CR BT Dispr Wrote:
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> James' comment about the 4-4-0 becoming less
> popular with the advent of steel rails is somewhat
> misleading. It's true that the two events did
> coincide and were related, but that's incredibly
> understating things.
I agree it's severely under-stated. Could've gone much more into depth but elected not to since it's kind of a side topic. Point being (like you said) that the 4-4-0 dominated as long as it did in no small part because the use of iron rails put a practical cap on the weight and speed trains could economically run as well as the weight and axle loads of engines. It could pull most the loads and hurt the track less doing it. A few roads with particularly heavy traffic started adopting consolidation engines in the late 60's or early 70's but the majority of those roads unsurprisingly started going to steel rails early as well (the PRR comes to mind as an example here). The 4-6-0 was around from the 1840's but never really caught on except for niche usage until much later for much the same reason--too big, too heavy, hurt the track too much if run at speed, and didn't necessarily tolerate crummy roadbed as well as the standard type either. Most iron rail from that era wasn't rolled as a single piece but was more usually a series of shaped bars welded together. Wrought iron did not like being rolled to any great thickness. Numerous trials conducted on both sides of the Atlantic demonstrated wrought iron rails past about 66 pounds per yard were found to have little advantage and past about 70-75 pounds per yard further increasing the rail mass offered next to nothing at all. The material couldn't keep scaling up like homogeneous steel could. Hammerblow and weld-delamination were constant evils. The technology was at its limit. Some of the congressional hearings and correspondence with respect to the great many problems encountered with wrought iron plate naval armor and boiler plate during essentially the same period is also of related interest.
Steel rail didn't just last longer but it could also be produced far more quickly than iron could, and quicker soon enough meant cheaper, fueling the explosion in route mileage that lasted into the 20th century. I'll leave it at that. A paragraph is enough since we're already offtopic and we're preaching to the choir here anyway. In hindsight maybe I've spent too much time poring over microfilm and archived material.
