KR-600 with the GH120 head and TGR-155 branch shear for the District Roads Authority (PZD) in Koło

A rig for maintaining the road corridor has been delivered to the Powiatowy Zarząd Dróg (District Roads Authority) in Koło: the six-metre-class ROLMEX KR-600 boom mower, the GH120 mowing head in the 30-hammer version and the TGR-155 branch shear. It is a typical set-up for a unit that has to handle both verge mowing and the removal of scrub and branches encroaching on the clearance envelope with a single carrier. Below we describe what follows directly from the machine’s parameters in such a configuration.

What the rig for the PZD in Koło includes

• ROLMEX KR-600 boom mower – six-metre reach class,
• GH120 mowing head in the 30-hammer version,
• TGR-155 branch shear.

One carrier with an arm and two interchangeable heads cover two different jobs: mowing roadside greenery and cutting woody scrub. Both heads work on the same arm and use the same hydraulic system, so changing the type of work comes down to swapping the attachment, not changing the machine.

KR-600: which parameters decide the match

The product page of the KR600 boom mower from the KR POWER series lists for this model:

• maximum boom reach: 6.5 m,
• power: 68 HP,
• required tractor power: 110 HP,
• minimum tractor width: 220 cm,
• minimum tractor weight: 4500 kg.

The last three items are read together. Power alone is not enough, because with the arm extended, the stability of the rig also depends on the track width and the weight of the carrier – which is why the manufacturer lists the minimum width and weight next to the power. For comparison, the smaller KR520 has a reach of 5.6 m and requires a 100 HP tractor, 200 cm wide and weighing 4000 kg. The 0.9 m difference in reach thus translates into clearly higher requirements for the carrier.

Three design features of the series also matter to a roads authority: mounting on the tractor’s rear three-point linkage, a transport height below 3 m that allows the tractor to be parked without removing the arm, and an independent hydraulic system with an oil cooler and a pump delivering up to 130 l/min. That last parameter comes back with every subsequent head.

How a mowing head is matched to the job

The GH-120 flail head has a working width of 120 cm and weighs 270–340 kg depending on the optional equipment; for arm load calculations it is safer to assume the upper value. The cutting shaft runs at 3000–3100 rpm, the shaft works in both directions, and the inside of the body is protected by an additional HARDOX400 steel liner.

What decides the character of the work, however, is not the body itself but the shaft and the knives or hammers fitted to it. The manufacturer provides for four configurations:

• Precision ROTOR – a shackle-mounted shaft with a Y knife and a centre knife, for precise grass mowing,
• the UniversalROTOR2 universal shaft with Y and YI knives – bushes and twigs up to 5 cm of dry wood,
• T6 hammers on the same universal shaft – woody regrowth up to 6 cm of dry wood,
• a shaft with H360 FORESTAL rotating hammers – shredding regrowth up to 10–11 cm in diameter.

The practical conclusion for a road unit: swapping the shaft or the knife set changes the purpose of the same head, without buying a second machine. The head delivered to Koło is the 30-hammer version.

A branch shear is a different tool from a flail head

A flail head shreds the cut mass and leaves it in place. A shear cuts – it suits places where a branch is too thick for flails and the material is to be cut off whole, for example when restoring the road clearance envelope. In the ROLMEX range, the branch and bush shear comes as the TGR-155 model: working width 1550 mm, maximum diameter of cut material 120 mm, head rotation range 180–235 degrees, weight 240 kg. The stated work rate is 0.2–0.7 km/h, and to work with this head the tractor must have a creeper gear – worth checking before purchase, because not every carrier is equipped with one. The rotation range lets you set the cutting plane independently of the arm position, so the same head cuts vertically at the clearance line and horizontally over the ditch without repositioning the tractor.

The same boom through the whole season

The KR-series arm takes all ROLMEX working heads, not just the mowing ones. For ditch work there is the PR80 ditch cleaner with an 80 cm working disc and a weight of 300 kg, cutting roots up to 10 cm in diameter; fitting and removing it takes 3–4 minutes. For profiling the verge there is the SP90 verge cutter with a working width of 90 cm, fitted with 51 knives made of Hardox 550 steel.

Here the hydraulics question comes back: the PR80 requires a minimum of 110 l/min at 200 bar pressure, or 85 l/min at 300 bar, and the SP90 – a minimum of 110 l/min. The pump delivering up to 130 l/min in the KR POWER series therefore leaves a reserve for attachments other than the mower. When planning a purchase, it is worth settling the full list of heads for the coming years right away, because it is that list, not the mowing alone, that sets the minimum requirements for the carrier and the hydraulic system.