As part of the SIA Fall Tour (2007), we toured the ghost town of Hamilton City, NV. Around the Hamilton City were gobs of abandoned mining equipment.
I found several belt-driven devices, all of which had wheels where the spokes were straight. In later years, metallurgists were able to determine that the straight spokes often led to cold shuts, where molten metal flowed into each side, but did not bond together; the piece may have looked like it was solid, but there was really two areas of metal that pressed against each other without fusing. Spokes were often slanted to increase the surface area of the molten metal as it passed through, meaning it moved through the spoke like water in a puddle rather than water through a straw.
I also really liked the old sluice boxes that were on site as well.