REVO Hyperion A Lantern
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: REVO Hyperion A
Date: Late 1950s - Early 1960s
Dimensions: Length: 40", Width: 9", Height: 8"
Light Distibution: Semi Cut-Off (BSCP 1004 Part One:1952)
Lamp: 135W SOX (originally 200W SLI/H)
The REVO Hyperion A was the first SLI lantern developed by REVO
in the late 1950s/early 1960s. Like many of the new SLI lanterns appearing on the market,
it featured a long extruded canopy, perspex bowl with refractor plates and no option
for gear. (Which, at the time, was too big and bulky to put in the lantern's body.)
By 1963 the model had been modified to take the newly introduced 200W and 300W SOI/H lamps.
This required the removal of the second lamp connection at the street-end of the lantern.
The lantern was again modified when 150W SOX became available.
The 150W SOX lamp (later re-rated to the 135W SOX lamp) was slightly shorter than the
original 200W SLI/H the lantern was designed for and so didnít illuminate the whole
of the refractor panels.
The lantern was partially redesigned after the publication of BS 1788:1964
and reappeared in modified form as the REVO Hyperion B.
The lantern was extremely popular and could be found installed throughout the
UK. It was also used in many column manufacturers' adverts in the 1960s.
The lantern is easily identified by its elongated profile, unique bowl catch at the street-end of the lantern, and characteristic "bulge"
of the bowl profile near the lamp holders.
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 REVO Hyperion A In My Collection
This lantern came from Newmarket Road, Cambridge. It was probably installed
in the late 1960s/early 1970s so saw over forty years of service.
The REVO Hyperion A featured a unique bowl catch. Two metal lugs were
screwed onto the street-end of the bowl and engaged with a hinged catch at the end of
the canopy. It didn't exert much pressure on the bowl but proved to be a good design as I
never saw any Hyperions with missing or open bowls.
The only modification to the lantern in service was the addition of a photocell.
I had to replace the original bowl as it had sheered through by the lamp holder
end of the lantern.
The lantern had a wide canopy which tapered upwards where the bracket spigot entered the lantern.
The only identification marks on the lantern could be found on the
canopy where "REVO Made In England" was cast in raised letters.
The 135W SOX lamp was shorter than the lantern body as the lantern
was originally designed for the slightly longer 200W SLI/H lamp.
In this shot, the hinged bowl catch can be clearly seen. By 1963 the
lantern was being offered in two slight variations with the hinge being
located at either end of the lantern.
This shot shows the slightly rimpled texture of the replacement bowl
(which partly diffuses the downward light) and the white painted
interior of the canopy.
When opened, the bowl swings down to the column side of the lantern. The two
lugs at the end of the canopy were for the second lampholder of the SLI/H lamp Ė these
weren't included when SOI/H or SOX/H lamps were fitted.
The spigot fixing method used two bolts and a metal clamp to secure
the lantern to the bracket. Other internal fixtures were extremely
minimal: the incoming power supply was connected to a porcelain
terminal block on the lampholder support and there was no provision
for an earth connection.
REVO Hyperion A: As Aquired
This REVO Hyperion A originally came from Newmarket Road, Cambridge.
It was #46 and was probably installed in late 1969 when Newmarket Road was duelled and
the Elizabeth Way bridge was built over the Cam.
The Newmarket Road installation was interesting as it appeared that the lighting engineer was
trialling 150W SOX lanterns (later 135W SOX). A short run of Thorn Alpha 5s
was then succeed by a run of REVO Hyperion As and then
Philips/ELECO Goldenray GR150s.
It was removed as part of the Cambridgeshire PFI in late 2012. My thanks to
Cambridgeshire County Council and Balfour Beatty for saving this lantern for me.
Unfortunately the bowl had split at one end of the lantern but the rest of the canopy was
intact although a little dirty. It cleaned up well and I replaced the now-cloudy and split
bowl with a new one.