,,, if you tied 100lbs to a tree limb, thru a pulley,, then tied the end back to the tree,,, with your logic,, that 100lbs just turned into 200lbs... it doesn't work that way... almost every one i know thinks the same way....

i'll tell you what!!!! rb, and spyder... i guess you have a pulley...go to the tackle store, and buy 2 fish scale each (cheap ones) rig a scale between the tie off, and one over the pulley...add a wieght.... if the 2 scales dont read the same as the load,, i'll buy the scales,, and a case of beer for each of you..if im right send me a case each!!! deal?????? taste it now, nice cold free beer!!!

Ummmmmmm; i busted too many fish scales wit'my crazy ****; so have tested these things with 2 dynamo-meters (2500 and 3500#)i bought off ebay over time. i think i've seen that page before, thanx. Lots of guys around'ere think more of beer than i do; so ya might want to limit your offer to the first 100 takers or so... ; or give RB both shares

"Nature to be commanded, must be obeyed" -Sir Francis Bacon

Mayhem is actually an inverse example of how a man lifting climber thru pulley is 1:1; while climber lifting self thru same is 2:1. While man lifting climber places 2x climber weight on support; climber lifting self only places 1x climber weight on support. Took a lot of hits on that one too... http://www.mytreelessons.com/climber%20lift.JPG

i think fiddle blocks work as regular blocks; only more precisely inline; more focused; for less loss of force by angle and lines rubbing. It all works on the fact that only force can overcome distance; so that the inverse that any change in distance on side A of the equation, gives a change of force on the other side B of the equation(if distance isn't equally changed). Everything must balance out; A must = B; everything has an equal and opposite(and force travels until it finds it's mating/opposite). Pulley Loading Patterns Mayhem Theory/Puzzle solution is shown in (S)(alos werks on Dynos). Spanish Burton (P) contains a form of 2Handing Theory; insamuch that it contains an imbedded system that pulls on target load from both ends/ insted of only 1 with other end pulling on an anchor.


If 2 legs of line thru pulley are pulled on; 2x the distance is incurred for the same work; thereby 2x the power. If that 2x runs through the load position; 2x line tension on load. But, if 2x distance runs through pulley on support, then 2x load/line tension on support; just as fairly. This is for inline axises with pulleys; but the tradeoff is same for perpendicular/leveraged/ non-inline pulls; just harder to see. This force working for you is line sweating; against you is as loading a Speedline Calculator

Intro to my 2Handing Theory; also proven with dynamos; that just simply allows distance to be input from both ends instead of 1, for more power.

Regardless of the debate about the mechanical advantages of blocks, which I will leave alone, one important thing should not be overlooked. And that is the force applied to the various points, like the tree used as a spar. If you reeve multiple blocks so that you are exerting many thousands of pounds of pull, something will either hold or give. I got my pickup full of firewood stuck, I used up all my wire rope, three blocks and my Tirfor to get it out. I made sure I was out of the bight, the truck came out, no big deal. However my bush bumper that is welded to the frame had a bracket weld broken and was a little bent. Something to think about, sorry to be repetitive.

clearance said:

Regardless of the debate about the mechanical advantages of blocks, which I will leave alone, one important thing should not be overlooked. And that is the force applied to the various points, like the tree used as a spar. If you reeve multiple blocks so that you are exerting many thousands of pounds of pull, something will either hold or give. I got my pickup full of firewood stuck, I used up all my wire rope, three blocks and my Tirfor to get it out. I made sure I was out of the bight, the truck came out, no big deal. However my bush bumper that is welded to the frame had a bracket weld broken and was a little bent. Something to think about, sorry to be repetitive.

Click to expand...

Happy for you that you got it out Clearance with limited grief.

Spydie,
You are a rigging GOD. Where RBtree is the rigging devil...lol
I continue to read you pics, post and flash animation. I still cant understand it I still cant fathom it, but I read it constnatly in the hope that one day it will sink in. I cant wait to apply that much pressure to a fusing hindge.
I will own a GRSC. Whereas: these pencil pushing geek wads fly a bucket and fertilize trees and make millions. ha.
Fertilizing bucket flyers please dont post to this most excellent thread. I bet you bucket flyers carry pulpwood on your shoulder and then fly it to a drop zone impact area a big NO NO> your name is now NO NO.:hmm3grin2orange:

Edit: look for pic sof todays rotten hollow rigged tree under the rebels name

hate to admit this,, i was wrong,,got my head out of somewhere and thought about it!! i owe some beer!!! oh well...

Ummmmmmmm thanx fer the vote of competance; but i think i prove daily to myself if not others that each man alone is his own savant; self included. It is the harmonized gathering all our forces in total that is this immensecity.

Some more stuff to distill out of this rigging example:

The more legs supporting load(for more power); the less the total support loading is; the greater the SWL or load force to line tensile is. This is the macho; raw strength everybody seems to reach for with blinders. But another line quality is the elasticity; or the forgiveness while still holding on option; that can easily be forsaken. For more elasticity is returned when the SWL is low; or more of the tensile strength is used (elasticity is also adjusted by length of line). Mountain lines stress elasticity, the forgiveness but still hold; that places less dynamic load on body, support, knots, connections etc. Our DdRT places us on 2 legs of support, so reduces the amount of elasticity returned per the loading; the closer to TIP when we dynamically load the system; the more shock/ less shock absorbing line available.

So, that though adding an extra leg of support raises the amount of static load force that can be supported; it can decrease the amount of dynamic force that the support, connections or climbers body can take. Or just more shake to the support the climber is sharing with load etc.

A bearing pulley will have will be more efficient (by less friction) than a bushing pulley of same size/ratio. A larger sheave to axle ratio will have more efficiency(by more leverage over axle). Bearing pulley can't take impact;bushing can. Less efficient won't pretighten as well; but will give less support loading when lowering.