GPO Vehicles

LINE CONSTRUCTION UNIT (Experimental)
Reference:- I.P.O.E.E.J. Vol. 55, Part 4

Application Pole erection and recovery and all forms of overhead construction.

General description
The unit described is the American Tel-E-Lect line construction unit and comprises a L.H. rear corner mounted derrick with pole hole borer, complete with utility body. The vehicle on which the equipment is mounted is a forward drive BMC 5/7 ton chassis/cab.

Stabilizing jacks are provided to maintain stability during lifting and boring operations.

All movements of the derrick, borer and jacks are hydraulically controlled from a control panel at the rear of the vehicle. An auxiliary hydraulic connection enables a pole jack and tamper supplied with the unit, to be operated from the hydraulic system. The derrick has full circle slewing and an extendable section on which the borer is mounted enabling holes to be bored at a radius of up to 23 feet. A fibre-glass cage can be mounted on the end of the derrick which enables overhead work to be carried out up to 34 feet above ground. A pole bolster has been added which enables a number of poles to be carried on the unit.

Capacity

Derrick - 1 ton at 4 ft. radius height 34 ft. max. - 10 cwt. at 23 ft. radius height 3.5 ft. mm.

Pole Jack - 20 tons max. lift.

Borer - 12 in. and 16 in. diameter holes up to 8 ft. deep.

Dimensions - Travelling position - length 21 ft. 9 in.; Width 7 ft. 6 in.; Height 12 ft. 3m.

Weight - 7.5 tons unladen.

Transport Maximum permissible speed on Public Highway - 40 m.p.h.

Capital cost - £6,500.

An extract from
The Post Office Electrical Engineers Journal
Volume 55, Part 4 - Dated 1962

A LINE-CONSTRUCTION VEHICLE
By W. C. Ward
 

A new type of utility vehicle equipped with hydraulically-operated mechanical aids is described. These aids include a derrick that can be rotated through 360 degrees, a pole-hole borer and a heavy-duty winch.

INTRODUCTION

The line-construction vehicle is essentially a utility vehicle for use by a general-purpose external working party. It is equipped with a versatile power-operated derrick and a heavy-duty winch; a pole-hole borer may be permanently attached to the derrick if required. Units of this type have been in use in America for a number of years, but until recently all had derricks, operated either from the front or the rear of the vehicle, that were incapable of rotation. While such units can operate efficiently where there is space to manoeuvre, they would be severely handicapped under the conditions usual in the British Isles, where telecommunications external plant is almost invariably at the roadside, and a large vehicle positioned across the highway could not be tolerated in most situations where it would have to work.

Recently, corner-mounted rotating derricks have been developed in America, and these enable the derrick and pole-hole borer to operate over a large area with the vehicle parked at the kerb-side, and there appears to be good scope for the operation of such equipment in this country. A small number of similarly-equipped vehicles is therefore being obtained for trial. Their use should remove much of the heavy lifting and digging from external work and should increase output. The fact that ample power is available for all operations and that all loading and unloading can be carried out mechanically should materially reduce accident risks.

THE NEW VEHICLE

The chassis is a 5/7-ton British Motor Corporation diesel unit (i.e. a nominal 5-ton chassis with 7-ton 2-speed rear axle). The drive from the rear of the engine is fed to a split-shaft power take-off that enables full engine power to be used, if required, to drive hydraulic pumps for operating the mechanical accessories. This full-power take-off is in effect a mechanical switch that connects the drive either to the back axle for propulsion or to the hydraulic pumps for operating the mechanical aids; it is controlled electrically from a switch in the cab. When the power take-off is coupled to the hydraulic pumps, a brake is applied to the shaft that drives the vehicle rear axle, to take the place of engine braking.

The tandem hydraulic pumps circulate oil at 2,000 lb/in sq and 45 and 14.4 gallons/minute, respectively. Alternatively, if facilities for operating a pole-hole borer are not needed, a single pump can be used and a light-duty power take-off, known as an S.A.E. (Society of Automobile Engineers) power take-off, is fitted to the side of the gearbox.

The body is of plated-steel construction and of the open-well type, with cupboards and lockers on the outside; the open well in the body facilitates loading and unloading. The derrick and winch between them can be used to load and unload all heavy stores and tools. The side cupboards and lockers store the lighter tools, stores and clothing; they give good access without the necessity for climbing inside the vehicle, although they have the disadvantage that some are necessarily on the side of the vehicle exposed to traffic.

The vehicle is intended for operation by two men, and the bodywork is not designed for conveying additional staff. The vehicles will probably be used in conjunction with 110-volt generating sets and a range of electrically-operated tools, and these, together with the other mechanical aids, should go far towards mechanizing the work of external working parties.

Derrick
The boom of the derrick is 17 ft 2 in. long from its centre of rotation, but it has an extending section called a 'stinger' that extends the length to 2.5 ft. The derrick reaches from ft above the ground to a maximum height of 33 ft. It has a head sheave over which the winch-line passes and it can lift 2,000 lb at 23 ft radius. It can be rotated continuously in either direction.


Winch
The heavy-duty winch is mounted immediately behind the cab and is fitted with a wire-rope winch-line 300 ft long that can be passed over the head sheave of the derrick or can be used for a direct pull. The winch-line runs under a false floor in the vehicle body, so that it is not obstructed by any tools and stores carried in the vehicle.

The winch is driven by a hydraulic motor and has a maximum pull of 15,0001b. It has a shaft extension, accessible through an aperture in the side of the vehicle body, to which can be attached a wire-recovery reel or a capstan that can, for example, be used for pulling cable.

Stabilizers
Hydraulically-operated stabilizers are provided at the rear end of the vehicle to give the necessary stability when the derrick is in use. These comprise an outrigger on the corner of the vehicle where the derrick is fitted and a simple hydraulic jack on the opposite corner.

Pole-Hole Borer
The pole-hole borer is driven by a hydraulic motor of approximately 35 h.p. It is suspended at its upper end from the derrick and is strapped back to the derrick when not in use. Downward thrust is applied by the derrick operating under hydraulic pressure, and by control of the derrick position the angle of boring can be determined, e.g. when setting stay anchorages.

A fibre-glass boom-extension and personnel bucket can be fitted to the derrick for lifting men aloft, e.g. for tree cutting, aerial-cable maintenance or work on decayed poles. If a personnel bucket is fitted, the hydraulic controls may be extended to the bucket if required, and under these conditions a hydraulic power supply is available on the bucket fox operating tools. The whole of the bucket system is insulated to guard against accidents due to contact with power wires.

The derrick can be used for a variety of operations, including loading and unloading the vehicle itself, loading and unloading poles on and from pole stacks and stores-carrying vehicles, setting or recovering poles, supporting decayed poles, lifting personnel and steering the pole-hole borer.

When not in use, the boom extension is retracted and the derrick stows diagonally across the vehicle body.

Auxiliary Functions
At the rear of the vehicle a hydraulic power take-off is provided for operating auxiliaries such as an earth-punner or a 25-ton pole-pulling jack.

Control Panel
A control panel is fitted at the rear of the vehicle so that the operator has a clear view of all the functions. Controls are provided for extending and retracting the stinger, lifting and lowering the boom, rotating the derrick, operating the borer, and controlling the stabilizers, hydraulic power take-off and governed engine speed. The last may be varied according to the power requirements of the operation being performed and is increased or reduced in steps by flicking a switch up or down.

Last revised: January 21, 2024