Atlas Gamma 8

Lantern acquired in August 2020.

With thanks to fellow collector John Thompson for letting me have this lantern. This was one of several Gamma 8s (or "Gamma Eights", as they are labelled!) that lit a cul-de-sac off "Newhouse" in Stirling, Scotland until early 2020, when they were replaced, along with their characteristic triangular 'Leader' aluminium columns. The Gamma 8 was not common in Derbyshire; the only known surviving examples these days being on St. Helen's Close in Chesterfield, although one used to exist by some (now-demolished) flats on Portland Street in Shirebrook. Gamma 8 (or, more likely, AEI Ashby) lanterns were, also, employed around the parking areas of the former GE Lighting lamp factory in Leicester, which was built for AEI before transferring to Thorn, and finally, GE ownership.

A Google Street View image of one of the Gamma 8 installations on the cul-de-sac; I do not know whether this is the lantern that entered the Collection or not, however.

The Gamma 8 started out as the AEI 'Ashby' lantern, and was designed specifically to be mated with the AEI 'Leader 15 / 15ST' aluminium column, designed by Jack Howe (1911 - 2003), a Fellow of the Royal Institute of British Architects. The Leader column was approved by the Council of Industrial Design for inclusion in 'Design Index'. A portion of this remarkable design remains attached to the lantern, and I don't intend to discard it - ideally, I would like to have a post-top stand made that incorporates the column section.

The Gamma 8's canopy is secured to the rest of the lantern by tightening a central locking bolt that is located in the centre of the canopy. The lantern is in (more-or-less) original condition, having never been drilled for photocell operation.

The lantern measures 527 mm (2075 inches) in width, and 395 mm (15562 inches) in height; the considerable width and the shape of the bowl combining to concentrate the majority of the luminous flux down and to the side of the lantern.

The cut 'Leader' column cross-section allows the construction to be appreciated - three pieces of aluminium are slotted together and then secured using epoxy resin. Owing to the non-standard triangular spigot causing potential reduced sales, later versions of the Gamma 8 had the option of a conventional 76 mm (3 inch) diameter spigot instead, allowing the lantern to be installed on a much greater number of column types.

Removing the canopy reveals an inside with the usual sooty marks created by the many lamps that this lantern has run over its lifetime.

The identification label states that the lantern can accommodate a single 40 Watt SOX (the original rating, prior to the adoption of indium oxide as a thermal insulator in 1967/8, which brought an increased efficiency, allowing the 40 Watt rating to be reduced to 35 Watt), 100 Watt - 200 Watt tungsten filament (GLS) lamp, or an 80 Watt / 125 Watt MBF lamp. As the label also makes reference to BS 1788:1964, the lantern's approximate age can be determined.

The canopy thumbscrew locates on a fixed thread attached to a figured steel plate that is attached to the lower casting by three screws that fix into diagonally-positioned rods. Within the rust patch that surrounds the thread, two unused screw holes are visible. These are the fixing holes for the lampholder when the GLS and MBF options are selected; the length of the SOX lamp prevents it from being positioned vertically, and so a modification is made that allows it to sit horizontally.

 The wiring between the connector block and lampholder is not original; this has been replaced during the lantern's lifetime. The renewed wiring hangs loosely between the two components, whereas the previous wiring would have been attached to the nearest support rods with metal clips.

Looking into the lantern, following the removal of the top plate. Notice that the triangular spigot continues into the casting.

Corrosion to the lower support ring prevented the lantern from being disassembled any further than that seen in the picture above, and so the lantern was handed over to TAS Engineering, of Burton-upon-Trent, to remedy all of the seized fixings. The grub screws that attached the lantern to the column were seized too, and in the end, the spigot had to be cut away from the rest of the Leader column. I was surprised at how narrow it was without the lantern's base casting attached.

A triangular stand, based on the dimensions and profile of the Leader column stump and spigot was fabricated by TAS too. I had planned for the finished fabrication to have a Bright Zinc Plate finish; however, apparently, it was too long for the plating tank, and so was painted light grey instead. The backboard seen in the background, with age-appropriate sodium lamp control gear, may have something to do with the Gamma 8's future operation..!

The spigot was an exact replica of the original, although this and the stand itself were steel, rather than aluminium. The design for the mini Leader column is saved on TAS's machining computer; should anyone require their own version producing, please contact the company for more information.

The canopy's exterior was painted light grey too...

...while the interior was painted gloss white. The identification plate was reinstated after this picture was taken, and a new self-adhesive gasket strip applied around the rim.

The internal components were painted in the same way. The twists of wire wrapped around each of the support rods are left over from the painting process - the rods being supported by the wires.

The base casting received new fixings (where required) and was also painted light grey.

With the old column spigot now removed from the base casting, the join created during the casting's more visible.

The lantern was re-assembled and connected up, all ready to be brought back to life.

The bowl had sufficient transparency to allow the lamp's glowing arc tube to be visible through the plastic.

The electrodes were plainly visible too.

Around ten minutes later, the lamp was running at full brilliance.

The translucence was sufficient for the light to 'fill' the bowl, however.

Testing with my energy monitoring device revealed the following results:

Test Voltage (V) Current being drawn at full power (A) Measured wattage (W) Apparent Power (VA) Frequency (Hz) Power Factor True Power (W) Difference to rated wattage Percentage Difference
247.8 0.48 67 119 49.9 0.57 67.80 32.80 93.71%

Lantern operation video:

ASD Micro Highway Diamond | Thorn Gamma 4




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