Chapter 2 EQUIPMENT FOR TEMPERATURE ADJUSTING

7.Various Methods Available.

Two boxes are necessary for temperature testing. One fitted up to maintain a temperature of about 90° Fahr. and the other maintaining a temperature of about 40° Fahr.

The method employed in obtaining the high temperature varies in different styles of boxes, while the low temperature is always obtained through the use of ice. When only an occasional test is made, any simple method whereby approximately close results in the two extremes can be obtained, may be used. For instance, the watch may be enclosed in a tin box and placed in sand that is kept at a temperature of 90 or 95 degrees F. A thermometer placed in the sand indicates when the temperature rises too high or falls too low. The ordinary household refrigerator may be used for testing the cold. Tests by this method are advisable only for short periods and for an approximate idea as to the extent of error.

If frequent tests are made and accurate results are expected, it is quite important that the special boxes be used. Such boxes are often constructed with a capacity of four or five hundred watches, or they may be constructed to receive only half a dozen watches. Some are made with a zinc or copper tank in which warm water is placed and which surrounds the chamber in which the watches are deposited. The water is kept at the desired temperature by means of a small adjustable flame. In other instances electrical arrangements are used, in which case no water is required.

In either instance a thermostat controls the source of heat.

8.Electrically Equipped Oven, Description and Dimensions.

A very practical arrangement for testing a few watches at a time in the higher temperature is shown in Fig. 1. This is electrically equipped and will maintain an even temperature at all times.

The outside of the box is constructed of about one-half inch lumber and the inside is lined with asbestos. It is about fourteen inches high by ten inches wide and eight inches deep.

"A". Is an incandescent lamp set in a porcelain base.

"B". Is a porcelain plug through which the wires "C" enter the box.

"D" and "E". Are metal uprights with a thumbscrew on the top, under each of which a wire terminates.

"F". Is the compensating bar, one end of which is fastened solidly to "D" with rivets.

The opposite end is free and rests against the end of a thumbscrew which passes through "E."

The thumbscrew is to be adjusted so that the free end of "F" will rest against it in a temperature of 70° Fahr. or any lower temperature. As the temperature rises the free end of the bar moves away from the end of thumbscrew, breaking the circuit and extinguishing the light, which cuts off the source of heat. As the temperature decreases the bar again comes into contact and creates the circuit.

This bar can be made of various compensating metals, one combination of which is a strip of zinc about six inches long by three eighths of an inch wide and one thirty-second of an inch thick. On the outside of this soft solder a strip of tin six inches or a trifle less in length, by one fourth inch wide and one thirty-second of an inch thick. Both metals should be bent to a curved form before they are soldered together as shown in the cut.

Fig. 1

It is generally preferable to have the bar taper to a slightly narrower width at its free end, and near this free end it is necessary to solder a small strip of platinum at the point where the end of thumbscrew comes in contact.

"G", "H", "I" and "J" are ventilating holes one inch in diameter and covered by a swinging slide so that the holes can be opened or closed as desired for regulating the ventilation. "K". Is a shelf of brass screen located about five inches from the top and on which the watches and a thermometer are placed in testing.

"L". Is a handle for the purpose of convenience in carrying the box. The front is to be enclosed by a door made in two parts, the upper section of which is glass which will admit of observing the thermometer. Proper adjustment of the thumbscrew and bar makes the box ready for use.

9.The Lower Temperature Box.

Fig. 2 shows a box specially made for testing watches in cold. It is constructed of wood and stands about twenty-four inches high without the legs and about eighteen inches square.

A double partition packed with about one inch of sawdust will be most reliable.

The upper half of the box should contain a watertight zinc tank for holding cracked ice and about an inch of space should be left above for circulation of the air.

The chamber for receiving the watches may be about six inches square and supported by a crosspiece and attachment to the front. It should be covered above to prevent particles of ice from falling on the watches which are to be placed on the floor or on a shelf of the chamber, but the sides may be left partly open to improve the circulation of cold air. The door may also be filled with sawdust but does not require glass as the moisture would prevent observation of the thermometer which should be inside for checking up the temperature when the door is opened.

Fig. 2

The bottom of the tank should be slightly higher on one side than on the other, with a one-half inch drain pipe fitted to the low side. The inlet end of the pipe should be covered with a fine screen to prevent dirt from accumulating in the pipe and the outlet may be either at the extreme bottom or on one of the sides as shown in the cut. The upper part or cover of box should be made so that it can be easily removed for filling and cleaning the tank.

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