Publication: Western Electrician
Chicago, IL, United States
A New Insulator Pin.
In the description of the transmission line and third-rail system of the Long Island Railroad, published in the Western Electrician of June 9th, attention was called to the new type of iron insulator pin employed. This pin, which is a radical departure from previous practice in pin design is the invention of W. N. Smith of Westinghouse, Church, Kerr & Co., who has applied for a patent on the device. The design has been further improved and arrangements are now being made for manufacturing and placing it on the market under the name of the Smith grip insulator pin.
It combines several important advantages as follows: It does away with the necessity of boring holes in the cross-arms, thereby conserving, the whole strength, of the arm and lengthening its life; the metal composing it is distributed in the most effective manner possible, as its cross-section is greatest, next to the arm where the greatest resistance to bending is required; and, finally, the shrinkage of the arm can effectively be taken care of by the U bolt and strap, as there is no tendency to distort the bolt, and consequently there is no possibility of the pin standing crooked upon the arm after the shrinkage has been taken up. Furthermore, it is practically indestructible, and instead of being one of the weakest factors in line construction this pin is expected to be the strongest.
More than 8,000 of the pins as originally designed and shown in the accompanying illustration were used in the transmission line construction of the Long Island Railroad, carrying 250,000-circular-mil cables in spans averaging 150 feet in length, and no failures have yet been reported after over a year of service. A dozen or more standard sizes of the improved design are being worked up to fit several sizes of cross-arms and pole-tops and to carry insulators of varying sizes up to the highest voltages in practical use. The pins will be made of either cast or malleable iron to suit the purchaser's conditions.
While it is designed particularly for use with wooden cross-arms, it can readily be adapted to steel cross-arms and to such special fixtures as are often necessary in heavy transmission-line construction. On account of its superior mechanical design, it will also without doubt find a place in heavy catenary, trolley construction, which is now being actively developed for the electrification of railways by the single-phase system.