Issues in Developing a Taxonomy of Suspension Insulators

Should Radio Strains Be Included? The design of many radio strains fits that of suspensions. Larger strains such as those used for towers include metal caps just like modern suspensions. Some radio strains used arcing rings just like used on towers that used strings of suspensions.

Further strengthening the connection between radio strains and suspensions is that many companies made both. Lapp, Knox, Porcelain Products, and Ohio Brass are a few examples.

The shape of radio strains, however, can be distinguished from that of the typical suspension due to the lack of design features that increase the leakage distance. Most large radio stains consist of a long cylinder whereas a suspension would include petticoats or fins to add to the leakage distance. The availability of catalogs from manufacturers further assists in distinguishing radio strains from suspension insulators.

Should Guy Strains Be Included? Except for the Hewlett design for suspension insulators, all suspensions used a metal cap of some type on one side of the insulator and usually a different connecting piece of hardware on the other side of the insulator. Combinations include the ball and socket, eye and clevis, and hook and eye. Jeffrey-Dewitt spider fittings were one of the few types of fittings that were the same on the top and bottom.

The concept of the Hewlett design where the connecting hardware looped around itself with an insulating material separating the loops is the same concept used in many guy strains. In fact, some Hewlett insulators have been used as guy strains and some guy strains have been used to terminate a line.

The two main distinctions between suspension insulators and guy strains are the size of the insulator and the orientation of the separating material. First, because suspensions are used with higher voltages, they are generally larger although some guy strains used on very large towers exceed the size of some of the smaller Hewlett suspensions. Second, suspensions, as a rule, have horizontal separations between the top and bottom while guy strains have vertical separations.

Should Modern Polymers be Included in the Classification? Modern Polymers, due to their lighter weight, have different shapes than earlier glass and porcelain suspensions so including them would expand the number of insulators in the chart. Because they are relatively new, few people collect them so omission of them would not concern many people. A range in the chart could be set aside for them or they could always be added to the end of the chart at some later time.

Should Suspensions be Separated Based on Their Material? Most early suspensions were made out of porcelain. In later years, glass insulators were made. Whether an insulator was made out of glass or porcelain would be an obvious way to distinguish one suspension from another. Also, many collectors may wish to specialize in glass insulators so grouping all of these together would facilitate that interest.

Should Classification Numbers be Assigned Sequentially? The number given a particular insulator could be pretty much arbitrary or the number itself could be linked to characteristics of the insulator. For example, in the multipart classification system developed by Elton Gish, the first number represents the number of parts that make up the insulator. For a suspension classification system, the number assigned to each insulator could be composed of alphanumeric characters that indicate such things as whether the insulator is glass or porcelain, how wide it is, and what type of insulator it is (e.g., Hewlett, fog-type, modern).


Guiding Values

  1. Place priority on grouping insulators based on how people are likely to collect them. For example, it is more likely that a person would collect glass insulators rather than 10" wide insulators.
  2. Shape should take precedent over size.