# End load lmit of overhanging 2x10 beam on a tree?



## sylercider (Dec 6, 2010)

My sons want a tree swing and a climbing rope in the backyard, but we have no trees with thick horizontal limbs that would support much weight.

So, I'm thinking about overhanging a 2x10 about 15' high on the trunk. I would also add a 45 degree support from the tree to the 2x10 beam.

I would use lag bolts to secure the beams to the tree.

I want the overhang to be at least 6' so they don't smash into the tree as they swing or climb.
How much weight can a 2x10 support at its very end if it's overhanging by 6'?
Does the 45 degree support beam need to go from the tree to the very end of the overhanging beam or can it just go to the middle of the beam?
Can I overhang even farther? The farther the better so that they can swing all around!

Something like this:

||_____ 
|| /
||/
||
||
||
||
||


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## Underdog (Sep 4, 2009)

I think you aren't considering all of the forces that will act upon your swing. The swing will not only have to support the weight of your son, but it will also have to support the dynamic forces applied through his swing. You'll have forces in the Z direction (up and down), and in the X-Y directions (forward and sideways through his swing plane). I think you will have a harder time designing for the X and Y directions

To design it properly, you will have to figure out the physics of your son's swing. If you haven't taken a physics course lately, I would suggest buying a swingset.


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## sylercider (Dec 6, 2010)

loftezy,
I do understand that it's not as simple as designing it to support my 50 lb child as he just hangs motionless from the swing.

But, to say that "If you haven't taken a physics course lately, I would suggest buying a swingset. " is a little extreme, don't ya think?

How many clubhouses, forts, tree swings, etc. have been built by the average joe that never took a physics course?
I understand that there is some danger in my design, but that's exactly why I was asking for some help.

I guess I could just build a mock-up of my design about 6' off the ground and then see if will support me as I wildly swing back and forth.


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## Bondo (Dec 8, 2007)

Ayuh,... I think you'll be happier if ya use the tree for 1 side, 'n a couple of 2xs, teepee'd on the other end of the horizonal...


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## Underdog (Sep 4, 2009)

I guess my comment did sound kind of a-hole-ish but I didn't mean for it to be that way. I just would hate to give you advice on building a swing, especially when your son will be swinging on it, when the physics aren't simple. 

Here are a few things to consider though:

A 2x10 of that length will need lateral bracing (something to stop it from twisting and breaking when your son swings). This means that you will likely need 2x10's on each side of the tree trunk with webing and bracing to keep them from twisting failure. You'll also need lag bolts that go all the way through the tree trunk and big enough washers to keep the bolts and nuts from pulling through the wood. 

And by all means, test it with a sand bag before your kids jump on it 

Also, it would be much easier if you didn't design it as a cantilever (one end of the 2x10 unsupported).


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## sylercider (Dec 6, 2010)

loftezy,
I really appreciate your replies.

When I read your 2nd reply, I now fully understand what you mean by "all of the forces that will act upon your swing". I hadn't thought about the twisting force the 2x10 will receive from the swinging. I was only thinking of the up & down force.

That twisting force makes me realize that I need to rethink my design. But, I'm a diy-er through and through, so this is just a setback, not a sign of giving up.

Bondo,
I can't visualize what you were trying to describe.


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## Bondo (Dec 8, 2007)

> Bondo,
> I can't visualize what you were trying to describe.


Ayuh,... Visualize 1 end of a wooden swing set on the end without the tree....

An "A"-frame supporting the end...


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## sylercider (Dec 6, 2010)

I made a little Google Sketchup of my design:
http://sketchup.google.com/3dwarehouse/details?mid=4d39fda1f339f7e273b29e96a3435de&prevstart=0

It's basically a triangle lying horizontally on the tree with a 45 degree support from below. My concern is that this still won't stop the twisting force. The whole triangle will just move side-to-side with the swing, right?
Darn those laws of physics!


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## sylercider (Dec 6, 2010)

Bondo said:


> Ayuh,... Visualize 1 end of a wooden swing set on the end without the tree....
> 
> An "A"-frame supporting the end...


Oh, ok, I get it. I would have an A-frame supporting one side of the beam, while the tree supports the other side.

This definitely would work, but I'm trying to do this without any other support on the ground besides the tree trunk.


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## sylercider (Dec 6, 2010)

Hey, I got another idea!

I have a 2nd tree about 12 ft away. If I got 2 2x10's that were about 18' long, then I could secure them to each tree and have my 6' overhang.

I don't think I would need any other support.

Like this:

||________||____
||________||____|

Does that sound reasonable?


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## NASCAR9 (Jun 17, 2009)

sylercider, I'm no expert but I will throw in my 2 cents. Why not put the swing inbetween the two trees? It would be supported on both sides. I would still use 2 2x10's. Be safe.


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## sylercider (Dec 6, 2010)

NASCAR9, that is a great idea... except that I have a treefort between the trees already.

You can see it here: http://www.diychatroom.com/f19/treefort-treehouse-structural-integrity-38984/#post235302


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## 4just1don (Jun 13, 2008)

*trees*

you have built wood on 3 sides of the tree. Trees are living, growing things. Where will this tree grow to?? How will the diameter expand?? Building into trees have long term health effects to the trees. 

Same as silly people tieing there dog chain around a tree,,,and wondering why the resulting ringing of it killed the tree??? Lags and nails into trees are injuries to the tree.


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## sylercider (Dec 6, 2010)

4just1don,
Your comments are for the other topic, but I'll explain here...

Actually, the wood is only attached to the tree on one side. The upside down triangular support is the only piece that is attached to the tree.

The fort floor is "floating" on these triangular supports via metal brackets that allow for movement.


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## WaldenL (Jan 9, 2009)

sylercider said:


> ... I have a 2nd tree about 12 ft away. If I got 2 2x10's that were about 18' long, then I could secure them to each tree and have my 6' overhang....


So you're going to attach two decent sized trees 12' apart from each other to one another using 2 rigid 2x10 pieces of wood? Watch those pieces of 2x10 snap in the first mild breeze, never mind a good wind storm. If it wasn't for the sway of the two trees your idea would be sound, but since they _will_ move independently of each other there's not way you're attaching them with 2x. Your treefort doesn't attach the two trees, the floor floats.

Since you've got the tree fort already, can you cantilever a swing off the treefort?


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