Making Z rig?

[IllinoisJim]

I want to make a Z rig out of amsteel but haven't been able to find details. The main question I have is how to make the eye in the line that holds the pulley that aids in pulling the line. I would think this would be an eye in the end of a short section of line with the other end buried into the main line. But the force on the buried line would be twice the force on the main line constricting it. Not sure if this would be enough to hold it. Could do a longer bury. Or I could be all wrong. Can someone point me to some details? Thanks.

 

[BC WetCoast]

I'm assuming your Z rig is another name for a "3 to 1", "poor man's come along" or a "truckers hitch". When I teach my Boy Scouts to make this, we use a Figure 8 on a bight for the loop, but it sounds like you want something more permanent.

Other situations I've done have used a prussic loop to connect the pulley to the line, this way it becomes more adaptable to various situations.

You could also use a mechanical cam lock to hold the pulley.

 

[tree md]

You need to tie a mid line knot as BC mentioned. A prussic will be more adjustable but could slip under a heavy load (although I have never had one do so). Mostly I just tie a mid line knot. I prefer a plain old butterfly knot as it is pretty easy to untie after it has been loaded. I usually get everything set up and get a good pull to see where the most optimal point to tie a knot will be.

 

[IllinoisJim]

Z rig

Yes, I am referring to a 3:1 pulley arrangement. I figure I will be using it a lot for tensioning the line but not always.

My concerns with knots is that they will weaken the line. That's why I was thinking of a burried splice for an eye.

Haven't looked at cams. Wouldn't they also weaken the line by concentrating the stress? My guess is this may be more of an issue with amsteel than other types of line.

Perhaps I should just put an eye on the end of the line and use a seperate short line for the Z-rig. That would maintain strength and give me some flexibility in setup...

 

[2FatGuys]

...I prefer a plain old butterfly knot as it is pretty easy to untie after it has been loaded.

IF I am tying a mid-line knot, the butterfly is all I use. A "figure-8 on a bight" is ok if you aren't heavily loading it, but may be very difficult to untie depending on rope type and how symetrical it was set prior to loading.

...A prussic will be more adjustable but could slip under a heavy load (although I have never had one do so)...

WHAT???? The prussic setup is our standard. We have never had one slip! If tied and set correctly, using the proiper cordage, it's safer than the butterfly knot! There are no severe bends in the loaded line.

We also use a prussic and slack tending pulley on the anchor end of the loaded line to "capture" any progress made while pulling. While it takes a minute or so to set that up, it completely eliminates having to have someone hold the progress and also eliminates any risk of losing ground.

SherrillTree has a kit designed to be used similar to how we do it:

http://www.sherrilltree.com/Professional-Gear/Mechanical-Advantage-Kits_2/Tree-Pulling-Kit-1492

Go watch the video....

 

[Josh777]

Maybe instead of putting an eye in the line, you could consider a rope grab of some kind that could be installed mid line (aka petzl microcender or the like) to hold the pulley. It would be very easy to then move it back up the line in the case that you had limited space and needed to apply another good long pull. Or like was mentioned before a good solid purssik would do the job just as well. I just think the rope grab is a little quicker, throw it on and attach the pulley with a biner and away you go. Good luck. -Josh

 

[tree md]

IF I am tying a mid-line knot, the butterfly is all I use. A "figure-8 on a bight" is ok if you aren't heavily loading it, but may be very difficult to untie depending on rope type and how symetrical it was set prior to loading.



WHAT???? The prussic setup is our standard. We have never had one slip! If tied and set correctly, using the proiper cordage, it's safer than the butterfly knot! There are no severe bends in the loaded line.

We also use a prussic and slack tending pulley on the anchor end of the loaded line to "capture" any progress made while pulling. While it takes a minute or so to set that up, it completely eliminates having to have someone hold the progress and also eliminates any risk of losing ground.

SherrillTree has a kit designed to be used similar to how we do it:

http://www.sherrilltree.com/Professional-Gear/Mechanical-Advantage-Kits_2/Tree-Pulling-Kit-1492

Go watch the video....

Yeah, I've never had a prussic slip, I've been warned that it can slip under very heavy loads though. I figured I would put it out there for the guy to consider even though I have had no problems whatsoever using one.

 

[Damon]

my understanding about prusiks slipping is that it only occurs when they are quickly loaded with a large force i think as long as you slowly load them and allow it to constrict on the rope there is no problem we use one in a similar rig occasionaly with a gin pole to load logs in the trailer when i decided i didnt need to bring the loader and 2 grunts with peaveys just arnt makeing it

 

[ddhlakebound]

Yes, I am referring to a 3:1 pulley arrangement. I figure I will be using it a lot for tensioning the line but not always.

My concerns with knots is that they will weaken the line. That's why I was thinking of a burried splice for an eye.

Haven't looked at cams. Wouldn't they also weaken the line by concentrating the stress? My guess is this may be more of an issue with amsteel than other types of line.

Perhaps I should just put an eye on the end of the line and use a seperate short line for the Z-rig. That would maintain strength and give me some flexibility in setup...

First, why amsteel?

It's expensive, it doesn't wear very well with friction, it doesn't do terribly well with knots, and most importantly for the application, it doesn't stretch.

In a Z rig, that stretch is your friend....once the Z is tensioned, the stretch will keep pulling as the tree starts to come over.

You'll also need your midline anchor at a different point pretty much every time you set up, which either means knots or prussics....I'd avoid the rope grabs for this app.

For versatility, prussics provide the most adjustability, and as mentioned, you have no sharp bends in the pull line.

Z rig pieces...

150' (or more) half inch or better arborist rope (with some stretch)
sling and block for main anchor.
prussic, biner, and pulley for midline anchor.
sling, biner, and prussic for permanent capture of pull (can be clipped to main anchor sling, but I prefer to use a second one)

and it's handy to have one more biner and prussic to lock off the main line and re-adjust your midline anchor if needed.

When you look at the forces produced, between the leverage of the distance from the hinge to the tie in point in the tree, and the 3-1 MA, you can create a HUGE amount of force at the hinge with a couple guys pulling with a regular 6k rope.

 

[Bermie]

I've only ever used friction hitches for a Z rig. I use distel hitches, 10mm hitch cord on 9/16" bull rope.
A capture hitch at the anchor allows you to get everything set right before the final pull.

 

[pdqdl]

First, why amsteel?
...

Yep! What he said.

Furthermore, amsteel is an unbelievably slick rope. This means a friction hitch is unlikely to hold your z-rig pull, so that will be a problem too.

I used my 3/8ths amsteel rope to pull out my 19,000 lb chipper/crane truck a few days ago. We wrapped the free end of the line around a 12" oak tree...about 15-20 times before it would hold the load of the winch. At about 8 wraps on a tree, two men couldn't hold the rope from unwinding off the tree. We had to do many more wraps before that slick line would not un-spool off the rough oak tree.

THEN it cut through the bark and stripped the tree down to the cambium like a chainsaw! :jawdrop:
I never imagined that soft little rope would do that to a tree. It was horrible.

After that, it stalled the winch on the truck before it was able to pull it out of the mud, and we had to rig a doubling pulley back to the truck for twice the power. And...we finally got out, without ever damaging the 3/8 rope.

It's an amazing rope, but I wouldn't use it for rigging. It should only be used where you need steel cable strength without the weight or resistance to heat, cutting, or friction. Wrapped around almost anything, including itself in knots, it becomes a destructive death-choker.

Oh yes. Somebody is pretty upset about the dead tree, too. I'm going to remember this for a long time. I am going to be doing a lot of free tree trimming now for a customer...

 

[tree md]

Yep! What he said.

Furthermore, amsteel is an unbelievably slick rope. This means a friction hitch is unlikely to hold your z-rig pull, so that will be a problem too.

I used my 3/8ths amsteel rope to pull out my 19,000 lb chipper/crane truck a few days ago. We wrapped the free end of the line around a 12" oak tree...about 15-20 times before it would hold the load of the winch. At about 8 wraps on a tree, two men couldn't hold the rope from unwinding off the tree. We had to do many more wraps before that slick line would not un-spool off the rough oak tree.

THEN it cut through the bark and stripped the tree down to the cambium like a chainsaw! :jawdrop:
I never imagined that soft little rope would do that to a tree. It was horrible.

After that, it stalled the winch on the truck before it was able to pull it out of the mud, and we had to rig a doubling pulley back to the truck for twice the power. And...we finally got out, without ever damaging the 3/8 rope.

It's an amazing rope, but I wouldn't use it for rigging. It should only be used where you need steel cable strength without the weight or resistance to heat, cutting, or friction. Wrapped around almost anything, including itself in knots, it becomes a destructive death-choker.

Oh yes. Somebody is pretty upset about the dead tree, too. I'm going to remember this for a long time. I am going to be doing a lot of free tree trimming now for a customer...

That's what my thinking was. I was under the assumption that the Amsteel should be used in place of a steel cable and only for the same applications.

 

[pdqdl]

I guess I should add that I have used the amsteel rope to pull a tree over, but only when it was attached to my one ton truck. I needed the truck because it was a heavy side leaner, and I needed to be able to tell the driver to STEP ON IT! I never tried the amsteel rope with a z-rig.

Unable to tie it with knots onto the truck, I rigged our portawrap to the rear of the truck to hold the amsteel at the correct length without knotting it.



The number of times that 150' rope has been used in over a year of ownership: 4 or 5. I have been amazed almost every time. So slick. Soooo strong!

I bought it for those long distance rescues where you never have enough chain.

 

[squad143]

I perfer to use a vt knot, as I find it comes undone no matter how much it is loaded. Don't know about using a friction hitch on amsteel, never done it.

 

[BC WetCoast]

I had a very experience arborist/trainer set up a 5:1 using a prussic and explain that the potential for the prussic to slip was what prevented the 5:1 from overpowering the SWL of the rope.

Made sense to me at the time when he explained it.