Relite Hyperion 135 A42.401
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: Relite Hyperion 135 A42.401
Date: Early 1970s - Mid 1970s
Dimensions: Length: 35", Width: 8", Height: 8"
Light Distibution: Semi Cut-Off (BSCP 1004 Part One and Two:1963), BS 1788:1964
Lamp: 135W SOX
The Relite Hyperion was the third, and final version, of the popular
Hyperion lanterns first made by REVO. This lantern was a complete
departure and redesign from its REVO forebears and had no resemblance to the early lanterns.
Two versions were designed for 135W and 180W SOX respectively and both featured the same aluminium-alloy
canopy and slim Perspex bowl. The lantern was extremely compact as it was designed exclusively for
the SOX lamp and not the slightly longer SLI version.
Adverts for the lantern first appeared in 1972 where the lantern was described as new.
However, it isn't known if Simplex continued to manufacture the lantern
when it took over Relite in 1975, so the lantern may have only had a short manufacturing run.
Despite its relatively short manufacturing run, the Hyperion 135 and Hyperion 180
were relatively popular lanterns and were installed in large numbers by various
authorities around the country.
Identification can be tricky as the lantern is very similar to the GEC Z9554 and
Z9564 lanterns. The bowl in profile is slightly slimmer on the Hyperions,
but the real difference is the refractor panels which are fitted along the entire length of the
bowl on the Hyperions.
The semi-cut-off light distribution is provided by the two refractor
panels the length of the bowl. The interior was also painted white to redirect
flux emitted directly above the lamp within the canopy of the lantern.
The gear was too big to mount in the lantern and so had to be provided remotely.
The Relite Hyperion 135 A42.401 In My Collection
This lantern came from Newmarket Road, Cambridge. It was probably installed
in the mid 1970s so saw over forty years of service.
It was not a popular lantern in Cambridge was was used as casual replacements in a couple of places
in the city. A small number of these lanterns lit the section of Newmarket Road where it passed over
the railway line near the football ground.
My thanks to Cambridge County Council and Balfour Beatty for saving
this lantern for me.
The lantern was extremely compact with the bowl being just wide and deep enough to surround the large 135W SOX lamp.
Each side of the bowl was fitted with two refractor plates. These filled the entire profile of
the bowl (unlike the GEC Z9554 which had no refractors near the lamp holder).
The design of the refractors is unique. A normal plate refractor is stuck along the length of the bowl but
there's also a second refractor (which is only one thick prism) stuck below it.
The lantern used four stainless steel clips to secure the bowl as opposed to the end bowl clips used by the earlier versions of the lantern.
There was no manufacturersí mark or name on the smooth, slim canopy of the lantern.
The lamp could be accessed by undoing two clips on the side of the lantern with the bowl swinging to the side on two hinges. This had almost become an industry standard by the early 1970s.
The base of the bowl was flat unlike the previous Hyperion B
model. This was due to a relaxing of the specification which had been considered
too rigid. Interestingly there was also an extra sheet of plastic stuck to the
base of the bowl inside the lantern.
The canopy was painted white to reflect any flux emitted above the lamp.
The lamp was held in the lantern by the lampholder and a separate hook near the road-side.
Two stickers were also stuck near the road-side of the lantern which gave the manufacturer
name, a handwritten catalogue number (although this was printed on some other examples) and
the BSI Kite Mark.
The electrical connections were minimal and included a terminal block for
incoming power supply and a separate terminal block for the photocell. The
lantern was secured to the bracket by four grub screws Ė a departure from
the clamps used in earlier Hyperions.