I am going to build a swing set for the kids.
I want 4 spots for swings with ample room.
I am working with 2 different books on swing set design.

My frame will be 2 vertical 4x4 posts that sandwich my main beam.
Then 2 4x4 posts will be at 30 degree angles to create an A frame on
the ends.

The center beam will be 18 foot long. It will be 3 2x6's bolted
together (to make a 6x6 beam)
This beam will be close to 10 foot off the ground

I am really not sure about the vertical 4x4's and the angled ends.

I am not really sure how to do a beefy a frame design

On May 28, 12:42*am, theedudenator wrote:
I am going to build a swing set for the kids.
I want 4 spots for swings with ample room.
I am working with 2 different books on swing set design.

My frame will be 2 vertical 4x4 posts that sandwich my main beam.
Then 2 4x4 posts will be at 30 degree angles to create an A frame on
the ends.

The center beam will be 18 foot long. *It will be 3 2x6's bolted
together *(to make a 6x6 beam)
This beam will be close to 10 foot off the ground

I am really not sure about the vertical 4x4's and the angled ends.

I am not really sure how to do a beefy a frame design

I don't quite follow. You have two books on building swing sets, what
do you not like about their designs? "I am really not sure..."
doesn't give people much information to work with - what aren't you
sure about?

R

"theedudenator" wrote:

The center beam will be 18 foot long. It will be 3 2x6's bolted
together (to make a 6x6 beam)
This beam will be close to 10 foot off the ground

You're comments above indicate a lack of understanding of the design
fundamentals of beam design.

I don't want to burst you're bubble, but you have some serious
engineering study ahead of you before attempting to design a structure
that could possibly inflict serious bodily harm to the users if it
fails.

Lew

On May 28, 12:19*am, "Lew Hodgett" wrote:
"theedudenator" wrote:
The center beam will be 18 foot long. *It will be 3 2x6's bolted
together *(to make a 6x6 beam)
This beam will be close to 10 foot off the ground

You're comments above indicate a lack of understanding of the design
fundamentals of beam design.

I don't want to burst you're bubble, but you have some serious
engineering study ahead of you before attempting to design a structure
that could possibly inflict serious bodily harm to the users if it
fails.

Lew

What am I missing on beam design? sandwiching 2x6's to make a beam is
not correct???

"theedudenator" wrote:


What am I missing on beam design? sandwiching 2x6's to make a beam is
not correct???

Not really, it is a waste of material resulting in a heavy and weak
beam.

Find a Strength of Materials engineering text and learn an
understanding of the term "Section Modulus" and how it applies to beam
design as a starter.

Lew

"Lew Hodgett" wrote in message
news
"theedudenator" wrote:


What am I missing on beam design? sandwiching 2x6's to make a beam is
not correct???

Not really, it is a waste of material resulting in a heavy and weak beam.

Find a Strength of Materials engineering text and learn an understanding
of the term "Section Modulus" and how it applies to beam design as a
starter.

Lew




Here's a link for the convenience of the brave reader:

http://en.wikipedia.org/wiki/Section_modulus

Challenging looking stuff to say the least...
I hope this doesn't keep the kids from getting a swing set!

Bill

theedudenator wrote:
I am going to build a swing set for the kids.
I want 4 spots for swings with ample room.
I am working with 2 different books on swing set design.

My frame will be 2 vertical 4x4 posts that sandwich my main beam.
Then 2 4x4 posts will be at 30 degree angles to create an A frame on
the ends.

The center beam will be 18 foot long. It will be 3 2x6's bolted
together (to make a 6x6 beam)
This beam will be close to 10 foot off the ground

I am really not sure about the vertical 4x4's and the angled ends.

I am not really sure how to do a beefy a frame design.

I just want to be clear on what you're proposing--you're talking two 4x4
uprights equally spaced and on each end an A-frame made of 4x4s so that the
beam is supported in four places and the longest span is about 6 feet?

On May 28, 12:42*am, theedudenator wrote:
I am going to build a swing set for the kids.
I want 4 spots for swings with ample room.
I am working with 2 different books on swing set design.

My frame will be 2 vertical 4x4 posts that sandwich my main beam.
Then 2 4x4 posts will be at 30 degree angles to create an A frame on
the ends.

The center beam will be 18 foot long. *It will be 3 2x6's bolted
together *(to make a 6x6 beam)
This beam will be close to 10 foot off the ground

I am really not sure about the vertical 4x4's and the angled ends.

I am not really sure how to do a beefy a frame design

I just built one for my princesses. A couple of thoughts...

18' is too long if you plan on having no center support. Even 3 2x6s
will flex and wobble with a swing in the middle and a 60lb kid
swinging on it. And they keep growing...

My 'beam' is 2 2x6s screwed together from both sides with 2 3/4" deck
screws. This barely flexes with an 8' span. The point is that it
does flex at only 8'.

I think the vertical posts are overkill and won't do much. On the A-
frame side of mine I used 2x6s at an angle with a plumb cut to hold
the 'beam' vertical. Then I bolted a horizontal 2x6 on either side of
the angled 2x6s to support the 'beam'. Similar to the collar tie
he
http://qcfocus.com/files/Collar%20Tie.JPG

If you are planning on only having a swingset (no fort or platform)
you'll also need to address the side to side forces. For example this
appears to be a death trap:
http://www.justoutdoortoys.co.uk/sto..._Swing_Set.jpg

The swings, bolts, chains, screw hooks, etc. are *very* expensive.
You are probably better off buying a diy kit complete with hardware
and plans. It will probably end up costing the same as if you design
it yourself and buy all of the bolts, swings and so forth you are
going to need.

On May 28, 1:35*am, theedudenator wrote:
On May 28, 12:19*am, "Lew Hodgett" wrote:

"theedudenator" wrote:
The center beam will be 18 foot long. *It will be 3 2x6's bolted
together *(to make a 6x6 beam)
This beam will be close to 10 foot off the ground

You're comments above indicate a lack of understanding of the design
fundamentals of beam design.

I don't want to burst you're bubble, but you have some serious
engineering study ahead of you before attempting to design a structure
that could possibly inflict serious bodily harm to the users if it
fails.

Lew

What am I missing on beam design? *sandwiching 2x6's to make a beam is
not correct???

Lew's point is that a beam gets _much_ stiffer with increasing depth/
height of the beam as compared to increasing the width/thickness.

You definitely want a stiff beam.
You definitely want a shorter continuous span, so either have an
intermediate A-frame support, or build two swing sets and put them
together. I'd think that having two separate swing sets would be a
little more work, but not much, and would be more interesting for the
kids to play on. They could more easily see each other and have
competitions and such.

R

On May 28, 12:19*am, "Lew Hodgett" wrote:
"theedudenator" wrote:
The center beam will be 18 foot long. *It will be 3 2x6's bolted
together *(to make a 6x6 beam)
This beam will be close to 10 foot off the ground

You're comments above indicate a lack of understanding of the design
fundamentals of beam design.

I don't want to burst you're bubble, but you have some serious
engineering study ahead of you before attempting to design a structure
that could possibly inflict serious bodily harm to the users if it
fails.

Lew


The book I have is suggesting what I posted, that is why I wanted
suggestions.
It didn't not seem correct to me, but I never designed swing sets
before.

I am an engineer....

On May 28, 1:24*am, "Lew Hodgett" wrote:
"theedudenator" wrote:

What am I missing on beam design? *sandwiching 2x6's to make a beam is
not correct???

Not really, it is a waste of material resulting in a heavy and weak
beam.

Find a Strength of Materials engineering text and learn an
understanding of the term "Section Modulus" and how it applies to beam
design as a starter.

Lew

I understand those terms.
Why would a book on swing set design say to use 3 2x6's or a single
4x4
Thats why I asked, seemed odd to me also.

On May 28, 6:59*am, Limp Arbor wrote:
On May 28, 12:42*am, theedudenator wrote:

I am going to build a swing set for the kids.
I want 4 spots for swings with ample room.
I am working with 2 different books on swing set design.

My frame will be 2 vertical 4x4 posts that sandwich my main beam.
Then 2 4x4 posts will be at 30 degree angles to create an A frame on
the ends.

The center beam will be 18 foot long. *It will be 3 2x6's bolted
together *(to make a 6x6 beam)
This beam will be close to 10 foot off the ground

I am really not sure about the vertical 4x4's and the angled ends.

I am not really sure how to do a beefy a frame design

I just built one for my princesses. *A couple of thoughts...

18' is too long if you plan on having no center support. *Even 3 2x6s
will flex and wobble with a swing in the middle and a 60lb kid
swinging on it. *And they keep growing...

My 'beam' is 2 2x6s screwed together from both sides with 2 3/4" deck
screws. *This barely flexes with an 8' span. *The point is that it
does flex at only 8'.

I think the vertical posts are overkill and won't do much. *On the A-
frame side of mine I used 2x6s at an angle with a plumb cut to hold
the 'beam' vertical. *Then I bolted a horizontal 2x6 on either side of
the angled 2x6s to support the 'beam'. *Similar to the collar tie
hehttp://qcfocus.com/files/Collar%20Tie.JPG

If you are planning on only having a swingset (no fort or platform)
you'll also need to address the side to side forces. *For example this
appears to be a death trap:http://www.justoutdoortoys.co.uk/sto...stic_Maxplay_S...

The swings, bolts, chains, screw hooks, etc. are *very* expensive.
You are probably better off buying a diy kit complete with hardware
and plans. *It will probably end up costing the same as if you design
it yourself and buy all of the bolts, swings and so forth you are
going to need.

I think, but not sure that the center vertical 4x4's are supposed to
address that.

I am going to work up a 3 leg tripod type design for each end.
Then a 2 leg tripod to place in the center.

On May 28, 1:59*pm, theedudenator wrote:
On May 28, 6:59*am, Limp Arbor wrote:



On May 28, 12:42*am, theedudenator wrote:

I am going to build a swing set for the kids.
I want 4 spots for swings with ample room.
I am working with 2 different books on swing set design.

My frame will be 2 vertical 4x4 posts that sandwich my main beam.
Then 2 4x4 posts will be at 30 degree angles to create an A frame on
the ends.

The center beam will be 18 foot long. *It will be 3 2x6's bolted
together *(to make a 6x6 beam)
This beam will be close to 10 foot off the ground

I am really not sure about the vertical 4x4's and the angled ends.

I am not really sure how to do a beefy a frame design

I just built one for my princesses. *A couple of thoughts...

18' is too long if you plan on having no center support. *Even 3 2x6s
will flex and wobble with a swing in the middle and a 60lb kid
swinging on it. *And they keep growing...

My 'beam' is 2 2x6s screwed together from both sides with 2 3/4" deck
screws. *This barely flexes with an 8' span. *The point is that it
does flex at only 8'.

I think the vertical posts are overkill and won't do much. *On the A-
frame side of mine I used 2x6s at an angle with a plumb cut to hold
the 'beam' vertical. *Then I bolted a horizontal 2x6 on either side of
the angled 2x6s to support the 'beam'. *Similar to the collar tie
hehttp://qcfocus.com/files/Collar%20Tie.JPG

If you are planning on only having a swingset (no fort or platform)
you'll also need to address the side to side forces. *For example this
appears to be a death trap:http://www.justoutdoortoys.co.uk/sto...stic_Maxplay_S...

The swings, bolts, chains, screw hooks, etc. are *very* expensive.
You are probably better off buying a diy kit complete with hardware
and plans. *It will probably end up costing the same as if you design
it yourself and buy all of the bolts, swings and so forth you are
going to need.

I think, but not sure that the center vertical 4x4's are supposed to
address that.

I am going to work up a 3 leg tripod type design for each end.
Then a 2 leg tripod to place in the center.

There isn't all that much side to side force on a swing set. The
tripod ends are overkill, the intermediate support legs are
necessary.. I hope you are planning on burying the legs in concrete
as the uplift force and fore/aft force can be substantial,
particularly with kids swinging in unison.

If you're an engineer, designing this thing should be trivial for you,
unless you're an electrical engineer which aren't real engineers.

R

"theedudenator" wrote:

====================================
The book I have is suggesting what I posted, that is why I wanted
suggestions.
It didn't not seem correct to me, but I never designed swing sets
before.

I am an engineer....
=====================================

Then it's time to dig our your Strength Of Materials text and review.

Sounds like whoever wrote the book you are reading may not understand
beam design.

Does:

Z = I/d
I = (b)(h^3)/12 + 1/2(A)(D^2)

whe
Z = Section Modulus
I = Moment of Inertia
b = base dimension of a rectangle
h = height dimension of a rectangle
d = distance from center of rotation to the outermost fiber (usually
h/2)
D = 0 for a rectangle when the axis of rotation is about the centroid.

Ring any bells?

Lew

Lew

The biggest issue you will have with such a long beam is that it will
want to bend laterally when multiple people start swinging on it,
particularly when they are all swinging in the same direction. I
design playsets for my website, www.arciplay.com, and though I do not
have a swing beam that meets your exact requirements, you could
lengthen the playset 1.2 swing beam a few feet if you replace the beam
I have shown with an 18' long 6"x6" or better yet 8"x6" (the base
design shows a 4"x6") (a beam like this will be very expensive) the
cables in the design will support the beam laterally. I do not
recommend using 3 2x6" together as you mention unless they are pre-
engineered and fabricated as 3 already combined 2"x6"s.

SFWIW, if you truly need an 18 ft open span beam, consider the
following:

1) Build an "I" beam construction consisting of 20 ft long 2x6 top and
bottom flange with a 2x12 web.

2) Since the web is basically dead weight and contributes "Zip"
towards strength, lighten it along the lines of a bar truss design for
a flat roof industrial building.

Start with a 2x12x10 ft timber and cut it into 5 pcs, 2x12x24" long.

Locate a 2x12 at each end of the 2x6x20 pieces, then space 30" to the
next 2x12x24 piece, then repeat.

What you end up with is a 20 ft long structure with 5-24" wood pieces
and 4-30" open spaces alternately spaced.

Assemble with some 3" galvanized deck screws with hex heads if you can
find them.

Drill pilot holes for the deck screws.

You end up with a beam that is "strong like bull" yet light enough
that two people can lift it into place.

3) Attachments.

I would use loops around the beam rather than drilling holes thru the
beam for bolts for the swing chains.

Have fun.

Lew

On May 29, 1:18*am, "Lew Hodgett" wrote:
SFWIW, if you truly need an 18 ft open span beam, consider the
following:

1) Build an "I" beam construction consisting of 20 ft long 2x6 top and
bottom flange with a 2x12 web.

2) Since the web is basically dead weight and contributes "Zip"
towards strength, lighten it along the lines of a bar truss design for
a flat roof industrial building.

Start with a 2x12x10 ft timber and cut it into 5 pcs, 2x12x24" long.

Locate a 2x12 at each end of the 2x6x20 pieces, then space 30" to the
next 2x12x24 piece, then repeat.

What you end up with is a 20 ft long structure with 5-24" wood pieces
and 4-30" open spaces alternately spaced.

Assemble with some 3" galvanized deck screws with hex heads if you can
find them.

Drill pilot holes for the deck screws.

You end up with a beam that is "strong like bull" yet light enough
that two people can lift it into place.

Deck screws are too light, and 3" is too short - only 1.5" of
penetration? And how many is "some"? Most engineering designs fail
in the connections and the lack of detailing.

If I'm understanding you, you're trying to give the OP a design for a
full length truss with no intermediate support, but it's not really a
truss. A truss joist has diagonals that are opposed. Where one
diagonal is pushing or pulling, the meeting one is resisting that
force - there is no distance between where those forces are applied.
In your design you are relying on the 2x6s on flat to resist those
forces, there is a distance between where the forces are applied, and
the screws at the ends of the 2x12 blocks will be required to carry
more load than 1.5" of penetration will allow. This will tend to sag
over time. I didn't run the numbers, but it will happen.

A swing set should be designed with a large factor of safety and it
should be designed for the occasional show off adults competition
really going at it. There's also the cyclical nature of the applied
loads, the combined tension and shear load on the screws with the 2x12
design, etc. A #12 wood screw has something like 200 lbs of pullout
resistance in SYP (PT wood) per inch of embedment - 1.5" =~300 lbs. I
would think you'd need a minimum of seven or eight hundred pounds per
fastener for the end conditions with the 2x12 design instead of three
hundred.

It would be better if the OP skipped the 2x12, which has problems with
shrinkage and twisting, and used some 3/4" pressure treated plywood as
the web. Even better would be to use the 3/4" plywood and PT 2x6s
(might be able to get by with smaller 2xs) and build a box beam joined
with construction adhesive and 2.5" epoxy-coated deck screws at 4" -
6" on center.

The top of the beam should be covered so there's no standing water on
top of the beam and water won't enter the edge of the plywood. The
plywood joints should be staggered and - belt and suspenders - screw
and glue plywood scabs to join the ends of the plywood pieces to each
other.

3) Attachments.

I would use loops around the beam rather than drilling holes thru the
beam for bolts for the swing chains.

Having the swings hung from the top of the beam is definitely
preferable with a truss or box beam. I have no idea what sort of
hardware is available for a swing set, so I can't recommend any
specific method of attachment. Another poster mentioned the hardware
is expensive, I'd price that stuff before finalizing a design.

Have fun.

The most important part!

R

"RicodJour" wrote:

Deck screws are too light, and 3" is too short - only 1.5" of
penetration?

In this application, fasteners are strictly in shear, so penetration
is
not an issue.

Don't like 3", use 3-1/2" or 4".

Deck screws that size are about the same as 16d common nails which
would do the job, if your arm is in shape to handle a 24 OZ framing
hammergrin.

And how many is "some"?

How about 3"-4" spacing or whatever looks good in the shower.

Most engineering designs fail
in the connections and the lack of detailing.

This is about as classic a design as it gets. The fasteners are in
shear, supports are in compression. I wouldn't expect these joints to
weaken the design.
===================================
If I'm understanding you, you're trying to give the OP a design for
a
full length truss with no intermediate support, but it's not really a
truss. A truss joist has diagonals that are opposed. Where one
diagonal is pushing or pulling, the meeting one is resisting that
force - there is no distance between where those forces are applied.
In your design you are relying on the 2x6s on flat to resist those
forces, there is a distance between where the forces are applied, and
the screws at the ends of the 2x12 blocks will be required to carry
more load than 1.5" of penetration will allow. This will tend to sag
over time. I didn't run the numbers, but it will happen.
=================================
Not quite.

The bottom 2x6 is in tension, the top 2x6 is in compression, and the
2x12
web provides the diagonal support.

No details have been specified for the end terminations; however, the
beam must rest on an adequate support.

Fasteners will not carry the load by themselves.

I'm lost about your fastener concern?

====================================
A swing set should be designed with a large factor of safety and it
should be designed for the occasional show off adults competition
really going at it.
====================================
Yep.

====================================
There's also the cyclical nature of the applied
loads, the combined tension and shear load on the screws with the 2x12
design, etc.
===================================
You lost me.

====================================
A #12 wood screw has something like 200 lbs of pullout
resistance in SYP (PT wood) per inch of embedment - 1.5" =~300 lbs. I
would think you'd need a minimum of seven or eight hundred pounds per
fastener for the end conditions with the 2x12 design instead of three
hundred.
====================================
You lost me. The beam must rest on an adequate support.

Fasteners in tensile will fail.

====================================
It would be better if the OP skipped the 2x12, which has problems
with
shrinkage and twisting, and used some 3/4" pressure treated plywood as
the web. Even better would be to use the 3/4" plywood and PT 2x6s
(might be able to get by with smaller 2xs) and build a box beam joined
with construction adhesive and 2.5" epoxy-coated deck screws at 4" -
6" on center.
====================================
Building a box truss with plywood is certainly an approach; however,
using pressure treated lumber for anything other than a ground contact
member is way down on my list of acceptable materials.

Exposed exterior construction would require considerable preventative
maintenance, thus wasn't considered.

====================================
The top of the beam should be covered so there's no standing water
on
top of the beam and water won't enter the edge of the plywood. The
plywood joints should be staggered and - belt and suspenders - screw
and glue plywood scabs to join the ends of the plywood pieces to each
other.
=============================

Having the swings hung from the top of the beam is definitely
preferable with a truss or box beam. I have no idea what sort of
hardware is available for a swing set, so I can't recommend any
specific method of attachment. Another poster mentioned the hardware
is expensive, I'd price that stuff before finalizing a design.
==================================
3/4", 3 strand nylon, replaced every other year.

Works for swings and dock line for my boat.

Have fun.


Lew