The red lines indicate the joint positions for 4 section wheels

The Blue line shows the joint position for 2 section wheels

Material

The rims are made from steel tube with an outside diameter of 33.7 mm  and a wall thickness of 3.25 mm

The steel specification is DIN 2458 ST 37.2

The diameter of a wheel is measured to the outside diameter of the rim before the PVC covering is applied