3 July 1998

Super-strong

stone-picking, Welsh style

By Ian Marshall

MANUFACTURERS do not build equipment strong enough. That is the blunt assessment of Denbigh contractors Edward Contract Cultivations of Bryn Tirion, Bodfari.

Their views are based on 20 years experience designing and building their own machinery for open cast restoration and preparing and constructing public leisure and sports facilities.

Stone removal is an essential element of the work and, over the past two decades, the Edwards – father Derek and brothers Robert and Alan – have fully mechanised the operation.

"It is quicker, more thorough and cheaper than employing gangs of pickers for days at a time," says Robert Edwards.

And much of the initial stages of the operation is done with equipment they have designed and built themselves having found that not only is commercial machinery not strong enough to handle the stresses or operating speeds, it will not cope with the size of material they have to work with.

Handling stone the Edwards way involves either tearing out and removing or burying rubble from as little as 1/4in diameter to rocks up to 1.2m (4ft).

Preparatory work is done with various designs of sub-soilers and stone rakes all working behind the Edwards two Fastracs, a 1135 and a 155 High Speed. Virgin and seriously compacted ground is loosened up to a depth of 100cm (3.9ft) with either a 3m (10ft) twin legged heavy duty sub-soiler – which broke rock in a quarry on the back of a D8 Caterpillar in a previous life – or a 4m (13ft), 7-leg unit made-up in the Edwards workshop.

The aim then is to bring as much stone as possible to the surface, the job of a series of tined stone rakes, the type depending on conditions and the depth of cultivations required.

Shallow cultivations, up to 15cm (6in), is done with a 4m (13ft) Kverneland.

Deep work is the sphere of the yet to be officially named "discy thing", a home-made cultivator train made up of free-floating banks of chisel tines, discs and tines or crumbler rollers, which combine to both break up the soil and crush clods and smaller stones.

Or there is the option of the big blue thing, another home-made trailed cultivator, which does the job through a combination of specially designed cultivator fins, spring tines, a crusher blade and a crumbler roller.

Neither Robert nor Alan have engineering qualifications. "Once the need for a machine has been identified, the overall shape of the machine and the angles of attack of its components are calculated by eye and then refined over successive models – the current big blue thing is mark two," says Alan.

Debris is then swathed with a 3m (10ft) or 4m (13ft) wide combination rake/windrower, before being picked up by either an elevator or a 3.5t bunker collector. Here the Edwards have found commercially manufactured machines which meet their expectations.

"Once at the collection stage we are looking at outputs of up to 120t/hour, depending on conditions. We need two 10t dumper trailers running alongside the collectors," says Robert. "The collectors will take anything that fits into their 2m (7ft) wide, 1m (3ft) high pick-up throats."

A clean product is another benefit of mechanical collection – the spin off being that it can be sold for a range of purposes, from decorative to being used as hard core for roads and tracks.

If stone is to be buried, a powered, Italian-built machine can put material down to a depth of 15cm (6in) at speeds of up to 0.8ha (2 acres)/hr. It has a bladed rotor which throws material against a screen, this allows soil to pass through to be deposited on top of the stones, which can be sieved out down to some 6mm (1/4in) through interchangeable screens.

Having refined their stone collection system, the Edwards intend to add the service to its agricultural arm – "diversifying into specialist areas," comments Robert – where it is seen as an answer to a perceived problem of disposal faced by potato and sugar beet growers who practice stone separation, but do not want to keep the material.

Robert Edwards (left), his father Derek, and brother Alan, believe they are the only firm in the UKto specialise in mechanical stone-picking.