Engine tests and boiler efficiencies by Buchetti J

Author:Buchetti, J
Language: eng
Format: epub, pdf
Tags: Boilers, Engines
Publisher: Westminster, Constable
Published: 1903-03-25T05:00:00+00:00

BRAKE HOESE POWER

149) absorbs nearly 15,000 foot-pounds of work per second per square foot of brake surface.

When only a limited amount of water can be applied it is better to use the formulae—

TT TT

The first equation gives K = 5400 foot-pounds. When the brake envelops the whole surface of the pulley and is cooled only by the lubricant it is necessary to make the pulley larger. In this case

To ^^ 7^

Finally, if the brake envelopes only a portion of the surface of the pulley, it is necessary to still further increase its dimensions.

For a given horse power the dimensions of the pulley are independent of the speed of the motor, as the frictional work per second on its circumference is the same at all speeds.

Bolts. —In order to find the dimensions of the bolts we will consider the equilibrium of the upper block (Fig. 145). Screwing up the nuts increases the small elementary normal pressures p,, in pounds weight on the pulley rim, and these produce frictional forces/j(?^.

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