Step 1:

We will start with the base that consists of two pieces.

First we have to make a rectangle with 500 x 700 mm constrution lines. At the top, we draw lines with a distance of 120 mm and 30 mm.Then down to 35 mm.

Next, we draw two 140mm lines on each side, slightly set back from the sides.

Step 2:

Then connect the upper rows with a 350 mm circle. We cut parts that we don't use.

Step 3:

We connect the top and bottom with "conic curve".

The two parts are the same except for the holes that will be used to connect them. The dimensions of these in A are 100 x 90 mm and 100 x 140 mm B.

these are in the lower half of the circle and the upper half of the base.

Step 4:

We extruded and then use both give a thickness of 100 mm.

Step 5:

We will make a 780mm circle for the last part.

Then extrude to 50 mm and then make boxes 100 x 120 mm in the same plane. Will use after construction lines 130 mm to position the rectangle, also use the central rectangle funsion.

We use extrude with -35 mm in the rectangles.