Somewhere in my pile o' reference books, I remember reading the J's were designed for operation up to 140 mph. Obviously, the profile of the N&W precluded that from happening, but they were very stable, very smooth-riding engines and I never heard of a J pounding the rails. N&W learned the hard way about that with some of their 4-8-2 engines.
I'd like to see that giant 4-8-4 with some second generation steam modifications. I'm sure with modern force variation balancing you could spin her up to 130 at least. I'm on the fence between "records were made to be broken" and "let Mallard keep her record" at the moment. They had a few less than perfect points in their run when they could have been going faster, and the locomotive tore itself up hitting that record. On the other hand... Mallard Pressure: 250 psi Tractive effort: 35,455 lbs Driver diameter: 80" Weight: 165 tons 611 Pressure: 300 psi Tractive effort: 80,000 lbs Driver diameter: 70" Weight: 396 tons
