400 watt SON lanterns

Thorn Alpha-2000 250/400w lantern. Not commonly found in the UK, the Thorn Alpha 2000 lantern is probably more at home in France. This is a well-built fitting, constructed from cast-aluminium and designed for use with 150w, 250w, and 400w SON-T lamps. The Alpha 2000 could be post top or bracket mounted, and was available with the three different bowl fittings: a flat lens cut-off lantern, a normal bowl for semi cut-off, and a deep bowled version. The fact that the bowls are made from thick glass adds to the weightiness of the lantern. Access to the control-gear is made by releasing the stainless-steel spring-loaded clip on the front of the lantern and lifting the canopy top-cover to reveal the inner workings. The Thorn 'Riviera' range of lanterns replaced the Alpha 2000 range, but the heritage line is very obvious.

The gloss blue painted 'gearless' Alpha-2000, labelled as a Thorn 'Carat' 400-watt lantern. The keys give an idea of the size of these lanterns.

The Alpha 2000 was normally available in a natural aluminium finish, but other coloured finishes could be specified. The 'Carat' example in the collection came from Bradstone Lighting of Glasgow, and is understood to have been obsolete stock from 'Thorn Lighting'. The lantern is factory-finished in gloss blue paint, coded 'Carat AGB' (AGB = Aluminium Gloss-Blue?), with a shallow glass bowl. Although new and unused the lantern came less its control-gear, so can only be remotely operated in its present guise. However, a spare set of 400w control-gear has been rescued from a scrap A2000 (see below), and this will be fitted to the Thorn 'Carat' lantern in the future.

Another Alpha 2000 lantern was acquired in October 2005. This example was kindly rescued from a skip for me, but originally came from one of the South facing ramps of the A38-A50 'Toyota' traffic island, Derbyshire, falling victim to a 'SON for SOX' lighting renewal scheme along the A38 that had unfortunately swept away some non-standard SON lanterns in the process. The replacement lanterns mounted onto the same columns were flat-lens 150w ZX3's. When rescued, this was the only Alpha 2000 left intact, as the rest had been de-lamped and their unique twist-lock lampholders removed and destroyed along with the lamps in an incinerator.

A flat-lens 150w Alpha 2000 in natural aluminium finish; although a little knocked about this example originally came from off the A38-A50 junction in Derbyshire in October 2005.

Control-gear layout of an Alpha 2000 150.4 (150w) SON lantern. The ballast unit in this lantern is a lot smaller than the 250w and 400w versions, although the physical dimensions of the lantern are the same for all models. The inside of the lantern is very clean and totally free from the ingress of water, particles, and insects.

Although generally uncommon in the UK, there are 100's of Alpha 2000's used on the A50 between the A516 in Derbyshire, through to Castle Donnington on the Nottinghamshire / Leicestershire border, and without exception all are flat-lens cut-off lanterns. It appears that at least two versions of the cut-off lanterns are used in the installation: 150-watt, 150.4 models mounted on twin-arm brackets on the main carriageway, and 250-watt, 250.4 lanterns on the traffic islands at the intersections. However, a damaged 400w 400.4 model, crudely converted to run a 250w SON lamp, was given to me for spares; this had come from the Castle Donnington junction, after its canopy was lost in high winds.

This in service 'Flat-lens' Alpha 2000 (150.4) 150-watt cut-off lantern is one of hundreds in use on the section of the A50 that runs from Derbyshire into Nottinghamshire and through parts of Leicestershire.

This wind-damaged Alpha 2000 is a 440.4 (400-watt) version that once stood high above the A50 on the Long Eaton/Castle Donnington traffic island, but had lost its canopy in high winds. Although it was a 400-watt lantern, it had actually been crudely converted to operate a 250-watt SON lamp, with the addition of 'unsecured' 250w HPS control gear dropped in alongside the disconnected 400-watt control-gear in the lantern. This lantern was later acquired for parts, when it was replaced with an Urbis ZX3 250w SON lantern in July 2005. The gear from it will be used to restore the Thorn Carat 400w HPS Lantern.

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Please note that all pictures are by Claire Pendrous, or are part of the Claire Pendrous photographic collection unless otherwise stated; none of these images can be copied without obtaining prior permission.