Atlas Alpha 8

Lantern acquired in November 2005.

Thanks to John Thompson for letting me have this lantern, which was removed from the Marble Arch area in London. This lantern bears little resemblance to the later Thorn Alpha 8 - most notably because of its twin-lamp configuration. Nowadays, this lantern is very rare; however, in the past, numerous examples were installed around (what was at the time) Derby town centre, but the energy crises of the 1970s saw all examples on public roads removed by the end of that decade, with Alpha 3s and the then-new, single-lamp version of the Alpha 8 being used instead. One local example in private ownership soldiered on until late 2011, when the installation disappeared completely.

This veritable behemoth of a lantern measures 47.5″ 21.5 12.75″ (1200 mm 550 mm 330 mm) and weighs 38 lb (17.2 kg). Owing to its considerable size, the aluminium bodywork is cast in two sections; the join can be seen approximately half way along the canopy. A NEMA socket is fitted to the lantern's rear shoe (which, on this lantern, forms part of the casting), although this is a 1980s' modification - the lantern having been designed with time switch operation in mind. A hinged panel on top of the lantern allows access to the two lamps - the lantern bowl being held in place with a number of screws.

 

Turning the lantern over reveals the slightly bellied appearance of the bowl. No refractor prisms are moulded into the acrylic; this allows the two lamps to be glimpsed within the lantern. A small section to the rear of the bowl is broken, which may be a contributory factor in the bowl being rather grubby - the fixed bowl and hinged panel idea being a way of reducing the build-up of dirt within the lantern. The underside of the shoe section is open, with a rather substantial clamp featuring three 316″ grub screws as a means of gripping the bracket; all of which are (thankfully) free.

 

The panel should be secured to the rest of the canopy by a couple of screws. These were missing from the lantern upon its acquisition, and probably had been for years, given the dull appearance of the two threads that the screws would have fastened into. Two 400 W SON-T lamps were fitted in this lantern, though judging by the heavy blackening of the rear lamp, the lantern is likely to have ended its days running only the front lamp. Incidentally, the rear lamp is a GEC 'Solarcolour' product, which suggests that the lantern ran only one lamp for a number of years; GEC-branded Solarcolour lamps being discontinued in the early 1990s, when the OSRAM name was applied to products. Notice that the polished internal reflectors within the lantern are curved - they are optimised for use with coated elliptical lamps; the Alpha 8 being designed to run two 400 W MBF lamps (though the Derby examples always ran one 250 W lamp and one 400 W lamp; the higher-wattage lamp being extinguished at midnight, leaving the 250 W lamp operating singly for the rest of the night).

 
 

After lying dormant in the collection for nearly twelve years, the lantern underwent restoration in August 2017. Removing the NEMA socket revealed the remains of an Atlas logo cast into the aluminium - if only the hole had been drilled a few millimetres further forward!

 

The lantern was stripped of all components, and the canopy given a scrub using an abrasive soap pad. The two reflectors were cleaned and polished, and the porcelain lampholders and bracket clamp were washed in soapy water.

 

Replacement 14″ BSW cheese-head screws were sourced for holding the hinged panel securely.

 

The inside of the panel was repainted in white. Oddly, only this part of the lantern interior was painted; the surrounding canopy was finished in bare aluminium.

 

The bowl was also given a much-needed cleaning; however, doing this revealed that the inside of the plastic was quite heavily scratched. Additionally, even after cleaning the bowl with full-concentrate industrial cleaning fluid, some of the old watermarks that I thought had been removed began to reappear.

 

Finally, the two lampholders were re-fitted and lamps inserted. I intend to run the lantern to the Derby specification with the front lamp being a 250 W MBF, and the rear a 400 W. Such is the enormity of this lantern that even the larger lamp looks incredibly undersized in this view!

 

By some minor miracle, the Alpha 8 was attached to a Mk II AC Ford AC 872 wall bracket on Thursday, 28th September 2017; the first lantern to be installed in what I have dubbed my 'overspill' lantern room. Owing to the walls in this room being plasterboard-based, I was concerned that the immense weight would rip any fixings straight out of the wall. Thankfully, the 'GripIt'-type fixings that I decided to use were man enough for the job, and clamped the bracket tightly to the wall.

 

A steel box housing the control gear for both lamp circuits was installed below the lantern, with a five-core flexible cable linking the two - the brown and blue cores run the 250 W circuit, whilst the black and grey cores (sleeved in brown and blue) run the 400 W circuit. The earth is common to both circuits. A two-gang switch was coupled to the box, in order to allow the two circuits to be switched individually.

 

With both circuits switched on, the lantern sprung into life. This picture was taken shortly after power was applied.

 

This side-on view demonstrates a slight difference in colour temperature between the two lamps as they warmed up - the OSRAM 250 W lamp having never been used, whilst the Philips 400 W had been run in the Alpha 8's sister lantern, the Alpha 3, for a while.

 

The colour imbalance evened out as the two lamps warmed up.

 

The 400 W lamp appeared somewhat dimmer than the 250 W lamp in this frontal view, though in reality, there was little noticeable difference between the brightness.

 

Even with both lamps at full power, the lantern was (surprisingly) not especially glary.

 

The 400 W lamp was then switched off, as a way of demonstrating how the Derby lanterns would have looked after midnight.

 

The operation was then swapped, for variety.

 

In a deliberate move, the much newer 250 W SON-T Alpha 8 was installed alongside its older namesake. Although not a small lantern by any means, the newer design is completely dwarfed by its 1960s' equivalent.

 

The video below details the various lamp circuits in operation.

Testing the lantern with my energy monitoring device revealed the following results; owing to the lantern having three different operational modes, the test was conducted this number of times:

Lamp Power 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
250 W 241.9 1.22 277 295 50 0.94 277.41 27.41 11 %
400 W 240.7 1.92 423 462 49.9 0.91 420.55 20.55 5 %
650 W (both operational) 240 3.14 692 754 50 0.92 693.31 43.31 7 %

I also own two Thorn Alpha 8s. Click here to see pictures of the original version, and here to see pictures of the later type, in order to appreciate how these differ from the original Atlas version.

WRTL Pathfinder | Thorn Alpha 2000


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