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Symbols of condition in column of algebraic work explained in previous table. Diameter of main journals, three inches; weight in main journals, 1,500 pounds.

TABLE IV.

PERCENTAGE OF TOTAL FRICTION AND OF RATED POWER.

6" x 12" Straight Line Engine, 20 H. P.

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Distribution of Friction; 12" × 18" Automatic Engine.—The remaining tests to be described were made at Lansing, Michigan, and on the engines built by the Lansing Iron and Engine Works of that place.

The first engine tested was a new 12" x 18" Automatic Engine. A series of trials to determine change of friction with change of

Per cent. of

Rated Power.

load was first made, which gave us the average friction, 8.91 H. P., whether loaded or light. Considerable difficulty was experienced in attaching the dynamometer, and it is found impossible to obtain the friction on each distinct part of the engine. For this trial the springs of the dynamometer were flexed in the opposite direction from that adopted when it was calibrated; the results were taken as proportional, and the total made to agree with the previous trial. The highest speed attained was 68 to 70 revolutions; the normal engine speed was in the previous trial 190 revolutions. The friction horse power in the last column was obtained by multiplying by the proper ratio. In any event the percentage would not change.

Table V. exhibits the distribution of resistances obtained in this case.

TABLE V.

DISTRIBUTION OF FRICTION LOG OF DYNAMOMETER TRIAL.
WORKS, 12" x 18" AUTOMATIC.

LANSING IRON

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2.96 8.88

42.5 68 1.51 4.53

Valve and eccentric also dropped. C 5.6 19.75 33.5 73 1.40 3.70

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The letters used under head of algebraic work stand for conditions shown in the other table.

Distribution of Friction, 7" x 10" Engine.-Locomotive Valve

Gear. The test was conducted in the same manner as the original Sibley College test, except that the power was supplied by a similar engine, and the dynamometer was located between the two. The engine was a traction engine used in thrashing grain; it had a common slide valve link and two eccentrics. It had been previously tested to find variation of friction with change of load. During the test the engine was taken to pieces in a thorough manner, as originally planned, and the results are in each case satisfactory. In the attempt to run with the connecting rod disconnected from the cross-head, a machinist held the free end of the rod. A speed of 206 revolutions, however, caused him to exert some force, so that this result is unreliable, as the test shows the same friction as with the main journals alone. The friction on the main journals was measured with the usual fly-wheel which weighed 320, and with one that weighed 70 pounds to note variation in journal friction.

Table VI. shows the method of variation of friction-resistances in this case, as the engine was gradually dismantled; and Table VII. exhibits its distribution among the several elements of the machine.

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NOTE. In the column headed Algebraic Work, the letters refer to conditions as denoted in preceding table.

DISTRIBUTION OF FRICTION.

Engine, Condenser, and Air Pump. Diameter 21 inches, stroke 20 inches. This engine, 21" x 20" in connection with an engine 12" × 10", made a compound condensing engine which drove the Thomson-Houston Dynamos, used for the electric lighting of the city of Lansing. A complete test for friction, with change of load had previously been made of these engines, separately and combined. This engine being larger than could be driven by power transmitted through the dynamometer, the plan was adopted of utilizing the connecting shaft between the high and low pressure engine, and of measuring the power necessary by indicator cards on the high-pressure engine. Metallic paper, and a fine brass point was used instead of the usual paper and pencil employed in taking indicator cards. Two dynamos were allowed to run light during the whole of this test, being driven by the high pressure engine; this friction being eliminated in the final result.

The method adopted was to take indicator cards of the high

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