Thorn Gamma-6 55w geared
lantern. One
of the more difficult-to-find members of the Gamma-6 family is the 55w SOX geared
version of the lantern that dates from the early 1970's. These first generation
'geared' Gamma-6's incorporated a large leak transformer for use with
either 35w or 55w sodium lamps, and required a deep-sided base
into which the bulky control gear could be fitted. The 55w version had an
extension to the canopy to allow the fitment of the longer 55w SOX lamp; the
35w
version doesn't have this feature. However, Thorn later developed a smaller,
dedicated ballast for the 35w SOX version, so the Gamma-6's base unit was downsized and the lantern was remodelled and became a popular seller for the
Company. It's possible that the 55w SOX lamped model was
discontinued around this time.
The
lantern in the collection came from the former RAF Bawtry Hall in South
Yorkshire, which had been No1 Group HQ for Bomber Command during WWII. After
the war, the site had continued in use with the RAF until it was eventually sold
off by the M.O.D. in the early 1980's, and was converted into a conference
centre by its new owners. Today, some of the site has again been sold off and
has been redeveloped into an upmarket residential housing development, although
the Hall remains. It was during the redevelopment of the site that some of the
old Gamma-6's that lined the entrance drive to the complex were taken down and
replaced. Fortunately, I went by the site when the works were in
progress and contacted the contractors, expressing my interest in acquiring an
example of one of the these rare lanterns. My sincere thanks to Jason Huay of Brett (Building Contractors) Ltd for
his kind assistance in saving this lantern for me.
Two
general side views of this unusual Gamma-6 lantern for
55w SOX lamps. Left: The lantern in acquired
condition with yellowed bowl, and also showing how the
aluminium canopy has been extended to accommodate the longer 55w SOX lamp. Incidentally,
this example looks slightly taller than it actually is, because it is
still attached to the column top, from which it was cut. The
lantern is fitted with a Zodion SS4 photocell. Right:
The same lantern seen with a replacement cone and Royce
Thompson, Monostar-1000 photocell.
![](Gamma6for55wSOXnemasocket.jpg)
In the same fashion as later model
Gamma-6's, the NEMA socket for the photocell is to be
found on the top of the lantern's canopy (seen
here with the photocell removed).
![](Gamma6for55wSOXcanopylockingrinf08feb07.jpg)
Unscrewing the plastic securing
ring allows for the removal of the thin aluminium canopy.
![](Gamma6for55wSOXcanopyremoval08feb07.jpg)
With the securing ring removed,
the canopy can then be lifted clear of the lantern and
access gained to the interior. The 35w version of this
early Gamma-6 is easily recogonisable, as it lacks the
raised section to the canopy.
![](Gamma6for55wSOXbowlretainer08feb07.jpg)
With the canopy removed,
the NEMA socket is revealed, as is the lampholder assembly
and cone retaining cover.
![](Gamma6for55wSOXretainingnut08mar07.jpg)
To remove the cone and
its retaining cover, the two securing nuts have to first
be unscrewed.
![](Gamma6forSOXgearinbase08feb07.jpg)
With the cone retaining cover
and the plastic cone removed, we can now see why the
base of the lantern is so deep, as it contains the lamp's bulky
control gear.
![](Gamma6for55WSOXselfstartballast0-8feb07.jpg)
By lifting the control gear tray
clear, the huge Thorn AME 53131-4 leak transformer designed
for use with either 35w or 55w SOX lamps is revealed,
along with the capacitor and fuse holder.
![](Gamma6for55wSOXgenassembly08mar07.jpg)
A view of the general assembly of
the Gamma-6 complete
with its 55w SOX lamp. Also note that even with the uplifted lamp holder, the
55w SOX lamp is only just accommodated in the available space. The
plastic prismatic cone is still available from Thorn Lighting, as it
was used on subsequent versions of the Gamma-6 lantern, and is also used on
the current
Thorn 'Basique' lantern.
![](Gamma6earlytypeNewtonNotts08jun06.jpg)
This is
an identical 55w Thorn Gamma-6, and is pictured
languishing away on the now disused airfield at RAF Newton in Nottinghamshire.
It would appear that the 55w model of the Gamma-6 was
the lantern of choice for the RAF in the early 1970's
and was used on many of its air bases.
![](ThornGamma6Borowashsmallimg.jpg)
A
example of the later remodellled 35w Gamma-6 with the
smaller base compartment. This dented example is seen
in Borrowash in South Derbyshire.
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