Porcelain Insulator News
by Jack H. Tod

Reprinted from "INSULATORS - Crown Jewels of the Wire", September 1978, page 21

These insulators were originally developed as a result of research studies of component materials for use on Hendrix Aerial Cable Systems. The company technical papers explain all this fully, but I won't bore you with the technical part of this which engineers can best cope with. In essence, the design solves an old problem of the erosion of cable insulation when insulated cables were mounted on porcelain insulators -- usually necessitating the removal of cable insulation at each point where cables were tied to the insulators. The polyethylene insulator has a low dielectric constant which is more nearly equal that of the cable insulation, whereas the high dielectric constant of porcelain insulators in comparison to that of the cable insulation causes an electrical over-stressing of the latter. The use of the more compatible materials also essentially eliminates the radio interference problems associated with this overstressing of the cable-to-insulator interface. Needless to say, the insulators are also very suitable for use with bare conductors, and they meet the A. N. S .I. requirements for radio-free insulators. 

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The drawings and cuts on the preceding page illustrate the plain top styles. The HPI-15, 23, 25 and 35 styles are rated respectively at 15 Kv, 25 Kv, 25 Kv and 35 Kv. The latter two are also available with 1-3/8" pin hole, numbered as the HPI-25L and HPI-35L. Crowns will accept preformed tie wires. 

The Vise-Top units shown below on this page are very interesting items as compared with clamp tops on porcelain pin types. Note the clasp is formed directly in the crown of the insulator, all parts being of the same polyethylene. The side hook of the clasp may be used for cornering positions or for horizontal insulator mounts. The sample of the HPI-15VT (Vise-Top) received is not identical with the HPI-15VT drawing but has a deeper and curved side groove more like the photo and drawing of the HPI-15 plain top style. 

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Even for a 1-1/2" diameter cable, the clamping screw threads are engaged at least 2". When the clamp is tightened, it is locked in place by two detent teeth integral with the head of the clamping bolt and which bite into the insulator crown in an irrevocable manner, The conductor is clasped by tightening the torque bolt with a hand tool or hot stick until the ring on the end of the bolt breaks away. 

There are several byproducts of the polyethylene design which are advantageous. First of all, the lightness in weight simplifies packing, shipping, storage and installation. Secondly, they are essentially indestructible in normal use, and they can be properly grouped with other forms of vandal-proof insulators. The company furnished photos and test data on specimens which had been mercilessly punished with shots from high-powered rifles, buck shot, shotgun rifled slugs. I'm sure you could threw rocks and bricks at these from 10' all day without damaging one of them to the point where they would become unserviceable. 

The sample Hendrix insulators and various data sheets were (by the time you read this) exhibited for everyone to handle and inspect at the NIA convention at Reno in July. Guess we should all be "looking up" during our travels so we'll have a chance to see these new items in action. Once again, many thanks to Matt Grayson for steering us onto this report and to Hendrix Wire & Cable Corp. for graciously furnishing us with the information and samples for the report and exhibit.

Scott Given (Lodi, Ohio) received letter confirmation from Ohio Brass Company that they use the new O-B logo on only new lines of items and that means not on pin type insulators.

Dear Jack: 

I recently found a U-206 transposition insulator on an old series street lighting circuit the power company was taking down. The circuit has been in service for at least 50 years. The insulator is a dark brown or black, has no markings on it, and looks very crudely made. I was wondering if you might have any clues as to when it was manufactured, or its manufacturer. 
Marvin Suggs 
Port Arthur, Texas

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Dear Marvin:

The U-206 originated with Ohio Brass Co. and was first cataloged by them in 1912. An engineering notice (unfortunately undated) indicates this item was subsequently discontinued from manufacture, but it was still in the 1919 O-B catalog. 

The earlier version was U-206A with a shorter skirt and a much bulkier crown portion and with a very heavy O-B embossed on the edge of the crown. These exist with a light, bluish-gray glaze in addition to the mahogany browns. 

Later versions are U-206, known to me only in various brown glazes which run to the extreme of essentially black. These have an O-B embossed marking on side of the top crown portion, but this can be faint to undetectable at times. 

Westinghouse in the 1920's continued on with Pittsburg's styles (U-202 transposition) but by 1939 had adopted one transposition approximating the U-206. It has a much smaller and flatter top crown portion than did the O-B ones, and my specimen is an unmistakable dark chocolate brown glaze and with a prominent incuse Westinghouse marking on the skirt. 

Putting all the above facts together indicates that May wheat will probably go to 345 and that you have an O-B tramp of about 1920 vintage. 

Jack

Dear Jack:

 ... Also, does the marking of the U-441 Fred M. Locke effect the $80 value you have in your book? If so, which marking is most desirable? 
John & Karen Sanville 
Broomfield, Colo.

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Dear John & Karen: 

The listed U-441 value is based on any marking showing it to be a Fred M. Locke item. Even though we know these were made in the Fred Locke era at Victor, an unmarked one would be drastically deflated in value. 

Jack

Matt Grayson (Roslyn, N.Y.) has for quite some time been using his spare time away from his college studies to methodically go through the old Journals of the American Institute of Electrical Engineers (AIEE). He's concentrated on the particular years which might give answers to questions we've had on early porcelain and glass insulators. He has recently sent a large stack of prints of AIEE articles which potentially have new information, and here's a sample.

In one period (roughly 1903), there were numerous meetings and seminars dealing with the problem of burning (charring) of the wooden insulator pins just below the insulators. The point of interest to me was that this was evidently a serious and widespread problem, whereas I previously thought maybe they were just overplaying it in the ads promoting use of the porcelain-based pins and the steel pins 

Mr. Etheridge was an active participant in these discussions, so it is not surprising that Etheridge insulators and their steel pins were pictured and described several times. Since I never had the full Etheridge patent of 6-25-01, this was the first time I found out just how the pin system worked on it. I've sketched at the right what the pin and spring insert looked like (A) and what it looked like with the spring in place (Figure B). The following is Etheridge's own description of its use:

"... It consists of a malleable iron tube 1-7/16" outside diameter and 1-1/8" inside diameter. On the outside of this tube-pin is cast a shoulder on which it rests when placed in the cross-arm. To lock this tube-pin to the cross-arm a flat high-carbon steel spring -- on each end of which is formed a gib -- is driven through the pin until the bottom end springs out over the bottom end of the pin and cross-arm. 

"The insulator, which has a plain hole to receive the pin, and a recess at the bottom of the hole to receive the top gib of the spring, is then forced down over the pin until the top gib springs out into the recess in the insulator. This combination very securely locks the insulator to the pin and the pin to the cross-arm; to unlock, place a screw-driver between the lower gib and the pin, force the gib back and drive the spring out through the pin again."

I doubt that anyone will ever find an Etheridge pin from bygone days, but this description should make it possible for those who have Etheridge insulators to make a pin and spring from scrap materials to complete their display.

One article of 6-30-98 concerned high-tension insulators in various systems and testing applications in the field, and it came close to hitting the jackpot for info on a couple of insulators -- glass and porcelain. 

One test line was in Telluride, Colorado On a transmission line of 2-1/4 miles length, and a direct quotation from the test report indicates even tests were in progress from December 1895 through mid-1896 and later. The line used two glass insulator styles and one porcelain insulator style on the double-circuit, three-phase line (6 insulators total per pole). The actual poles are shown in one picture, plus a close-up of each insulator style with the dimensions drawn in for each insulator. 

Guess what the porcelain one was ---- Wow, the U-744. We have never been able to attribute this early style to any manufacturer, but I have on numerous occasions said I thought it most certainly was made by either Peru Electric Mfg Co. or G.E. (Schenectady) before the era of Imperial-Locke-Thomas insulators. The 1895-1896 dates of the Telluride tests with this insulator seem to indicate I was on the right wavelength. 

Now, guess what the two glass styles were. Well, the CD-287 for one (Ho-hum) but ------ Wow, again, the CD-244 for the other one. That might be new info for a lucky owner of an SCA specimen of CD-244. In case any of the rest of you want to prospect for more of these jewels, the 2-1/4 mile line ran from the old power station near Ames (a few miles from Telluride) to the Gold King mill. In event you live in California and want to do your prospecting there, they said, "The large glass insulator [CD-244] is the same as that used on the circuit in the San Bernardino and Pomona plant." 

It may be of interest to some that the tests for several days in December 1895 were with 25 Kv and 33 Kv. This was then increased to 45 Kv for one continuous week in January 1896, and then to 50 Kv for a continuous run of 37 days in March 1896! Although the voltages were probably elevated so high only for the purpose of the "testing", I think most utility people today would say you were nuts if you told them a line with 62 poles of CD-287 insulators was operated at 50 Kv at that altitude and with all that rain and snow.

Another report of 2-26-04 concerned construction practices on European transmission lines, and there were several interesting points. 

The Europeans considered The U.S. porcelain insulators quite inferior to European units. Some U.S. shipments were totally rejected piece-by-piece by the inspector for visual defects -- even though the insulators were o.k. electrically. They had an aversion to accepting glazewelds or cemented multiparts because they felt the individual pieces had to be tested separately to locate defectives. They preferred to test all the parts and then assemble them in the field. 

They cemented insulators to pins and noted, "no attempt is ever made here to use threaded insulators, as it is difficult to obtain good insulators with thread of the exact gauge." 

Various insulators were pictured in the article, and I had quite a surprise when turning a page and seeing the one pictured at the right. (By scaling a metric dimension shown for the height of the central part, it gave the insulator's diameter as about 7-1/2".) The crown shape was typical of other insulators shown. 

If you'll dig out your copy of the November 1974 issue of Crown Jewels and look on page 15, you'll see that we ran a report of the insulator pictured at the left below. Note that the top shells of these two insulators are essentially identical. Some variation could stem from the facts that the insulator line drawings in the AIEE Journal were sometimes only fairly accurate, and the California specimen was drawn from dimensioned sketches without it being in hand here. 

You see, I couldn't help but remember the 1974 report of the California specimen, since I have always been very curious as to its origin. It was always clouded in deep mystery, and I couldn't even find out who turned it up -- or where it turned up first! It became even more firmly implanted in my memory when I learned that it had subsequently traded hands at a San Diego insulator show for the unbelievable price of $2500.00! That seems to me to be a helluva steep price for an insulator when neither the seller or buyer knew anything about it at the time -- its manufacturer, vintage, use, or whatever. I was told that the agent of the anonymous buyer, after a series of very secretive phone calls, met the buyer on a dark street corner where the insulator and cash finally changed hands. Naturally we've heard nothing of the specimen since then.

Many thanks to Matt Grayson for all this info, and we'll have more coming on it in upcoming issues.