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GROSS AND EFFICIENT POWER OF 12 AND 14 FOOT WINDMILLS.
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| Velocity | Gross | Net
SIZE OF MILL. | of Wind. | Horse-power. | Horse-power.
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12-Foot Ideal Power Mill | 10 Miles | 1/2 | 1/10
12 „ „ „ „ | 15 „ | 1 | 3/5
12 „ „ „ „ | 20 „ | 2 | 1-3/5
12 „ „ „ „ | 25 „ | 3 | 2-3/5
14 „ „ „ „ | 10 „ | 1 | 3/5
14 „ „ „ „ | 15 „ | 2 | 1-3/5
14 „ „ „ „ | 20 „ | 4 | 3-3/5
14 „ „ „ „ | 25 „ | 6 | 5-3/5
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The preceding tables are based upon tests of the _Sampson windmill_
as compiled by its makers, The Stover Manufacturing Co.; they deserve
careful study by those planning the introduction of aermotors.
_The power of a windmill_ depends—first, on the diameter of the
wheel; and second, on the velocity of wind. _To increase the diameter
of the wheel is to increase its power_ in proportion to the area of
the squares. Table I gives the horse-power of several sizes of mills
working in a fifteen-mile wind: if the wind velocity be increased or
diminished, the power of the windmill will increase or decrease in the
ratio of the squares of the velocity. Table V will show the comparative
power or force of the wind in velocities from eight to forty miles per
hour for each square foot of surface.
_Rules for approximately determining size of windmill to use._
The daily water consumption must be given as a basis for calculation.
Divide this by 8 to find the hourly capacity of windmill, as if loaded
aright the mill will pump on an average eight hours daily.
_Multiply the quotient by total water lift in feet and with the
co-efficient given in Table II._
The product will in Table I show what mill to use.
The size of the cylinder and discharge pipe will be found in Table III.
[Illustration: FIG. 466.]
Table I gives the maker’s number of the pumping mill, and the number
of gallons each will raise one foot high per hour, with a wind having
a velocity of fifteen miles per hour. Example: No. 9 pump will raise
24,000 gallons of water one foot high in one hour. Now if the water is
to be raised 50 feet then by dividing 24,000 by 50 the quantity raised
becomes 480 gallons per hour.
From Table V it will be seen also that a wind velocity of fifteen miles
per hour develops a power three times as great as an eight-mile wind,
and a twenty-mile wind is twice as powerful as a fifteen-mile, or six
times that of an eight-mile. Hence, _a small increase in velocity
greatly increases the power of the windmill_, while a low velocity
gives but little working force.
From Table VI it is seen that a twenty-five mile wind gives six times
as much power as a ten-mile wind, but really gives twenty-six times
_the net efficient power of the ten-mile wind_, therefore it will not
be proper to calculate on using a power windmill in as low a velocity
as ten miles.
From Table VII it is seen that the net efficient result is six
times as great in a fifteen-mile wind as in a ten-mile wind, and
sixteen times greater in a twenty-mile wind than in a ten-mile wind.
Therefore, _power windmills give best results when working in fifteen
to twenty-five mile winds_. A 12-foot power windmill working in a
fifteen-mile wind will do more work than an average horse, and when
working in a twenty-mile wind will do more work than two average horses.
_Example._—A person in Atlanta, Ga. uses 2,600 gallons of water
daily. He has a well in which the water stands 30 feet from ground
level. To obtain pressure, the water is to be elevated into a tank 50
feet above ground. 2,600 ÷ 8 = 325 gallons to be pumped hourly when
windmill works.
Average wind velocity at Atlanta is 9 miles per hour, answering to
coefficient 1.4 in Table II, and total water lift is 30 + 50 = 80
feet. 325 × 1.4 × 80 = 36,400 gallons.
If first estimate of 2,600 gallons daily was liberal, so that for
instance 2,400 gallons would be sufficient, Table I shows that a
10-foot mill can be used, but to keep on the safe side, choose a
12-foot mill. 325 gallons hourly gives us in Table III 3-1/4-inches
cylinder with 2-inches discharge pipe as proper sizes. If the 10-foot
mill is chosen take the 3-inch cylinder.
A 14-foot windmill working in a fifteen-mile wind will do more work
than two average horses, and when working in a twenty-mile wind will do
more work than four good horses, while in a twenty-five mile wind it
will do more work than six good horses.
_Giving the above tables a practical application_, a little thought
will disclose what a wealth of power stands unappropriated and ready at
hand to do many of the drudgeries of work for which large expenditures
are annually made.
The uses of power windmills are so well understood that it seems out
of place to elaborate upon them; the brief space allowed to giving
information as to the power of this class of mills when working in
different wind velocities, is best expressed in tabular form, Table VI.
Fig. 466 represents the working barrel of a _deep well pump_, such as
are used frequently in connection with the larger sizes of aermotors.
The tube is usually made of heavy brass—this is _drawn_ so perfectly,
as to size and smoothness, that a re-boring is not needed.
The plunger is here shown with four cup leather packings, with one ball
valve; the bottom valve is also a ball with the seat resting within a
conical coupling at the bottom, this with a leather packing makes a
water tight joint.
Should any accident happen to the bottom valve it may be withdrawn by
lowering the sucker-rod until the threaded portion comes in contact
with the nut underneath the plunger. By turning the sucker-rod the
nut engages the thread on the top of the lower valve-cage. Then by
withdrawing the sucker-rod both valves may be drawn up for examination
or repairs.
ROTARY AND
CENTRIFUGAL
PUMPS
[Illustration: FIG. 467.]
[Illustration: FIG. 468. (See page 199.)]