I designed this gate in Autocad several years ago. Autocad comes in very handy because if you draw curves, it tells you the length of the curve. This is very useful because it allows you to estimate the length of a straight piece of iron pre-bending. All the scrolls were cold bent around old pulleys and round bars of various diameters held in a vice. Rather than cutting the iron for each section, I used the leverage of a long length to aid bending and then cut off the waste. I used a long bar with a slot welded onto the end for additional bending operations. Some heating was probably necessary to heat and match up the scrolls which were identical on both sides.
I used 2 x 1 box for the perimeter of the gate. I decided to make a polygon for the top, which gave the appearance of a semi-circle. I divided up the straight length of box into equal sections, cut slots in three of the four sides between each section and bent the box into a curved shape. I tried to make the slots v-shaped to so that the slots would close up ok. Then I welded everything closed and ground everything smooth.
Total build time was about 80 hours.