Timberdown
How to make a profit in thinnings
Nobody expects the Timberdown NH-1900 harvester to add significantly to the growing stacks of timber that are lining the roadsides in our larger coniferous forests. After all, it is no heavyweight. With a base machine weight of a fraction over 5 tonnes and a machine width of only 1.9 metres, its role will be markedly different from that of the machines churning out the softwood sawlogs that currently appear to have outstripped the British sawmillers’ demands.

When economic downturns cause even large-scale harvesting operations to look distinctly unhealthy, there may be those who advise that any thoughts of early thinning operations be quickly eradicated from the mind. On the other hand, there will be some who see the slow-down in produce uplift as an opportunity to concentrate on timber that requires a lesser investment – both in terms of stumpage price and machinery: the small coniferous blocks, for example, dotted about our countryside, that in recent years have often been passed over by the timber buyers.

Small tree size, poor timber quality and quite often a total lack of access (added to a shortage of available contractors) have often persuaded all concerned that harvesting many of these scattered stands was just not a financially viable option. In many cases, the postponement of what many forest managers would still consider vital silvicultural operations has exacerbated the problems – stand stability has been compromised and the chainsaw operator, when he eventually arrives, knows he is going to struggle to ‘take down’ many of
the trees.

The Timberdown NH-1900 harvester is the machine that has been designed to bring this largely untapped resource into viable production – despite the currentgloomy economic outlook. There are those who are confident that it will be able to bring back the viability of thinning operations in patches of woodland that have been seen by many as economically unworkable.

Long experience of compact skid-steer machines had led Northumbrian contractor Gregor
McArthur to investigate the possibility of using a mini-excavator as a base for mechanised harvesting. Now on active service in the north of England, the Timberdown harvester has already been put through its paces on a couple of contracts within easy striking distance of the McArthur Forest Services base at Whitley Chapel, just south of Hexham. It proved competent to handle the drawn out trees of an overdue thinning in the Slaley area in the south of the county.

It was also able to show what it could do north of the River Tyne in the heart of Northumberland’s farming country, near the village of Stamfordham. Both sites, as it happens, were in UPM-Tilhill’s portfolio of contracts and north of England harvesting manager Nick Martin was pleased to see the trees starting to come down: not least because the owners
can see a profit – albeit a small one – for the produce that comes out of the woodland. Both Nick Martin and Gregor McArthur are confident that the machine to bring marginal value stands of smaller timber back to profitability is the Timberdown harvester.

Nick Martin sees the main benefits of the system in allowing the undertaking of a first thinning without having to remove a rack, thus maintaining the canopy and reducing the risk of windblow; thinning for continuous cover given the light footprint; and also recovering biofuel from undermanaged plantations. About 500 tonnes of Norway spruce at South Fens, near Stamfordham, was due for clearfelling and replanting. Not the sort of contract where it was envisaged that the Timberdown harvester will compete most effectively, but it presented
the ideal opportunity for the Bobcat 337/Kesla 20SH combination to show its capabilities.

Some machine specialists may well have been sceptical that such a lightweight base machine could perform adequately in conjunction with a standard harvesting head. The carrier, in fact, would weigh in at a little over its plated weight of 5100kg. While the standard Bobcat
ROPS cab complies with all safety requirements for construction purposes, additional forestry guarding was fitted by McArthur Forest Services. As is commonly the practice with Bobcat’s operating attachments considerably heavier than the fairly standard 610mm bucket, counterweighting on the rear of the machine was also increased.

A further modification to the standard Bobcat 337 was the fitting of an additional hydraulic pump to bring the auxiliary hydraulic capability well within the range required for a harvesting head. As a machine designed for construction use, power from the Kubota 4-cylinder turbo diesel engine is primarily directed to the traction, slewing and boom functions. Out in the forest, the hydraulic demands of these operations will normally be considerably less than on the construction site and an extra percentage of engine output has been reserved for harvesting head operation.

While the Bobcat range of tracked excavators is wide, machines suitable for conversion to timber harvesters are limited; especially given Gregor McArthur’s determination to keep the machine width below 2m. Despite its small size, the 337 was able, with modifications, to take
on the role of a carrier for Kesla’s smaller stroke harvesting head, the 20SH.

The Kesla 20SH weighs in at 520kg (without rotator) and has a maximum cutting diameter capability of 450mm. Saw motor displacement is 10cc. The stroke technology endows the three delimbing knives (two moving, one fixed) with a substantial delimbing force (41kN) and a minimum hydraulic requirement. The upgrading of the Bobcat 337 by McArthur Forest Services has brought the auxiliary output of the Kubota diesel into the specified range for the 20SH (a power of 20-44 kW and an oil flow of 70-120 l/min at 175-220 bar).

With the unit designed to be capable of ‘rackless’ thinning operations in young crops, the Bobcat (a ‘G Series’ model built in 2005) retains its Bridgestone rubber tracks to minimise any risk of damage to the remaining stems and root systems. While the 337 is not one of the manufacturer’s ‘zero tail swing’ options, the main boom side slewing facility will certainly prove of great benefit in the tight spaceswhere the Timberdown harvester will be expected to perform.

The Czech-built Novotny forwarder was also being assessed on the South Fens site for its suitability to partner the Timberdown NH-1900 harvester. One basic requirement was obvious from the machine’s specification sheet – an overall width compatible, when fitted with narrow tyres, with that of the Bobcat. An unladen weight that allowed similar savings in transport cost onto and off site was also critical. If demand dictates, the Timberdown may in future be
adapted to carry a feller/buncher for harvesting the raw material for chip or firewood production. The chosen extraction system will need to be able to cope with those products,
too.

The Norway spruce on the South Fens harvesting site had been allocated to contractor Darren Turnbull (DJ Contracting of Stannington near Morpeth) by UPM-Tilhill for motor/manual felling and processing. Inside the stand there were few heavy branches to challenge the
delimbing power of the Kesla stroke harvesting head, but the chainsaw and its operator had proved invaluable in cutting a way in through the rough ‘outsiders’ edging the rolling Northumbrian arable fields. Strangely, the development of the Timberdown harvester is likely
to increase rather than decrease the amount of chainsaw work Darren Turnbull and his regular subcontractor, Richard Thornley, undertake for UPM-Tilhill in England’s border county. After all, while the aim of the design is to bring into production thousands of hectares of woodlands where the exclusive use of motor-manual harvesting operations would see the likes of Darren and Richard really struggling to earn a living, there will be fairly few sites where a chainsaw operator will not be required in some capacity.

Such was the case with the oversized and very roughly branched edge trees at South Fens. Nick Martin already has a considerable number of contracts in the area which will see the
Bobcat/Kesla combination making its mark. Enquiries from any woodland owners who feel they may be able to benefit from the new development in timber harvesting technology will, of course, be very welcome. Hilary Burke

The powerful delimbing capability of the stroke head will no doubt be of
benefit in the rougher crops encountered by the Timberdown harvester. The
‘ProStroke’ partial stroke function assists the processing of crooked stems and
the head is well suited to handling whole trees delivered to a landing.