8 August 1997

High hopes for extension

"HARVESTING standing oilseed rape is not so much about the threshing as the feed of the crop into the combine," maintains Martin Smart, farm foreman for Wadswick Farms based at Corsham, Wilts.

Hence his interest in a new rape header extension which fits on to an existing conventional combine header and, he claims, increases output by as much as 50%.

Built by Austrian manufacturer, Biso – a company probably better known in the UK for its straw chopping attachments – the CX 100 header extension shifts the point at which the rape is cut in front of the table auger forwards by about 70cm (28in).

This allows the rape to fall headfirst towards the auger and provide an even feed – rather than have it bunched up against the auger and knocked about by rotating sails as it awaits its turn to move along the bed and climb the elevator. Slight steps in the extension prevent the crop falling off the table.

A totally independent unit, the extension has its own bed knife and two hydraulically powered vertical, double reciprocating knives, one at each end of the bed to allow the combine to work in bouts.

An initial modification to the existing header – four bolt-holes to enable four over-centre hooks to be attached, and an extra pulley on the knife drive to provide hydraulic power for the vertical knives and a mechanical drive for the extensions own bed knife, is all that is required. Biso claims it can be fitted or removed in a matter of minutes.

At Wadswick Farms, where some 180ha (450 acres) of oilseed rape is grown, the extension is attached to a 20ft header belonging to a New Holland TX68 combine.

"We normally harvest with a 24ft header," says Mr Smart, "But with only one extension in the UK at present we had to borrow a smaller header from Biso supplier, APH based at Peterborough."

Even so, work rates have improved dramatically, he claims. "Weve been harvesting over eight acres an hour rather than the four or five with our standard 24ft header. And the vertical knives are so much better than the electrically powered single knife we used before."

Impressive as this clearly appears, use of the Biso extension calls for an extra element of driver skill.

"You have to be very careful when entering a crop," explains Mr Smart. "With the length of the extension it is possible to have over 3ft of crop, 20ft wide keen to climb up the elevator and into the drum – all in one go. To avoid sudden, time wasting drum chokes, you have to ease it into the crop, usually at an angle – but once the crop is flowing you can just keep driving."

APH plans to have a range of Biso CX 100 extensions available for next years oilseed rape harvest. A 20ft version carries a £7444 price tag and a 24ft, £8098.n

Biso extension attached. Note the extra distance between knife and auger the system affords, which allows the crop to flow into the combine. Inset: "Output improved by up to 50%," says Wadswick Farms foreman Martin Smart.