six block rigging

[olman60]

Cary, I've had problems in the past with your suggestion. The pulley might twist, wrapping the rope around itself, increasing friction significantly. (This is more of a problem with three-strand rope than with braided.) But I make a point of keeping some minimum distance between the anchor tie-off and the redirect pulley. You can use the same tree if it's big enough, and the tie-off and pulley are far enough apart.

TreeCo, keep in mind that as the pulley moves toward angle 2, the leaning cottonwood is.... co-operating. But, still an excellent point. When setting up the rigging, the distance the pulley moves must be figured into the equation. And the pulley you've focused on moves the most of the three.

 

[caryr]

That certainly could be a problem. I've only used braided rope so I may have had fewer problems because of that. I also use the third dimension (vertical) to keep a bit of distance between the two anchor point which as you imply also makes things better. The redirect with its larger load should be on the bottom if possible.

Ignoring stretch and a few other minor things the rope connected to the truck will move 8' for every 1' the rope connected to the tree moves. The pulley in question will move 4' under these same conditions. Stretch will make things worse and the tree will actually move less than the rope connected to it because of the vertical angle between the rope and the tree.

Well time for some shut eye before the big feast.

Cary

 

[Mark Chisholm]

Spydie is right again. I just messaged him that I need to stop skimming these messages and really read them. Sorry gang. I'll stop now.

 

[TheTreeSpyder]

Sorry if a little thick

i think that the 2 cubed is right way to express this. i think of different Pulley System leading to another as a series connection; increasing "rope voltage" by multiplication \ geometrically; while pulleys within a system are pairallell connections giving an additive\mathematical increase.

Until we get into "2Handing" or the likes a a Spanish Burton; essentially doing the same thing; inside a system; by 'grounding out' less of it's 'rope voltage' internally.

Systems will be Potential - (in-efficiencies of angle on dynamic/moving pulleys but; all friction on pulleys/positions dynamic or static). So line angles on dynamic positions decrease power(bad), but on static positions; they help by decreasing anchor loading (good) static positions decrease anchor load; and change the load force direction(ggod opr bad depending on strongest anchor fortification angle). For pulley power is forces capitalized by being inline pull; whereby lever force is capitalized on by being not inline/ perpendicular. Pulley lines conserve the most force on pulley inline(so line tension has most leverage over pulley at this angle); gradually decreasing as angle widens; so much so that at 120 that inverts to the pulley having more leverage over the line( rope only leverages to resist bending when stiffened by laoding or in small bight) gradually increasing till just under 180 staight and having very high leverage of pulley over line at that point Then after that is just 180/ another inline 1:1 non rotational pull on ends.

On the friction; i think i said it backwierds as Mark. Within a system the most efficient pulley first seems best; but in the last system to load. System efficiency is one to watch; lower input, line tension, traction, anchor loading etc.

 

[AxeKnot]

I get Olman60's first diagram to be an 8:1 mechanical advantage.

It was a little bit confusing with all those angles!

 

[skew]

No disrespect intended but it looks like over kill to me- abeit tough to say with out seeing the actual scenario. Failing that it is a geometric equation that could only be described as practical genius- the kind that only a well schooled tree ninja could execute

 

[olman60]

Skew, it wasn't overkill. If I hadn't used rigging with all three yellow blocks, my little toyota pickup would've spun it's chained wheels on the packed snow driveway. If the driveway had been bare and dry, I'm sure I could have eliminated the yellow block nearest the pickup.

 

[Mark Chisholm]

Neat idea though. And to bring up my first reply where I read in reverse, that would really be useful for moving a load a long distance with a lot less pull. I'll keep that in mind for the future.

 

[TheTreeSpyder]

We've used a 50' drive for pulling brush piles up a 100' hill at half power, but need to be careful; because that makes brush moving 2x as fast as truck.

 

[skew]

I guess I sort of try to avoid using vehicles to pull with because of the potential for operator error. As well as if you need to re-rig something in mid pull I prefer a block and tackle for the reason of it probably won't break a rope whereas pulling with a vehicle could concievably tax your gear more. Still pretty nifty sytem you came up with there.

 

[olman60]

I use my little toyota 4x4 pickup all the time to pull over trees. My step-by-step routine has worked very well, all probably familiar stuff for you guys:
-Assess the situation, design your rigging/strategy, including height of rope tie-off, anchor tree(s), path of pulling vehicle (preferably downhill), potential damage from low-hanging or outreaching limbs, behavior of butt on impact, rope diameters (overkill is good), etc.
-Set up your rigging.
-Pull rigging tight, making sure that tree is supported by rigging, so that, ideally, the back cut starts to open up as you cut, but not too much, avoid barber chair.
-At this stage, pay attention to your instincts. If something doesn't feel right, stop and figure it out.
-Before cutting, double check knots, blocks, and ropes.
-Cut the notch. Go slow, make sure the notch is accurate.
-Take last minute precautions for vehicles, residents, pedestrians, dogs.
-Give instructions to vehicle operator - somebody qualified. You might be telling them to wait for your signal, or to pull when tree starts to move, to pull gently, or to pull for increasing momentum.
-Do the back cut. As adrenaline starts to pump, slow down, stay focused, watch both sides of the trunk.
-If necessary, signal vehicle operator to pull.

What'd I forget? Comments?

 

[TreeCo]

[ QUOTE ]


What'd I forget? Comments?

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I think you've pretty well got it covered. I've been using vehicles to pull trees over for 20 years without a mishap.

My most frequently used rig for pulling trees is a 150ft. 5/8" rope, a pulley, and a 120ft. half inch rope using a Masdam rope puller set up for a 2/1 MA.

 

[skew]

Sound like you have a carefully thought out plan- reflected also by the time you spent rigging it up- Good on ya.

 

[stephen]

Would the problem be lessoned with an increase in torque/winching power at the pull end therefore negating the use of the complex mechanical advantage multi-rigging that was used?? eg.tifor winch 5 tonne pull or mechnical vehicle based equiv at the one end through two re-directs to tree. a pulley could be placed tree's own stump and double the winching power, pulling the tree over on it's own stump. Right tool for the right job .
Beautifull example of rigging though and respect to you for working in those conditions!! Apologies if i've mis-interpreted your spec.

 

[caryr]

Possibly, for a given load if you can increase the input pull enough that you can use a smaller multiplier you can usually reduce the complexity of the system. Also this is olman60's work. I just provided some analysis.

 

[olman60]

Stephan, if I had a heavy enough truck with a strong enough winch, I could've certainly pulled this tree over without all the rigging. But I don't.

Truth is, something about two guys arriving on the job with all the required tools in a single truck appeals to me. Thousands of $ worth of hardware and machinery gives one confidence, but there's a challenge, and a confidence based on experience, and the desire for an elegant solution to the problem, using the brain more and the heavy equipment less, that, for me anyway, makes this removal interesting.

 

[stephen]

I like the ingenuity of it and hats off to you, but personally if I don't have the kit for the job I price in a rental overhead and don't take the risks !!! Nicely worked rigging though and no mistake!!!