There is yet a good deal to do in successfully applying the roller
process to small mills of from 25 to 100 barrels capacity. There has
been a great deal done, no doubt, but one thing is lost sight of in all
the patents that have been granted so far, and that is cheapness, not
only in the price of the machine, but also in its application to the
existing or original plant in the mill. It should be of such a nature
that as few changes in the machinery as possible should be made.
If a grain of wheat is examined, it will be astonishing to see the
chemical laboratory that is locked up in it. The most valuable
substances, gluten, is placed near the air and light, while the little
cells of the interior are composed of starch, which being the softest
is the first to break up under the influence of the rolls. Hence,
the flour of the first and second breaks is mostly composed of that
substance.
About three and a half per cent. of woody fiber can be removed from
a kernel of wheat by a moistened cloth; it is of no value, whatever.
The next coating holds nearly all the iron, potash, soda, lime, and
phosphoric acid. This wrapper is the granary, so to speak, in which
is deposited all the wealth of the berry, and like a good safe is the
hardest to open, by either the rollers or burrs.
The use of rolls in cleaning bran is now generally recognized, and they
have proved very useful and practical for this purpose especially in
large mills. Bran, however, can only be thoroughly cleaned by several
operations, and the previous condition of the bran has a great deal to
do with the number of operations it has to undergo on the rolls to be
well cleaned.
Each passage through the rolls changes the condition of bran, and the
oftener it goes through them the lighter and cleaner it becomes, until
all the floury portion is removed.
The Austrians use corrugated rolls for the purpose of cleaning bran,
the finest being on the last, as in the break rolls. It is more
scientific and philosophical to clean the bran in this way than to rub
off the flour between burrs in this way than to rub off some of the
branny portion as well as the glutinous part.
Rollers for the first cleaning are from eight to ten inches in
diameter and from three to five hundred corrugations are used, and
this increases up to one thousand for the last rolls used; but fine
corrugations wear out soon, and the rolls have to be frequently
corrugated or the bran has to be finished on burrs.
The use of rollers is preferable to that of stones for bran, and their
use is considered an important advance in milling by most German
experts.
As the advantage of the use of rolls instead of burrs consists in the
production of a greater amount of middlings, this advantage should be
experienced in the cleaning of bran. As the small starchy particles
adhering to the bran are separated in the shape of middlings instead of
flour, a better quantity of flour is produced from these middlings both
in color and strength than that which is made from the stones' product.
Differential speed in rolls is not only better in making middlings, but
in grinding bran as well. This has been proved by several experiments.
There is no doubt but that there is less care bestowed on the hanging
and care of shafting than upon any other means used in applying power
to manufacturing purposes. If the steam engine or the water wheel is in
good order, and performing their work properly, and the machines driven
by them are also in good order, there is seldom a thought bestowed upon
the media between the actuating power and its ultimate development,
except the necessary attention which must be paid to the belting, and
oiling of the machinery.
Often, when the result of the power is not satisfactory, it is not the
driving power that is at fault, but the result may be found in the
shafting, or other intermediate transferers of the power. Generally, in
such a case, the belts are examined and their condition assumed for the
imperfect transmission of the power from the prime mover.
The condition of the belts is a very important point in all
manufacturing, but more particularly in mills where a steadiness of
motion is a desideratum, and attention to them will save many dollars
in the course of a year; but there are other as important elements
which are not always taken into consideration, and the principal one
is the condition of the shafting. A line of shafting running perfectly
true, without jumping or jerking, turning smoothly and noiselessly, is
a delight to the mechanical eye; and the first thing always examined by
a thorough millwright when he enters a mill, is the shafting.
Perhaps there is nothing will strike a person who has been out of the
milling business for some time so much as the change in the system of
bolting. This is caused by the numerous separations, and it is in this
the whole secret of gradual reduction lies.
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