So here is a support we built. Following a similar idea you can build your own, and hang your own fun stuff on it.
At 3 meters long, our swing support has holders for three individual swings, or one big swing (three-four places) or a hammock.
It consists of a metal pipe (2' diameter), a wall-support (you may need two depending on your balcony), and 6 holders made of pipe-holders and eye bolts.
It is very stable and silent, great!
Note: If your balcony is short, please consider the danger of kids falling out of it from the swing. Do this swing only if sizes safe.
Step 1: Materials
1 Metal pipe 2'' diameter (3 meters in my case)
1 Metal scrap (round works best)
1 Metal pipe 1.5'' diameter (can be 20 cm short)
(you may need two wall supports depending on the balcony)
6 round pipe hugs
6 matching eye bolts
By using carabiners, the whole thing becomes modular. You can exchange the place of swings, or remove them altogether when you need the space beneath them. You can have one day the large all-family swing, and the other 3 smaller swings. Or remove all and hang your punching ball. Use carabiners in yours too.
Step 2: Paint Blue (or the Color of Your Choice)
You can ask your kids to chose the color.
We chose blue, because it is nicer than red and stands out less than yellow. However, you are not limited to primary color.
Another good idea is to paint it with more than one color, and/or have your kids help you paint it.
Note: Remember, you are painting metal, so use a metal paint, with non-rusting property.
It is recommended to remove the rust from any part of the materials that is rusty.
Step 3: Assemble the Wall Support
The idea is that once the support is on the wall, you can insert the pipe on it (or remove it completely when necessary).
Because the small pipe and the large pipe are round, the large pipe will try to rotate when you swing on it. A vertical bolt traversing both the swings will solve this problem.
Note: This bolt is not holding the pipe's weight (that's why it's vertical), it just prevents rotation.
See the picture, the wall support looks like a 3D 'T'.
Drill holes to put the bolts through, strong jumbo bolts are best. This piece is the piece that holds ALL the weight of the swing set, so don't skimp in this step: Good welding, good metals, good will.
Step 4: Assemble the Swing-holders
Put a Carabiner on the eye-bolt.
Note: We looked for an eye bolt that fits tight into the pipe-hug. This way, you don't need to make a big effort to fasten it (the pipe+pipe-hug will hold it steady). See the zoomed picture for more details.
Note: Pipe-hugs have one fixed part and one nut+bolted part. We welded the fixed part for enhanced safety, and left the other open. This is important, as by opening the nut+bolt a bit, you can move the holder over the pipe length.
Insert them on the big pipe, you will be able to move them later.
Step 5: Preparing the Support
I used three jumbo screws.
On the other side, there is a smaller wall, so I am using an U fastener.
You can see in the picture that I used inner-tubing of a bicycle tire (you can get these for free at bike-repair stores) to avoid metal-on-metal noises (like small 'clanks')
Step 6: Putting It All Together
When placing the swing (or any other stuff) holders, it is recommended to put them as far apart as you can.
Normally people hang the swings with the ropes parallel, but that is a mistake, as the swings can swing sideways too, or spin. See the notes in the other picture below for details.