Directional Signals.--Following the lead of other states, the New York legislature has just passed a bill that will undoubtedly lead to reduced wear and tear on automobile horns and brake linings and drivers' tempers. Far more important, it may well help check the rising accident rate.
The new measure requires the installation of electrical directional signals on every motor vehicle manufactured for use in New York State after January 1, 1952. These inexpensive direction indicators so effectively cut down the hazards of turning in traffic that police and other specialists in highway safety are beginning to rank them with stop lights and rear vision mirrors as "musts" for really safe driving.
So may late-model automobiles are equipped with these winking arrows at front and rear that most drivers are already familiar with them. However, few know the remarkably ingenious but fool-proof principle that makes them work. Into an ordinary circuit is coupled a flasher relay, or current intermittor. In the type of intermittor made by Tung-Sol Lamp Works, Inc., Newark 4, N. J., the flow of current is rapidly turned on and off by a spring-biased armature actuated by a length of Nichrome* resistance wire.
When the driver flicks the hand switch to indicate a turn, current flows through the Nichrome wire, heating it up until thermal expansion lengthens it. The spring-biased armature then snaps shut a pair of contacts so that the current bypasses the Nichrome wire, lighting the directional arrows. The wire cools and contracts, until it snaps the contacts open again and the light s wink off. All this occurs in a second or less; various Tung-Sol intermittors have flashing rates of from 40 to 180 times per minute.
According to Tung-Sol, Nichrome turned out to be the ideal material for this key actuating part of their intermittors. They report: "It has high tensile strength under elevated temperature conditions. It has high specific electrical resistance. It has a high temperature coefficient of linear expansion. At the same time, it is corrosion resistant and does not oxidize under elevated temperatures. It can be welded. It has good stability, including low creep, and is'_fatigue resistant."
Precision Scale for Architects and Engineers (Bakelite Review, Vol. 22, No. 1).--A precision triangular scale for architects and engineers made of Vinylite rigid plastic sheet strips gripped by an aluminum core gives far longer wear than conventional scales at less than one-seventh the price. Notable for its dimensional stability, this plastic is also resistant to water, oil, grease, and most chemicals. Neither it nor the aluminum core is subject to warping, and the fins and core are interlocked by a special process which allows for the different expansion coefficients of the two materials. Markings on white edges of the scale fins are also applied by a special process, then coated with a Vinylite resin base liquid so they will withstand continuous wear without rubbing off.