The Electrical Device Attached to the Clock Records Contacts Made by the Opening of a Door, and the Using of a Telephone
Two rings of ¹⁄₁₆-in. brass, one within the other, and having side arms, are mounted on the front of the clock, as shown in the illustration. The ring on arm A should be slipped under both hands, and should have spring enough to hold it in contact with the small clock hand. The ring fixed to arm B must be in contact with the large hand, but must be some distance from the small hand and the smaller ring, so that they will not come into contact when the hands cross each other. An offset in the arm A, and a piece of mica insulation, are provided where the larger ring crosses the bar A. On the surface of each ring, between it and its respective hand, is glued a piece of white paper, cut to conform with the ring, but ¹⁄₁₆ in. larger, so as to extend over the outer edge of the brass rings. The rings of paper are saturated in a solution of potassium chloride and permitted to dry, before being placed on the brass rings.
A high-tension current, passing through the coil D, enters the arm A, passes to the small hand, to the large hand, and out at the terminal on arm B. Black dots will appear on the prepared paper at the position of the hands, when the contact is made.
The primary wires E and F may be attached to a doorbell or to a contact on the door, indicating on the prepared paper the length of time the door was held open, as well as the time at which it was opened. The arms A and B must be well insulated from one another. For greater accuracy in recording time, to within ¹⁄₂ minute, prepared paper dials, with hour and minute marks, coming into contact with the hands at small projections punched in the hands from their upper surfaces, should be used. An ordinary secondary coil from an automobile may be used, and if the clock has a wooden case, the arms may be fastened directly to it.
Practical Memorandum for Odd Jobs
Not infrequently home or shop mechanics find that trifling odd jobs are neglected repeatedly, simply because they are not of sufficient consequence to warrant getting out the tools or materials necessary for the work. A convenient method of insuring that these small jobs are not overlooked is to make a memorandum of them and place it with the tools required for the work. For instance, if a small job of soldering is to be done, a memorandum placed with the soldering outfit will not easily be overlooked, and the work may be done while the coppers are hot for use in a larger job. Likewise with small painting jobs. Sometimes only a brushful of paint is needed and one does not care to mix a small quantity of paint nor clean the brush afterward. A memorandum of the job makes this unnecessary.—John Hoeck, Alameda, California.
A Homemade Vulcanizer
Tire tubes may be vulcanized satisfactorily in the home garage, or even on the road, with the simple device shown in the sketch. It is made as follows: Obtain a piece of sheet iron, ¹⁄₄ in. thick, 3 in. wide, and 5 in. long. Drill a ¹⁄₄-in. hole at the middle of each end. Fit a strip of similar stock, 1 in. wide and 5 in. long, to the first piece with bolts, as shown. Procure a tin cover without embossing on the top, such as is used on baking-powder cans. Cut several disks to fit in the cover, from heavy cardboard; soak them thoroughly in a saturated solution of saltpeter, and dry them. Wrap each disk in oiled paper, and keep them in a water-tight container.
This Homemade Vulcanizer Utilizes the Heat from a Slowly Burning Disk of Cardboard