A field strewn with rocks is bad news for power harrows, mowers and forage harvesters.

This fact was not lost on Llantwit Major contractor Rhodri Davies who, two years ago, decided that a mechanical stone and rock picking machine would be a useful addition to his farming and contracting business.

“The industry can no longer afford to use manual labour to pick rocks and stones out of fields as they used to,” he says. “So I thought there would be a demand for a service which could offer stone and rock clearance using a machine.”

Spring 2010 saw him take delivery of a rock picker system built by Canadian company Schulte. The system comprises two machines – one to rake up the stones into a windrow and another to physically gather up the windrowed stones into a hopper and cart them off the field.

Both are powerfully built units which, according to Mr Davies, are clearly designed to withstand a lifetime of serious abuse.

“These machines can handle rocks as big as wheel barrows,” he insists. “And they seem to thrive on the challenge.”

The rake unit, the SRW1400 rock windrower, gets its drive from a pto which is protected from the inevitable shock loads that occur by both a slip clutch and a shear bolt.

The business end of the machine is a 4.3m long shaft on which tines have been welded in a spiral. The 15cm tines are made from 16mm-thick hardened steel – as the shaft rotates they move the stones across the machine to leave them in a windrow at one end.

With a forward speed of just 3kph and the rotor working at 117rpm, it can be a steady job. Output is about one hectare per hour. In some fields where the rock population is not that high it is possible to push one windrow on to another.

“At first, we found it difficult to set up the rake so it could take an even bite at the soil and rocks across the full width of the rotor but we eventually got the hang of it,” he says

With the rocks in a tidy windrow, it’s time for the rock picker to swing into action. The High Rise 8000 is used in an offset position and has a 3cu m hopper which can hold up to 2.5t.

Rocks are swept into the hopper by a hydraulically powered reel having three tine bars which rotate at 36rpm and pull the rocks up and over a sloping grate area positioned at the entrance to the hopper.

“The tine bars are spring loaded so that if they meet a large rock at just the wrong moment the spring stretches to absorb the shock loading,” he explains.

Initially, Mr Davies charged customers by the tonne of stone removed – £10/tonne. But he now offers an hourly rate for the two machines plus one tractor and operator – the other tractor and operator is provided by the customer – for a charge of £60 per hour.

“There’s no doubting the potential of the machines,” he says. “They are more than capable of doing any work I require of them but the problem has been finding a window of opportunity to do the work.”

“I’m confident we shall see work for the machines but not perhaps on the scale or the type of work I first envisaged. I can see us doing more work in smaller areas where there is a concentration of rocks or where the land has been disturbed by say, a new pipeline but as for whole field jobs, I am not too sure.”