n details, but
the principle is the same. For feeding a band conveyor it is important
to give the material a horizontal velocity, approaching that of the
band. The grain should therefore be fed through a spout rather less in
breadth than half of the width of the band, and set at an incline of
42-1/2 deg. to the horizontal. Band conveyors run at a speed of 400 to
600 ft. per minute, according to the nature of the material; oats, for
instance, would be liable to be blown off the band at a speed in
excess of 500, which would be suitable for wheat. Nuts, maize and the
heavier seeds could be carried at 600. The power consumption by a
grain-laden band compares favourably with any other form of conveyor.
An 18-in. band 100 ft. in length running 500 ft. per minute would
carry 50 tons per hour at an expenditure of only 4.5 H.P.

While the band conveyor is an ideal conveyor in warehouses and mills, it
is also capable of rendering good service in handling such heavy
materials as coal and minerals. Of course for such purposes the band and
its fittings must be of much more substantial construction. The central
portions of the band carrying the load, being subjected to great wear
and tear, are often made of solid india-rubber extending to nearly half
the thickness of the band in the middle, and tapering off towards the
edges, while the surface facing the guide rollers is of insertion coated
with india-rubber. Bands properly prepared and stretched will bear a
strain of 3 tons to the square inch. Balata bands may be used in place
of india-rubber, but though less expensive are not so lasting. Bands
that have to carry coal or minerals are usually curved along the entire
length of the upper or loaded strand into a trough shape by guide
rollers (fig. 7). Bands of woven wire are sometimes used with
coal-washing plants, but have the disadvantage of lack of durability.
They are more liable to stretch and are high in price. They may be run
as high as about 600 ft. per minute, but to ensure proper grip-driving
terminals must either be faced with leather or made of wood.

[Illustration: FIG. 7.]

The speed of band conveyors loaded with coal or minerals greatly depends
on the size of the fragments; the proper speed for large pieces would be
150-200 ft. per minute, while smaller material could be carried at a
maximum velocity of 700-750 ft. Band conveyors will carry in an upward
direction, up to 24 degrees, without any lo