Here are some of the most popular things you can include in a playground:

Climber
See-saw

What kind of swing set do you want to anchor? If it's a standard swing with a swing frame, you need to drill holes in the ground like described in this tutorial. If your swing set is just a simple one (like a toddler swing), check this how to … Read more

Means that something is powered by mechanical forces, no electricity or fuel is used.  See the definitions by Wikipedia here. See for example what are mechanical toys or mechanical clock.

If tin is not non-corrosive, it rusts yes.

You need to know the weight of a liter sand. This will vary of the type of sand and its humidity so there isn't universal formula. If you have the sand around you, get a 10 litters water pail and fill it with sand. Measure the weight and you'll have the weight of 1 litter … Read more

Sorry forgot to log in and couldn't post the link. For a wooden frame you need two triangle frames in the form of letter "A" and a horizontal beam. This article has more detailed explanation: How to build a swing … Read more

For maximum safety you can dig about 50 cm (20") in the ground, but even the half of that would do. The concrete-filled holes can be about 10"-15" (30 cm) in diameter. You can calculate the volume easy - (2 * 30 * 3.14) * 50 = 35357 cubic cm. That's not much. 

I could … Read more