Rigging Friction Saver 2

Re: Rigging False Crotch

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Which is worse putting double the load on the crotch or over straining some rings?

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Its not the rings I'd worry about, made of steel they be plenty strong in most cases. Its the bend radius of the rope running through the rings which Id be worried about. A 1/2" line needs a 2" bend ratio minimum. It doesnt really concern me much in a climbing application as the generated forces are usually low in comparison to rope SWL. But in a rigging application its a whole nother story.
 
Re: Rigging False Crotch

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Jamin's illustration is also called a floating false crotch when it's used for climbing...do you know where the SRFC name came from? Too confusing...

John...as the loads are scaled up the configuration of the pieces is scaled up too. Using my ring/ring FC for limbwood and no-drop logs works fine...for me. I've worked through the numbers and I'm comfortable.

If the loads are larger a pulley/block could be substituted for one of the rings just like in a climbing FC...scaling up the gear as needed of course.

Using the Adjustable Rigging FC gives me lots of flexibilty and I can move the block up or down to put it in just the right place. Most of the time that doesn't make a difference but there have been times when the adjustability makes a lot of difference.

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I agree there are SOME situations where it would be acceptable to rig from a ring- ring. But knowing when not too is the key.
 
Re: Rigging False Crotch

I saw a demonstration of what Jamin' diagrammed but tied off at the crotch in a manner that is still retrievable from the ground. That eliminated the doubling of the loads on the crotch. Unfortunately, I've only seen it the one time and don't remember how it's done.
 
Re: Rigging False Crotch

Yeah thats what i was thinking of. I saw that at a seminar at the local vermeer dealer. I can't remember quite how it was set up. Jim Roachy was one of the presenter maybe he can tell us.
 
Re: Rigging False Crotch

I know what you're talking about. It's like running your line through a butterfly knot. It's just like you'd set a single line or something of that nature but unlike the rigging fs you have one more rope to mess with in the tree and on the ground. This poses problems as far as getting things crossed and getting branches stuck and tangled.
 
Re: Rigging False Crotch

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Well, this is what I call it. See illustration.

And, this is not to be mistaken for a Static Removable False Crotch. This can be found on page 100 in The Art & Science of Practical Rigging
wink.gif
--I'm too lazy to scan it at the moment.

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Jamin;

Nice illustration. But, it shows a floating false crotch for rigging, not a static removable. 'Static' implies that the block is secured with a sling of some sort and the force on the limb is 2x's the load. In your illustration the block can be moved up or down and thus is not static, and the force on the limb is 4x's the load. Similar to a floating false crothch for climbing.

'Removable' (sometimes called retrievable) means that the block can be removed or retrieved from the ground, which your setup can be. But it's not static.


More here:

http://www.treebuzz.com/forum/showflat.p...p;vc=1&nt=2
 
This is 1 I've been using for years. I got the cordage from Ron Danise when he was still with Charlotte Rigging Supply. That's how old it is. It's a 5/8" polyester 3 strand called "Silverlon", I think from Wall Rope. The rings are 5/8" pear links that the shop welded for me. It can be installed with throwline and retrieved from the ground with the lowering line and controlled with string.
It comes in handy when I can't find a usable branch union for the "Static Retrievable", which I prefer to use due to the larger radius turn on the block. I had the rigging FC way before I learned the Static Retrievable from Sohner.
 

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Re: Rigging False Crotch

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In Jamin's illustration,there is 4 times the load up in the branch union,because it is a rigging open system,correct?

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Yes, correct. Excellent observation.
If it were a 100 pound log, the forces on the branch union would be 400 pounds (4X).
 
Re: Rigging False Crotch

Norm, that rigging FC is VERY cool! I think I may have one made. Are you ever concerned with rope bend radius when using it? Of course it would be best to use a smaller diameter line to compensate for the bend radius, Im thinking a 1/2inch bull line would be good. What diameter are you typically using?
 
Re: Rigging False Crotch

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Norm, that rigging FC is VERY cool! I think I may have one made. Are you ever concerned with rope bend radius when using it? Of course it would be best to use a smaller diameter line to compensate for the bend radius, Im thinking a 1/2inch bull line would be good. What diameter are you typically using?

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We use 1/2" ropes on it. Nothing to heavy either. 1,000 pounds max weight. We don't use it that often, but comes in handy when we need it. Much better than natural crotchin.
 
Re: Rigging False Crotch

Norm,

Your rings are a fine example of true wit and solution/alternative for "just do it" light rigging scenarios.

It's a good practical example of your experience.
 
Re: Rigging False Crotch

We do it often.... as long as the crotch has some subsantial size, it can easily hold huge loads. And I mean huge, as we've done storm leaning or hung trees weighing 2-5 tons that way. Never had a failure of any kind.
 
Re: Rigging False Crotch

no good setting a false crotch from the ground without pulleys if the only way of tensioning rope is by GRCS or equivilent.
this can be set up and brought down without damaging the pulley.
if you go to the effort of a false crotch set from the ground you may as well use pulleys .if you use rings you loose too much energy on the friction they create.
but short term solutions call for quick fixes and rings will help you out if need be but not good for long haul
 
Re: Rigging False Crotch

That can be done, chopper.... Norm could add a block to one side of his FC, just as I do with my climbing FC, and it can be set and retrieved remotely. That reduces the friction to about half....
 
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