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It combines a fifteen horse-power specially wound motor and a drum hoist. The outside dimensions of the entire machine are fifty-six and three-eighths inches by fifty-four and three-eighths inches. The motor shaft carries a small pinion which engages the first large gear wheel. This, in turn, carries a small pinion on its shaft which meshes into the large gear wheel of the drum. The total speed reduction from the armature shaft to the drum is twenty-nine and one-tenth.
The friction clutch consists of a stout band of steels lined with small friction blocks made of wood. The movement of the clutch lever tightens this band upon the drum. The connection becomes, for the time being, positive, but possesses the advantage (and this is where any form of cone clutch is weak) that the disengagement is equally positive, and all danger of the clutch sticking, and consequently winding up of the drum too far, is avoided The length of the controlling arm gives tremendous leverage, and slipping is practically impossible.
The speed of the motor, and, consequently, of the hoist, is under control through the rheostat, which is placed entirely out of sight under the bed plate. The segments are connected to the contact board on the side, and the rotation of the contact arm is controlled by rack and pinion. This arrangement does away with a heavy rheostat arm, requiring much muscular effort in its operation, and substitutes an equally effective while much easier operated controlling device. The reversing switch when used is conveniently placed next to the rheostat contact board. The brake, consisting of a heavy iron band extending almost entirely around the drum circumference, is operated by a foot lever.
Fig. 9 gives a general view of this hoist, while Figs. 10 and 11 show end and side views of the same machine.
These hoists are particularly desirable for storehouses and warehouses, because they can be mounted upon trucks and easily moved from one portion of the building to the other, wherever needed. A plant of this description is in use on one of the large docks in Brooklyn. The wharf is wired in all parts, plugs being inserted at intervals so that the supply of power can be obtained from the main wires at almost any point and at a moment's notice. Flexible wires are used between the mains and the hoist motor for conducting the current.
On Constitution Wharf, in Boston, a large forty-five horsepower motor is used to drive an elevator and also a long line of shafting running the entire length of the building, from which four friction whip hoists are operated. These whip hoists are used in handling light loads rapidly. They are comparatively inexpensive and do away with dummy engines, or of a horse at one end of a rope, slowly pulling up a barrel or bale at the other end, consuming a great deal of time, patience and money. These small friction whips, after the design used at Constitution Wharf, should receive the approval of mill men for use in cotton, wool, or cloth storehouses. To-day, in a great many places, a dozen or more
men are required to do the same amount of work that two men with a whip hoist could perform more quickly and easily.
An arrangement has been designed by the ThomsonHouston Motor Company in which a travelling overhead trolley carriage is used in connection with the friction hoist. With this arrangement a load can be picked up at one part of the storehouse and deposited in another part at any height desired.
It might be well to again press upon you the fact that the freedom from danger of fire is a great point in favor of electric hoists, especially where cotton and wool are to be handled.
Within the past year electricity has been applied successfully to elevators. The Thomson-Houston Motor Company has designed a machine for this special work. The hoisting drum is mounted upon the same bed plate as the motor, and is driven by means of worm gearing. The worm shaft is connected directly to the armature shaft by a coupling, insuring positive motion between the motor and hoisting drum.