The Armstrong 80pr cannon on the dwarf carriage and wooden traversing platform, slides wood on metal slides. But, when the carriage and its heavy barrel (4+ tons) are returned to the firing position, there are two small bronze wheels to make the return easier.
Two strong gunners lever the rear of the carriage and barrel slightly, so the two small wheels at the front of the carriage take some of the weight, and the carriage runs forward. In fact, the return was a bit uncontrolled, so a rope was added to the rear of the carriage, thrown around the bollard at the rear of the slide, and a third gunner added some control to the return.
Today I made the 1:10 scale wheels. They are 20mm diameter, and 10mm wide. 13mm wide if the hubs are included. I spent a couple of hours with the design. And another couple experimenting with various CNC processes. Not many photos of all of this I am afraid. I learned some new V Carve Pro commands, including nesting commands using the same milling cutter, but there was some trial and error. The first two wheels took a couple of hours. The final two took only 30″.
NB. these parts are not finished. Sharp edges remain. I will probably put them in the gemstone tumbler to smooth the edges.