“It has already been discussed in much earlier posts that Shay #12 and #15 could climb Cumbres Pass with one less car than the K-36 at the same speed that is presently being operated.”
I’ve got to disagree with that statement. According to David Conrad’s book, shays #12, and #14 (#15 is a diesel) have only 25,830 lb tractive effort, vs. 36,200 for a K-36, a considerable drop.
The speed of the train is determined by horsepower, and there is an even larger difference there. Anyone can see that the boilers on the shays are little more than ½ the size of the K-36 boilers. ½ the size means ½ the heating surface, which means ½ the horsepower, which means ½ the speed. If the shays are not superheated, the difference becomes more pronounced. The first Berkshires were merely 2-8-2’s with four wheel trailing trucks to carry a larger boiler with more superheat. They couldn’t pull a train any longer than the 2-8-2’s they replaced, but they could pull that train ½ again as fast due to the higher horsepower of the larger boiler. The same thing applies here.