Shearex VM-25SK excavator mulcher

The case for a 70 cm head on a 5 to 8 tonne carrier

The VM-25SK is the smallest head in the Shearex VM excavator mulcher range, and the only one whose argument is access rather than output. A 5 to 8 tonne excavator can sit on a sealed shoulder and treat the far batter of a table drain, work the wet side of a boundary fence, or reach under a guardrail nothing else will get to. That reach is what the buyer is paying for. The 70 cm rotor is the most a boom this size can swing responsibly, not a production claim. Where the unit of work is hectares rather than lineal metres, the VM-35SK starts the answer and the VM-40SL finishes it.

Much of the commercial case sits in what the carrier avoids. A 7 tonne machine travels on a tandem float behind a rigid truck, occupies a shorter lane closure, and can be walked through a gate. Those savings repeat on every mobilisation, and on the short, scattered jobs councils actually issue they often outweigh the fact that a larger machine would have finished sooner.

Reading 70 cm and 13 cm as job-planning numbers

The published cutting width describes the cut, not the working width. On this class of boom the practical measure is how far the operator sweeps before tracking forward again, so plan the day in metres of drain line or fence line rather than area. Under 13 cm, the published optimal target material diameter, is the second planning number, and on a light carrier it is also roughly where the material starts pushing the boom around instead of the other way round. Blackberry, lantana, privet and roadside saplings sit inside it; maximum diameter versus production diameter explains why quoting on the occasional big stem is how a small contractor loses a season.

At 499 kg the head is light in absolute terms and awkward in relative ones, because a 6 tonne excavator stretched out over a drain has little in reserve. Take the mass of the configuration quoted, add bracket and hoses, and read it off the chart at the radius the operator will work at rather than the one that flatters the machine; lift chart and attachment mass sets out the method.

Hydraulic circuits, the door and the option stack

Every VM head ships with a hydraulic door as standard, and because this is the smallest carrier in the family it is where the circuit question bites hardest. This section is the full treatment for the range; the larger VM pages point back here.

The rotor motor takes the pressure and return lines and needs a case drain returning to tank with minimal restriction, because case pressure is what kills motor shaft seals on a mulcher long before anything else wears out. Shearex’s guidance is that the door runs on those same pressure and return lines with an electrical diverter deciding whether oil goes to the rotor or the door cylinder, so the carrier has to supply a switched feed in the cab as well as the plumbing. On a machine that left the factory with a hammer circuit and a single toggle, that feed is a wiring job, not a plug.

The options change the picture again. Tilt is better served by its own double-acting auxiliary line than by being diverted off the main circuit, because an operator tilting the head while the rotor is loaded wants both live. Tilt and grapple together is best done with two double-acting auxiliary circuits plus the case drain, which at this tonnage frequently means an auxiliary kit the machine does not have. A heel is the least demanding of the three and the least often needed at this size.

What a light carrier can actually supply

Continuous flow of 57 to 83 L/min is modest against the rest of the range and demanding for this tonnage. The published minimum carrier power of 50 hp (37 kW) rules out the soft end of the 5 tonne market outright, and the VM range’s maximum operating pressure of up to approximately 410 bar has to be checked against the carrier’s auxiliary relief setting rather than assumed. The real limits on a machine this size are rarely the pump: they are a small tank, a small cooler, and the fact that many 5 to 8 tonne excavators leave the factory with no case drain at all.

Ask for auxiliary flow measured under load at temperature, the pressure available at that flow and the return pressure the carrier imposes, then put those figures through the hydraulic power calculator. The full worked arithmetic lives on the VM-50SR page; here it is enough to say that a carrier sitting on the published minimum will stall the rotor in dense material. See hydraulic matching and hydraulic cooling and heat.

Where the VM-25SK earns its keep

The natural work is council parks and urban vegetation, tight-reserve road corridor clearing and asset-protection work inside bushfire fuel reduction programs. Record output per shift as lineal metres treated at an agreed finish, and log the knockdown pass separately from any tidy-up pass. Tooling choice follows the ground rather than the vegetation: drains, batters and old road formations hide stone and buried concrete, which argues for carbide on most corridor contracts even where green material would cut faster on blades; blades versus carbide teeth weighs the two.

Where it runs out, and what replaces it

There is nothing smaller in the catalogue, so the step down leaves the category: if the work is mostly grass and light scrub, a slasher does it for less. The step sideways is worth modelling. On flat, traversable ground the front-mount HM-60 covers more than twice the width per pass and travels while it cuts; excavator mulcher versus skid steer mulcher sets out where each wins. The step up is the VM-35SK, triggered by stems consistently over 13 cm or by sites open enough that reach stops being the point.

Consumables on a head that works part of the year

A small operator is the most exposed to a parts delay, because the attachment only earns in the weeks it is booked, so ask Machinery Specialist what sits in Australian stock and what comes from the factory; wear parts to price before buying lists what belongs in the quote. Mulching packs dry fines into the belt housing and the carrier’s engine bay, so a daily blow-down and a weep check are fire housekeeping rather than tidiness; see fire risk in clearing operations.

Reaching over a drain: what the geometry really costs

The selling point of this head is also the hardest part of operating it. Working across a table drain means the machine stands on the shoulder with the boom extended over ground it cannot occupy, and three things change at once. Lift capacity falls with radius, so the margin over 499 kg plus bracket and hoses shrinks exactly where the operator needs the most control. Visibility of the rotor drops, because the head is below the track line and often behind the drain lip. And the recovery position, the place the operator retreats to when something binds, is behind the machine rather than in front of it.

The practical response is to plan stances rather than to chase material. Work out how much drain length a single stance covers at a comfortable radius, then track that distance and repeat, rather than stretching one stance to save a move. On a light carrier the time lost tracking is small and the time lost recovering a stalled rotor at full reach is not.

Lane discipline sits on top of that. A machine working a road reserve has a slew envelope that crosses the traffic lane whether or not the operator intends it to, so the exclusion zone has to account for the tail swing and for material thrown by the rotor, and everyone on site should be working to the relevant WHS procedures and the manufacturer’s instructions rather than to habit. Where the work touches remnant vegetation, clearing may also need approval under state and local rules; native vegetation approvals sets out what to check before the machine is booked.

Why traffic control often decides the job, not the head

On council and road reserve work the machine is rarely the largest line on the cost sheet. Traffic management usually is, and it is charged by the day regardless of how much mulching gets done inside it. That has two consequences for a head this size.

The first is that production rate matters less than setup count. A contractor who can treat 400 metres of reserve inside one closure is better off than one who covers 600 metres across two closures, even though the second is faster on paper. The second is that a small carrier earns its keep by needing a smaller closure in the first place: a 7 tonne machine working within the shoulder often needs a shorter, simpler arrangement than a 20 tonne machine whose tail swing crosses the lane.

Buying used, and what to look at first

Small mulching heads lead hard lives in the hands of general contractors, and a used VM-25SK is worth inspecting in a specific order. Start at the rotor: check balance by running it up off the ground and listening for a beat, then look for missing teeth or holders that have been welded back on crooked, since a rotor that has lost balance will chew bearings regardless of how it sounds on the day. Move to the belt housing and look for fines packed hard against the belt, which tells you what the daily routine was. Then check the door for bent linkages and the case drain fitting for signs it was blanked off and run without one, which is the single most expensive shortcut an owner can take on a head like this.

Finish with the skid shoes and liner, because those tell you the ground it worked: evenly worn shoes suggest paddock and verge work, gouged ones suggest rock. Inspecting used forestry attachments covers the full process, and on a head this size the difference between a good example and a tired one is usually a year of someone else’s housekeeping.

Confirm before ordering

• Auxiliary flow measured under load at temperature on the specific 5 to 8 tonne machine, not the brochure figure
• A case drain routed to tank, and the return pressure the carrier imposes with it fitted
• Switched electrical feed in the cab for the door diverter, and who is doing that wiring
• Whether tilt or grapple is wanted, and therefore whether a second double-acting circuit is being built
• Head mass as configured, plus bracket and hoses, read off the chart at working radius over a drain
• Tank and cooler capacity for continuous work in summer
• Australian stock for teeth, holders, belt and bearings, and the delivered price with bracket and hoses

Frequently asked questions