Brake horsepower is a measurement of actual usable power delivered to the crankshaft
of the engine. Brake power= indicated power-friction power. A dynamometer can be used to
find the brake horsepower of an engine.
The engine under test drives the shaft to which the rotor is directly coupled. The shaft bearings
are inside the casing containing the stator, which is free to serve... trunion supports. Each face
of the rotor has pockets or cells of semi-elliptical or oval cross section divided from one another
by oblique 45 vanes. The stator inlet channel, entering between 45 vanes and passes into a
rotating rotor. The water constantly circulated around the cells in as torque is transmitted from
rotor to stator via the water. This torque tends to turn the stator, this action being resisted by a
load measuring device so that the resisting torque will equal the applied torque and thus being a
measured.
Shaft power equals torque applied by weights time 2pie N. For testing in both directions of
rotation two rotor are provided, one used astern, the other ahead. In modern practices the load
measure devices are much simplified by use of levers. In some designs resistance to motion is
caused by a measure of field coil resistance which causes variation of eddy current resistance to
rotor rotation, in place of the hydraulic resistance.
Brake horse power = (2pie N X torque) / 60
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