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CD 244 - Insulator of the Week on Mon, 21 Apr 2008


Pomona; Westinghouse Pomona; 244 Crosstop

Related Patents

(related) Utility Patent 517,634 issued to George H. WINSLOW on April 3, 1894


Embossing: none.

Colors: Only found in light to medium purple.

Purple CD 244


It appears that the large bell-shape design of the "Pomona" was to accommodate the use of a separate oil cup, however many were evidently installed without the cup. Broken specimens have been found with the oil cup actually molded out of the inner skirt (I believe these were found in Colorado).

High Tension Page 2

Known areas of usage are near Telluride, CO; Bodie, CA; and Pomona/San Bernardino, CA. Two mint Pomonas were found in a Los Angeles area antique shop back in 1986---they were previously used as lamp shades on small table lamps! On the Bodie, CA line the Pomonas were only used on the top steep ridge poles (CD 162 Brookfields were used elsewhere). With two Pomonas used at each ridge point, it is estimated that as few as a couple of dozen Pomonas may have been installed on the 13 mile line. Here is a photo of one that survived: PicturePoster #213375100

These brief comments on the Insulator of the Week are not intended to be complete and are presented to encourage discussion and additional information from ICON. Now it's your turn to share info and/or post a photo of your CD 244!




Bob Stahr commented on Mon, 21 Apr 2008

I can add the following from an article on the Pomona line that appeared in the New York Times:

The New York Times

New York, NY, Sunday, August 25, 1895 vol. 44, no. 13,731, p. 20, col. 1-3

..............It is needless to say that great care, was taken with the pole line, or running track, for this lightning sprinter. There are, in reality, two transmission lines, one 13 3/4 miles to Pomona, and the other 28 ¾ miles to San Bernardino. Each is built of No. 7 B. & S. gauge of copper wire. At first it was intended to use insulators with oil in their curled rims, but the builders of the line fell back on a double-petticoat, flint glass form, which has answered admirably. As a matter of fact, the oil would not last long in the blistering sun of that region. The poles are Santa Cruz redwood, 23 feet long, and set 125 feet apart................

James Doty commented on Tue, 22 Apr 2008

CD 162 Brookfields were used elsewhere.

Having walked this line, They also had 287 locke on it or used for replacements. Also found was a nice iron pin with cast lead threaded top.

James Doty commented on Tue, 22 Apr 2008

Another picture of 244

Bill Meier commented on Tue, 22 Apr 2008

There is another interesting article in The Electrical Engineer

New York, NY, Wednesday, July 31, 1895, vol. XX, no. 378, p. 116


......... The wires are supported upon large double-petticoat flint-glass insulators designed for this plant. These insulators are of perfectly clear flint-glass, which gives a better surface-insulation than is attainable with any other kind of glass.

It was at first proposed to use oil insulators. The reason they were not used was because the glass companies which had undertaken to furnish them found on trial that they could not make them without considerable experimenting, which would have delayed the installation of the plant. This was no doubt fortunate, as the country through which the line passes is subjected to hot, dry winds which not only blow dust onto the insulators, but also inside them, and during the day the sun beats on the insulators until they become so hot that they nearly blister one's hands. If oil were used under these conditions it would soon evaporate and thicken, and become filled with dust. It would therefore seem undesirable to have used oil insulators in this case, or to use them in any other until an increased voltage makes them necessary, and the transmission of greater amounts of energy over the circuits justifies the additional expense necessary to keep the insulators in good condition. .........

Note the comment that the insulators were made of perfectly clear glass!!! Thus, these we have in the hobby have no doubt turned purple in the sun...

Does anyone know what shade variations, if any, we see in the Pomona's?

I guess it also says that flint glass is better than other types of glass because water doesn't adhere to it as well?

Brad Dahlquist commented on Tue, 22 Apr 2008

The Pomona was one of the first 'radical' insulators I had ever seen. In 1972 my friend Ray Richter came into the antique shop that I hung out at after school. He'd been on one of his insulator road trips and had a box of nice insulators. He unwrapped a Pomona that I recall had about 3/4 of the outer skirt cleanly missing but was otherwise very nice. I was amazed. Here was an insulator that had not one, but several desirable features all in one; it had a 'cross top' it was 'hi-voltage', it was a 'large glass' type, and it was purple to boot! I remember him saying that even in that condition, it could go for $50! I often wonder what happened to that piece. Hope it was never repaired.

Rick Soller commented on Tue, 22 Apr 2008

I have one of the Pomona's with an oil cup. Perhaps they deserve a new CD number since the oil cup is molded into the inner skirt.

Lee Southern commented on Tue, 22 Apr 2008

The following text is from a book entitled "Electric Power Transmission Plants and the Use of Electricity in Mining Operation" written by Thomas Haight Leggett, published in 1894. It is in reference to the line at the Standard Consolidated Mining Company at Green Creek, near Body, Mono County, California.


The length of the line is 67,760 ft., or 12.46 miles. The poles are of round tamarack timber, 21 ft. long, 6 in. in diameter at the top, set 4 ft. in the ground; poles 25 ft. long being used through the town, and along the line wherever there is danger of deep snowdrifts. They are placed 100 ft. apart, and fitted each with a 4 by 6 in. cross-arm, boxed into the pole, and held by one bolt and lag-screw. The object of chamfering the ends of the cross-arms is to leave less room for the lodging of snow under the insulator.

The line crosses extremely rough country, not 500 yds. of which is level beyond the town limits. Most of the ground is very rocky, over 500 lbs. of dynamite being used in blasting the pole-holes.

The wire is of No. 1 (B. & S.) gauge, soft-drawn bare copper, and is attached to standard, double-petticoat, deep-groove glass insulators carried on Klein patent iron pins. The distance between the wires is 3 ft. 8 in., and there are over 16.5 tons of copper in the line. The only objection found to the iron pins is their liability to be withdrawn from the cross-arm during a gale of wind, whenever there is an upward pull on the wire. To obviate this a number of pins were drilled with an 1/8 in. hole near the end, and in all such places these were used, and held firm by driving a wire nail through them.

The wire was first attached to the insulators by tie-wires of No. 10 galvanized iron wire. Later it was found advisable to insulate the linewire at the insulators, and for this purpose ordinary sheet-rubber 1/8 in.thick, such as is used for gaskets, was cut into strips 1.5 in. wide and 12 in. long. These were wound spirally about the wire and held in place by two close wrappings of Manson's tape. The whole was then well daubed with asphalt paint, and the insulated wire re-attached to the insulators by tie-wires of No. 6 weather-proof copper wire.

The line crosses a number of very steep ridges (from 300 to 800 ft. in height), and on these the wire necessarily pulls heavily on the top pole, and especially on its pins and insulators. In all such places the ordinary double-petticoat insulators were replaced by the large "Pomona" insulator, on which the wire is carried in a groove across the top, and its weight is therefore directly down upon and in line with the center of the pin.

The line has given no trouble whatsoever, and has carried the high potential of 3,000 volts without a leak, even during a severe storm of ten hours' duration, the rain changing to sleet and ice toward the end; but this severe test, it must be admitted, occurred after the wire had been wrapped at the insulators as described. In fact, one of the chief objects of this insulation was to render the line proof against just such a storm as this. Snow-storms have no effect whatever.

Brent Burger commented on Tue, 22 Apr 2008

This is news to me. How about a photo ?

Dwayne Anthony commented on Tue, 22 Apr 2008

James wrote regarding the Bodie line: I believe these were CD 287.1 Lockes in light blue. They were added later at the top of the pole on side pins when the line was upgraded from single-phase to three-phase. The original insulators were the CD 162 Brookfields (dome arc/skirt date) and the CD 244 Pomonas, all mounted on steel pins with lead threads.

Caleb Thimmel commented on Tue, 22 Apr 2008

The Colorado line extended from the power station near Ames to the Gold King mill- a distance of 2 1.4 miles. There were 62 poles with each using two cd 244 double petticoat Pomona's mounted on the top crossarm, two triple petticoat Locke cd 287 insulators on the middle crossarm and two double petticoat porcelain U-744 General Electric insulators mounted on the bottom crossarm. The large glass insulator used in Colorado was the same as the one used on the Pomona and San Bernardino plant. (Sources: Elton Gish multipart Porcelain Insulators Second Edition, 2000; and Transactions of the American Institute of Electrical Engineers, Vol XV, 1898).

When was the line upgraded from single phase?

James Doty commented on Wed, 23 Apr 2008

No, I think there 287. I will have to look for the broken piece to compare with the book picture

Andrew Gibson commented on Wed, 23 Apr 2008

Bill commented

"Note the comment that the insulators were made of perfectly clear glass!!! Thus, these we have in the hobby have no doubt turned purple in the sun... "

But what exactly does "perfectly clear flint-glass" actually mean? There are people who will say that "clear" is not a color, it is the state of transparency. As such, the Pomonas definitely are very "clear" in the sense of transparent. Theoretically, there's nothing to say that they couldn't have been purple when put up to begin with.

I'm not sure what the 1895 concept of "clear" was. Does anyone have an idea?

Rick Soller commented on Wed, 23 Apr 2008

I've added to my web site a picture of the CD 244 I own with the oil cup. Unfortunately it is nowhere near complete.

CD 244 with oil cup

Robin Harrison commented on Wed, 23 Apr 2008

Awesome! I never knew that specimen existed. Do you know which line it was found on (since at least one article mentions the oil cup NOT being used)

Brent Burger commented on Wed, 23 Apr 2008

I know these Pomonas are common as 42's and a person can get tired of looking through piles of them looking for that one "odd" one with the oil cup, but it really is worth the effort, right ?


Thanks for posting this. I never knew these existed like this !

Andrew Gibson commented on Thu, 24 Apr 2008

"This is a CD 244 with an oil cup so it seems it would need a new CD number since the oil cup is fused to the insulator."

Is the oil cup a separate piece that is somehow "fused to the insulator", or is that an integral piece with the rest of the insulator (similar to the way the CD 180 Liquid Insulator oil cup is formed)?

Justin Byers commented on Thu, 24 Apr 2008

Hello ICON We've been talking about insulators with oil cups and what not. What the story behind the 245 Oil insulator in the 2003 price guide?

Brad Dahlquist commented on Thu, 24 Apr 2008

The same kind of 'clear' when used for windows, bottles, food jars, and so on.

Rick Soller commented on Thu, 24 Apr 2008

The oil cup seems to be fused to the insulator.

Andrew Gibson commented on Thu, 24 Apr 2008

I'm not Woody so this isn't official in any way, but I would tend to suspect that this wouldn't/shouldn't get a new CD number. The 142.4 has an inside piece that is cemented in place somehow, but it is listed as a 142.4 with or without the glass insert (according to the McDougald's Price Guide, anyway). Other CDs certainly exist with an "extra" piece (albeit not attached in anyway), such as the 211 or 180.5, and they are certainly the same CD whether or not the extra piece is there.

Does it appear "fused" in the sense of it was attached while hot (so the glass pieces fused together), or does it appear to be cemented somehow?

Either way, that's a really neat piece to see -- thanks for posting the pictures!

Andrew Gibson commented on Tue, 29 Apr 2008

Who made the CD 244, and when?

From all the article documentation, it would appear that these insulators were installed on lines around 1894/1895. On these lines, it "was at first proposed to use oil insulators. The reason they were not used was because the glass companies which had undertaken to furnish them found on trial that they could not make them without considerable experimenting ". That seems to say that the design of the insulator was a new one, since the glass companies had to experiment to make something that would work. In my mind, that seems fairly obvious that the CD 244 design originated around 1894.

So who made them? I seem to recall that someone (William McLaughlin?) had a recollection of producing large power insulators at the Valverde Glass Works operated by Robert Good. Robert Good arrived in Valverde in 1895, and certainly by 1897 was producing insulators. McLaughlin worked there starting in 1897. These dates are close to the 1894/1895 time when the Pomonas were installed, though perhaps a little late.

Are there any other theories as to who may have made these insulators?

Paul Greaves commented on Wed, Apr 30 2008

I think the large glass power insulator type made by R. Good is most likely some of the CD288 Mershons. Specifically, the triple ridge type, and the single ridge type marked just "By R.D. Mershon". They were found on a line in Colorado that I remember reading a historical reference that said the insulators had been specially made for it. The quality of their glass also seems consistent with R.Good. (There are also some unmarked CD288s that look old & crude, is it possible that Good was also associated with these? I don't know... it seems possible.)

The CD244 on the other hand are very high quality glass, and extremely well made. I think the main (original) installations of the CD244 "Pomona" were all associated with Westinghouse... some of us in the power history area of interest have speculated that either Westinghouse made them, or contracted someone to make them.

Andrew Gibson commented on Wed, Apr 30 2008

According to the McDougald's Volume 1, the Westinghouse Electric & Manufacturing Company operated their own glass house from 1896 to 1898. They made the WESTINGHOUSE embossed insulators, styles 2, 3, 4 and 6 (not the Telluride types from Hemingray). The Pomonas seem like they were installed in 1894/1895, so a year or two before Westinghouse would actually have been making insulators themselves, if those dates are correct. On top of that, the only "purple" that Westinghouse is known to have made is the "purple tint" CD 113, which (though I've never seen one) seems like it would be a considerably different color than the relatively dark purple the CD 244 comes in. It seems more likely to me that they would have contracted someone else to make them.

Do you think that Westinghouse may have made their own insulators prior to 1896?

Thanks for the thoughts!

Paul Greaves commented on Wed, Apr 30 2008

I have no idea! I would lean toward the idea of them contracting someone else to make them though... perhaps that is what inspired them to try making their own glass for a while? It is interesting that the article stated "the glass companies which had undertaken to furnish them found on trial that they could not make them without considerable experimenting"... perhaps Westinghouse approached several glass companies in their attempt to get them made?

Caleb Thimell commented on Wed, Apr 30 2008

"The plant for supplying the town of Pomona, CA with engery has the distinction of being the first long-distance high-potential plant in this country. A waterfall on the San Antonio River, about sixteen miles due north of Pomona, furnishes the enrgy for operating the generating-station. ...*The line consists of *No.7 B&S hard-drawn bare copper wire, supported on the top of* special double petticoat glass insulators, designed by the Westinghouse Company for this particular installation.* The insulators are placed on iron pins set in cross-arms upon redwood poles. The line rests in grooves directly over the pins, so arranged as to almost entirely relieve the insulator from lateral stresses. Oil insulators are not found to be necessary, as the climate of Lower California is sufficiently dry to render but little danger from moisture leakage..." (The Electrical Transmission of Energy: A manual for the Design of Electrical Circuits" by Arthur Vaughan Abbott, published 1895).

So whoever made the Pomona insulators (at least the ones used in California) were designed by Westinghouse prior to 1895. And this article further suggests that the oil version Pomona insulator originated for trial on the transmission line in Colorado which receives a lot more rain than Southern California. Further evidence comes from the fact that the Colorado plant was installed in 1890 while the Pomona plant was installed in 1891.

"In the Mill Creek Power House No.1 of the Redlands Electric Light & Power Co., near Redlands, California, installed in June 1892, and first put into operation on Septermber 7, 1893, were two hydro-electric three phase units, each of 250 kw ouput, ....These were the first three-phase generators made in the United States, and this was the first three-phase transmission system to be put into service in the United States. (Transactions of the International Engineering Congress, 1915)

So it would seem to me that all of the insulators used on the transmission lines in California and Colorado with Pomona insulators were all made prior to 1893.

Caleb Thimell commented on Wed, Apr 30 2008

I just re-read Bob Stahr's quote from NY Times article which states oil version (cd 244) insulators were originally planned for the California line but (paraphrasing) they realized the hot sun would render them worthless for their intended purpose. So its possible they were originally designed for use on both California and Colorado lines, but perhaps only tried them out in Colorado after already having them made.

Elton Gish commented on Wed, Apr 30 2008


I sent Woody the photos and he said he had the information on his PC that was stolen. He said, "assuming it's the same as 244 except for the oil cup, I've entered it as CD 244.3.

Rick, can you please send Woody (via snail mail) all the overall dimensions so he can complete is file on this style?

Reini Criss commented on Thu, 1 May 2008

I was thinking about the question about the ponoma insulators mostly being purple, yet being marketed as "clear flint glass", and I realized that the definition of "clear" in insulators was if one could see through the insulator. I came to this conclusion because the Hemingray catologues all say that Hemingray insulators were made of "clear glass". The catalogue is online somwhere, and I think it is on but I am not sure. Just throwing out an idea.

Bill Meier commented on Fri, 2 May 2008

A catalog is at (note our new domain!!) [2]

and the page that references "clear glass" is [3]

down at the bottom... Note they also say "transparent -- the glass is clear)

But, I still think since we know "clear glass" with magenism does turn purple, there is also a reasonable chance it meant "clear" as in the color we call "clear" ... ambigous wording for sure...

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