?8 MODERN PAPER-MAKING

does away with indirect drive and saves much room. This arrangement has
another desirable feature in that it eEminates the driving belt which may upset
the alignment of roll and bed-plate.

The roll can be raised or lowered on to the bed-plate at will by means of
a lifting gear attached to the bearings, and operated by a wheel or handle
through a fine adjustment screw.

The iron roll is cast with alternate longitudinal projections and spaces, or
grooves, around its circumference. The grooves serve as a housing for the
flybars, and are about 4 inches wide. There is also a channel left round each
end of the roll into which fits the iron ring used to hold the bars in place.

FIG. 20.-

-FRONT EIJEVATION OF BED-PLATE AND SECTION OF ROLL, SHOWING ROLL BARS ARRANGED IN CLUMPS OF

FOUR AND BEVELLED

The flybars may be of steel, bronze, or other alloy, and they are usually
arranged in clumps of two, three, or four, although there is no reason why
they should not be equally spaced around the roll. When arranged in clumps,
the bars are usually about I inch apart, and the clumps are about 4 inches apart.
The idea of leaving a space between the clumps is to make the first bar of the
clump act as a paddle to pick up stuff and carry it down, into the nip between
the pkte and the roll (Fig. 20). No doubt this arrangement of the bars in-
creases the speed of the circulation, but it does not necessarily follow that
more fibres are treated in proportion to the increase of speed. In fact, some
consideration will show that the increase in circulating speed means that so
many more fibres pass untouched by the bars and plates. The bars may be
sharp at the edges, and bevelled down to ^ inch for beating free stuff, such