The Elusive Thomas M-3890

M-3890 is a monster of a porcelain insulator and one of the largest ever manufactured. The insulator was designed based on the C. C. Chesney patent, 761,760 granted on June 7, 1904, which covers the lily-shell shape of the skirts. M-3890 was used on the Niagara, Lockport and Ontario Power Co. line that operated at 60,000 volts. The line was placed in operation in July 1906. The two lily-shell skirts makes it very attractive and with an early Thomas glaze it could easily be one of the most sought-after multiparts. There are several M-3890's in a powerhouse museum in Idaho mounted on the ceiling. In 1901, Ron Yuhas found the first M-3890 in captivity at a yard sale. It has a beautiful mottled reddish Thomas glaze with lighter mustard areas. The original owner decided to make a water fountain out of it had tried to drill a hole down through the top. He actually drilled down about 5-6" before giving up. It has a couple of chips on the skirts but still a beautiful insulator.

Note that the insulator had a much different crown than M-3890 and the height is 1" taller. I decided to assign M-3890A to this specimen. So far no specimens of M-3890 have been reported that match the catalog drawing. This same style of M-3890 is shown in an early Thomas catalog.

We do know New Lexington made M-3890 with that same type of crown. Jack Tod gave me a crown with the New Lexington marking. He sent a note ahead of the box arriving saying he was sending me a near mint insulator. As you can see, it is just the crown. The marking includes the Oakman patent just like the M-4325A's Mike Spadafora found on the Borel line. The marking is:

PATENT                 
June 7, 1890            
4                            
NEW LEXINGTON, O.

Note the "4" struck below "June". It is not part of the marking, but may be a manufacturing code number denoting a trimmer operator.

Some years ago, Steve Jones gave me a beautiful unmarked top to M-3890. It was found at a dumpsite along the Niagara line along with a lot of broken M-3250's and other early insulators when Steve, Ken Willick, and Bob Berry were searching the area. The beautiful speckled tan glaze is obviously New Lexington. There are lots of drippy runs in the glaze and finger marks on the crown. The top shell has a large piece broken off and glued back, but otherwise it is almost mint with just a small chip.

I recently obtained a Xerox copy of a 1907 Thomas catalog. There are lots of early styles making it very interesting to look through and a great early reference. It has an illustration of M-3890 with the measurements 14.5 x 19, which is the same as for the drawing used for M-3890. However, there is a second size listed with the illustration that has the size 14.5 x 20. We may never know what that one looks like for sure. We can only assume it is the same basic shape. On the next page is an illustration that matches the M-3890A specimen as far as crown detail. However, the size is listed as 14.5 x 19. That is the same as M-3890, but one inch shorter than M-3890A. We now know Thomas cataloged the large crown style, but the height measurement doesn't match with the specimen of M-3890A. Maybe the second one listed with the M-3890 illustration is the specimen we now call M-3890A. If we could remove the wooden pin still stuck in M-3890A, maybe we could tell if it has a 1" pinhole or 1-3/4" pinhole.

There is no surprise that few M-3890's and ? survived. The extremely long inner bell-shaped skirt must have been very fragile making it susceptible to breakage from both horizontal strains and cement expansion. More importantly, the larger height to diameter ratio of M-3890 resulted in it being easily damaged by lightning strikes and flashovers from nearby lightning strikes. Forty percent of the insulators on a duplicate line for the Niagara, Lockport and Ontario Power Co. line failed a three-minute flash-over test at 195,000 volts. The tests were conducted after several hundred insulators on the primary line were damaged during summer lightning storms in 1906-1908. Over 81 % of the insulators that failed involved the long center shell.

The numerous failures of the the tall M-3890 lily-shell style brought a quick end to this beautiful style. As a side note, the Nicholson arcing ring was developed in an effort to protect the M-3890's on the line. In 1909, the shorter 4-part, gray Victor cross-top, M-4338, was used to replace the top M-3890 on each pole. It proved better suited for the service by providing a more balanced distribution of voltage. This was accomplished by the shorter design, which, to prevent damage to the insulator, allowed surface creepage rather than flashover and puncture.