Farm Ireland

Wednesday 21 February 2018

Mercedes' mega mower more than makes the cut

Specialist hedge and verge trimmer is extraordinary bit of kit

Bruce Lett

Hedgecutting and verge mowing in Ireland is carried out principally by tractor and hedgecutter combinations. There are many different specifications of hedge cutter but they can roughly be divided into two categories, farmer- specification machines and contractor-specification machines. There are more specialised trimming systems available, though, particularly on the continent.

For maintaining grass margins and hedges they have two or more hedge trimmers mounted up front on a machine. To my surprise, there is one such specialist piece of kit here on our shores, a Mercedes Benz Unimog, which is equipped with two verge mowers up front.

This unusual machine belongs to Motor Distributors Ltd, who is the importer and distributor of Mercedes Benz cars and commercial vehicles here in Ireland. It is the company's demonstrator machine. The Unimog falls under the commercial vehicle wing here in Ireland and used to stand beside the MB Trac, Mercedes Benz's tractor once upon a time.

There are many types and models of Unimog available and many variants and build specifications within these. This Unimog, though, is a U400, which is certainly the most 'different' looking of the Unimog family and perhaps the closest Unimog relation to a conventional tractor. In layman's terms it is part truck, part tractor, but Mick Merrigan, area service manager with MDL, gives the 'Mog' its correct title of implement carrier.

I visited the outfit in Kildare to see it in action trimming the roadside, with MDL demonstrator driver Heinz Eggert at the wheel. Equipped with verge trimmers from German firm Mulag, the Unimog can 'trim' two 1.2m-wide strips in a single pass. Both units operate at the front of the Unimog where visibility is excellent.

A PTO-driven hydraulic pump supplies the oil for the hedgecutter heads. There are front, mid and rear PTO options available on the Unimog.

Before trimming can begin, the front axle of the Unimog has to be 'locked' because, like a truck, it has suspension on all four corners and would be a little unstable with hedgecutters hanging out to one side. In transport, the front mowing unit is folded neatly into the Unimog, while the trimmer arm is slung over the Unimog's cab resting in a cradle in the rear.

Going to work, the front unit folds out automatically while the larger and more conventional trimmer is manually swung out from the rear into work from the in-cab controls.

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Marks on the jib and boom indicate that the arm is clear of the cab and there is also an additional guide on the arm's slewing unit to aid the positioning of it in the rear storage position.

In work, the smaller unit is fully automatic in its operation with sensors in its rear roller that move the unit to contour the ground.

This unit will also cut around a pole or sign -- a sensor bar at the front detects the object and operates a slewing ram to steer the head around the object. The big arm hedgecutter similarly follows the contours on the ground but requires more operator involvement to negotiate around obstacles.

The big hedgecutter can slide the full width of the front of the vehicle for extra reach and manoeuvrability. The heads on both units are primarily for cutting grass and light material; the lads at MDL also have a heavy-duty finger-bar type head for the big hedgecutter that can cut branches up to 80mm.

The demo Unimog U400 has a 200+ hp engine powering the vehicle, which is equipped with a three-way tipping body, multiple hydraulic points, and permanent four-wheel drive with diff locks all-round. The transmission is similar to what is used in the Mercedes Benz trucks, only with more gears and an auto-reverse facility.

The intelligent-shift automatically selects the appropriate transport gear. An auto-reverse facility allows reverse to be pre-selected and when the clutch is pressed the electro-pneumatically controlled transmission will select reverse. There are road, working and crawler gear ranges available on the Unimog. Tyres used are 365/80-R20s all-round, but to aid ground clearance on these sized wheels the Unimog uses portal axle-reduction units to keep the axle clearance height high above the mid-wheel position.

The Unimog is a specialised and extraordinary vehicle, operating on the fringes of the tractor world. Here it demonstrated just one of its many capabilities with the hedgecutters attached.

Last winter, with the Mulag hedgecutting unit removed from the front DIN attachment plate, Heinz had the rare opportunity to attach the snow plough up front for some snow-clearing duties. Also on the rear of this demonstrator machine there is a Finnish-made Oy Coveston back-actor which, as Heinz demonstrated, could lift and handle a half-tonne fertiliser bag with ease.

Irish Independent