Page:Popular Science Monthly Volume 88.djvu/498

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��Popular Science Monthly

��Electric Door-Opener for a Garage

THE unpleasant climax to a motoring trip on a wet evening is the neces- sity of climbing out of the machine when the garage is reached, walking through the downpour and opening the door. This undesirable experience can be averted entirely if the garage door can be made to open by an electric motor, started by the closing of a contact in the roadbed,

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���Wiring diagram of door-operating mechanism

by the weight of one of the wheels.

A small pit should be cut in the con- crete path at the entrance of the garage. The pit should measure 1' across and 1' in depth. A stout wood post should be erected from the floor of the pit and capped with a thick disk of copper or brass to which is attached a well-insu- lated wire. A well-seasoned board about 1" thick, which will fit loosely in the mouth of the pit, should be cut and on the bottom of it screwed a heavy plate to which another wire is attached. The two wires should lead through a conduit, placed at an angle so that water will not leak into it, and terminating in the ga- rage. The board should be supported, flush with the roadbed, by a heavy spiral spring. To drain the pit, a pipe of suffi- cient size should lead from one corner to a sewer connection. A white post, or a signal mark of some kind, should be put in the path close to the pit, for the purpose of marking its location when the automobile is driven upon the con- tact.

The door of the garage must be of the sliding type, and the rollers which run along the suspension track above should be oiled thoroughly, so that the friction is reduced to a minimum.

A motor, y^ or ^ h.p., should be se- cured, by screws or lugs, to the door as near to the top as possible and very close to the edge which opens. The shaft,

��which should point upwards, should be fitted with a large friction pulley with wide flanges at both ends. A stout, non- stretching, braided rope should be attached to a screweye in the door jamb, at the same level from the floor as the pulley of the motor, three or four turns wrapped smoothly about the pulley, and fastened taut to a screweye in the op- posite jamb. When the motor is oper- ated, it is obvious that the rope will wind and unwind on the pulley, and the door will be pulled open.

A circuit breaker should be installed above the door at the back, so that when the door is wide open, the current will be shut off from the motor. Some pains must be taken in the construction of this circuit breaker, as it is a most important part of the apparatus. A short wooden peg projecting upward should be fas- tened to the top of the door. When the door slides open, this peg strikes a lever arm, and the circuit is broken. The lever arm should consist of a 4" length of brass, Y^" wide and 14" thick. A small hole should be bored through its center to serve for pivoting purposes. At the lower end, a "trigger" of somewhat light- er and more springy metal should be soldered. When the peg strikes this trigger, the breaker will not be thrown out so suddenly as to derange the rest of the apparatus. The contact arm

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��Wiring diagrams of important parts

should be screwed to the center of some sort of wooden base upon a thick washer. The washer will act as a bearing. A light spiral spring, to insure a quick break, should be attached to the upper part of the arm and its other end held by a screweye set in the base. The contact spring should be cut from rather

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