Railroad construction. Theory and practice by Webb Walter Loring 1863-

Author:Webb, Walter Loring, 1863- [from old catalog]
Language: eng
Format: epub, pdf
Tags: Railroads
Publisher: New York, J. Wiley and sons; London, Chapman & Hall, limited
Published: 1903-03-25T05:00:00+00:00

§324.

ROLLING-STOCK,

357

-—r^/'

Crank-pin 110 lbs.

boss 150 ''

One-half side rod 240 "

Back end of connecting-rod 190 ^'

Total 690 lbs.

If the stroke is 24", the radins of rotation is 12'', or 1 foot. Then Gv^ 690 X4;r2l 2x3252

gr 32.2X1X602

= 24821 lbs.,

which is half as much again as the weight on a driver, 16000 lbs. Therefore if no counterbalancing were used, the pressure between the drivers and the rail would always be less (at any velocity) when the crank-pin was at its highest point. At a velocity of about 48 miles per hour the pressure would become zero, and at higher velocities the wheel would actually be thrown from the rail. As an additional objection, when the crank-pin was at the lowest point, the rail pressure would be increased (velocity 60 miles per hour) from 16000 lbs. to nearly 41000 lbs., an objectionably high pressure. These injurious effects are neutralized by ^'counterbalancing." Since all of the above-mentioned weights can be considered as concentrated at the center of the crank-pin, if a sufficient weight is so placed in the drivers that the center of gravity of the eccentric weight is diametrically opposite to the crank-pin, this centrifugal force can be Avholly balanced. This is done by filling up a portion of the space between the spokes. If the center of gravity of the counterbalancing weight is 20'' from the center, then, since the crank-pin radius is 12", the required weight would be 690Xi|=414 lbs.

In addition to the effect of these revolving parts there is the effect of the sudden acceleration and retardation of the reciprocating parts. In the engine above considered the weights of these reciprocating parts will be:

Front end of connecting-rod 150 lbs.

Cross-head 174 "

Piston and piston-rod 300 ''

Total 624 lbs.

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