X-rigging rings

I finally found the micro edges thing RescueMan was talking about. As seems to be standard, he's off base, or at least his explanation is shit. What can happen is that once the hard coat anodization is worn away, the aluminum underneath, being much softer wears very quickly. The cutaway edges of the hard anodization will then become razor sharp.
So as this has been protocol from the very beginning with XRR, once you've worn through the anodization, retire them. Not news to anyone here, but apparently to RescueMan (the SWL tables were already available as well).
Ironically, I found this in the book Technical Rescue and in the previous paragraph they extol the virtues of hard coat anodizing for descent devices talking about how it dramatically increases the lifespan. As with anything, it has limitations and drawbacks. Nothing does everything perfectly.
No shit.
 
I think everyone needs to pop a top and have a drink. Wyo I like how you don't play favourites and call it straight as you see it. Not every one is a perfect angel, but that doesn't make him the devil either, just human.
 
wyoclimber said:
And the reason the "wagons were circled" is simply this. You're a dick.
I don't always agree with X. I don't get why he calls himself X-Man, I think he can be a dick sometimes and he's far from the most eloquent person I know. But I can recognize that he's a damn good Arborist and a damn good rigger. I can recognize that he brought a product to our market that has made things easier and dare I say, safer, for many Arborists. That's definitely something I can get behind. Plus, you went after him right after he promised to send a bunch of people on here a free XRR and well, we Arborists love free shit.
Click to expand...

Well I agree with this except for David being a dick, he is my friend I have spent time with him personally down here in Barbados with his family....I can honestly say that he is one of the most genuine and kind people I have met lately...happy family man with great values...I respect him as a man of good character...I will not allow someone to come on here and try to sabotage a product that has been fully tested....He is not an irresponsible man who is trying to get rich selling junk...He is genuinely bringing a product that can change the way we think and work in trees...make our jobs safer with less fatigue and a bunch of unnecessary slamming....RINGS are good and worthy to be part of our rigging arsenal....
 
RescueMan said:
Each change of direction reduces the line load by the "pulley" efficiency ratio, but any line angle less than 120° will multiply the average (line in, line out) force at the anchor resultant vectors (big arrows).

Mark Chisholm explains this well in his article (archived on this site), Engineering a Tree Removal. One major advantage of this kind of complex rigging is that it forces the multiple stems toward each other rather than away from the primary stem (kind of like temporary cabling).

I've taken his "figure 5" and added the line loads and resultant Change-of-Direction (CD) anchor point loads - in this case assuming 90% efficient blocks and a 1¼ wrap around the GRCS. Note that two blocks (1 and 3) experience more force than the actual load, including the 3rd one which had the initial load significantly reduced by block friction (it has the smallest angle).

View attachment 30014
Click to expand...

Hi RescueMan, I have been following the XRR thread and I have a few questions that I was hoping that we could discuss. I certainly don’t want to add fuel to the fire, nor do I want you to think that I am attacking you for your views. I DO NOT operate that way (as anyone who knows me on the Buzz will tell you) and I would much rather discuss things logically. Here’s a little of my background;

Besides being a Certified Arborist and owning a small tree service, I have worked the past 26 years for the NH DOT as a civil engineer designing highways. 99.9% of the Treebuzz members do not know this, as I do not like to goad people into thinking that I am some book-worm rigger, when in fact I have come up like many others through the “tree ranks.” I am also a Certified SPRAT Technician (working towards my Level 2 cert), so I understand the differences in the high angle rope trades. Currently I am working on a program for the NH DOT to set up a team of Rope Techs for bridge and rock scaling inspection work (though I’ve run into a few walls with the heads of various bureaus). I am not telling you all this to try and impress you, but to let you know that I have a professional background in both engineering work and rigging work.

Anyways, my questions are in concern to some of your references to Mark Chisholm’s Engineering a Tree Removal article. I am trying to do the math behind your figures (for my own inquisitive mind) but having a hard time coming up with the same numbers. A couple of things that I want to mention are that in tree rigging, we are taught to assume worst case scenarios (hence our 10:1, or even 20:1 SWL, whereas in industrial work, a 5:1 SWL is used), such that the load in Mark’s “figure 5” sketch is assumed to be static, balanced and being held still. Like he mentions, this is an ideal case (which we won’t see in reality) situation, such that the block/pulleys are 100 percent efficient (no friction), resulting in a 1,000lb load on the working end of the line (at Block 1) and a 1,000lb line pull load being applied to the running end of the line (at Block 4), before entering the top of the friction device.

We do not (as you show in your “figure 5), assume that the 1000lb load on the lowering line is being dissipated (or spread out) along the rigging points (even though in reality, some of this does occur). The reason that we do not do this, is both to simply the computations AND to compute a worst case scenario at our rigging point (i.e. – block, sling and tree). It all depends on the rope ANGLES, and as Mark pointed out and you mentioned in your post, the direction of pull (trying to use the tree’s natural strength to our benefit). In the past, we have not been concerned with a "block efficiency ratio," though this may change in the future?? Hell, over half the industry probably still doesn't use blocks/pulleys!

Now again, we only use this assumption for ease of calculations and in theory, the load entering the friction device will be closer to your 656lbs than an assumed 1000lbs, due to, as you mention the “pulley efficiency” and the coefficient of friction in the pulley. For an arborist block with a dry bushing (unlike a rescue pulley) and a sheave diameter giving a 4:1 bend ratio, studies have been done by the late Dr. Peter Donzelli (see- Journal of Arboriculture March 1999) that a coefficient of friction at the block of between 0.12-0.12 normally occurs for a load being suspended by an arborist block. This is assuming that you have a 180 degree Angle of Deflection or a 0 degree Interior Angle (depending on which Load Multiplier chart you like to use). Most arborists use the Interior Angle chart, whereas other rope trades (access rescue included) use the Angle of Deflection chart. Again though, the coefficient of friction is not something that arborists concern themselves with knowing. It's better to Know Your Angles.

So, when I calculate the reaction forces at the various multiple-block rigging points as shown in “figure 5, this is what I come up with:
Given – CD-1, 2, 3, 4 are equal to the Interior Angles used for the Multiplication Factors for Rope Angles at Blocks and are rounded to the next highest 5 degrees in the chart for computation purposes;
Block 1 reaction force (assuming an angle of 120 degrees) = 1000lbs x 1.00 = 1,000lbs
Block 2 reaction force (assuming an angle of 110 degrees) = 1000lbs x 1.15 = 1,150lbs
Block 3 reaction force (assuming an angle of 90 degrees) = 1000lbs x 1.41 = 1,410lbs
Block 4 reaction force (assuming an angle of 130 degrees) = 1000lbs x = 840lbs

Notice how my reaction forces at the rigging points are higher than yours? Except for Block 1, where they are pretty even. By using the Arborist Multiplication Factor chart, with the higher assumed load in the rigging line throughout the tree, we are better able to err on the side of caution and follow the KISS principle when designing a rigging system.

How did you come up with your figures and what charts did you use? Where did you get the 90% efficient block number? Again, not trying to badger you, just curious. Thanks.

I am not trying to turn tree riggers into engineers (believe me, it’s not all that it’s cracked up to be), but I agree with you that the prudent arborist will learn as much as possible. X-Man is doing a great job of bringing new ideas and discussions to our industry and for that I thank him very much!

BTW, David your personal email mailbox is full. Tried to send you a couple of emails this morning.
 
chris_girard said:
Hi RescueMan, I have been following the XRR thread and I have a few questions that I was hoping that we could discuss. I certainly don’t want to add fuel to the fire, nor do I want you to think that I am attacking you for your views. I DO NOT operate that way (as anyone who knows me on the Buzz will tell you) and I would much rather discuss things logically. Here’s a little of my background;

Besides being a Certified Arborist and owning a small tree service, I have worked the past 26 years for the NH DOT as a civil engineer designing highways. 99.9% of the Treebuzz members do not know this, as I do not like to goad people into thinking that I am some book-worm rigger, when in fact I have come up like many others through the “tree ranks.” I am also a Certified SPRAT Technician (working towards my Level 2 cert), so I understand the differences in the high angle rope trades. Currently I am working on a program for the NH DOT to set up a team of Rope Techs for bridge and rock scaling inspection work (though I’ve run into a few walls with the heads of various bureaus). I am not telling you all this to try and impress you, but to let you know that I have a professional background in both engineering work and rigging work.

Anyways, my questions are in concern to some of your references to Mark Chisholm’s Engineering a Tree Removal article. I am trying to do the math behind your figures (for my own inquisitive mind) but having a hard time coming up with the same numbers. A couple of things that I want to mention are that in tree rigging, we are taught to assume worst case scenarios (hence our 10:1, or even 20:1 SWL, whereas in industrial work, a 5:1 SWL is used), such that the load in Mark’s “figure 5” sketch is assumed to be static, balanced and being held still. Like he mentions, this is an ideal case (which we won’t see in reality) situation, such that the block/pulleys are 100 percent efficient (no friction), resulting in a 1,000lb load on the working end of the line (at Block 1) and a 1,000lb line pull load being applied to the running end of the line (at Block 4), before entering the top of the friction device.

We do not (as you show in your “figure 5), assume that the 1000lb load on the lowering line is being dissipated (or spread out) along the rigging points (even though in reality, some of this does occur). The reason that we do not do this, is both to simply the computations AND to compute a worst case scenario at our rigging point (i.e. – block, sling and tree). It all depends on the rope ANGLES, and as Mark pointed out and you mentioned in your post, the direction of pull (trying to use the tree’s natural strength to our benefit). In the past, we have not been concerned with a "block efficiency ratio," though this may change in the future?? Hell, over half the industry probably still doesn't use blocks/pulleys!

Now again, we only use this assumption for ease of calculations and in theory, the load entering the friction device will be closer to your 656lbs than an assumed 1000lbs, due to, as you mention the “pulley efficiency” and the coefficient of friction in the pulley. For an arborist block with a dry bushing (unlike a rescue pulley) and a sheave diameter giving a 4:1 bend ratio, studies have been done by the late Dr. Peter Donzelli (see- Journal of Arboriculture March 1999) that a coefficient of friction at the block of between 0.12-0.12 normally occurs for a load being suspended by an arborist block. This is assuming that you have a 180 degree Angle of Deflection or a 0 degree Interior Angle (depending on which Load Multiplier chart you like to use). Most arborists use the Interior Angle chart, whereas other rope trades (access rescue included) use the Angle of Deflection chart. Again though, the coefficient of friction is not something that arborists concern themselves with knowing. It's better to Know Your Angles.

So, when I calculate the reaction forces at the various multiple-block rigging points as shown in “figure 5, this is what I come up with:
Given – CD-1, 2, 3, 4 are equal to the Interior Angles used for the Multiplication Factors for Rope Angles at Blocks and are rounded to the next highest 5 degrees in the chart for computation purposes;
Block 1 reaction force (assuming an angle of 120 degrees) = 1000lbs x 1.00 = 1,000lbs
Block 2 reaction force (assuming an angle of 110 degrees) = 1000lbs x 1.15 = 1,150lbs
Block 3 reaction force (assuming an angle of 90 degrees) = 1000lbs x 1.41 = 1,410lbs
Block 4 reaction force (assuming an angle of 130 degrees) = 1000lbs x = 840lbs

Notice how my reaction forces at the rigging points are higher than yours? Except for Block 1, where they are pretty even. By using the Arborist Multiplication Factor chart, with the higher assumed load in the rigging line throughout the tree, we are better able to err on the side of caution and follow the KISS principle when designing a rigging system.

How did you come up with your figures and what charts did you use? Where did you get the 90% efficient block number? Again, not trying to badger you, just curious. Thanks.

I am not trying to turn tree riggers into engineers (believe me, it’s not all that it’s cracked up to be), but I agree with you that the prudent arborist will learn as much as possible. X-Man is doing a great job of bringing new ideas and discussions to our industry and for that I thank him very much!

BTW, David your personal email mailbox is full. Tried to send you a couple of emails this morning.
Click to expand...
Thanks for taking the time to post that Chris.
 
chris_girard said:
Hi RescueMan, I have been following the XRR thread and I have a few questions that I was hoping that we could discuss. I certainly don’t want to add fuel to the fire, nor do I want you to think that I am attacking you for your views. I DO NOT operate that way (as anyone who knows me on the Buzz will tell you) and I would much rather discuss things logically. Here’s a little of my background;

Besides being a Certified Arborist and owning a small tree service, I have worked the past 26 years for the NH DOT as a civil engineer designing highways. 99.9% of the Treebuzz members do not know this, as I do not like to goad people into thinking that I am some book-worm rigger, when in fact I have come up like many others through the “tree ranks.” I am also a Certified SPRAT Technician (working towards my Level 2 cert), so I understand the differences in the high angle rope trades. Currently I am working on a program for the NH DOT to set up a team of Rope Techs for bridge and rock scaling inspection work (though I’ve run into a few walls with the heads of various bureaus). I am not telling you all this to try and impress you, but to let you know that I have a professional background in both engineering work and rigging work.

Anyways, my questions are in concern to some of your references to Mark Chisholm’s Engineering a Tree Removal article. I am trying to do the math behind your figures (for my own inquisitive mind) but having a hard time coming up with the same numbers. A couple of things that I want to mention are that in tree rigging, we are taught to assume worst case scenarios (hence our 10:1, or even 20:1 SWL, whereas in industrial work, a 5:1 SWL is used), such that the load in Mark’s “figure 5” sketch is assumed to be static, balanced and being held still. Like he mentions, this is an ideal case (which we won’t see in reality) situation, such that the block/pulleys are 100 percent efficient (no friction), resulting in a 1,000lb load on the working end of the line (at Block 1) and a 1,000lb line pull load being applied to the running end of the line (at Block 4), before entering the top of the friction device.

We do not (as you show in your “figure 5), assume that the 1000lb load on the lowering line is being dissipated (or spread out) along the rigging points (even though in reality, some of this does occur). The reason that we do not do this, is both to simply the computations AND to compute a worst case scenario at our rigging point (i.e. – block, sling and tree). It all depends on the rope ANGLES, and as Mark pointed out and you mentioned in your post, the direction of pull (trying to use the tree’s natural strength to our benefit). In the past, we have not been concerned with a "block efficiency ratio," though this may change in the future?? Hell, over half the industry probably still doesn't use blocks/pulleys!

Now again, we only use this assumption for ease of calculations and in theory, the load entering the friction device will be closer to your 656lbs than an assumed 1000lbs, due to, as you mention the “pulley efficiency” and the coefficient of friction in the pulley. For an arborist block with a dry bushing (unlike a rescue pulley) and a sheave diameter giving a 4:1 bend ratio, studies have been done by the late Dr. Peter Donzelli (see- Journal of Arboriculture March 1999) that a coefficient of friction at the block of between 0.12-0.12 normally occurs for a load being suspended by an arborist block. This is assuming that you have a 180 degree Angle of Deflection or a 0 degree Interior Angle (depending on which Load Multiplier chart you like to use). Most arborists use the Interior Angle chart, whereas other rope trades (access rescue included) use the Angle of Deflection chart. Again though, the coefficient of friction is not something that arborists concern themselves with knowing. It's better to Know Your Angles.

So, when I calculate the reaction forces at the various multiple-block rigging points as shown in “figure 5, this is what I come up with:
Given – CD-1, 2, 3, 4 are equal to the Interior Angles used for the Multiplication Factors for Rope Angles at Blocks and are rounded to the next highest 5 degrees in the chart for computation purposes;
Block 1 reaction force (assuming an angle of 120 degrees) = 1000lbs x 1.00 = 1,000lbs
Block 2 reaction force (assuming an angle of 110 degrees) = 1000lbs x 1.15 = 1,150lbs
Block 3 reaction force (assuming an angle of 90 degrees) = 1000lbs x 1.41 = 1,410lbs
Block 4 reaction force (assuming an angle of 130 degrees) = 1000lbs x = 840lbs

Notice how my reaction forces at the rigging points are higher than yours? Except for Block 1, where they are pretty even. By using the Arborist Multiplication Factor chart, with the higher assumed load in the rigging line throughout the tree, we are better able to err on the side of caution and follow the KISS principle when designing a rigging system.

How did you come up with your figures and what charts did you use? Where did you get the 90% efficient block number? Again, not trying to badger you, just curious. Thanks.

I am not trying to turn tree riggers into engineers (believe me, it’s not all that it’s cracked up to be), but I agree with you that the prudent arborist will learn as much as possible. X-Man is doing a great job of bringing new ideas and discussions to our industry and for that I thank him very much!

BTW, David your personal email mailbox is full. Tried to send you a couple of emails this morning.
Click to expand...

I was always taught life support has a 10:1 safety factor and rigging is 5:1. A 20:1 safety factor on rigging seems drastically high we'd be running 1" db for everything.
 
KevinS said:
I was always taught life support has a 10:1 safety factor and rigging is 5:1. A 20:1 safety factor on rigging seems drastically high we'd be running 1" db for everything.
Click to expand...

Kevin, who taught you this if you don't mind me asking? Was it an arborist or someone from the industrial rope trades? For decades, tree workers have always been taught to use a 10:1 for both climbing and rigging not a 5:1 for rigging. The reason for this is it gives us another safety factor cushion for the weights that we are ALWAYS just estimating. In industrial rigging, the loads are known, therefore a 5:1 safety factor (sf) is fine to use.

With regards to a 20:1 safety factor, this is not as drastically high as you might think, nor do you have to use a 1" db rigging rope. A 20:1 can be applied to a 1/2" line, just as easy as it can be to a 1" line. It's all a matter of perspective and what and where you are rigging. Just ask people who have ever rigged anything over glass structures (such as myself) or people like Don Blair, Ken Johnson, Robert Phillips and Gerry Beranek, who have rigged some big Redwood pieces that you and I can only dream about.

Also, I highly doubt that if you applied a 20:1 sf to a 1" db that you'd be running it for everything. A 1" db rigging line has a 39,200lb MBS and if you apply a 20:1 sf, you end up with a 1,960lb SWL (aka WLL) for the pieces that you are rigging and I'm assuming that you are letting your pieces run. Seriously, do you do this daily? Think about it.

I can tell you that I have many, many times through my years of rigging, used a 20:1 sf on a 3/4" Samson Stable Braid line when piecing wood out over a roof or power lines with no room to let them run and having to "snub it off" (aka worst case scenario) and wanting to take as big a piece as I could without worry. The 3/4" line was actually overkill, but I knew it and was comfortable knowing it. Again, just think about it...a 3/4" db has a MBS of 20,400lb and if you apply a 20:1 sf, you end up with a 1,020lb SWL and I can take pieces weighing 200lb (around 4' in length) and drop them 4' snubbing them off and knowing that I haven't exceeded my SWL and I have thousands of cycles to failure. Even if I were to exceed my SWL for the 20:1, I've built in a safety cushion if I should accidently over shock load the line and reach the 10:1 or even 5:1 sf, which I wouldn't because I'm watching the size of my pieces.
 
chris_girard said:
Kevin, who taught you this if you don't mind me asking? Was it an arborist or someone from the industrial rope trades? For decades, tree workers have always been taught to use a 10:1 for both climbing and rigging not a 5:1 for rigging. The reason for this is it gives us another safety factor cushion for the weights that we are ALWAYS just estimating. In industrial rigging, the loads are known, therefore a 5:1 safety factor (sf) is fine to use.

With regards to a 20:1 safety factor, this is not as drastically high as you might think, nor do you have to use a 1" db rigging rope. A 20:1 can be applied to a 1/2" line, just as easy as it can be to a 1" line. It's all a matter of perspective and what and where you are rigging. Just ask people who have ever rigged anything over glass structures (such as myself) or people like Don Blair, Ken Johnson, Robert Phillips and Gerry Beranek, who have rigged some big Redwood pieces that you and I can only dream about.

Also, I highly doubt that if you applied a 20:1 sf to a 1" db that you'd be running it for everything. A 1" db rigging line has a 39,200lb MBS and if you apply a 20:1 sf, you end up with a 1,960lb SWL (aka WLL) for the pieces that you are rigging and I'm assuming that you are letting your pieces run. Seriously, do you do this daily? Think about it.

I can tell you that I have many, many times through my years of rigging, used a 20:1 sf on a 3/4" Samson Stable Braid line when piecing wood out over a roof or power lines with no room to let them run and having to "snub it off" (aka worst case scenario) and wanting to take as big a piece as I could without worry. The 3/4" line was actually overkill, but I knew it and was comfortable knowing it. Again, just think about it...a 3/4" db has a MBS of 20,400lb and if you apply a 20:1 sf, you end up with a 1,020lb SWL and I can take pieces weighing 200lb (around 4' in length) and drop them 4' snubbing them off and knowing that I haven't exceeded my SWL and I have thousands of cycles to failure. Even if I were to exceed my SWL for the 20:1, I've built in a safety cushion if I should accidently over shock load the line and reach the 10:1 or even 5:1 sf, which I wouldn't because I'm watching the size of my pieces.
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Yes Chris I used a 1" line as an over exaggeration on purpose, I should have put that clearer. Like Boom I started learning this in college I'd have to go digging for the sources. My instructors were arborists with many years of experience between them. They also have a rope breaker for testing knots, etc.

As well if every one did redwoods we'd want higher safety factors to lengthen lye life of the lines. Same with locking things off there are times this is needed but we try to avoid them as much as possible.

If you're using a line that can safely take 5x the load you put on at its max that usually makes me feel ok because if I need to count on a 20:1 sf just for my rope what kind of strain is on my rigging point?

I've rigged over green houses, skylights, solar panels, etc. but whether its a skylight or a tin shed I'd rather not hit either. So far I've been fairly lucky and if I'm in doubt of my 5:1 on a 1/2" line I'll get out the 5/8" or whatever but shock loading the piece over target, with double the strain on the t.i.p seems like a last resort, but redundant back ups never hurt.

With that 5:1 in place as a wll the 2nd L is for limit so staying under that line often makes it a higher sf if you figure it out for each piece
 
Boomslang said:
My college profs taught me 10:1 for life support and 5:1 for rigging applications also.

Here's the section of the training manual we used pertaining to rigging (safety factor on page 4):
http://arboristsafeworkpractices.com/ASWP 05_Work at Heights.pdf

That's not to say a 10:1 or 20:1 or even 50:1 safety factor can't be used, but I feel that many arborists operate on, and are comfortable with, a 5:1.
Click to expand...

Boomslang, you're from Canada right? As is KevinS and it looks like our friends from the north are taught a different safety factor for rigging than what we are taught here in the States. Does that make it wrong? Not at all, as long as you understand the principles behind the teachings and from what I've read, you guys are doing just fine.

Thanks for posting the link. This is a very good discussion, but I don't want to take away from David's XRR thread.

Oh yeah, I own 5 XRR slings and they go out on every job I have, whether I need them or not. Standard part of my rigging kit.
 
chris_girard said:
Boomslang, you're from Canada right? As is KevinS and it looks like our friends from the north are taught a different safety factor for rigging than what we are taught here in the States. Does that make it wrong? Not at all, as long as you understand the principles behind the teachings and from what I've read, you guys are doing just fine.

Thanks for posting the link. This is a very good discussion, but I don't want to take away from David's XRR thread.

Oh yeah, I own 5 XRR slings and they go out on every job I have, whether I need them or not. Standard part of my rigging kit.
Click to expand...
There's a thread for showing that rigging kit as well ;) Show it up !
 
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