Attachments — Shears, Grapple Saws and Grapples

Tree shears

Tree shears are one of the fastest-growing attachment categories because they turn ordinary excavators into controlled tree-cutting machines.

They are particularly attractive for road clearing, utility corridors, regrowth control, invasive trees, plantation thinning, farm clearing, biomass, fence-line clearing, shelterbelt removal and fire-management work.

A tree shear normally:

1. grabs
2. cuts
3. retains
4. places

the stem. This offers a major operational advantage over simply pushing trees over with an excavator.

OMEF Big Inch Australian range

Randalls distributes OMEF attachments in Australia. The current Big Inch range includes:

The BI600 requires approximately 250-300 L/min and operates in a much heavier category than the compact shears commonly sold for mini excavators.

TMK 300

The TMK 300 is a useful benchmark for the medium-commercial shear market:

• approximately 310 kg bare attachment weight
• suitable for approximately 6-20 tonne excavators
• up to approximately 250 mm hardwood
• up to approximately 300 mm softwood
• hydraulic configurations supporting roughly 50-150 L/min depending on cylinder arrangement

Note that the hardwood and softwood figures differ. In Australian conditions the hardwood number is usually the relevant one.

Commercial lesson

A contractor clearing 100-200 mm regrowth should not necessarily buy a head because its brochure says "maximum 450 mm". Maximum cutting diameter often represents an occasional capability. Production diameter is more important.

The commercially important questions are:

• How many stems per minute?
• How many stems can be accumulated?
• Can multiple stems be cut before placing them?
• What happens in stringy eucalyptus?
• How often does the blade require attention?
• Can the carrier safely hold the tree at full reach?

Tree shear versus feller buncher

A land-clearing business doing 500 hours of tree cutting annually may obtain better asset utilisation from a 25-tonne excavator plus tree shear.

A harvesting contractor doing 3,000+ productive felling hours may justify a dedicated feller buncher.

The threshold is not a rule of thumb about machine size. It is annual paid felling hours.

Grapple saws

A grapple saw is commercially different from a tree shear. The machine grips the tree or branch before or during cutting, then keeps control of the severed section.

This is valuable around buildings, roads, utilities, railway corridors, waterways and sensitive assets.

OMEF GS400

Current Australian distributor specifications include:

• 5-8 tonne excavator class
• 390 kg
• 950 mm maximum trunk hold
• 1,500 kg maximum workload
• 400 mm maximum cut diameter
• 30-60 L/min hydraulic flow
• 360-degree control

GMT grapple saws

GMT035 — approximately 275 kg, 850 mm grapple opening, 400 mm single-cut capacity.

GMT050 — approximately 420 kg, 1,220 mm opening, 550 mm single-cut capacity, 800 mm double-cut capacity, 2,500 kg maximum grapple load, 45-65 L/min recommended flow.

GMT050 TTC — adds a Total Tree Control braking system and weighs approximately 555 kg.

The critical commercial rule

Cutting diameter does not equal allowable piece weight.

The grapple might cut a 550 mm limb. That does not mean the boom can safely lift a long 550 mm hardwood limb.

The limiting factor may be:

GMT itself emphasises that the weight of the severed tree section must be evaluated against the crane or carrier's lifting capacity.

For eucalyptus work this becomes particularly important because timber mass can be substantial. A green hardwood limb is significantly heavier than the equivalent softwood section of identical diameter.

Forestry grapples and log grabs

A forestry grapple should be selected according to material flow. Different jobs require different geometry.

Main grapple classes

Forwarder grapple — optimised for repeatedly collecting multiple cut-to-length logs.

Loader grapple — optimised for loading trucks and handling piles.

Sorting grapple — designed for individual log control.

Bunching grapple — designed for multiple stems.

Fixed grapple — simple and robust.

Rotating grapple — better log orientation and placement.

Grapple saw — adds cutting functionality.

Australian grapple brands and suppliers

Relevant brands include Randalls, Duxson, Rotobec, Hultdins, Indexator, Cranab, Ponsse, John Deere, Komatsu and Waratah.

Randalls manufactures rotating logging grapples in Australia and also distributes Ponsse, SP Maskiner, SANY, Duxson, Indexator, Clark Tracks, Falcon Forestry, Risutec and OMEF equipment.

Duxson equipment, manufactured in New Zealand and represented through Randalls, targets applications including felling, bunching, log loading, woodlot thinning, sorting and stacking.

One detail routinely forgotten in the weight budget: grapple plus rotator plus coupler is the mass that comes off the lift chart before any timber is picked up.

The weight budget, worked

The single most consequential calculation in attachment-based work is rarely written down. It should be.

The carrier's lift chart gives what the machine can hold at a given reach and slew angle. Everything between the boom and the timber comes off that figure before any material is picked up:

Lift chart at working reach and slew
- quick coupler
- rotator (and its linkage)
- attachment
= what is left for the timber

Worked through for a grapple saw on a mid-size carrier, using the published figures in this chapter:

GMT050 attachment                     420 kg
Rotator and linkage           say     120 kg
Quick coupler                 say     150 kg
                                    --------
Deducted from the lift chart          690 kg

If the chart allows 2,200 kg at the reach the job actually uses, the timber allowance is about 1,510 kg — not 2,200. And a long green hardwood section reaches 1,510 kg at a smaller diameter than most operators estimate, which is why the saw's 550 mm cutting rating is the wrong number to plan around.

Coupler and rotator masses vary by make and model — the figures above are placeholders to show the shape of the calculation, not specifications. Get the actual masses from the supplier, in writing, and run the chart with them.

Couplers, rotators and the plumbing between

Three components sit between carrier and attachment, and each one carries a decision.

Quick couplers determine how fast an attachment changes and, on a machine changing function several times a week, that time is unbillable and it accumulates. A coupler that allows hydraulic connection without breaking hoses is usually the cheapest productivity purchase in an attachment-based fleet. The trade is mass on the lift chart and one more mechanical interface to maintain.

Rotators are what convert a cutting attachment into a placement tool. On grapple saws and grapples they are the component that delivers the control the attachment was bought for, and on a used unit they are the first thing to inspect — a worn rotator degrades precisely the capability that justified the purchase. Continuous-rotation and limited-rotation designs behave differently on sustained duty; confirm which is fitted.

The hydraulic plumbing is where an otherwise sound match quietly fails. Hose sizing, coupler flow capacity, return-line sizing and case-drain provision all affect what actually reaches the attachment motor, and a case drain that is absent or wrongly connected can destroy a motor quickly. These are covered in hydraulics and carrier matching, and they are separate checks from the power calculation.

Own or hire

Attachments are where the own-versus-hire question is most often answered by habit rather than arithmetic, and where getting it wrong is cheapest to fix.

The logic is the same as for machines and the numbers are smaller, which is precisely why it is worth being disciplined about: an attachment used a handful of days a year carries capital cost every day and earns on very few of them, and hire converts it into a job cost that can be passed through. It also keeps the coupler free for the attachment that earns daily.

Wear is the running cost

Attachment purchase price is visible and attachment running cost is not, and for several classes the running cost dominates over an ownership period.

Shears consume blade edges and work pivots and cylinders hard. Cutting close to the ground picks up grit, and hardwood works the blade harder than softwood at the same diameter.

Grapple saws consume chain and bar like any saw, plus rotator service. Urban and roadside material carries grit and occasional foreign objects, which affects chain life more than clean forestry work does.

Mulching heads consume teeth and tool holders at rates that respond sharply to ground contact and soil abrasiveness — the single largest control an operator has over the cost of mulching work.

Grapples wear at tips, pivots and the rotator, and their condition determines placement precision rather than raw capability.

Track all of these per unit of output rather than per hour. Teeth per hectare, chain per cubic metre, blade service per stem: those figures should be stable, so when one moves, something has changed — technique, material, soil or a component heading for failure. Tracked per hour, that signal disappears into how hard the machine happened to be working.

A buying sequence for attachments

1. Confirm the carrier first. Lift chart at working reach, continuous auxiliary flow, working pressure at that flow, cooling for sustained duty. An attachment chosen before the carrier is a constraint discovered late.
2. Size against the material that fills the day, not the largest stem you will ever meet. Production diameter, not maximum diameter.
3. Run the weight budget with actual coupler and rotator masses, at the reach and slew the work uses.
4. Establish wear cost per unit from someone running the same attachment in comparable material. This is the figure least likely to match a supplier's estimate.
5. Decide own versus hire on days per year, not on whether the capability is useful.
6. Confirm support — what wear parts are held in Australia, where, and what the lead time is. Blades, teeth and chains are consumed continuously, not occasionally.

See tree shear versus feller buncher and grapple saw versus tree shear for the head-to-head decisions, and hydraulics and carrier matching for the compatibility calculations in full.