I am attaching four different curves for the N&W J. The 1st curve appeared in Railway Mechanical Engineer, in the December, 1946 edition. The curve is contained in an article authored by Pond. I consider this a primary source document and this, and the fact that he was Asst Supt of Motive Power for N&W, I regard as factual. (I attached pages 656, 657, and 658.)
The second curve appeared in the Jeffries book on p. 59, and this curve is the same curve as that contained in the Pond article.
The 3rd performance curve appeared in the Miller book on the N&W J. The 3rd curve that compares the "J" to a PRR T-1 and a 5400 HP diesel electric has obvious errors. For example, it shows tractive effort of 25,000 lb at 75 mph for the "J". (Drawbar pull would be lower than tractive effort and, without using a dynamometer car, the effort to haul the engine and tender at 75 mph would have to be subtracted.) The formula for drawbar (at rear of tender) horsepower is drawbar pull times the speed in mph, and this divided by 375, which is the horsepower constant in US units of measure. So... 25,000 lb TE at 75 mph is 5000 hp. The problem is that both the Pond curve and the Jeffries curve show this engine with 4200 HP at 75 mph, not 5000.
The 4th curve in the Miller book on page 69 is closer to the Pond curves but is not the result of an actual test. It is a calculation. What is interesting to me about this curve is that the actual test points from a dynamometer test are shown and NONE of these test points are at a speed greater than 45 mph.
