Three Steyr sets with KR 600 Power+ arms for the Provincial Road Authority in Lublin

The Provincial Road Authority in Lublin (ZDW) has taken delivery of three complete sets: Steyr tractors equipped with Rolmex KR 600 Power+ hydraulic arms. The machines will work in the Provincial Road Districts (RDW). Below we describe what the set included and the criteria by which such a machine is matched to the tasks of a road manager.

What the delivered sets included

• carrier: a Steyr tractor,
• hydraulic arm: a Rolmex KR 600 Power+ power arm mower,
• a hydraulic system with an output of 130 l/min at a pressure of 230 bar,
• a mowing head with a triple, replaceable skin made of Hardox 550 steel.

The data sheet of the KR600 power arm mower from the KR POWER series gives a maximum arm reach of 6.5 m and a power of 68 HP. The requirements for the carrier are 110 HP of power, a minimum tractor width of 220 cm and a minimum weight of 4500 kg. By comparison, the smaller KR520 has a reach of 5.6 m and requires a tractor with 100 HP of power, a width of 200 cm and a weight of 4000 kg.

What a road authority uses such a machine for

A power arm mower works to the side of the tractor and below the level of the carriageway, so it makes it possible to mow the verge, the slope and the bottom and slopes of the ditch without driving the machine down into the ditch. The operator drives the tractor on the hard surface while the tool works off it. The flail head shreds the cut material instead of laying it in a swath, so it usually does not have to be collected.

A reach of 6.5 m translates directly into the width of the strip processed in a single pass and into the ability to reach the counter-slope of a wider ditch. For typical verge maintenance the 5.6 m version is enough, while wide drainage ditches and high slopes are an argument for the longer arm.

What 130 l/min and 230 bar give in practice

Pump output and working pressure decide how much power reaches the head shaft, and therefore whether the machine will hold its revolutions under load. The KR POWER series has an independent hydraulic system with a pump delivering up to 130 l/min and a high-performance oil cooler with a thermostat, a soft start function and a self-cleaning reverse rotation. The series data sheet also lists the possibility of fitting an additional hydraulic pump, for example for a grass blower or a sign washer.

Spare output has a second meaning as well — it decides which working heads can be supplied from a given arm. The design provides for an additional hydraulic return line straight to the tank, intended for operating additional working heads.

The carrier is chosen in three dimensions

Tractor power alone is not enough. With the arm extended, the stability of the set is also decided by the width and weight of the carrier, which is why the KR600 data sheet gives all three values together: 110 HP, 220 cm and 4500 kg.

Matching the head to the job

One arm handles several different jobs during the season, and the character of the machine is decided by the head that is changed:

• GH-120 and GH-130 flail head — 120 or 130 cm wide, weighing 270–340 kg and 280–350 kg respectively, cutting shaft speed 3000–3100 rpm; the choice of rotor and blades changes the working range from precise grass mowing to shredding regrowth up to 11 cm on H360 FORESTAL rotating hammers,
• TGR-155 cutterbar — working width 1550 mm, maximum diameter of cut material 120 mm, head rotation 180˚–235˚, weight 240 kg; the output of 0.2–0.7 km/h given in the data sheet is worth taking into account when planning the brush clearing schedule,
• PR80 ditch cleaner — 80 cm working disc, weight 300 kg, root cutting up to 10 cm, required minimum oil flow 110 l/min at 200 bar; fitting and removal take 3–4 minutes,
• SP90 road side milling machine — working width 90 cm, 51 blades made of Hardox 550 steel, weight 300 kg, required minimum oil flow 110 l/min; it cuts away the turf built up at the edge of the carriageway and restores water run-off from the surface.

The same two limitations apply to each of these heads: the oil flow available in the working tool circuit and the permissible load on the end of the power arm, which decreases as the arm is extended. Three hundred kilograms of attachment is a figure that has to be compared with the lifting capacity of the specific arm, and not assumed in advance.

Everyday operation in the road right-of-way

Working under traffic sets requirements beyond mowing itself. In the KR POWER series the transport height of the machine is less than 3 metres, and the tractor can be parked without removing the arm. The equipment includes a set of road lights and a stiffened structure improving safety in transport and at work, and control is handled by a proportional joystick with a head soft start system. An FFS floating head system and an optional SV camera are also available. The main components come from European suppliers — Danfoss and Casappa.

For units planning a similar purchase we recommend preparing three pieces of information before the request for a quotation: the make, model and power of the tractor, the list of tasks for the season, and the actual oil flow in the working tool circuit. On that basis we confirm the choice of the arm and of the set of heads.