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eleco hw 846 golden ray mk vii

Genre: Enclosed Horizontal Traverse Low Pressure Sodium Lantern

The low pressure sodium discharge lamp was developed by Philips in 1932. After two successful trial installations (including the first low pressure sodium installation in the UK along the Purley Way, Croydon) the first commercial installation was installed by Liverpool Council in 1933 using specially commissioned lanterns from Wardle.

The development of lanterns continued through the 1930s and accelerated when it was determined that the lampís brightness and its long length made it less susceptible to glare. Lanterns with bare bulbs suspended over an overhead reflector (the so-called "seagull" lanterns) quickly followed. Glass manufacturers were initially slow as the first plate refractors for low pressure sodium lamps didnít appear until the end of the decade.

The advantages and disadvantages of low pressure sodium were readily debated, especially when an alternative (the medium and high pressure mercury discharge lamp) was also available. The monochromatic light was considered especially useful for arterial and traffic routes, the lampís shape cast a wide beam across the road surface, the light was also considered more penetrating in foggy conditions and it was the most efficient light source being manufactured. However, the light was also considered inappropriate for high streets, promenades, civic areas and residential streets and so some lighting engineers restricted its use to traffic routes only. Therefore low pressure sodium became known as "the driversí lamp."

The arrival of plate glass refractors resulted in large lanterns made of metal frames enclosing heavy glass sheets. These bulky lanterns continued to be made into the 1950s until being usurped by lanterns with plastic bowls and machined or moulded plastic refractor plates. The lanterns were still large; the size dictated by the bulky control gear, but their design and construction was becoming simpler.

The 1950s and 1960s saw huge improvements in the construction and efficacy of low pressure sodium. Early two-piece designs (dubbed SO) were replaced by the one-piece, more efficient integral design (called the SOI). The development of linear sodium (SLI) broke the one hundred lumens per watt barrier, lead to a radical rewriting of the British Standards of street lighting and prompted the development of new families of streamlined lanterns. But it wasnít until the arrival of a new heat-reflecting technology (called SOX) that a cheap family of extremely efficient bulbs became available.

The energy crisis of the 1970s saw a rethink in street lighting and lamp efficiency became dominant when fuel was both in short supply and expensive. This saw the large scale removal of colour corrected high pressure mercury, fluorescent and ancient tungsten lamps by low pressure sodium replacements. The old arguments that the smoky-orange lamps were inappropriate for residential areas no longer applied. By the end of the 1980s, low pressure sodium was the dominant street lighting lamp used in the UK.

The use of low pressure sodium came under scrutiny again. High pressure sodium, finally developed as a viable technology in the 1960s, was coming of age and offered a compromise of slightly less efficacy with better colour rendering. Questions were being asked about the physiology of the eye and visual adaptation under low lighting levels; previously the wavelength of low pressure sodium had been deemed the most suitable, but research now suggested that the eye responded better to white light. Concerns were raised about light pollution and the low pressure sodium lamp was seen to be the chief culprit (although it was more to do with older non-cutoff and semi-cutoff optical designs rather than the lamp itself).

By the turn of the century, the age of low pressure sodium was seen as coming to an end. Research in white light technologies, especially metal halide and a renewed interest in compact fluorescent coupled with the advantages of using white light at low lighting levels, saw the end of the low pressure sodium lampís dominance. Its use was discouraged in the specifications, lantern manufacturers started to wind down their production and bulb manufacturers followed suit.

By the end of the first decade of the 2000s, low pressure sodium was in stark decline, and less and less of the UKís streets were being lit by its characteristic orange glow.


Name: ELECO HW 846 Golden Ray MK VII
Date: Late 1950s - Early 1960s
Dimensions: Length: 20¼", Width: 11 3/8", Height: 8½"
Light Distibution: Semi Cut-Off (BS 1788:1951)
Lamp: 35W SOX




History


ELECO catalogue

ELECO was one of the most prolific manufacturers of low pressure sodium lanterns producing two separate families of lanterns each called Golden Ray. The first was a selection of typical deep-bowl "boxy" lanterns, which originally appeared in the 1950s, the lengthy dimensions were required to hold the cumbersome leak transformers and gear of the period. By the 1960s, a new family of Golden Ray lanterns appeared, with sleek angular aluminium canopies and equally slim elegant bowls.

The ELECO HW 846 (or Golden Ray Mark VII) was their standard low-pressure sodium lantern for side roads. Developed in the early 1950s, it featured the classic design motifs of the era, namely a large aluminium alloy canopy, deep bowl with refractor plates, and provision for the large and bulky gear of the period. It was this provision for gear which dictated the dimensions of the lantern. It was developed throughout the 1950s and early 1960s, but was eventually replaced by slimmer designs as smaller gear was made available.

The long entry boss was designed to blend perfectly into ELECOSlim concrete columns.




Popularity

The lantern was extremely popular and was installed on Group B roads throughout the country.




Identification

The lantern is easily identified by its size, profile and the stainless steel bowl clip mounted along the side of the lantern. It also has the ELECO logo cast into the top of the canopy.




Optical System

The primary optical system comprised of two plate refractors positioned either side of the bulb. As the low pressure sodium lantern already casts a wide beam in azimuth, the horizontal refractors simply alter the flux elevation by fashioning two main beams in a semi-cut-off distribution (in accordance with BS 1788:1951). The rest of the bowl was slightly patterned to allow diffusing.

The top of the canopy acted as the secondary optical system, being stove enamelled white to reflect further flux. An optional metal reflector was also available.




Gear

Gear was optional and could be fitted to the various lugs cast into the top of the canopy.




the eleco hw 846 golden ray mk vii in my collection

facing profile

I obtained this ELECO HW 846 from fellow collector Claire Pendrous. I donít know its previous history or where it was installed.




front profile

The bowl was not original. It was a polycarbonate pressing with integral refractor plates Ė the original bowls were made of Perspex with separate glued-on refractor plates. However it had the same dimensions, and the same optical system, as the previous bowl so was a worthy replacement.

It was slightly stippled like the original bowls Ė this diffused the light from the sides and ends of the lantern, ensuring it was more evenly distributed and lessened the glare.




trailing profile

The cheap polycarbonate had gone yellow with age, but the lamp could still be seen. The lamp steady was at the "road end" of the lantern; mounting points within the lantern allowed the position to be changed to "path end" if required. In fact, early catalogues showed it with this configuration.




canopy

The extra long side-entry spigot was designed to blend seamlessly with ELECOSlim concrete columns. This was a worthy aesthetic consideration but most side-entry lanterns didnít bother with this embellishment and instead mounted flush against the bracket. The securing grub screws were also mounted externally here (instead of within the lantern's body which was the norm at the time).




logo

The maker's logo was cast into the lanternís canopy Ė which was standard for most ELECO lanterns. The model number was also cast into the underside of the canopy: in this case is was the model number which was HW 846.




pedestrian view

In this view, the stippling on the bowl can clearly been seen, along with the moulded refractor plates. The bowl was secured in position by a bowl ring, held by a single stainless steel toggle catch; this was mounted centrally along the side of the lantern. The two grub screws which secured the lantern to the bracket spigot could also be seen.




vertical

The lamp was mounted centrally within the lantern. The lamp cap was mounted at the "path side" of the lantern, which is how it was obtained. (I could've changed it as mounting lugs allowed either configuration to be chosen.)




open bowl

The lantern didn't have its optional gear or secondary metal over-reflector. However, the lugs cast into the canopy clearly showed how and where these would've been mounted. There were also lugs allowing the lamp holder and lamp steady to be swapped around. Asbestos wiring was used from the lamp holder to the porcelain terminal block, whilst other features were an earthing screw and cable clamp.




the eleco hw 846 golden ray mk vii as aquired

A popular side-entry lantern, this ELECO HW-846 was obtained from fellow collector Claire Pendrous.

The bowl isn't original, being a reproduction, but doesn't detract from the lantern's appearance (although it's going yellow with age being polycarbonate, rather than milky as the original would've been Perspex).