Siege engine base

The images below show the creation of the base of the siege engine. The base is created using simple boxes and cylinders for the wheals. In order to keep all the parts the same size and therefore the model proportional, the parts are mainly copies of each other and then moved and rotated into place, and the length was changed. But the main thing was to keep the width and height of the beams the same. The main problems I have had with the base was to make sure all the parts line up correctly and also to ensuring everything is level. As the two lower images show I had a problem keeping the base structure flat and the wheals all at the same level, though I eventually overcame this problem.