Windmills can be divided into two general classes according to the
inclination of the shaft: 1, _Horizontal mills_, in which sails are so
placed as to turn by the impulse of the wind in a horizontal plane,
and hence about an axis exactly vertical; and, 2, _vertical mills_, in
which the sails turn in a nearly vertical plane, _i.e._, about an axis
nearly horizontal.
On account of the many disadvantages connected with the horizontal
windmill, it is seldom brought into use, being employed only in
situations in which the height of the vertical sails would be
objectionable, and this is liable to occur only in extraordinary cases.
In this kind of mill six or more sails, consisting of plain boards, are
set upright upon horizontal arms resting on a tower and attached to a
vertical axis, passing through the tower at its middle part. If the
sails are fixed in position, they are set obliquely to the direction
in which the wind strikes them. Outside of the whole is then placed a
screen or cylindrical arrangement of boards intended to revolve, the
boards being set obliquely and in planes lying in opposite courses to
those of the sails. The result is, from whatever direction the wind may
blow against the tower, it is always admitted by the outer boards to
act on the sails most freely in that half of the side it strikes, or
from which the sails are turning away, and it is partly, though by no
means entirely, broken from the sails which in the other quadrant of
the side are approaching the middle line.
[Illustration: FIG. 461.]
NOTE.—The great objections to the horizontal windmill are: first,
that only one or two sails can be effectually acted upon at the same
moment; and, secondly, that the sails move in a medium of nearly
the same density as that by which they are impelled, and that great
resistance is offered to those sails which are approaching the
middle. Hence with a like area of sails the power of the horizontal
is always much less than that of the vertical mill.
The illustration on page 184, Fig. 460, is a representation of the
_Corcoran windmill_: it contrasts most interestingly with the same
apparatus shown in Fig. 459—a windmill of the early part of the 17th
century.
The figure below, 462, exhibits in detail _the rear view of the
Corcoran mill with the governor_. As the speed of the wheel increases
it swings the “tail” around, so as to bring the wheel at an angle with
the direction of the wind; the latter failing to strike the blades
squarely communicates less force, and in consequence the speed is
diminished; in case of a very high wind the tail turns so as to present
the wheel almost edgewise towards the direction of the blast.
NOTE.—A windmill of this type was erected at a station on the Long
Island R. R. to pump 5,000,000 gallons of water yearly. In order to
test the work of the windmill, a water meter was attached to the pump
during six months, and it was shown that the average work of the
windmill had been 22,425 gallons per day, 4,260,750 gallons during
the time stated and an average rate of 8,000,000 gallons per year.
The weight of water pumped was 16,168 tons gross and was raised to a
height of 66 feet, and the work was done without mishap with little
attention given to the pumping machinery.
[Illustration: FIG. 462.]
Fig. 461 represents a Corcoran double action suction force pump. The
base is hollow and contains the suction and discharge valves; a flange
at the left-hand side receives the suction pipe while a corresponding
flange on the right-hand side connects with the discharge pipe. An air
chamber is attached to the discharge end. The valves may be reached by
removing the bonnets on top of the base.
[Illustration: FIG. 463.]
Fig. 463 is intended to represent an _Ideal steel tank tower_; the tank
is herein located near the top. A _force pump_ is used where water
is delivered into an elevated tank as in this case; a _lift pump_ is
employed to discharge water at the spout and not to elevate above it.
_The common term “Windmill pump” distinguishes a wind power pump from
a hand pump_, the difference being in an extension of the piston rod
above the upper guide with a hole for connection with the pump rod from
the windmill.
Such a pump, with the “pit-man” extending from the pump upwards into
the tower, is shown in Fig. 465. This figure is introduced to show the
tank connections with a regulator on the base of a four-post tower. The
float in the water tank throws the mill in or out of gear according as
the water rises or falls in the tank.
When the tank is filled with water it pulls the mill out of gear and
stops the pump; as a result there can be no overflow or waste. The
tank is thus not allowed to become empty and permit its drying apart,
inducing leakage. But through the medium of the float in the tank, when
the water has been lowered but a few inches, the mill is again put in
gear and the tank refilled to the desired height, at which the float is
set.
NOTE.—These have long been erroneously termed _windmill pumps_ dating
to the time when wind furnished the power for driving _the grist
mills used in grinding grain, etc._ More properly they may now be
named _windmotors_ or _airmotors_.
_The syphon pump_ here illustrated, Fig. 464, is used to force water
from shallow wells to elevations. The cylinder or barrel is situated
within the standard and very convenient for inspection. It has an air
chamber which is detachable.
[Illustration: FIG. 464.]
_The subject of tanks and cisterns_ is one almost vital to the
successful operations of ordinary windmills, owing to the irregularity
of the power to be utilized by the use of aermotors.
In another part of this work this important subject will be further
explained and illustrated.
_One of the most valuable special features of this windmill is its
governor._ It is so contrived that it insures immunity of the mill from
injuries in destructive storms. It consists of a steel coiled spring of
great resiliency, located at the base of the vane frame. Its strength
is of such a character as to hold the wheel in the teeth of the wind
under all ordinary conditions but is sure to yield under greater
pressure.
[Illustration: FIG. 465.]