by A.L. Harris, Industrial Department
In Golden Gate Park, where nature has done much to enhance the general scheme of design, there is a chain of artificial lakes which stretch from northeast to southwest, and, surrounded as they are by native shubbery bamboos and grasses, add much to the natural charm of the landscape, while also serving an important purpose as reservoirs.
In reclaiming the sand wastes from Strawberry Hill to the Pacific Ocean, the Park pumping plant was found insufficient to supply the additional water most essential to the life of the Park, on account of the limited supply of the wells. A survey and inspection of the vast area west of Strawberry Hill revealed a capacious flow of water toward the ocean, and in order to utilize this natural drainage for the reclaiming of the middle and western divisions of the Park the trade winds were harnessed to give the power necessary to lift the water to an altitude of 200 feet. The north Dutch windmill, adding a picturesque feature to the landscape, was installed, with a capacity of 30,000 gallons of water per pump per hour, supplying and replenishing Lloyd Lake, Metson Lake, Spreckels Lake and the future Lincoln Park. In the dry season the sump, 12 feet deep ... has a mill capacity for two sets of pumps for twelve hours, and drains the back hills through springs in the following period. The water is fresh, purified and filtered through the sand hills, and has no taint whatsoever of the saltwater in the ocean close by.
From time immemorial, humanity has utilized the wind for pumping power purposes, but Holland, a land below sea level, was the first country to use the sail mill and construct large units, depicting on the Delph, Royal Copenhagen china and other manufacturers, their country's safeguard. Here was an old idea with foreign insurance companies to equip ships with windmill for pumping ships, and a Norwegian square-rigged ship may be known by the windmill before the main mast. A sailor is better operator of the Dutch windmill than an engineer, for the winds are erratic in their course and nature's laws must be obeyed to give up the unseen power.
From the ground one hardly realizes the size of the Dutch windmill in the Park. The base consists of 5 feet solid concrete, 33 feet outside diameter, the walls for one story 3 feet thick and above the structure is heavy mill construction. The arms are 102 feet, tip to tip, made of Oregon pine 16" x 20" at the center, reinforced 16 feet either side of the hub by two iron plates 3/4" x 16" straps bolted together every 12 inches. The sail is stretched on a frame, the ribs of which, spaced a foot apart, are strapped and bolted to the arm, across one edge, and its propeller shape is formed by different angled wedges on one side of the arm, held in place by rib-holding straps. The dome-shaped top with sails is separate from the building, constituting a turntable, revolving on 24 flat wheels, operated by a small windmill placed diametrically opposite to the sail arms to adjust the mill to the direction of the wind; and the movement between the four points of the compass is controlled by a weighted friction clutch on the main shaft. The turntable weighs 12 tons; hub, shaft and bevel gear 18 tons; the vertical 5" transmission shaft through five floors and four solid couplings 6.5 tons, revolving on a ball-bearing immersed in oil.
Operating in mesh with the bevel gear at the foot of the shaft revolve two bevel gears on the ends of shafts connected to adjustable cone-shaped pulleys (in two parts), belt- to the gear shaft, meshed to the gears on the pumps. The transmission belt is made up of sections (two pieces of wood 14" x 3 1/2" x 1 3/4" bolted together with leather belt between), the friction power being taken from the ends of the same on the cone pulleys. By operating a cleaver-screw hand-device, at the same time that the driver cone pulley is separated (lessening the pulley diameter) the driven cone pulley is drawn together, thereby adjusting the speed to the velocity of the wind. Beyond the limit of the adjusting device the sails on the arms must be shortened, allowing the wind to go through the lattice work of the frame. In Holland, shutters take the place of sails and can be automatically opened or close as the velocity of the wind requires.
The pumping equipment consists of two Dow Vertical Triplex Pumps 8" x 10" plungers, three stage and 45 R.P.M. with 6.53 G.P.R. The capacity of the mill with wind power is limited to 80 lbs. pressure, and with development of Lincoln Park a pressure of 180 pounds (corresponding to approximately a head of 400 feet) was needed, necessitating additional power. For this purpose, the Pacific Gas and Electric Company installed a 60 horse-power G.E. 2,200 volt 2-phase 900 R.P.M. motor for each pump, thereby giving sufficient power to accommodate the limit in capacity of the machinery installed. With a rawhide shrouded pinion on the motor for direct connection, the motor by one screw on the base may mesh with the gear on the shaft for the motor drive when additional pressure is needed or the velocy of the wind is insufficient to operate the mill under 80 pounds pressure. With limited space for the 2,400 volt compartment, the installation was made with absolute safety by the Farnsworth Electric Works under plans and specifications submitted by our Industrial Department. The result, with the distribution of lights, reflected credit on both.
The public spirit of Samuel G. Murphy is well manifested in his donation to the Park of the south Dutch windmill, the largest in the world, together with the Lodge close by, at a cost of $25,000. This mill has a capacity of 40,000 G.P.H. under 80 lbs. pressure, 40 R.P.M.
And it is but a matter of time when this windmill also will be equipped
with motors to supply the much needed water for irrigating that side of the
Park. Superintendent John McLaren, who looks upon Golden Gate Park as
his life's work, has more than once expressed his appreciation of the
enormous benefit to the north side rendered by the electrical installation
dscribed here and by which "Pacific Service" contributes this power.