The Cochran bells pictured on the right appear to be glass, but the insulating material is actually wood. Glass covers the wood to keep it clean and dry. Other wood insulators (left page) include strain insulators in varying lengths for electric trains and trolleys.
Rubber insulators in varying styles were widely used for railroad signaling and other low voltage applications. The Continental
Rubber
Mica
Mica is a good insulating material and was the main ingredient Many types of composite materials have, and still are, used for electrical insulating applications. Today’s composites tend to be light weight and very strong making them easier to handle and install. These modern composites are being used for very high voltage applications (i.e. high voltage transmission lines) replacing the very heavy glass and porcelain suspension insulators.
We’re all familiar with plastic that was also used to make pin-type insulators like the H. K. Porter shown on the left. These were very light weight and the elements.
With all of the various materials used for electrical insulators to date, the two that are by far the most prevalent for open
Plastic 11
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