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I copied the drawing for the conrod and made it directly. Many manufacturers of the day used Steel for the most part due to costs, just small amounts of Gunmetal for shells.Perhaps you could draw both options? I must admit your rendition looks much prettier!
You are the only person who got any of the Bronze castings I assume you are using 38mm diameter bore on the cylinder. You could have machined rings out of 40mm diameter CI Jo