Trying to repair a split tree with bolts(s)

[UpstateNY]

Trying to repair a split tree bolts(s)

I have a tree that split down the middle from high winds, about a 5' long vertical crack. The crack extends from about 2' off the ground, and up 5' from there, it's about a 2" crack at it's worst, it's otherwise a healthy maple, about 30 ft tall. I like the tree and want to make some effort to save it, if it doesn't' work I'll just chop it down.

I hooked a 4,000 come-along to it and got the crack to close somewhat. I not necessarily looking for arborist advice, my question is to any mechanical engineers on this site.

If I drill a "few" 3/4 holes up the trunk of the 14" diameter tree, and pass a threaded rod through the tree, with some 1/4 " steel plates on each side, and a nut on each side, can any ME's tell me that if I torque the nut to X foot pounds it'll yield X PSI of compressive force. The steel rod will come from Home Depot so you get an idea of the strength / quality of the rod. Not sure what "grade" the rod is from HD, but I figure some might have that info.

I'm trying to understand approx. how much compressive force I'll achieve per bolt. Would 1 bolt yield the same force as a 4,000 lb come-along ?

Anyone have similar experience ? Would threaded rod(s) / bolts give me enough force to close the gap or does a bolt pale in comparison to a come along ?



Thanks.

 

[srmofo]

How did you hook the come along to it?

I'm going to go out on a limb and say that the bolts will exert way more force than the come along. I would probably even skip the plates in favor of a counter bore with the nut recessed into the tree. If just work them a little at a time evenly up and then back down until the gap was closed up.

Out of curiosity, how close is the tree to any structures

 

[Git]

My neighbor's tree split very similar to what you describe several months ago. He was away at the time and I was able to use a ratcheting cargo strap further up to keep it together - but not fully close the gap. Also, his tree was not nearly as big as yours

When he got back, first thing he did was some major pruning that was long overdue. He then drilled holes and used threaded rod like you mentioned to get it pretty well closed up. Finally he sealed the split with some spray on stuff (like tar) made for trees

Tree looks like it is still doing well

 

[rlitman]

When that tree finally does come down, and your arborist puts it through a chipper, he's going to be mighty pissed when he encounters the steel in it.

 

[AndrewDouglasBird]

Here is exactly what you need:

http://www.engineersedge.com/calculators/torque_calc.htm

100 ft. lbs. of torque on the nut of a 3/4" diameter bolt will provide a bit under 700 lbs of force.

Interestingly enough, if you go with a smaller diameter bolt, the clamping force goes up. I suppose you put a LOT more than 100 ft. lbs. of torque on a 3/4" bolt though.

 

[Farmall450]

We used 2 pieces of channel plus 2 threaded rods to really clamp her together.

 

[Dustball]

Your 2-ton cable puller is actually probably only pulling 2,000 lbs on the very first wrap of cable on the drum.

The 4,000 "pull" is when it's double-lined with a ****** block and on it's first drum wrap. Each additional layer of wire on the drum reduces the pulling force.

 

[Boomer343]

Re: Trying to repair a split tree bolts(s)

I tried that with a smaller tree and the crack slowed but didn't stop. I checked it once when the wind was getting up and it was shifting. Just a matter of time before it came down so I choose the time.

 

[AndrewDouglasBird]

Here is a torque chart for various size bolts as well:

http://www.engineershandbook.com/Tables/torque.htm

You may consider buying high strength rods from McMaster. They are only slightly more expensive than what you can buy from Home Depot.

http://www.mcmaster.com/#standard-threaded-rods/=117qf5h

 

[dodgejunkie]

When I was a kid (40 years ago)an elm tree split from wind also. My dad pulled it together with a couple threaded rods. You didn't even see the rod, or nuts after a couple years. That tree stood until about 2 years ago when the current homeowner cut it down! Up until that point the tree did fine.

 

[turbowoodworker]

Not an expert but my BIL has an old sycamore (Southern California ) that was splitting similar to your description. He ha d aprofessional place cables from one limb to the next much higher up the tree from the split. I can't remember if there is a turnbuckle or if there are through bolts or just screw eyes. I doubt screw eyes as through bolts would be much stronger.

 

[holdover]

"100 ft. lbs. of torque on the nut of a 3/4" diameter bolt will provide a bit under 700 lbs of force.

Interestingly enough, if you go with a smaller diameter bolt, the clamping force goes up. I suppose you put a LOT more than 100 ft. lbs. of torque on a 3/4" bolt though."

Me thinks has to do with threads per inch, pushing an object up a steep ramp VS a shallow angle one..

There are many old trees held together with rods, put a backing plate on each side and seal the crack.

 

[matt_i]

Me thinks has to do with threads per inch, pushing an object up a steep ramp VS a shallow angle one..

You are exactly right. If you chose a 3/4-10 "coarse" thread 100 ft-lbs will get you so much tension. If you choose a 3/4-16 "fine" thread then the same 100 ft-lbs will get you a lot more tensile load. That said, there is not free lunch in just always using a fine thread as the base material has to be up to the task of taking on more load with a shorter thread "root".

The main problem I see with wood is that its compressive strength is much lower than the steel. The rod is an ideal way to induce the pull, but the washer might just crush a hole in the side of the bark.

Maple looks to be in the 500psi cross-grain tensile strength. I had it in my mind that SPF was about 250psi.
http://www.gutenberg.org/files/12299/12299-h/12299-h.htm#I_04

So the issue will be getting a very large washer that's up to spreading out the load without bending itself. Will be a thick washer ideally, I personally would turn one on the lathe, maybe 3" dia x 1/2" thick.

To answer the question about relation between torque and load, the classic equation is Torque = (k) * 0.2 Force * dia. k is a constant of nominal value = 1 that you modify by experimentation...it also has to do with lubrication of the threadform, eventually 100% of the load is "lost" to friction, so things like oil or even better anti-seize paste will help you get more tension.

In practical consideration, 1" diameter would be even better, so would 2" diameter, etc, etc, but you can find the cost of the rod would go up and up, and you have to have a way of drilling the hole. 3/4"-10 standard coarse thread is a nice balance in practicality of both. The key is going to be in the thick washer in my mind, as well as placing multiple rods...the tree will eventually be under dynamic load. Also the deep pruning as suggested will help reduce the loads on this part of the arm.

Last thing, if its a silver maple, deep cuts on the leaves, silvery underneath, and not broad like a Toronto Maple Leaf, its probably not worth messing with, those are known brittle and easily outgrow their ability to structure the growth.

 

[beakie]

did the crack result in a fork?
exagerated obviously, but does it look like a "Y" or is it just a pressure crack that starts & ends in the main trunk?

there are right & wrong ways of fixing a crack, sometimes you just support each side together but with a "lasso" around each that can slip slowly with time but stays tight in wind (think Chinese finger trap)

any plate that is big enough to support a bolt will either deform over time as the tree grows, or if too strong the tree will eventually break the threaded rod (depending on size of course).
if you just use a bolt & nut, however tight you make it, will simply compress the tree, slowly tearing surrounding area and causing as much damage as whatever you are trying to fix.

the tree is growing, if you use a plate & threaded rod, do so just to put enough pressure to keep the crack from growing. leave a few inches of rod sticking out either side, and be sure to loosen it every year or so, to keep the plate/rod & tree in good condition.

 

[SIX225]

Had a tree that was too close the my house and the neighbor to begin with that did the same. Tree company came out for an estimate to take it down and I asked about bolting it. They said that if was bolted it and it came down later, insurance company might have issues with it because I knew there was a problem. Sales pitch to take it down? Maybe, but then again it was too close to the house. I suspect mine started out small and water got in it, froze, and expanded. Add in a couple of wind storms and it big enough to put my hand in. I miss my shade.

 

[theoldwizard1]

1 - 3/4" thread rod is likely adequate. Be careful with you choice of rod. Most of what you can buy is the equivalent to a Grade 2 or 3 bolt. You want at least Grade 5.

 

[58Yeoman]

I had a 50' tree that was splitting in two. I chained it together for a year or so. If it fell, one side would've hit my shop. I called a local tree climbing arborist, and he said that he wouldn't climb it, as he was afraid that it would split with him up there. I had to call a tree service with a bucket truck to take it down.

Now, I've got a cottonwood that keeps dropping limbs, and they look rotten. I guess I'll have to call another tree service to either top it or take it down. It's huge, and if it falls, it'll fall on my blacktop driveway and yard where my field tile is. Damn old trees.

 

[Kevin54]

You can bolt it and plate it, but as far as torqueing it to so many foot pounds, forget it, just tighten it up. The reason I say that is that as the tree grows it will put more force on the plates throwing your torque specs all off.

Just out of curiosity, what type of tree is it, and how old is the tree. If it is sort of a fast grower, the tree will consume the plates and threaded rod, meaning that the tree will soon grow around the plates. We have a Sunset Locust that was a very small tree when we moved here in '93. It's probably 2 1/2'-3' in diameter now. It is slowly covering up the large hooks that was screwed into it for the bird feeders. These were large "Z" shaped hooks, and the vertical leg of the hook is probably buried an inch into the tree now. This has been in probably an 8 year period. All that is sticking out now is just a straight piece with a little bend on the end

 

[MScott]

did the crack result in a fork?
exagerated obviously, but does it look like a "Y" or is it just a pressure crack that starts & ends in the main trunk?

If it is a fork, maybe consider cutting one side of the tree off. This will remove the force tending to widen the split. The tree will send new branches into the "void" left and will eventually become a full shade tree again.

 

[Git]

We used 2 pieces of channel plus 2 threaded rods to really clamp her together.

that sounds like the way to go

 

[lakeroadster]

You can bolt it and plate it, but as far as torquing it to so many foot pounds, forget it, just tighten it up. The reason I say that is that as the tree grows it will put more force on the plates throwing your torque specs all off.

As I envision the OP's idea, that's kind of the beauty of through bolting it... going out later and backing the nuts off, then re-torquing.

How about something less intrusive? We had a thorn tree that split at our home when we lived in Ohio. I installed a chain in the branches above the split. That was in the late 1990's. We were back in the area last summer and the tree still looked healthy.

The chain method helps to hold the tree from further splitting, but still allows it to grow naturally.

 

[manwithtools]

Here is exactly what you need:

http://www.engineersedge.com/calculators/torque_calc.htm

100 ft. lbs. of torque on the nut of a 3/4" diameter bolt will provide a bit under 700 lbs of force.

Interestingly enough, if you go with a smaller diameter bolt, the clamping force goes up. I suppose you put a LOT more than 100 ft. lbs. of torque on a 3/4" bolt though.

Nope, it not 700 lbs. - it's more like 8000 lbs of clamping force. The calculator is a bit deceiving, the input for torque is in inch pounds, not foot pounds. You need to input 1200 for torque and then you'll get right at 8000 lbs. for clamping force.

When I saw the value you referenced I instinctively knew it could not be right. I've broken or bent too many things over the years while tightening bolts.

I would not drill through the tree, make a couple of saddles out of 3 x 3 angle and bolt them together with all-thread outside the trunk. Drilling holes in the tree will potentially introduce another point to split from in years to come. Your arborist will be able to plainly see them when the tree ultimately gets cut down, he will thank you for that.

 

[manwithtools]

Also, that calculator appears to be making assumptions based on bolt diameter. The fact the clamping force is shown to be higher for 1/2" than 3/4" is based on thread pitch assumptions.

If you were to use a 3/4 -16 it would have significantly higher clamping force than 1/2-13 due to the fact that its larger diameter and the pitch of the thread is lower. For that part of EngineersEdge it's very misleading unless you study things very closely.

 

[ALinCarolina]

When Hurricane Hugo came through here in 1989 we had over 75 trees down. One of the largest of our trees, a 30 to 36" diameter Red Oak, didn't fall but had a crack develop. We had an arborist come out and he drilled and placed two bolts through it. It did fine until this year when it finally started to die so we had it taken down. The bolts were covered over by now of course. My tree service guy is a friend who sells firewood on the side. I made sure he knew about the bolts and he had no problem.
So I would say the bolts were a success, especially since this was a Red Oak which which seems to be more susceptible to dying than my White Oaks.

 

[UpstateNY]

Guys, thank you very much for all your excellent ideas and info re: the bolts.

To answer a couple of questions, yes, the maple tree did split because 8' of the ground it does "V". And the one side of the Vee is quite a bit larger as the tree grew so as to acquire the sunlight available over my access road. My house is situated in the "middle" of a 12 acre mixed, deciduous forest with every hardwood tree you can imagine.

The tree in peril is a maple, but I need to determine what type as someone posted above and see if mine is the type that is known to crack, that'll help my decision making process. I realize it is the type of tree ( a Vee tree) that mother nature destines to die because it is growing in a non-ideal manner, but if I can add a few man-made materials to it to keep it alive, I will. The tree is not near the house or any other structure and presents no threat to life or "limb".

Even though I have 12 acres of hardwood trees, this tree is in my front yard, and is a nice shade tree. My other trees are towering 60' hardwood trees, so this tree is essentially the only decorative one in my front yard, so I'd like to save it.

Because someone asked: the come along is currently tied between the damaged smaller tree and a nearby maple 50' tall.

I'll try the bolts and / or channel idea, goop the tree with a dressing to keep out moisture and bugs and hope the thing can heal itself over time. The tree is structurally stable for now, I'll wait for a bit of a thaw and get on with the repair, and hopefully it'll sprout some leaves in the spring and acquire enough of the sun's energy it needs to repair itself.

You guys are the best, you have given me hope I can save the tree.

 

[AndrewDouglasBird]

Nope, it not 700 lbs. - it's more like 8000 lbs of clamping force. The calculator is a bit deceiving, the input for torque is in inch pounds, not foot pounds. You need to input 1200 for torque and then you'll get right at 8000 lbs. for clamping force.

You're right, good catch. I thought that seemed awful low.

 

[Kevin54]

Scroll over the pics of the Maple Tree leaf and it will tell you what type of Maple it is if you can remember what the leaves look like. If you have a Silver Maple, I'd try to save it, but I wouldn't worry too much if it died. And if it is close to your leach bed, I think I would take it down (if a Silver Maple) as they are a tree known to trash many a sewer line and leach bed. Here is the link http://www.bing.com/images/search?q...tion&qpvt=maple+tree+identification&FORM=IGRE

 

[CNGsaves]

Do both . . . use cables and turnbuckles to pull up on branches to relieve pressure on the crack. Then use the through bolts and perimeter clamp(s) to hold it together until it heals.

Let's SEE some PICTURES . . . . this IS indeed GJ you know !!

 

[UpstateNY]

Scroll over the pics of the Maple Tree leaf and it will tell you what type of Maple it is if you can remember what the leaves look like. If you have a Silver Maple, I'd try to save it, but I wouldn't worry too much if it died. And if it is close to your leach bed, I think I would take it down (if a Silver Maple) as they are a tree known to trash many a sewer line and leach bed. Here is the link http://www.bing.com/images/search?q...tion&qpvt=maple+tree+identification&FORM=IGRE

Kevin,

Thank you, I'll do my best to identify the tree, but I may to wait until it sprouts leaves. The tree is over 100 ' from the leech field.

 

[UpstateNY]

Do both . . . use cables and turnbuckles to pull up on branches to relieve pressure on the crack. Then use the through bolts and perimeter clamp(s) to hold it together until it heals.

Let's SEE some PICTURES . . . . this IS indeed GJ you know !!

Ok, ok, I'll try and get some pics, they are worth a thousands words after all.

 

[dbabicky]

Just cut the thing down. LOL !! I guess I just don't see the point of trying to save the thing. Maybe because I live in the middle of the woods in NE Wisconsin and I have over 60 acres of hardwoods around my house that I own and another 1500 acres around that owned by my family and neighbors.

 

[UpstateNY]

I make it clear above why I want to save it. My house too is completely surrounded by mixed hardwood trees, no conifers, all hardwood. But that's not the point.

 

[Finky198]

What I tend tell clients in your situation (I own a tree care company) is that the damage is done. We try our best to repair the visual damage, but it's up to the tree to heal. In Most instance when they are not dealt with early enough they have multiple issues that lead to the demise of the tree be it bugs, mold, stagnant water, ect. Thus I don't recommend repairs as there costly and the failure rate is high... But moving on.

The goodnews is that you seem to be on top of it. when we do actually do a repair like this. I like to use grade 5 1/2" threaded rod as it seems to work best. get a large flat washer which on impact usually forms to the tree...then a lock washer and nut. No plate or any other hardware should be needed just place the bolts evenly apart and pull them together like a zipper. A little at a time until the gap slowly closes.

I would not worry about the torque nazi as The bolts under normal stress will hold it together ( if for any reason they pull, snap or stretch) its time to take it down the tree as it dangerous and can cause harm. Regardless of how pretty the tree may be its not worth getting hurt over.

 

[Kaizen]

http://www.thisoldhouse.com/toh/video/0,,20822555,00.html

 

[xtremek]

My wife, the biologist, says that most pruning should be done in the winter. If that's the case, I would think the optimum time to make the repair would be right now while it's still a little cold out. Which reminds me, I need to prune the apple tree.

 

[sublimate]

I'm going to go out on a limb and say...

Ouch.

 

[revkev6]

Had a tree that was too close the my house and the neighbor to begin with that did the same. Tree company came out for an estimate to take it down and I asked about bolting it. They said that if was bolted it and it came down later, insurance company might have issues with it because I knew there was a problem. Sales pitch to take it down? Maybe, but then again it was too close to the house. I suspect mine started out small and water got in it, froze, and expanded. Add in a couple of wind storms and it big enough to put my hand in. I miss my shade.

not a sales pitch at all. a healthy tree falling is considered an "act of god" to the insurance company.. on with a crack isn't. my neighbor had a HUGE pine fall on my property because it split down the middle crushing my shed. I got the neighbors insurance to pay for it because i could prove it was cracked before hand.

I have one tree left on my property and I'd cut it down if I could. love the shade... hate the leaves and branches falling on my stuff!

 

[Finky198]

^^^ Your are totally correct ^^^

 

[UpstateNY]

What I tend tell clients in your situation (I own a tree care company) is that the damage is done. We try our best to repair the visual damage, but it's up to the tree to heal. In Most instance when they are not dealt with early enough they have multiple issues that lead to the demise of the tree be it bugs, mold, stagnant water, ect. Thus I don't recommend repairs as there costly and the failure rate is high... But moving on.

The goodnews is that you seem to be on top of it. when we do actually do a repair like this. I like to use grade 5 1/2" threaded rod as it seems to work best. get a large flat washer which on impact usually forms to the tree...then a lock washer and nut. No plate or any other hardware should be needed just place the bolts evenly apart and pull them together like a zipper. A little at a time until the gap slowly closes.

I would not worry about the torque nazi as The bolts under normal stress will hold it together ( if for any reason they pull, snap or stretch) its time to take it down the tree as it dangerous and can cause harm. Regardless of how pretty the tree may be its not worth getting hurt over.

Finky,

Excellent, will do it as exactly as you suggested and do it ASAP. Winter here still, no bugs yet, but I will also put on tree dressing on it to keep the water and bugs out of the damage.

to all others, excellent ideas, you guys are the best.

 

[Finky198]

No problem and yes spectracide prune seal is messy, but works well its avail at most big box stores.