GPO Vehicles

Make	Morris
Model	Leader
Type	Motive unit
Body Builder	Brockhouse chassis - Trailer No. 1
Use	Mobile Post Office
Registration Number	GPO 1 and GPO 2 (used many times)
Fleet Number	10883 (GPO 1) and 13009 (GPO 2)
Date of picture	1937

The trailer was made by Brockhouse. The trailer chassis was a Brockhouse "Kwikfiks" articulated attachment.

An extract from
POEEJ Volume 29, Part 3 - Dated October 1936

A Mobile Post Office
By W. G. DUNK and C. F. MILLS

A recent innovation in Post Office services is a “Post Office on Wheels”. It is designed to afford essential post office facilities at important open-air functions, such as exhibitions and sports meetings.

Introduction
The provision of telegraph, telephone and postal facilities at what are officially termed “special events” presents very interesting problems. Generally, for race meetings, etc., which occur at stated intervals, buildings are permanently wired for the telecommunication services, the apparatus being sent to the site before the meeting and recovered directly afterwards. The smaller event is, however, more difficult to cater for, especially in regard to telephone facilities, as telephone call offices which give reasonable sound qualities are not easily erected and dismantled. To meet these conditions it was decided to build a motor vehicle which would provide facilities for these services and thus reduce preliminary work to a minimum.

As a result of discussions between representatives of the Headquarters Departments concerned it was decided that the under mentioned facilities should be provided in a motor vehicle:-

Telegraph - Acceptance of telegrams from the public and receipt of telegrams at the vehicle.
Telephone - Trunk and local telephone service from two telephone cabinets built in the vehicle.
Postal - Sale of stamps, acceptance of letters and parcels and registration of letters and packets.

Type of Vehicle
After the services were decided consideration was given to the type of vehicle most suitable for the work, bearing in mind the many governing factors, e.g., limitation in size by the Road Traffic Act to overall length of 33 ft. and overall width of 7 ft. 6 in.; ability to manoeuvre; economy in capital cost and in maintenance costs; maximum floor space; low floor position for the staff and the public telephone cabinets; convenient height for the counter and windows used by the public. With these factors in mind, it was decided that the most suitable vehicle would be the articulated type, i.e., with the tractive unit separate from the body portion, which would allow a vehicle to be produced of maximum length of 33 ft. This type of vehicle is easier to manoeuvre than a rigid vehicle of the size required, a factor which is important in view of the certainty that the vehicle will be used at functions held in fields approached by narrow and twisting lanes and narrow gateways. A saving in cost was also effected, a rigid vehicle costing appreciably more.

The body of the vehicle, which is referred to as the trailer, had to house two telephone call offices and provide accommodation for three counter clerks with facilities to conduct telegraph and postal business, and provision for these had to be made in a body of maximum over-all horizontal dimensions of 22 ft. long by 7 ft. 6 ins. wide. The lay-out adopted is shown below.

Trailer layout

The window height was important as service to the public for postal and telegraph business had, of course, to be at a convenient height. A Brock-house drop frame trailer was accordingly selected which enabled windows to be fitted 3 ft. 11 ins. from the ground. A floor height of 1 ft. 5 ins. was also obtained. The trailer is marketed by Messrs. J. Brockhouse & Co., Ltd., and is fitted with that firm’s patent “Kwikfiks ” attachment. This attachment allows the tractor, which is equipped with the other half of the coupling, to be linked up to the trailer by simply backing the former to the latter until the king-pin on the trailer engages with a hooked coupling on the tractor. The connexion is automatic and at the same time the brake on the trailer is coupled to a lever on the tractor. The “Post Office” body is built upon the trailer and its shape was designed on lines which are considered to be the most attractive and pleasing consistent with utility. It is partitioned into three compartments, the rearmost portion housing the telephone cabinets, the centre portion the office proper and the front what may be termed a store room. The three postal and telegraph counters are situated in the vehicle at the offside and accommodation for the teleprinter is provided on a counter at the nearside.

The two telephone cabinets are reached by a folding step, single tread, between the ground and the platform forming the floor of the cabinets. In order to facilitate entry and egress and to allow as much interior room as possible, access to each call office is by a two-sectioned folding door, set at an angle and hinged to a pillar fitted centrally on the partition which forms the backs of the cabinets. When the vehicle is not in use a rear door encloses the platform which gives the vehicle an orthodox rear view. This door, when the vehicle is “on duty,” is fixed open with a door adjuster at an angle of 90° and the inside of the door thus exposed is fitted with a grip handle to assist entry of the public to the call offices. A similar handle is fitted just inside the shut pillar. The following notice is inscribed in Roman Trojan type engraved on black with cream lettering on the inside face of the door “Public Telephones - Local and Trunk Services.”

The usual type of folding door is fitted to the cabinets and the construction generally follows that used for cabinets in public offices, thus allowing as large a measure of sound-proofing as possible.

The Call Offices
The call office layout is that used in the new Jubilee kiosk, one minor modification having to be made to the offside call office to allow for the passage of the letter chute. This was effected by altering the directory pigeon-hole and in no way detracts from the appearance of the layout or lessens its utility.

To provide connexion with any type of exchange, Magneto, CBS Nos. 1, 2 and 3, CB, and automatic systems, including unit automatic exchanges, necessitated the design of a special circuit and to avoid change of instruments in the vehicle or provision of special plant at exchanges, postpayment coin boxes were necessary. This arrangement has certain traffic disadvantages as postpayment working in prepayment areas will sometimes be occasioned, but the Traffic Branch, viewing all considerations, did not anticipate any considerable difficulty in this direction as they will have due notice of the special event and sufficient time to prepare suitable instructions for the guidance of the operating staff.

In the circumstances in which the vehicle will be used it may be assumed that a considerable number of persons wishing to use the call office will require connexion to tow ns not in the immediate vicinity of the event, and to prepare comprehensive lists of charges for such calls and provide accommodation for them, would cause difficulty. Skeleton lists will therefore be prepared.

A special call office circuit was designed using a Telephone No. 196 LB lilted with a Dial ,Automatic No. SS 11 FA, three dry cells and a six point two-position switch for changing from loop to earth ringing. The latter connexion is required in CBS No. 1 areas only. In CB and CBS areas the operators' attention will be called by lifting the receiver and for magneto areas a generator is provided. In non-automatic areas the dial of the Telephone No. 196 LB is covered by a cap. The generator is housed in the coin-collecting box and when not in use the hole for the handle is covered by a screwed cap, the handle being stored in the battery compartment of the parcel receptacle. In automatic areas the attention of the operator is obtained by dialling 0 or the local two digit code.

The call offices are connected to Protectors HC and F 2/2 mounted on a board immediately below the roof of the vehicle at the nearside of the trailer. From this board connexion to the telephone network will be made by Cable IR Aerial 8 pair/20, the cable passing through the side of the trailer. The entry is so arranged that rain will not enter. A third telephone circuit is provided for telephoning telegrams when the teleprinter is not in use or is temporarily out of service. This telephone connexion is paralleled to the public counter and can thus be used for service messages when required. It was not considered necessary to make special arrangements for direct connexion to underground cables.

Telegraph and Postal Equipment
Telegraph service will normally be provided by Teleprinter No. 3A. Unit Auxiliary Apparatus No. 72 is used with the teleprinter and provides facilities for simplex, duplex and YQ workings. A pair of leads from the teleprinter position is brought to a Protector HC and F 2/2 on the terminal board on which are also mounted the telephone protectors and the line connexion is made here.

From the charging panel a lead is connected to the teleprinter position giving 110 volts. This is required for the motor drive. Across the 110-volt leads a potentiometer consisting of 4,000 + 4,000 ohms is connected, thus giving 55 + 55 volts positive and negative potentials from either side of the centre tap, and is used to provide the line and local currents.

Adjacent to the public counter are two stamp-selling machines (1/2d. and Id.) and a letter chute. When the vehicle is not in use the stamp-selling machine mechanisms are removed and a shutter covered with aluminium sheet is inserted in the aperture and held in position by two Bloxwich spigot budget locks. A spring-loaded hinged louvre type of cover is fixed over the letter chute aperture and a temporary shutter is placed over this cover when the vehicle is “off duty.” One end of the chute is attached to the posting box aperture and the chute continues to the mouth of a mail bag so that handling of postal packets is reduced to a minimum. When the vehicle is in use two mail bags are utilized; they are held on detachable hook arms similar to but smaller than those used in sorting offices. As previously stated one of these bags is under the letter chute and the other is for parcels.

As far as possible, having regard to the space limitations of the trailer, the drawer and shelf accommodation normally provided in Post Offices has been installed. This is an important feature as the postal and telegraph personnel will be drawn from the local stall', and as rush times may be expected, it was essential that the personnel should carry out their duties under conditions of accommodation as near normal as possible.

Stamps, cash, etc., will not be kept in the trailer when the staff is not on duty. The stock of stamps, cash, etc., will be handed over to the local postmaster for safe custody at the end of the day’s business. It is the usual practice to keep this stock in metal deed boxes and racks at the backs of the three knee-holes under the service counters have been provided to accommodate them during “office hours.” Separate locked cupboards are provided for registered letters and parcels. These cupboards have framed doors with expanded metal fronts so that when the cupboards are being cleared, packages are not overlooked.

For the convenience of the public, a sloped writing ledge, in three pieces, but forming a continuous shell, is fitted under the three public windows. The ledge is removable and is mounted on four detachable mild steel brackets which slide into brass brackets screwed to the side of the vehicle.

Staff amenities have not been overlooked. A wash-basin of the ship cabin tip-up type, purchased from Messrs. Beresford & Sons, Ltd., is installed, water being drawn from a tank of six gallons’ capacity fitted near the roof and filled from inside the vehicle. An electric kettle is included and this is filled from a tap fitted in the feed pipe connecting the storage tank to the wash basin tap. A table is also provided with cupboard space for staff use. On the front of the partition which forms the back of the call offices is a luggage rack, similar to those fitted to modern motor coaches.

Seats for the staff are of the type used by phonogram operators, generally referred to as the “Tan-Sad" type. These chairs have been specially upholstered and finished to match the general internal colour scheme of the vehicle.

The public counters, teleprinter and staff table tops are constructed of plywood, covered with black Bakelite and are edged with stainless steel. These tops were manufactured by Messrs. Tucker Armoured Plywood Co., Ltd.

Power Supplies
Provision of electrical energy for the teleprinter and lighting of the vehicle presented a certain amount of difficulty.

At first it was considered that a petrol or diesel engine-generator set, housed in the fore part of the vehicle, would be a suitable means, but examination of various charging sets revealed the fact that such a scheme was undesirable owing to lack of space, noise and vibration. It was ultimately decided to mount the generator on the tractor and to drive it from the engine of that unit by means of a power take-off from the gear-box, which is controlled by a lever in the floor of the cab.

Although normally the generator will be used while the vehicle is stationary, it will be possible to charge the batteries while the vehicle is travelling.

The generator, a light weight, enclosed, ventilated, shunt compound machine producing 15 amperes at 98/150 volts, runs at 1,500 r.p.m. It is housed in the driver’s cab on supports underneath the passenger’s seat and is easily accessible.

The generator supplies current to charge two batteries of 54 cells at a normal charging rate of 3 amperes. The batteries were supplied by Messrs. The D. P. Battery Co., Ltd., being their MEZ traction type. Sealed ebonite containers are used and the cells are assembled in three hardwood crates each containing 18 cells.

The batteries are carried in the fore part of the vehicle on light section steel racks (Fig.5). The two under trays are arranged to draw forward to allow for taking hydrometer tests and topping the cells when necessary. In order to facilitate this work the battery trays rest on rollers and when attention to batteries is required, detachable bracket arms affixed to the rack at the level of the bottom of the tray provide a support for the tray and battery.

The charging panel allows for the charging of the batteries separately or in parallel and also for the supply of current direct from the generator to the lighting circuit should this be necessary. As the space in the vehicle is limited iron-clad switch gear was provided. The charging panel was supplied by Messrs. The Power Equipment Co., Ltd.

Connexion between the generator and the charging panel is effected by a multi-core tough rubber type cable. Included in this cable is a pair of wires for the rear light of the trailer, current for which is supplied by the ordinary lighting dynamo on the tractor. The cable connectors are of the watertight plug and socket type.

For the guidance of the engineering staff, the necessary instructions, circuit diagrams, etc., have been bound into folders in duplicate. The instructions include circuit diagrams of the call-office circuit, charging panel connexions and instructions regarding the removal and packing of the stamp-selling machines. A set of call office instruction cards proper to each area will also be carried on the vehicle.

Constructional Details of Trailer Body
The framework of the body consists of 24 vertical pillars attached direct to the. trailer chassis, each point of attachment being reinforced with a mild steel bracket. There are five horizontal body rails which are halved into the vertical pillars and reinforced where necessary with mild steel plates. At the rear these rails are equally spaced, but at the sides they are arranged to suit the service windows, the bottoms of which are 47 ins. from the ground. At the offside an additional rail was inserted 5 ins. below the cant rail to provide a cavity for the awning rail. Furthermore, on this side of the vehicle special framing was required for the stamp machines and letter box aperture. Also the nearside framing was reinforced to hold the auxiliary unit for the teleprinter. Twelve curved roof rails, five longitudinal and seven transverse, complete the main framing and these are checked into the cant rail.

In addition to the skeleton, framing for two partitions was necessary. The rear partition, which is fixed, isolates the telephone cabinets and the other divides the front portion of the body from the main compartment. A roller shutter has been provided in the latter.

Each of the outside doors is framed by two vertical pillars and five horizontal rails, the latter being mortised and tenoned into the former. All the framework is constructed of English ash.

The flooring consists of tongued and grooved deal boards 1 in. thick placed longitudinally. The normal construction of motor van bodies provides for crossbars, but the inclusion of such members in the body under review would have negatived to a certain extent the advantage of the low frame height. It was accordingly decided to dispense with them and bolt the boards direct to the trailer frame.

Panelling
The vehicle is panelled externally with aluminium sheet 16 s.w.g., and the joints of the panels are covered with 1 in. x 3/16 in. half-round aluminium moulding. Panelling of the inside of the body is effected with birch plywood 3/16 in. thick on all flat surfaces and with aluminium sheet 16 s.w.g. on the curved surfaces and the under side of the roof. InsulBoard, marketed by Messrs. G. D. Peters & Co., a proprietary material, has been provided in the walls of the telephone cabinets to obtain maximum sound proofing.

Windows
The design of the three windows over the service counters on the off-side of the body presented some difficulty. Motor coach windows on the market are normally of the “half drop” or “side-sliding” types. The kind of windows required for the vehicle was a “half-lift ” pattern, a type which did not appear to be marketed. It was therefore necessary to design and manufacture special windows. They are 36 ins. wide x 30 ins. high and are made of 1/4in. Triplex toughened glass. Behind each there is an inside pane 36 ins. wide x 12 ins. high, also of Triplex toughened glass, with a pigeon-hole cut from the bottom and in the centre. It is recognized that pigeon-holes have certain disadvantages but it was decided that they were essential in order to minimize draught through the windows and so cause as little inconvenience as possible by papers, etc., on the counters being disturbed. The outer glass extends over the full width and height of the window frame and lifts sufficiently to expose the pigeon-hole in the smaller pane. The small panes of glass in the two forward windows are fixed, but that in the rearmost window has been made to lift so that parcels may be passed through the window to the counter clerk. In order to promote easy operation of the windows they are fitted with a balance mechanism on the spring loaded roller principle. On the nearside there are four windows, two large and two small. The larger ones are fixed at the bottom but are provided with hinged louvre ventilators at the top. The two smaller ones are in the nearside telephone cabinet and over the wash basin respectively and are fitted with opaque glass.

Awnings
Protection for the public from sun and rain is afforded by an awning over the service windows, which extends from a point 18" forward of the foremost service window to the nearside of the rear door and is in four pieces, each being 4' deep. Green “Willesden” canvas has been utilized for the awning and a scalloped and bound frill enhances its appearance. It is supported by eight removable stays, each 3' 6" long which are made of steel tubing, their free ends being linked together with steel tubes to which the bottom of the awning is attached. The awning supports are so designed that the awning can withstand the strongest wind. The recess or cavity which houses the awning rail is provided with a wooden cover which is placed into position when the awning is not in use.

Duckboards
Six heavy duckboards 4' x 2' 6" are available for use on wet or muddy ground. They are constructed of oak, treated with external solignum and are sufficient to cover the ground in front of the service windows and that round the offside rear corner to the door leading to the telephone cabinets.

Tractor
The tractive unit is a standard Morris Commercial 3-ton “Leader Tractor” chassis with a four cylinder engine rated at 24.8 h.p. It is fitted with a specially designed cab to conform as far as possible with the lines of the trailer body but departure from the ideal was necessary owing to the appreciable clearance required for the rear and sides of the tractor when driving the vehicle along roads with acute bends. Such roads will frequently be met in the districts where the vehicle is used.

Decoration scheme and Ventilation
The exterior colour of the trailer and tractor is generally “Post Office Red,” British Standard colour No. 38 and cellulose finished. The roof of both units and the mudguards and cover plates are black. The “flying wing” ornaments on the cover plates of the rear wings are red. With a view to improving the attractiveness of the general appearance of the outside, the waist moulding on the trailer body is finished a golden colour. Gold leaf was considered for this moulding but for reasons of cost and durability it was decided to utilize anodized aluminium moulding for this purpose, as metal so treated is more durable and less prone to disfigurement than a gold finish. The “G.P.O.” monogram, also in golden anodized aluminium, appears on each side of the trailer body, as well as on the rear door.

The mudguards or wings were designed lo be in keeping with the general lines of the body. The rear ones on both the trailer and tractor follow a similar streamlined contour and are each fitted with a detachable cover plate with a “flying wing” ornament placed in a suitable position, It was essential that detachable cover plates be provided in order to secure accessibility to the wheels and tyres for replacement and repair purposes. The front wings of the tractor are the orthodox curved type. It was not possible to lit cover plates on these as it was necessary to allow for the turning lock of the front wheels.

The interior colour scheme is black and grey with most fittings chromium finished. This scheme creates an impression of spaciousness (Fig. 6). The roof and as much of the remainder of the interior as practicable is lined with grey Rexine, which is washable, uncovered parts being painted dove-grey. Dreadnought-grey linoleum covers the floor.

Ten “Ashanco" ventilators are provided in the roof, one over each telephone cabinet, six equally spaced over the main body compartment and the other two over the forward portion. Each ventilator is fitted with a “hit-and-miss” grid so that air currents may be controlled when necessary. In addition the pigeon holes in the service windows and the open portion of the two large nearside windows afford adequate circulation of the air.

In order lo minimize the heat inside the vehicle during hot weather the roof is lined with Alfol marketed by Messrs. Alfol Insulations, Ltd., a proprietary heat-resisting and insulating material. This is inserted between the outer covering and the inside lining of the roof.

For publicity purposes and in order to provide adequate and efficient illumination for the staff and to harmonize with the general decorative scheme special attention was paid lo the type and position of the internal electric light fittings. In addition to eight “D” section roof lights in the main body similar fittings are affixed to the body pillars over the service and staff counters. The latter were considered necessary as the roof lights might cast shadows which would hamper the counter clerks in their duties. Furthermore, each counter is provided with a plug point for a table lamp, which might possibly be required, e.g., by the teleprinter operator.

Locks
To prevent the entry of unauthorized persons into the vehicle each door has been equipped, in addition to a slam lock, with two locks, one a Yale type and the other a Bloxwich spigot budget type. Similar type locks are fitted to the cab doors.

The internal locks are Yale pattern and a separate key combination is provided for each counter position. A padlock is provided to secure the roller shutter of the storage compartment.

Prevention of Fire
Four Pyrene chromium plated fire extinguishers have been provided, three in the trailer and one in the tractor.

Miscellaneous Accessories
The front or store compartment of the trailer has a higher floor level than that in the main body and is reached by a folding step. In addition to holding the batteries it is equipped with racks for the awning, awning stays, duckboards, writing ledges, tools, spare parts and accessories for the use of the staff responsible for the maintenance of the vehicle. The accessories include a broom, mop, cleaning rags, polishing cloths, a step ladder, a can for filling the water tank, a pail for emptying the waste tank and a plank for placing beneath the parking wheels of the trailer to prevent them from sinking into soft ground.

Registration
For publicity reasons the Ministry of Transport was approached with the request that the registration index letters GPO should be allotted to the General Post Office for use on special publicity vehicles such as the Mobile Post Office. The Ministry agreed and this index mark has been allotted to the London County Council for the exclusive use of the Post Office. The registration number of the Mobile Post Office is accordingly GPO 1.

The vehicle was build by Messrs. Duple Bodies & Motors, Ltd., and thanks are due to this firm and the other contractors concerned for many helpful suggestions.

It will no doubt be appreciated that the vehicle is in the nature of an experiment and experience gained with its use will probably suggest modifications and improvements.

An extract from POEEJ Volume 31, Part 2 (October 1938)

Mobile Post Office No. 2

As an appreciable number of the demands during 1937 for the first Mobile Post Office could not he met owing to prior bookings, it was decided to build a second Vehicle and this was completed in April last. It was formally inaugurated by the Lord Mayor of
Leeds, at Leeds, on 13th of that month. This vehicle is similar to the first but the under mentioned improvements, which suggested themselves after experience in service of the first, were incorporated:-

An aperture above the pigeon hole in each service window, to facilitate conversations between public and counter staff.
A notice plate above the posting box on the offside, to indicate to the public "Office hours" and "times of collections."
A folding step under the door leading to the office compartment.
More accommodation for counter clerks by reducing width of each counter by 3ins.
Counter tops of matt finish Bakelite. (It was found that the highly polished surface of the counters in the first vehicle soon became disfigured by scratches). Fronts of drawers also faced with this material.
Hinged flap in rear nearside office window through which telegrams are handed from counter staff to messengers.
Drawer for filing telegrams.
To provide for telegraphic traffic beyond the capacity of one teleprinter an auxiliary unit for a second teleprinter was installed. This necessitated the supply of batteries of 50Ah. capacity instead of 30Ah. (Only one teleprinter, however, is carried on the vehicle ; the second, when required, is supplied locally).
Extractor fan in battery compartment and another in office compartment.

In addition, the items mentioned below, which were added to Mobile Post Office No. 1 subsequently, were incorporated in the second vehicle:-

Metal rectifier for the charging of batteries when mains current is available. This addition was made to save wear and tear of the engine and the special dynamo on the tractor, which formally were the only means of charging the batteries.
Second clock.
Two auto-feed boxes for telegraph forms with fittings for attaching to brackets over public counter.
The original call office circuits in the first vehicle worked on a post-payment basis in all areas. This system had certain disadvantages and the circuits were altered to provide for prepayment as well as post-payment working.

The trailer and tractor bodies of the second vehicle were built b y Messrs. T. Harrington, Ltd., Old Shoreham Road, Hove, Brighton. -W.G.D. & C.F.M.