Publication: Street Railway Journal
New York, NY, United States
NEW STRAIN INSULATOR.
The accompanying cut shows the new type of strain insulator first exhibited at the Atlantic City convention by the Ohio Brass Company. It consists of a cup casting A compressed on a metal cone B with a heavy section C of formed sheet mica between the cup and cone on all sides. The device is firmly covered entirely with a body D of "Dirigo"' insulation as a weather protection.
Tests made upon the sample insulators before the "Dirigo" composition is put on show that the elongation between the eyes is not measurable even when the load is run up beyond the breaking strength of the largest steel cable with which the insulators could be used. This construction, therefore, removes all strain from the insulating compound, placing the strain directly upon the sheet mica and distributing it over the entire bearing surface between the cup and cone. A pressure of over sixty tons is used in compressing the cup, hence it is evident that the mica cannot be further compressed by any load which could be applied to the ends of the insulator.
Electrically the insulator is said to leave nothing to be desired. The best sheet mica is used in sufficient thickness to insure against puncture under any and all operating conditions. The "Dirigo" composition serves perfectly as a weather protection. Under test these insulators generally are over before puncture occurs, proving their great electrical strength. More than eighteen months have been spent in demonstration and test work on these insulators, so that in placing them upon the market at this time the company does so feeling absolutely that they will meet fully the most severe requirements.