Biggest stuff lowered on rope?

[iamdevildog]

Hey all, I'm wondering what the biggest piece of wood you have lowered on rope and what rope you were using. Reason I ask is that we were taking down a pine and to make the job work we needed to get 12'6" logs for the mill. With no way to bomb logs, we had to lower them with a block. First log was 66' up the tree and 22" diameter. Cut the log and had rigged a 3/4" sling with a block - logs falls and bam! brand new sling breaks and log falls free. Luckily no one was hurt and the log fell clean right at the base. we've dropped 16' logs 18" diameter before on all the same rigging gear so I'm trying to figure if I got a bad sling or what.

 

[flushcut]

No you needed bigger rigging and ignored you cycles to failure. How did you have the block tied off? Wrong knot could have cut itself in two.

 

[iamdevildog]

this was a brand new sling, we think the bowline might have been too tight around the block, ie not allowing the block to move enough in the loop and that could have cut the sling. Again, I'm pretty sure we have dropped as big or bigger on the exact same setup, just wondering if anyone has ever experienced a bad sling or just bad operator, and how big a log have you guys dropped.

 

[beastmaster]

Some times you can hook up two pulleys in the tree on really heavy wood, with two ropes. Tie the two ground ends together with a big prussic so you can control it with a single rope.
Slings are pretty strong, but if you hook em up wrong you can weaken them at the end where the splice is.
This is old school stuff but back in the day we used cable chokers with splced ends. They won't break.
Most the time slings are a lot stronger then the rope your going to use. I would bet you stressed it on its self causing it to fatigue. Did it break at the end where it crossed over its self? You might want to try a cow hitch to tie your slings on. Beastmaster

 

[John Paul Sanborn]

You cannot make the sling too tight, friction from it slipping as it chokes up can cause it to melt through.

Did the rope man allow the load to run, or was it caught? That is a lot off mass to drop static onto a rope.

I'm too dull witted to do the math on a 22 x 150 inch log right now.

 

[iamdevildog]

unfortunately we have not figured out how to "let it run" yet. We've been using a port-a-wrap for a while but haven't messed around with letting it run. I've always dropped logs static which is why I'm curious how big a log can actually be dropped on a tree. any pointers on letting it run would be appreciated!

 

[mattfr12]

depends on the size of the tree you drop to big of a log it will just break at some point i got a 1 inch rope in my truck with one of those 4.5 ton blocks from sherrill and we always let it run to some point if where not directly over a house or something. you dont wanna be just straight stoping stuff because a 500 pound log becomes 1500 pounds due to shock load thats hard on the equipment.

i usually have my ground guys walk twards the portawrap slowing down thier steps to ease it off.

ive had a half inch super braid break with a 500 pound pine top because of shock load before you gotta be careful with that stuff get the pully as close to the cut as you can and your first tie in such as your half hitch good and close to the top of your face cut and ease it off.

when your talking pine you throw a couple thousand pounds off one side and shock load it when your in it it could be death. that #### would be whipping like a car antena.

 

[mattfr12]

you also gotta remember if your talking a thousand pound log on a thousand pound rope that the rope cant handle that because for every knot you tie and pully your run it through deducts from that thousand pounds the rope can handle. same rule applies for slings. i always figure the rope can handle half of what it is rated for just to be safe. so if im lowering down 500 pound logs im using a 5/8 stable braid or more. with a 2 ton block. you cant go wrong by using more i dont use half inch lines for anything more than swinging limbs.

a safe work load limit on a 3/4 inch sling for me is around 1200 pounds. thier rated closer to a ton but by the time you tie and choke and all that other good stuff it get weaker. so with the shock load you probably exceeded that 1 ton rating a good bit im not really sure how much that log weighs but 6 foot by 22 is probably close 600-800 pounds so call it close to a ton with shock load its probably less but i always double to be safe.

 

[TreeClimber57]

you also gotta remember if your talking a thousand pound log on a thousand pound rope that the rope cant handle that because for every knot you tie and pully your run it through deducts from that thousand pounds the rope can handle. same rule applies for slings. i always figure the rope can handle half of what it is rated for just to be safe. so if im lowering down 500 pound logs im using a 5/8 stable braid or more. with a 2 ton block. you cant go wrong by using more i dont use half inch lines for anything more than swinging limbs.

a safe work load limit on a 3/4 inch sling for me is around 1200 pounds. thier rated closer to a ton but by the time you tie and choke and all that other good stuff it get weaker. so with the shock load you probably exceeded that 1 ton rating a good bit im not really sure how much that log weighs but 6 foot by 22 is probably close 600-800 pounds so call it close to a ton with shock load its probably less but i always double to be safe.

Well putting that into rigging software; the log comes out at 582kg.. peak force in rope is showing as 3313 daN/kp and the Shock load at rigging is 6626 daN/kp. With 3/4" Samson Stable Braid - the calculator is flagging as "Critical - Low safety factor" -- "Safe only when dynamic deceleration is absoutely guaranteed". Depends on knot used - I put bowline in calculator, as well as attachment points, etc. So a few variables. But for that load you do need some big gear. I would be using DMM large rigging block on top myself, and Hobbs or GRCS on bottom (and set up to let the piece run a ways).

As for sling, do not have specifics on it in post unless I missed it.. personally on heavy loads I prefer nylon rigging slings vs rope slings.

 

[TreeClimber57]

Hey all, I'm wondering what the biggest piece of wood you have lowered on rope and what rope you were using. Reason I ask is that we were taking down a pine and to make the job work we needed to get 12'6" logs for the mill. With no way to bomb logs, we had to lower them with a block. First log was 66' up the tree and 22" diameter. Cut the log and had rigged a 3/4" sling with a block - logs falls and bam! brand new sling breaks and log falls free. Luckily no one was hurt and the log fell clean right at the base. we've dropped 16' logs 18" diameter before on all the same rigging gear so I'm trying to figure if I got a bad sling or what.

12'6" X 22" = 582kg or 1,280 lbs
16' X 18" = 500kg or 1,100 lbs

So good assumption there.

Were you dropping the 16' longs from same height? 66' up tree..

 

[thepheniox]

Almost always human error. Gear seldom fails without over loading it or using it for too long without replacing it. Dropping large pieces statically will break stuff. Unfortunately now a days we can over rig with heavy gear. The good news is the gear broke before the tree.

 

[TreeClimber57]

Almost always human error. Gear seldom fails without over loading it or using it for too long without replacing it. Dropping large pieces statically will break stuff. Unfortunately now a days we can over rig with heavy gear. The good news is the gear broke before the tree.

I agree.. usually error..

But as for over-rigging. If you are in any way building in a safety factor to the gear, you need big rigging gear at times. Some guys will push their gear to the rated limit with no safety factor, but if you want a safety factor in there then big gear it is. Most items like rope; have a WLL already sitting at a 10:1 (break vs WLL) ratio. But for rigging, consider the shock impact, get some good rigging software (not expensive) and play with it to give you some idea. The Sherrill/ArborMaster software runs with a 3 times safety factor or thereabouts (on the WLL). That is why you need big rope, and big gear.

The DMM block is rated at 6,700 lbs WLL, and minimum breaking strength of 300kN. Does that mean you push it to 6,700 lbs.. NO. It does mean you can safely load a good sized piece of wood on it, and it will handle the shock of impact at rigging point. Having said that you also need a sling that will handle what the block will - we usually run a sling of twice the rating of the block. IMHO -- the rope should be the weak point. If you are running 3/4" rope then you need to put rigging gear into the system that makes the rope the weak point.

In this particular situation, the tree (I don't think but have not seen it) did not have any risk of failure.

You do not rig something this big on say a porty.. as an example (while it is technically rated up to 1" rope and 10,000 lbs -- again you are getting near the upper rating limits -- step up the gear). You need something that can easily and safely take the hit; and keep on going.

Now nobody was hurt; rule when doing big rigging.. ensure no objects or persons are in anywhere near where wood will drop if failure occurs. Keep person with rope a long ways back, and let load run. (not hard to do on Hobbs or GRCS).

If you do not have big gear and are trying to drop big wood.. something is someday going to fail.

Other item; rope is going to be the biggest point of failure (and will need to be replaced on somewhat regular basis as this will knock the crap out of it).

 

[iamdevildog]

12'6" X 22" = 582kg or 1,280 lbs
16' X 18" = 500kg or 1,100 lbs

So good assumption there.

Were you dropping the 16' longs from same height? 66' up tree..

Yeah I was at 82' and pulled a tape on the way down to cut exact 16'6" logs except the tree had a decent lean to it- made for a heck of a ride. I still want to know how big ya'll are taking stuff down on rope. it pretty much scares the crap out of me every time I have to block down logs 'cause I've never seen a tree break under a load and don't know what would do it.

 

[thepheniox]

I'm not saying the tree is the weak point. Just saying that it can be the weakest link in rigging. I know of two tree failures caused by over rigging. Just something to think about before using heavy rigging. Your Absolutely right that the tree should be ok but now he is mentioning a lean to the tree. P

 

[deevo]

unfortunately we have not figured out how to "let it run" yet. We've been using a port-a-wrap for a while but haven't messed around with letting it run. I've always dropped logs static which is why I'm curious how big a log can actually be dropped on a tree. any pointers on letting it run would be appreciated!

That's likely your main fault, if your attempting to lower down something that big and shock load it like that your not doing your gear any favours, or your self. If they don't let it run it could come back and possibly hit you, especially something that big. I haven't done anything that big before that high up, just because of that. Good thing no one got hurt. Letting it run starts with experience, start off with smaller sections, let your groundies get use to letting it run and slowing your pieces down and work your way up to bigger pieces gradually. It all comes with experience!

 

[TreeClimber57]

Yeah I was at 82' and pulled a tape on the way down to cut exact 16'6" logs except the tree had a decent lean to it- made for a heck of a ride. I still want to know how big ya'll are taking stuff down on rope. it pretty much scares the crap out of me every time I have to block down logs 'cause I've never seen a tree break under a load and don't know what would do it.

Well I have seen trees fail; and years ago had one fail I was on (all be it failed because of a skidder pulling on it and not a chunk of wood dropping). I saw it coming, uncliped and jumped (was maybe 25 feet up and marshy ground so was lucky - ended up to my knees in mud crap but other than that ok).

Generally speaking a large tree can take a lot - think of the stress put on it when heavy wind blows crown around. But I have never seen any perfect science for it. A lot of factors; species; health of tree; etc.

Personally I would not try much more than you are dropping, half a ton (or slightly over) is a lot of wood. But you do need gear to handle it (and with a large safety margin).

Personally if you are dropping much of that sized wood; I would get a large DMM rigging block, a nylon sling rated at at least 12,000 lbs working load, 3/4" rope (what kind you using - I use Stable Braid for heavy loads) -- or even 1" if you can find it but watch rating as some 1" is less than 3/4" Stable Braid, and something heavier than porta-wrap at bottom.

Letting a piece run is not as difficult as it sounds, but start on smaller wood and work up with practice. Groundman is doing the work, and he needs practice. You need enough wraps on friction gear that they can stop the piece at will if needed; but few enough that if they let slack into the rope it will slide. Practice with very small pieces. Essentially when piece is dropped initially they let some slack go out into rope; will not go at full speed as friction gear will still slow down some; but it will be pulling rope as it goes. If done right, when they stop it there will have been a significant amount of deceleration in the piece instead of a sudden static stop at end of rope. The nice thing about heavy gear is you can actually take slack up in rope as the drop begins -- shortening the amount of actual fall before the deceleration begins (you can not do this with porty) and then it is easier to control run on bigger pieces. The Hobbs in a pure dead fall will handle more than the GRCS; but in real world scenerio with safety factors built in they are essentially the same for rigging. (each has pros and cons and followers) The idea in letting wood run; especially heavy wood or when in weaker tree is to reduce the shock load or impact at the stopping point. This takes a significant amount of strain off of all the gear (rope, block, sling, friction point, tree, etc) and takes the climber for a significantly less thrilling ride.

I have seen a lot of variables and different techniques used since I have been doing this (started in '74), some good, some bad.. some down right stupid. But personally I prefer to over rig and have a huge safety factor in the gear.

Watch your rope as well; letting run under those loads can cause a lot of heat, wear and stress on rope.. although static stops will cause different kinds of wear as well.

 

[Tree Pig]

do you have another tree close to rig off of?

could try something like this

[video=youtube;6w4fxr3WtUk]http://www.youtube.com/watch?v=6w4fxr3WtUk[/video]

 

[iamdevildog]

Thanks to all who have responded on this, you guys put out some great info. Pretty much makes me just want to blow 3 ft chunks out of the tree and eat it on not getting logs to the mill. we're doing a small-ish pine tomorrow and we'll mess around with letting it run a bit with small loads and see how it works. We've only been doing this about two and a half years now and I won't get into how we got started 'cuz ya'll will lay into me, but thanks for the helpful info and words of caution.

 

[TreeClimber57]

do you have another tree close to rig off of?

could try something like this

[video=youtube;6w4fxr3WtUk]http://www.youtube.com/watch?v=6w4fxr3WtUk[/video]

Another excellent idea if available; although still need gear at least takes danger away from climber.

 

[TreeClimber57]

Thanks to all who have responded on this, you guys put out some great info. Pretty much makes me just want to blow 3 ft chunks out of the tree and eat it on not getting logs to the mill. we're doing a small-ish pine tomorrow and we'll mess around with letting it run a bit with small loads and see how it works. We've only been doing this about two and a half years now and I won't get into how we got started 'cuz ya'll will lay into me, but thanks for the helpful info and words of caution.

Be safe, have fun and let us know. Many of us have different history, it is not how you started or where you started but what you have done since to improve yourself and where you are headed (and what you are doing to get there). Not everybody starts in perfect situation, what is important is you begin to recognize what or where you should be and take steps to get there.

Heck, there are only one or two perfect ones on this site (and one of them ain't me )