Lynchburg Insulators

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Lynchburg Base Types

Dennis Bratcher

All early insulators had a smooth base rim. Toward the end of the 19th century, drip points (DPs) came into use on the base of insulators. Drip points were a series of glass extensions around the base of the insulator, most commonly cone shaped (usually called sharp drip points, SDP). The idea was to help water shed off the insulator more quickly thus reducing the risk of a short circuit between the wire and the pin. Drip points were originally patented May 2, 1893, by R. G. Hemingray and J. C. Gill, and the patent was assigned to the Hemingray Glass Company.  However, by the time Lynchburg started production in November of 1923, the patent had expired and the technique was available to Lynchburg.

There were different ways to make drip points.  The easiest and most common was a separate single "collar" around the base of the two lower insulator mold halves (after the late 1880s molds were three pieces with the crown or top third a separate piece). This collar had indentations machined into it that formed the raised drip points when the glass was forced into the mold. Since insulators were pressed with the crown down and the base facing up, this collar would be on the top during the manufacturing process. This accounts for instances of incompletely formed drip points due to air bubbles in the glass being forced to the top in the process of pressing glass into the mold.

In most instances, the collar containing the drip point mold could be interchanged with a smooth base collar without changing the actual insulator mold. This allowed the same insulator mold to occur with both smooth base and drip points. It also allowed different numbers and types of drip points on the same insulator style since various collars could be used on the same mold.


Example of various base collars used on a single mold, here CD 112 Mold 1: CDP:sm (left), CDP:n (center), NDP:b (right).

There may be instances of an originally smooth base mold being modified directly into drip points without the use of a collar, but by the 1920s this would be unusual. In a few cases the DP collar was not machined accurately or was done hurriedly and the drip points are of uneven spacing and height.

Most of the early Lynchburg insulators had fairly evenly formed and spaced CDP. The company later used RDP on CDs 106, 112, 122, 154, 160, 162, 164, 306. We are not sure of the reason for the switch, but was likely due to the tendency of CDP to chip easily (see Birmingham).

In its brochures, Lynchburg Glass Corporation advertised its insulators with drip points unless the customer specified a smooth base. As a result, most Lynchburg insulators are found with drip points. All styles of Lynchburg insulators occur with drip points, but not all styles occur with smooth base. And not all mold numbers of styles that occur with both drip points and smooth base are found with smooth base. Of the fourteen styles of Lynchburgs, only five occur with a smooth base: CDs 122 (rare), 162, 164, 205, and 251 (rare-unconfirmed).

Most collectors only identify three varieties of bases: sharp (or cone) drip points (SDP or CDP), round drip points (RDP), and smooth base (SB). The list below includes other varieties of bases as well as minor variations found on Lynchburg insulators.


Sharp/Cone Drip Points (small)

Abbreviation: CDP:sm

Conical sides coming to a clean point. CDP:sm occur primarily on CD 112 and are usually slanted inward. These are generically called Sharp Drip Points (SDP).

Sharp/Cone Drip Points (narrow)

Abbreviation: CDP:n

Conical sides coming to a clean point with no vertical sides. These are usually small and narrow (top), but do occur in large and broad types (bottom). These are generically called Sharp Drip Points (SDP).

 

Sharp/Cone Drip Points (wide)

Abbreviation: CDP:w

Conical sides coming to a point, on a broader base with short vertical sides; also occur with irregular or mixed sizes and occasionally occur slanted slightly inward. These are generically called Sharp Drip Points (SDP).

Nipple Drip Points (cone, small)

Abbreviation: NDP:sm

Small, flat conical sides on a base with short vertical sides, ending in a small expanded tip.

Nipple Drip Points (cone, regular)

Abbreviation: NDP:c

Conical sides often slightly rounded on a base with short vertical sides, ending in a small expanded tip, either pointed or flat.

 

Nipple Drip Points (rounded)

Abbreviation: NDP:r

Rounded sides ending in a small expanded tip, either pointed or flat.

Nipple Drip Points (extended)

Abbreviation: NDP:x

Short cylindrical shaft topped by a rounded end with an expanded tip, either pointed or flat (as photo). The shaft can be short, long, or mixed sizes (bottom photo).


Nipple Drip Points (banded)

Abbreviation: NDP:b

NDP end in a small expanded tip (which does not show on the first photo since the DPs are slanted inward). These are the same as NDP:r, but have a small band of glass connecting the base with the DPs. The extra width of glass is the result of retooling the body of the insulator. This style of base occurs primarily on CD 112, but there are also a few examples on CD 106 and CD 162.

Round Drip Points (flat)

Abbreviation: RDP:f

Rounded DPs with a wider, flattened base.

 

Round Drip Points (rounded)

Abbreviation: RDP:r

Rounded DPs that are close to hemispherical; occurs in various sizes.


Round Drip Points (extended)

Abbreviation: RDP:x

Rounded DPs that are a short sloping shaft ending in a rounded tip with no tip extension. The base can be very short (top photo) or more extended (bottom photo).

Smooth Base (small)

Abbreviation: SB:s

Base rim extends only about 2mm below the bottom of the skirt.

Smooth Base (large)

Abbreviation: SB:l

Base rim is larger extending about 4mm below the bottom of the skirt.

Uneven RDP:x

An example of uneven RDP resulting from irregular machining of the collar used to form the DPs. All molds using this collar would have the same uneven DPs.

Uneven NDP:r

An example of uneven NDP, resulting from irregular machining of the collar used to form the DPs. Also, the glass was too cold when this insulator was pressed resulting in a rough texture.

Anomaly: Melted Drip Points

These short and smoothly rounded RDP were the result of glass that was too hot and melted out of shape when it was removed from the mold.

Anomaly: Flattened Drip Points

These flat tipped CDP are also the result of glass that was still too hot when removed from the mold. When placed on the cooling tray the soft glass flattened under the weight of the insulator (here a CD 252).

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