Thorn Beta Five × 2

Lanterns acquired in April 2024.

These two top-entry Beta 5s were removed from the Leicestershire village of Hallaton, also in April 2024, when the pole brackets (mostly, dating from the 1930s) around the village were replaced in their entirety. The majority of the brackets ended their days supporting Beta 5s of varying types - most of the old brackets and their lanterns were saved, although I was particularly keen to acquire these two lanterns as they represented yet more variances in the overall Beta 5 design, of which I didn't have any examples already. With thanks to E-ON's Leicestershire team for saving these lanterns for me.

The 1976 Beta 5 is the lower example; the upper example is likely to date from around 1975, unfortunately, the capacitor is missing (making dating difficult), but thanks to how the 1976 version has evolved, I would be confident in saying that 1975 is a strong contender for when this example was made.

The aluminium casting of the 1975 version feels slightly rougher than the casting on the 1976 version does. A slightly revised surround to the bowl hinge exists on the newer lantern, suggesting that new casting dies were brought into use by then. Both lanterns have factory-fitted NEMA photocell sockets, with the 1975 lantern now running a Super6 cell, and the 1976, an SS5DR, both made by Zodion.

The 1975 version has a NEMA socket that is probably made by Zodion (Fisher Karpark) too, although it carries no identification. The 1976 lantern's NEMA socket is a Royce Thompson product, however.

There is no difference in appearance to the undersides of the two acrylic bowls - in fact, both bowls are completely interchangeable, and would fit all later Beta 5 models too.

No lamp was supplied with the 1975 version, and the one that was supplied with the 1976 model is a worn-out, internally-broken Philips product that was manufactured in March 2014 - I wonder how long the lantern had been out of lighting, prior to its replacement. Of note is that the gear trays of both lanterns are the same - although the 1975 version uses a larger leak transformer ballast (combining the functions of ballast and ignitor), an extra (unused) hole exists that would secure a newer, smaller ballast. This is not present on my 1970 Beta 5, as is to be expected, and suggests that 1975/6 was the transition period when Thorn began to use the smaller, more efficient components in their Beta 5 lanterns, but still had sufficient older gear components to use up. A second hole that is used to to allow the wires feeding the lampholder to pass through the gear tray on the 1976 version is also unused on the 1975 version; the wires passing over the end of the gear tray instead.

The identification label is missing from the 1976 version, but is present on the 1975 example. On this version, it is larger than the type seen on later Beta 5s is. Confusingly, both of these examples carry Mk 15 labels, however, but so does my 1982 version.

Opening the gear trays reveals more differences with the two castings - in the 1976 version, additional strengthening around the top-entry thread now exists, while the position of an unused boss is altered. The sprung metal strip above the ballast in the 1975 version is omitted in the 1976 version (though its unused rivet positions remain). The redesigned 1976 casting has also led to the second screw hole for the capacitor brace being excluded, leading to that end of the brace being insecure. As the capacitor on this example is situated on the gear tray itself, however, this is not a problem, as the brace only serves to hold the gear tray closed. By 1982, this had been cut back, and the brace became a strut for securing the gear tray only. Even though the capacitor in the 1975 example is missing, a separate support for it remains - this suggests that the brace wasn't used by then anyway, with the oval-shaped capacitor (as seen in the 1970 Beta 5) having been replaced with a slightly smaller, cylindrical capacitor that didn't fit the shape of the brace. In both cases, the supply cable clamp has not been used, with it missing completely in the 1975 version, and still as-new in the 1976.

In the 1975 version, the ballast is an AME 53182.4 type for 35 - 55 Watt lamps - a change from the AME 53181.4 seen in the 1970 example, which carried the original wattages of 40 - 60 Watt SOX. The G.53312.4 ballast in the 1976 lantern is for 35 Watt lamps only. About these ballasts, a wise man once wrote: "These were the first Thorn ignitor-ballasts, appearing around 1976. These ballasts appeared in with-gear Beta 5s until 1977"; indeed, the Beta 5 entry in the 1975/6 Thorn catalogue shows a lantern equipped with the older gear setup, but by the time that the 1977 edition was published, the newer gear setup was employed. The capacitor in the 1976 lantern carries the date code '7624', which tallies with this quote and the catalogue alteration, and suggests that the capacitor was manufactured during the 7th - 13th June that year; just in time for the famous heat wave that hit the UK later that month, and continued into July!

Another change made between both versions is the change from one continuous hinge rod on the gear tray in 1975 to two much shorter pins by 1976. I assume that the considerable reduction in weight, thanks to the different gear components employed, served as the catalyst for this alteration - the 1975 version being a meaty 7·64 kg (16·84 lb), compared to the 3·11 kg (6·86 lb) of the Beta 5 by 1979 (Thorn did not update the weight in their catalogues until then). Conversely, the two ribs that support the gear tray pin/s are thinner in the 1975 version, and the indentation for the bowl clip is only present on the 1976 version.

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