Re: Driver size and speed

Baldwin designed around "diameter speed", where the speed in MPH equals the diameter of the drivers in inches, or 336 RPM, which makes for a good base line, but that's all. A bruiser of a 2-10-2 with 57" drivers likely wouldn't be allowed over 35 MPH due in the inability of counterbalancing the very heavy driving gear. On the other hand, there were plenty of 80" driver'd engines capable of 100 MPH plus. The N&W J took this to the extreme, and the high RPM's they could survive weren't commonly duplicated.

On the narrow gauge, Bill Moedinger reportedly paced K-36's at 50 MPH on the flat. Legend has it that the T-12's were swifter than that.