|Donald Neuenfeldt posted|
John Deere model 22 1 16 inch mouldboard
Imitating much earlier British practice, American railroad men adopted cast iron wheels with chilled rims. Cast iron was a cheap, time-tested material that machinists had used for a variety of products. It was reasonably strong and could be easily cast in simple sand molds into almost any shape. It could be machined easily. Foundry men had discovered that cast iron developed an extremely hard crust or chill if poured against another iron surface. The chill, often as deep as 1 inch, could not be machined and so was avoided in normal foundry practice; but in the case of car wheels it was found to produce a tough, long wearing surface, and so the tread and flange were intentionally formed against an iron ring. While the running part of the wheel was as hard as glass, the plate and hub remained ductile and resilient, being cast in sand. They were relatively soft and could be machined as necessary to receive the axle.... Manufacturers were so confident of their products that 40,000 to 60,000-mile guarantees were common during the wooden-car era. In actual service, chilled wheels as finally perfected were considered good for around 500,000 miles. [Page 478]
Even after steel became cheap, some wheel manufactures continued to use chilled cast iron. "Several million of these wheels were produced each year until cast-iron wheels were outlawed by the Association of American Railroads in 1958. Some were still being produced as late as 1963, but all were gone within five years." [Page 481]In the case of a moldboard, the cutting surface part of the mold would use iron, but the rest of the mold would use sand. This provided a hard, glassy cutting surface but a machinable backbone that could be attached to the plow's frame.