Publication: Western Electrician
Chicago, IL, United States
Medbery Material as an Insulator in
Electric Railway Work.
BY W. R. MASON.
The extensive use of the Medbery material for insulating purposes in electric railway work dates back some five years. Because of its well-known insulating and its absolutely weather-proof qualities, as well as from its great strength, the Medbery material had been used as an ingredient in different compounds and for different purposes. Its superiority in such cases being recognized, it was naturally thought that it would stand the severe conditions of our climate and also the wear incident to electric railway service. Its use by a large number of the leading traction companies has proven the wisdom of such selection.
The necessity for exceedingly high insulating qualities, as well as firm texture in railway fixtures, is apparent when the large number used upon a road is taken into consideration. The leakage from a single fixture may be insignificant, but, multiplied through a line of several miles, becomes a serious loss.
So far, therefore, as insulation was concerned, the early styles of insulating material were all that could be desired, but they still lacked sufficient strength to be long-wearing under the trying conditions of line service. It was also found that many of these earlier styles of insulators, while showing good results in testing, were, however, unable to stand the climatic changes of heat, cold, rain, snow, etc. Attention was immediately given by a company to correcting these defects by special processes, and satisfactory results were obtained. The Medbery material was of such an extraordinary degree of hardness as to withstand the most severe service, while showing insulating qualities superior to any other material used for such purposes. The lack of certain desirable qualities in the earlier insulators has led to experiments with many other substances, and these will be continued as long as improvement will result. Thus far no one insulator has embodied all the desirable qualities found in the Medbery insulators, which have been in use on scores of roads for several years. Many compositions have been used and successively discarded during the time that "Medbery" has been held in favor by railway managers and superintendents. This has not been due to the disproportionately energetic push of the company in exploiting its material, for the sale of the different compositions which have been successively before the trade during the last few years has been engineered with zeal and a conscientious belief, however mistaken, that each was a substantial improvement over other material used. But from the introduction to the trade of the Medbery it has been used because of its inherent merit. It has proven its value as an insulator for railway service of extraordinary efficiency. And this involves not only its power as an insulator to withstand .any current used and under all conditions, but also its toughness and hardness to endure the changes of heat and cold and the effect of rain, snow, sleet and ice. Hundreds of tests have been made to determine its efficiency under all adverse conditions, and it is surprising to note its unaltered efficiency in all circumstances.
An important point to be noticed is the reliability of the Medbery material as an insulator. It is a fact, though not always one easy of explanation, that insulators have been manufactured of certain compositions, some of which were of excellent efficiency and others were found to vary considerably from a proper standard of efficiency This fault of varying efficiency has not troubled the users of Medbery material. It has been put to the severest tests for a number of years and has shown itself constant in its high insulating qualities. This is undoubtedly due to its simple composition.
It is well in considering the necessity for hardness and toughness of insulators for electric railway work to observe more explicitly the reasons for those qualities. It must of course be impervious to water, or it might soon become use-less as an insulator. It mast be of closest texture and greatest strength in order to endure the more or less frequent blows of trolley wheels and poles. A slightly brittle substance soon chips away, and makes a renewal of insulators often necessary. This same strength is necessary to bear the building strains of the line. For, it is in almost all cases a key to the construction as well as an insulator, and failing in its office in any particular impairs the efficiency of the whole line. For this reason, glass — so serviceable as an insulator in telephone and telegraph work — cannot be used to advantage on railway lines.
To produce a substance of highest insulating qualities, not affected by weather changes, strong enough to bear the strains of construction and neat enough in appearance to do away, as far as possible, to the objections to overhead work, was not an easy task, but the Medbery material, by long service, has demonstrated its high efficiency in all respects and all conditions. A reference to many of the early roads equipped with this material almost justifies the belief that the material is indestructible.
As a proof of the high standard the Medbery has reached, it is enough to cite the cases of many railway managers who, striving intelligently to reduce expenses, have tried the frequently appearing new insulators, only to decide finally in favor of the Medbery as the best. Some one feature may strike the fancy and reason in a new pattern, but when one quality is prominent, others seem to be lacking. The wide-spread use of Medbery insulators to-day seems to indicate that all the desirable qualities of a railway insulator come nearest to perfection in it, and its merit is not based upon theory now, but upon the practical recommendation of scores, even hundreds, of railway managers — its use by them on their lines.