GPO Vehicles

Make Land Rover
Model Pickup LWB 109"
Type Motive Unit
Body Builder  
Use Mobile Darkroom/X Ray vehicle
Registration Number PMG 580E
Fleet Number 201728 (PMG 580E) 1967
Date of Vehicle July 1968


Land Sections of Submarine Coaxial Cable Mobile Jointing and X-Ray Unit
Taken from External Plant News - No. 13 July 1969

The making of most submarine coaxial cable joints involves resistance brazing of conductors and injection moulding of polythene dielectrics and possibly cable sheaths.  In addition the high tensile steel strands of lightweight submarine coaxial cables require swaging and para-gutta insulated cables taped.  An X-ray examination of moulded joints is also made to ensure high integrity.  The techniques require sophisticated mobile jointing equipment, power supplies and X-ray facilities which are particularly designed for cables laid in ducts or buried direct in the ground.  To meet these needs a 'Minatic 21 Series' two-wheeled trailer towed by a Land-Rover has been fitted out and equipped as a Mobile Jointing and X-ray Unit.

The motive unit is a standard open body model Land-Rover with a 4-wheel drive and the body area has been fitted with a ball-type towing attachment to allow quick and easy coupling and uncoupling of the trailer.

Heavy items of submarine jointing equipment, jointing equipment, the tool kit, brazing machine and stores box are carried in the motive unit and a demountable tubular jointing trestle is secured in the space over the wheel arches on either side of the body.  Special clamps and leather straps are fitted around the sides of the body to secure the tubular tent frame to the Land-Rover.  The folded loft by 6 ft plastic tent cover is stowed on top of the stores box.  To provide the necessary power supply a 110V 9 kVA alternator has been installed in the cab of the Land-Rover between the driver and passenger seats.

The alternator is centre tapped to earth to produce an output of 55-0-55 volts and it is driven by three V-belts running in a three-groove V-pulley from the centre power take off of the Land-Rover.  This arrangement provides a safeguard against the loss of drive to the alternator if one of the V-belts breaks.  The control panel is fitted inside the cab on top of the alternator and the voltage output from the generator can be adjusted by operating the manual hand control throttle to fix the correct engine speed of the Land-Rover.  Any variation in the output of the alternator, due to load conditions, is controlled by the Land-Rover governor which maintains the engine speed at the hand throttle control setting. Two 60 amp output circuits are provided from the alternator, each protected by a fuse and with an ammeter to indicate the output current.  These circuits terminate on socket outlets fitted to the 'offside' panel at the rear of the Land-Rover.

The trailer is a standard two-wheeled commercial vehicle the inside of which has been modified so that it can be used as a mobile X-ray darkroom and site office.

The 'Luton Head' section of the trailer that fits over the body area of the Land-Rover has an equipment locker on each side.  These lockers are accessible from the outside and have been designed to take particular items of the jointing equipment.

The interior of the trailer has been fitted out with work benches having stores cupboards underneath and a floor-to-roof wardrobe on each end nearest the door.  The off-side workbench is termed the 'wet bench' where all the film processing and viewing of wet X-ray film is carried out.  It contains a stainless steel sink unit, and water is gravity fed from a 40 gallon fresh water storage tank situated in the centre of the 'Luton Head'.

Because it is illegal to release chemically contaminated water on the highway, the waste from the sink is fed into a 25 gallon tank fitted under the sink unit. Also situated on the 'wet bench' are the four X-ray film processing tanks (developer, stop bath, fixing and washing), and a wet viewing tank.

The wet viewing tank is a plate glass tank filled with water, and large enough to immerse an X-ray film.  Positioned behind the tank is a fluorescent illuminator arranged so that examination and assessment of the processed X-ray film can be carried out immediately it has been processed. The concentrated processing solution, measuring jugs, bottles and other equipment used are accommodated in the cupboard space under the .wet bench' and a space heating unit is fitted over the entrance door of the trailer to ensure that suitable processing temperatures are maintained during cold weather.  The near-side work bench is termed the 'dry bench' and it houses a fluorescent illuminated 'viewer' for examining dry X-ray films.  It also provides working space for carrying out all operations prior to processing. All the dry equipment and materials are stored in the cupboard space under this work bench.  The inside of the trailer has fluorescent lighting and a number of power points to feed the X-ray safe light and other appliances and a writing desk is provided.  Housed underneath the desk is the X-ray console, which has been designed to carry an X-ray camera, and other items required for X-raying the moulded coaxial core joints of submarine cables in jointing chambers between beach landing points and repeater stations.  The console is mounted on wheels and when released from its securing straps can be moved to, and operated adjacent to, the entrance of a jointing chamber.

It is not intended that the trailer should be moved to each jointing point along a route, but should be parked safely at a vantage point to serve a number of jointing points and used in this way, the unit has been found to provide all the facilities required for the installation and maintenance of land sections of submarine cables.


View inside the pickup.
Note the tow ball for connecting the trailer
Cab view
Control Panel of the 110 volt 9 kVA Alternator
View of the Wet Bench
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Last revised: February 06, 2021