470 



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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/Board 



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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 



