Talk:Pennsylvania Railroad class T1

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DYK	November 16, 2006

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power confusion[edit]

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)[reply]