Talk:Pennsylvania Railroad class T1

power confusion

This article suffers from the usual confusion which appears when unknowledgeable people write about steam engines, whether locomotives, marine, or stationary engines.

In the case of a locomotive, there are 4 horsepower values - boiler horsepower, which is calculated from the boiler dimensions (grate area, heating surface, etc); cylinder horsepower, which is calculated from the cylinder dimensions (and must be smaller than the boiler horsepower for a successful locomotive - see the Triplex for an example of what happens when the boiler horsepower is smaller than the cylinder); indicated horsepower, which is calculated by measuring the actual pressure in the cylinder (thus accurately accounting for pressure loss in the valve, exhaust backpressure, etc; it is always smaller than cylinder horsepower); and drawbar horsepower, which represents the power available to move a train and is measured with a dynamometer car (thus accounting for the power absorbed in moving the locomotive itself; drawbar power is always about 20% less than indicated power).

I changed some "hp" to "ihp" where the text was clearly referring to indicated horsepower. — Preceding unsigned comment added by 2601:589:300:CA70:0:0:0:B360 (talk) 22:14, 6 October 2022 (UTC)