Page:Popular Science Monthly Volume 90.djvu/938

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��Popular Science Monthly

��handling. The electric type of operator, although a little more bulky, gives real satisfaction and is very simple.

The illustrations plainly show the opera- tion of the device. The agitator proper consists of two magnets similar to those used in a call-bell. These when energized attract the armature above them attached to a long rod, which is attached to the shutter lever by a small wire hook movable on it so as to follow the camera front when focusing. The small weight on the rod is to steady the movement and to allow the magnets to operate on less current, being thus assisted by gravity. The windings from the coils are led to two small brass screws in the side of the base, and it is to these that the spring clips on the cable ends are fastened. The small clamp holds the apparatus to the camera bed without altering its action in any way and may be removed instantly when the camera is wanted for other work. No dimensions are given, as the instrument must be built to fit the camera for which it is intended.



��Dimensions for the wire carrier and battery, and the wiring diagram for the connections

The flexible lamp-cord used as cable is wound on a wooden reel which also holds the batteries. The core of the reel con- sists of two wooden end pieces connecting the flanges. The two double-cell flash- light batteries are slipped between the up- per and lower pieces of the frame where they make contact with "the spring brass clip fastened on the inside of the end piece. The wiring diagram shows the connection with the push button and camera.

The entire outfit, including plate-holders and other paraphernalia needed, may be fitted into a small rattan suit-case. The tripod legs when folded may be strapped to the outside of it. The only other requisite is an unlimited supply of patience, but as something of interest is always in progress in the woods and fields the time thus spent is by no means void. — C. Breder, Jr.

��Troubles with the Safety Spark- Gap on Motorcycles

THE owner of a single cylinder motor- cycle equipped with a well known make of high tension magneto, experienced some trouble with it which he attributed

���Most high tension magnetos are provided with a safety spark-gap to prevent damage

to weak magnets. He accordingly took ofT the magnets and had them recharged. Upon replacing them he found the performance of the magneto to be worse than before. He then dismantled the magneto to look for further trouble in the armature and found what he thought at the time was the cause of all the trouble. As is well known most high tension magnetos are pro- vided with a safety spark-gap, the purpose of which is to provide a path to ground for the high tension current generated in the armature, and thereby prevent damage to the insulation, in case the spark plug wire becomes disconnected or the gap in the spark plug is too great. These safety spark- gaps are arranged in various forms and in this particular type is arranged as shown in the accompanying illustrations.

The safety spark-gap back of the col- lector ring is clearly shown in the illustra- tion. In the diagram the armature winding



��A diagram of the armature winding to show how the safety spark-gap should be connected

in which the safety spark-gap is located is also indicated.

Anyone not experienced in the construe-

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