The distribution of power has not always received the judicious treatment
which its importance deserves. There are but few references to this
question in the books on the subject, and these treat of methods that are
not in accordance with the application of the art in its present state.
[3] Continued from SUPPLEMENT, No. 647, page 10331.
The lecture was illustrated by about fifty views on the screen, which
cannot be reproduced here, showing photographs of mills and mechanical
drawings of the methods of construction alluded to in the lecture.
The early form of the distribution of power consisted in placing a
vertical shaft extending through the whole mill and distributing the power
at each story by means of beveled gears, generally of skew-beveled form.
The mechanical defects of such a method of distributing power, with regard
to protection, repairs, and necessary care, are readily apparent, and
there have also been many severe accidents caused by the breaking of teeth
in these gears.
The present method of distributing power in this country is entirely by
lines of belts extending up through what is known as a belt tower, which
constitutes an element of great fire hazard to a mill. In some cases the
belts are carried from story to story, covered by a casing of wood, and in
other instances the tower forms a flue which may be the means of the rapid
spread of fire throughout the building.
Before the introduction of automatic sprinklers there was not, I believe,
a single instance of a fire entering the lower portion of a belt tower
during working hours without accomplishing the destruction of the mill.
Since the equipment of such places with automatic sprinklers, there have
been several fires of this nature extinguished with nearly nominal damage.
That is to say, the hazard of fire starting in such places is beyond the
capacity of any apparatus other than automatic sprinklers to cope with it.
It would be impossible to arrange the distribution of power in many mills
to conform to conditions of safety without reorganizing the whole plant,
which would, of course, be impracticable. But in many instances
modifications can be introduced which will diminish the hazard to a great
degree. When the pulleys and belting are covered with sheathing in each
room, the continuity of these flues can be broken by removing this
sheathing down to the height of four or five feet above the floor, so that
the covering will merely constitute a physical protection to any one
approaching the belting.
The best method of arranging the belt tower has been in the case of a mill
at Fall River, which was erected upon the ruins of a building destroyed by
a fire originating in the belt tower. The machinery is driven by a steam
engine situated in an ell projecting from one side at about the middle of
the mill; and the main belt communicates to pulleys in a stone masonry
tower located directly inside the walls of the main mill; and thence,
from pulley to pulley, the power is communicated to each floor by shafting
passing through holes left in the tower, and in no instances by means of
belts.
There is a separate stairway inside of the tower for lubricating the
journals, etc., and the top of the tower is covered with skylights
protected underneath by a wire netting. In case of a fire in the belt
tower, the heat will readily break the glass at the top, and the fire will
tend to go up and out of the tower rather than through the mill.