Thorn Beta 79

Lantern acquired in March 2007.

This lantern came from Chapel Street in Spondon - I had previously photographed it as a Survivor article. It was replaced when the road was relit with Iridiums running 100 Watt CDO-TT lamps - though a modern Beta 79 was used as this lantern's replacement. This is the aluminium-canopied version of the lantern and corrosion had set in quite severely in places, prior to the restoration. The original white P5 cell had been replaced with a modern cell before the lantern was removed however a clear P5 was fitted before I received the lantern to make everything more authentic - this type of cell was popular in the Spondon area in the 1980s. Jeremy can vividly remember the lantern being fitted with a Thorn pearl lamp, so I will try to obtain one to get the lantern 'authentic'. A standard GE 'Lucalox' SON-E lamp was fitted when the lantern was removed - this replaced a SON-T, which had been fitted in error. As far as I know, there are no other aluminium Beta 79s left in Derby itself; however, small numbers exist in other parts of the County.

The lantern is seen here whilst it was still in-situ. The old-style P5 cell visible in these photograph was later changed for a more modern electronic cell. A clear P5 is now fitted - see the photographs below:

Hold your cursor over the photographs to see the equivalent view of my newer 100 Watt Beta 79.

The lantern is now preserved in the collection - complete with 28 years' worth of dirt and corrosion! A large rubber washer spaces the NEMA socket from the lantern. The socket is an old Royce Thompson one - perhaps the white P5 came was original to the lantern.

The general shape of the Beta 79 has remained consistent over time - though the modern version secures to the bracket by tightening a plate onto the pipe - this version has two grub screws which hold the lantern in place.

The bare aluminium of the old version has caused corrosion to set in, with the gear tray retaining screw having sheared. The bowl on this example is also quite yellow in comparison to its modern equivalent.

The biggest difference in the lamp area is that the lampholder is the other way round in the modern version - however, this is due to the 100 Watt lamp being used - a 70 Watt lamp would be in the same place as it appears on the old example. The reflectors also change slightly between designs.

The gear in the old version is fastened into the lantern itself; whilst it is fixed to the cover in the newer version. It appears that the capacitor in the older version is a later addition - there is nothing in the gear area to secure it to the lantern body. One possibility is that the lantern was converted from running mercury vapour (MBF) lamps to SON, as the capacitor was manufactured in week eight of 1988 (the 22nd - 28th February), with the new ignitor taking the capacitor's place. Indeed, a stamp on the cover tells me that the lantern was tested in May 1979 (appropriately), which would support this theory, as low wattage SON lamps were still in their infancy at this time. The newer lantern dates from 2003, incidentally.

Following the lantern's restoration, the lantern was fitted to an AC Ford AC 872 wall bracket on Sunday, 15th April 2007. The P5 is not going to be used - the Horstmann 'Y' type time switch located below the switch bank will now control this lantern's operation.

The lantern was switched on and the new Sylvania lamp quickly warmed up to the familiar SON colour. The other Beta 79 can be seen in the background.

The reflectors are surprisingly quite effective - notice how they have even reflected some of the camera flash! The label seen here is new - I painstakingly obtained every single dimension from the old label and then recreated it as closely as I could. I glued the new label in place and then covered it in glaze to hold it there - and to offer some protection against the heat of the lamp.

A new bowl was obtained and it arrived on Thursday, 14th August 2008. Interestingly this bowl has a diffused path directly below the lamp.

The Thorn lamp looked very much at home in these surroundings!

The pearl finish made for a very different overall appearance when the lamp was in operation.

Lantern warm-up video:

The column is pictured again here - with the replacement lantern visible.

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