This toy crane is a simple wooden design, meant to be created by small kids with hand tools (except drilling) under close adult supervision. That said my 4yr old is quite good with power tools so we used them. The concept is my sons, I only help create realistic boundaries, and designs that he can make. That said he wanted a 5 meter crane (“top of house”), after some focus groups we settled on 750mm.
You could simply follow these plans but I really recommend that the child draws there version first and that you as a parent carefully steer them into these plans. Words like "I don’t think we have that special tool (triangular brill bit in my case), but we can do it this way" have always helped me and will engage the child.
The size of the holes in the boom, are only different sizes for the desired look. As well as the dowel rods. These could easily be replaced or changed depending on what you have at hand.
The plans attached are the easiest to follow. They were created after the project just for this Instructable and cover better ways of doing parts of this project.
As the parts are in pairs a tip is to always place the parts on top of each other and screw them together. Then saw and drill the parts according to the drawings. This way everything will alight just right when it comes time to assembly.
If the dowel holes are not quite right go back with a 10,5mm drill bit to make the holes a bit bigger and give yourself some wiggle room
Don’t drill the holes with nothing under them, you will suffer some really bad exit holes. Drill onto a sacrificial board that supports your piece.
Take it easy on the glue the more that squeezes out the more cleaning or sanding you will need to do.
Paint all the pieces after the test fit, its way easier! Then assemble. If needed you can always touch up after the final assembly