Thorn Beta 5

Lantern acquired in November 2019.

This lantern was attached to column 6 on Trowell Grove, Trowell, Nottinghamshire until this column was replaced as part of the County's programme to renew its lighting stock and fit LED lighting in place of its traditional 'lamped' street lighting lanterns. The column was a cast iron type, with a top-entry swan neck bracket - this may have granted the installation a bit of a reprieve if it was deemed unsuitable for accommodating an LED lantern. Whilst the Beta 5 was, once, a very common sight on minor roads throughout the UK, early examples with the lamp control gear housed with the lantern itself, such as this one, were considerably rarer. With thanks to E-ON Highways Lighting for allowing me to have this lantern; yes, the irony was not lost on me, either, Survivor #110D.

This screenshot from Google Street View shows the lantern as it appeared in October 2012. The column is concurrent with the age of the houses, and was probably original to when the road was constructed in the 1930s.

 

When viewed from the front, the column's ladder bars seemed especially narrow, even allowing for distortions created by the image.

 

The main part of the ESLA swan neck bracket had snapped off the fuse box that was sandwiched between it and the column. All that was in the fuse box was the old (original) porcelain fuse carrier and relay for the P42 two-part photocell.

 

The relay was manufactured in January 1976, suggesting that the lantern may have been operated on time switch control for the first few years of its life, though another possibility is that the original relay failed and had to be replaced with this one. The unit is calibrated to activate at 55 Lux.

 

The earlier Beta 5s incorporate slightly different refractor bowls to their later counterparts; not least, because the bowls on these lanterns are held in place by an aluminium ring, whereas later versions are attached directly to the lantern. The bowl fitted here appears to be a vacuum-formed polycarbonate replacement for a long-lost original.

 

The cream paint applied most recently to the bracket (and part of the lantern canopy too!) is wearing quite noticeably, revealing an earlier green, and possibly red, paint finish too, although the latter may be a red oxide primer showing through.

 

The bowl features side refractors only; these are embossed in relation to the surrounding plastic.

 

Opening the bowl reveals a rather grubby interior, along with a 35 Watt SOX-PSG lamp dating from October 2018.

 

Much of the retaining ring gasket is missing, as is the lantern's identity sticker.

 

Only the 'A' from 'BETA FIVE' on the label is left. At the time that this lantern was produced, it may have still been known as the AEI Amber Minor, although as the AEI name was dropped in favour of a consolidated Thorn Lighting in 1967 (AEI having been bought out by GEC), the alternative name may have been removed from the label by then - we shall never know!

 

The state of the porcelain lampholder's insides is testament to the number of lamps that this lantern has run during its working lifetime.

 

The gear tray retaining screw is missing, although, thankfully, the hinges are rather stiff, and so the tray will not hang open too easily. The beefy leak transformer takes up all of the top section of the gear tray, whilst the capacitor is attached to the inside of the canopy. A (slightly sprung) baffle plate is positioned above where the ballast rests.

 

The British Lighting Industries AME 53181.4 ballast states that it is suitable for running 40 - 60 Watt SOX lamps; the forerunners of the 35 - 55 Watt ratings that were introduced in the late 1960s after improvements in the lamp technology allowed the change.

 

The BICC-made AME C2280 capacitor appears to date to October 1969, making it just over fifty years old when the lantern was removed from service. Sadly, the insulation to the capacitor's wires is cracked, rendering the capacitor unsuitable for re-use. It will, however, be retained, as it is part of the lantern's history.

 
 

The lantern's restoration commenced on Friday, 3rd April 2020. I started by removing all of the components from within it, then set about separating the canopy from the swan neck bracket. A small amount of heating using a blowtorch was required, in order to accomplish this.

I was surprised at the shortness of the 3/4 inch BSP coupler between the swan neck's finial and the lantern; I suspect that it would have been longer when new, but had to be cut when the bracket's original lantern was removed, and the Beta 5 installed; the old lantern having seized to the coupler.

With the bracket removed, the full amount of paint applied to the installation over time could be appreciated!

The wiring within the lantern was in very poor condition, with much of it being cracked and burnt. The rubber of the P42 detector had perished, and proved difficult to remove, not least because the hole for it had (accidentally, I assume) been drilled very closely to the turret that supported the porcelain connector block for the supply cable to terminate into.


Although attempts were made to save the top box, these efforts proved fruitless, and so a replacement was fabricated by TAS Engineering of Burton Upon Trent; the completed bracket being collected in January 2021. Whilst not as elaborate as the original was, once it is painted, it will blend in with the rest of the swan neck. Notice that more of the original dark green finish has been exposed on the finial - a replacement ′′ BSP coupler has been installed, with the original requiring more heat treatment, in order for it to be removed.

The swan neck was sand blasted and then repainted into 'Holly Green' (BS 4800 14 C 39) by a local refurbishment company.

The 1930s' ESLA finial looked particularly resplendent in its new colour.

The lantern body was painted hammered grey, while the gear tray / reflector was repainted gloss white.

The inside of the canopy received the repaint treatment too.

A piece of wood was cut to fit inside the control box, and the old P42 relay installed within it, along with a replacement 16 F capacitor. The relay will not be used, but its terminal block will provided a convenient junction box for the incoming and outgoing wiring.

The swan neck was mounted to a 900 mm post-top stand that was also painted Holly Green. A 6 mm hole was drilled in the side of the box, and a brass bolt installed as a main earthing terminal for the structure.

The lantern canopy was threaded onto the new coupler (using a lot of copper grease to lubricate the thread) and secured using both its own 5/32 inch grub screw, as well as the locknut that had been provided for this task.

Next, the gear tray (complete with ballast, cleaned lampholder, support and the lamp itself) was installed, and a new adhesive foam gasket placed around the inside of the canopy.

Following a thorough cleaning, the bowl was the penultimate item to be returned, with the P42 detector being the last.

The British Lighting Industries brand may have disappeared into history, but the leak transformer bearing their name was still in perfect working order.

Whilst previously, the lamp couldn't be seen clearly through the underside of the bowl, the cleaning ensured that it could be once again.

The lamp seemed to warm up quite quickly, and within a few minutes, was operating at full brilliance.

The slightly more translucent sides of the bowl created an interesting view of the front of the lamp.

Testing with my energy monitoring device revealed the following results; despite the replacement capacitor being connected, the Power Factor remained rather poor, owing to the lossy leak transformer:

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
241.3 0.52 71 125 49.9 0.57 71.52 36.52 104.35%

Lantern operation video:

Thorn Beta 5s in the Collection

1970

1982

1983

1989

1996

1998

2001

2004

2006

2008

Philips XGS 103 | Atlas Alpha 3


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