GPO Vehicles

Make AB Westerasmaskiner
Model Snow-Trac ST4
Type Caterpillar Type Vehicle
Body Builder Petrol
Use Snow Emergency Vehicle
Registration Number BYM 572B
Fleet Number Ranges 19537 (BYM 572B) 1964
200835 to 200837 (EJJ 360C - 361C) 1965
200893 (JLO 55D) 1966
Date of Vehicle February 1965 (top picture)

General description and facilities
The 'Snow-trac' is a fully tracked snow vehicle, designed to run on reinforced rubber tracks which give a weight distribution 3/4lb. per sq. in.  The vehicle has rear access, seats for five passengers and a driver and left-hand drive car-type controls.  It is powered by an air-cooled Volkswagen engine.  Items of load may be carried on the external racks provided on each side of the vehicle.
The 'Snow-trac' will climb a 370 slope in deep or loose snow and will traverse a 370 side slope safely.  It is provided as part of the Snow Emergency Units (see A 0031) to be located at strategic centres for access to stations isolated by heavy snowfalls.  It may, however, be operated on rough, marshy, hilly terrain, where access to a difficult site is required on a temporary basis, i.e. outside television broadcasts.  The 'Snow-trac' is transported on a light two-wheeled platform trailer and is normally towed by a Landrover as near as possible to the vicinity of the emergency access point.  The transporter may be trailed by the 'Snow-tract if necessary.



Emergency snow vehicle unit Aberdeen

How to deal with snow
Taken from External Plant News - No. 3 January 1967

Not so many years ago, an emergency attendance at a station isolated by snow often meant one of the hardier spirits donning snowshoes for a lonely walk through the snow, perhaps dragging an improvised sledge.  Today, such emergencies are dealt with by one of five strategically located Snow Emergency Units.

The Snow Emergency scheme is a comprehensive national one, justified by the growing multiplicity of high revenue earning stations, particularly Microwave Radio Stations, located on remote sites.  Its guarantees of service are:-

(1) Access within 24 hours to deal with urgent faults.
(2) Access within 7 days for refuelling.

Each Snow Emergency Unit comprises a snow vehicle - the Snow-Trac - on a transporter trailer towed by a Land-Rover and it is always accompanied by a specialist snow vehicle driver.  The unit moves into the snow belt as far as possible by road before the Snow-Trac is unloaded; this reduces the distance to be traversed by the relatively slow moving snow vehicle (top speed 15 m.p.h.).

No engine freezing problem here as it has a 1200 c.c. air cooled engine unit.  The vehicle's dimensions are, length 12 ft., width 6 ft. 3 in. and height 6ft. 3 in.

The Snow-Trac is a fully tracked vehicle of relatively light construction-22 cwts. unladen and with the driver on board exerts a pressure on snow of only 0.75 lb. per square inch, which means that it leaves an impression of a little more than 1 in. deep in soft snow.  It will carry a load of to cwts. and can tow a further 10 cwts.  The tracks are twin fabric reinforced rubber bands with metal cross pieces which take the drive via forward mounted cog wheels; the other 14 wheels are rubber shod. The method of steering is by variation of the gearing to the individual tracks, giving a turning circle of only 8 ft. 3 in.

Within the cab the controls have the conventional look of car controls with steering wheel, gear lever - four forward speeds plus reverse - accelerator, foot-brake and clutch, although the driving technique is somewhat different.  Sitting high behind the front-mounted engine, the driver has a splendid view and can see the ground very close to the nose which is an important point in keeping a sharp look out for protruding rocks that could damage the tracks.  Its progress is relentless, up, down or across steep slopes and it is only likely to be defeated by hard icy slopes at approximately 45 degrees.

Not only does this vehicle have excellent performance in snow under the most awkward conditions, it is equally at home on a heather clad hill-side, marshy ground or rough tracks; thus it has uses for exceptional access problems outside the snow season.

There are many Snow-Tracs operating in remote districts, by concerns other than the Post Office and the snow emergency scheme allows for the friendliest possible co-operation with such operators in time of emergency.

The Snow-Trac vehicle is towed by the Land-Rover as far as possible by road.
Load-carrying platforms are provided above the tracks.
The seven-seat closed cabin version of the Snow-Trac adopted as the standard Post Office snow vehicle


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Last revised: February 07, 2021