I had started to make a treadle wheel using scrap maple as a frame, but discovered that the finger jointed and laminated pieces of maple I was using were very susceptible to splitting if exposed to moisture (of which there is plenty in a pottery studio), so I scraped it.
Coming around full circle, I have now made a Leach style treadle wheel almost entirely from steel. It is composed mainly of 3" square tubing and 1.5"x3" rectangular tubing. When finished it will be powder coated, making moisture almost and non-issue.
Here is the initial framework: