The central support unit

Make up the wood part of the seesaw central support unit.

Cut pieces A (the four vertical pieces) and piece B (the spacer) to the lengths given in the plan and parts list on page 2.
Drill 13mm (9/16") holes where shown in the plan on page 2.

Assemble the central support unit as shown in the picture. Refer to the plan for dimensions.

Prepare the tire for concrete

Lay some thin boards on the inside of the tire to cover the hole at the base.

Alternatively you can use sheet plastic, sheet metal or anything else that is able to cover the hole while still being strong enough to hold the concrete in until it dries.

Make up a batch of concrete

You will need approximately 3/4 of an average heavy-duty wheelbarrow full of concrete to fill up the insides of the tire.

To three-quarter-fill the average heavy-duty wheelbarrow, put in 6 spades-full of gravel, 4 spades-full of sand and 2 spades full of cement (which is a ratio of 1 part cement, 2 parts sand and 3 parts gravel).

Mix it all together before adding water.

Then add about half of a standard household bucket (more or less) of water. Add a little at a time. Mix with the spade from the bottom and fold over. Continue doing this and adding the water until the mix is a uniform consistency.

Tip: when mixing, a smaller spade is easier to work with than a larger one.