Pulling Tree Stumps Safely

[SPYDERLK]

Are you sure that is correct? I know that marine chain is rated by several parameters and one of them is % stretch before failure. All that energy from pulling with 40hp or whatever your tractor puts out has to be stored somewhere if you are tugging away at a stump. The stump itself must have some of it but a sudden failure in the chain must release a fair amount back towards the source of the energy too (ie tractor).Any physicists, mechanical engineers or material scientists out there?

There is elastic stretch and plastic stretch. Elastic stretch snaps back - plastic doesnt. All chains, and bolts for that matter, have initial elastic stretch that at some % gives way to yield - plastic stretch. All steel stretches elastically about the same, whether high or low stength. This means all steel has about the same stiffness. The difference comes in after the low stength steel begins to yield - it will no longer return to its original length when relaxed, whereas the hi strength will continue to stretch elastically. Perhaps it will stretch twice as far [taking twice as much force] before begining to yield. Twice the average force for twice the distance means it has 4x the stored energy. This energy surplus remains about the same as the two chains yield. When they break the low stength chain will be relatively well behaved in comparison to the hi. Standard logging chains are only moderate strength so they yield relatively easily and store less energy. Safer, but you pay for it by having to use larger chain to get the same strength. The energy surplus of the equal smaller chain of hi strength steel would then be 2xdistance and 1x force.... Twice the E.
larry

 

[AndyMA]

Instead of pushing them over, I've found it's easier to pull them out of the ground, drag them to the burn pile, then use the grapple to pick the tree up and place it on the pile. I connect 2 tow chains together, the end at the tree has a slip hook. I cleared out a corner of a our property quite nicely like this. Largest tree was about 4-6" diameter, just make sure the slip is up 5-6' off the ground.

When pulling on trees, it should be obvious but remember you are under the falling side or the tree and if you miscalculate the height or the tree springs free toward you, you are likely to get a very bad headache. Some branches may be quite a lot longer than you invision.

Andy

 

[AndyMA]

I think the Mythbusters determined that it would not slice you in two. I saw that episode and I don't think they made any determination on lethality...at least in my opinion. Blunt trauma can kill you just as well as penetrating trauma.

What I don't remember was how they got the cable to its breaking point. It seems like they did it in a fairly continuous, steady fashion. Is that right? Or maybe they cut it. Anyway, I'd be more concerned about a breakage due to a sudden, violent shock load.

Regardless, I would not want to be hit by any of these options.

I yanked on a 3/8 Grade 70 chain connected to a tree that snagged with my 44,000 excavator. The chain snapped and went right through a heavy steel plate. It may not have cut me in half but it certainly could have killed me had it hit me. It scared the cr** out of me.

Andy

 

[AndyMA]

In my area, non coastal New England it is so rocky that digging with a front end loader is useless. Ther is no way that I would ever get a 24" oak out of the groudn with anything other than a backhoe and several hours or my excavator and a hour.

Andy

 

[IslandTractor]

There is elastic stretch and plastic stretch. Elastic stretch snaps back - plastic doesnt. All chains, and bolts for that matter, have initial elastic stretch that at some % gives way to yield - plastic stretch. All steel stretches elastically about the same, whether high or low stength. This means all steel has about the same stiffness. The difference comes in after the low stength steel begins to yield - it will no longer return to its original length when relaxed, whereas the hi strength will continue to stretch elastically. Perhaps it will stretch twice as far [taking twice as much force] before begining to yield. Twice the average force for twice the distance means it has 4x the stored energy. This energy surplus remains about the same as the two chains yield. When they break the low stength chain will be relatively well behaved in comparison to the hi. Standard logging chains are only moderate strength so they yield relatively easily and store less energy. Safer, but you pay for it by having to use larger chain to get the same strength. The energy surplus of the equal smaller chain of hi strength steel would then be 2xdistance and 1x force.... Twice the E.
larry

Thanks Larry, That makes a lot of sense and explains why chain may indeed be safer as psj12 suggested. It seems your explanation fit with Andy's experience if he was using Grade 70 chain which being high strength must have more elastic stretch. I've been using grade 70 chain under the perhaps false assumption that it was safer but it looks like a larger size of lower grade chain would actually be the safest for stump pulling.

 

[outdoorstom]

I work on the St. Lawrence Seaway and we require the ships to use wires for mooring. The wires (28mm) are a lot less likely to hurt somebody when they break due to the fact they don't whip very much at all. They make a lot of noise though and scare you pretty good!

 

[Northland]

I use these wire ropes (aka slingchokers) all the time and have never had a problem. They are strong and very easy to get around a log(s). Everyone of my neighbor logger/skidder owners use these everyday in the forests around my home.

Bailey's - Pre-Made FSE Choker 1/2"x 14'
Pre-Made FSE Choker 1/2"x 14'(8 lbs)

 

[IslandTractor]

This is getting more confusing for me. The contradictions seem to be over whether 1) large but not high grade chain (so it breaks but doesn't stretch) or 2) wire rope is best. Why shouldn't polyester towing straps also join the contest for safest? Even if they break, they don't have much mass and assuming the broken side hook stays with the tree side, you would just have a nasty piece of pliable plastic webbing coming back at you rather than heavy steel. It might hurt like the dickens but is unlikely to take your head off.

What I get from this thread so far on chain/wire rope/straps is that one should clearly oversize them but additionally it seems there is a fairly wide range of products that are in use and considered safe. The other point seems to be that any of these can break but are most likely to break when applying a sudden rather than continuous force. The biggest risk then would be when you don't pretension the towing chain/wire/strap before applying towing force with a tractor. Again, the bottom line lesson to me is to get out the backhoe for stumps that are even close to a challenge rather than trying to yank them out.

 

[psj12]

While in the Coast Guard we were given the standard Navy training on broken line recoil and were shown the movie of manaquins being taken apart by a line when it parts. The example shown was Nylon mooring lines that will elastic strech up to twice their length. Additionally catapult lines are being pulled by huge hydraulics that continue to pull after the line separates.
Wire rope much like chain is made of steel. It tends to yield some when breaking. I have seen several large wire ropes part and they do jump considerably but they don't recoil to the point of wraping themselves around the anchor points.

 

[Northland]

Here's some links about the sling chokers and wire rope

Wire Rope - Grades of Rope Wire

http://www.slingchoker.com/pdf/WIREROPE.PDF