Every cutting attachment on this site publishes a diameter. None of them publishes a suspended-load capacity, because the attachment does not decide that number; the excavator does. A tree shear, a grapple saw, a forestry grapple and a root cutter all hold the object after the cut or the grab, and at that moment the only figure that matters is what the carrier can lift and control at the radius the operator is actually working at, with the attachment’s own mass already taken off. This guide explains how to read the chart, how to do the subtraction, how to estimate what a length of green hardwood weighs, and why the answer on paper is still optimistic once the boom starts to slew.
Buying rule
A cutting or gripping capacity is never a suspended-load capacity. Size the carrier on lift capacity at the working radius, over the side, minus the complete attachment package, and treat the remainder as the ceiling for the timber, not a target.What a lift chart actually shows
An excavator lift chart is a grid of rated loads at combinations of radius from the slew centre and height of the lift point above or below ground. Each cell is the smaller of two limits: a stability limit, conventionally a percentage of the tipping load, and a hydraulic limit, a percentage of what the boom cylinders can hold. Manufacturers publish charts for a specific boom, a specific stick, a specific counterweight, a specific track gauge and, usually, with the dozer blade down where one is fitted. Change any of those and the chart no longer applies. A long stick, a lighter counterweight or a narrow-gauge undercarriage for float width each reduce the figures, sometimes substantially.
Two rows matter most. Over-front figures assume the load is in line with the tracks, where the undercarriage is longest and most stable. Over-side figures assume the load is at ninety degrees to the tracks, which is where a tree ends up the moment the operator slews it towards a windrow or a truck. Because a forestry attachment spends much of its cycle over the side, the over-side row is the one to use. Note also whether the chart already deducts a bucket and a quick hitch. Many do, in which case you add that assumed mass back before subtracting the attachment you are actually fitting.
Finally, look at where on the chart your work sits. A figure at three metres radius and ground level is irrelevant to a contractor reaching seven metres down a batter to cut a tree that leans over a drain. Cutting height, reach across a fence line or a road verge and the need to place the stem clear of the next tree all push the working radius outward, and capacity falls steeply with radius.
The subtraction
The arithmetic is simple. The discipline is in using the right chart cell and including everything that hangs off the stick.
Use the chart for the exact boom, stick, counterweight and track gauge fitted. Check at the largest radius you will actually work at, not the most convenient one.
The attachment masses in this subtraction are not small. The published figures below are taken from the model pages and show how quickly a mid-size carrier’s over-side capacity is consumed before any timber is in the jaws.
| Attachment | Published mass | Carrier class |
|---|---|---|
| Powerhand EX25 forestry grapple | 400 kg with rotator | 8–12 t |
| Powerhand EX25 grapple saw | 651 kg | 8–12 t |
| Powerhand EX28 grapple saw | 986 kg | 12–25 t |
| Powerhand EX40 forestry grapple | 1,091 kg with rotator | 20–30 t |
| Powerhand EX36 grapple saw | 1,176 kg | 16–25 t |
| Shearex VM-60SR mulcher | 1,188 kg | 20–25 t |
| Trevi Benne WE10 root cutter | 1,190 kg | 11.5–18 t |
| Trevi Benne WE15 root cutter | 2,240 kg | 20–28 t |
Note the difference between base and rotator-fitted mass on the grapples. The EX40 is 875 kg bare and 1,091 kg with its rotator, and a quotation that lists the bare figure understates the subtraction by more than 200 kg. The same applies to a shear ordered with hydraulic rotation, a saw ordered with a tiltrotator, or a mulcher ordered with tilt and grapple options.
Worked example: a grapple saw on a 20 tonne excavator
Illustrative only. Assume a 20 tonne excavator whose over-side chart shows 3,800 kg at six metres radius and ground level, with the bucket and hitch already excluded. Fit a hitch weighing 250 kg and the EX36 grapple saw at 1,176 kg. The remaining capacity is 3,800 − 250 − 1,176, or 2,374 kg. The EX36 is rated to cut 650 mm, and a green hardwood log of that diameter can easily exceed 2,374 kg in a few metres of length, as the next section shows. The saw is not the limit. The chart is.
Now move the same machine to a heavy stump job with the WE15 root cutter. Assume the chart gives 5,200 kg over the side at four metres. Subtract the 250 kg hitch and 2,240 kg of attachment and 2,710 kg remains for the root ball. An extracted hardwood stump carries soil, stones and wet root wood, and large ones weigh more than most operators guess. The stump cutters guide covers why extraction is often a leverage and breakout problem before it is a lift problem, but the chart still sets the ceiling once the stump is out of the ground and being carried to the stockpile.
A mulcher rarely suspends timber, but the mass still counts. The VM-60SR at 1,188 kg held at full reach down a batter, on a machine already at the bottom of its 20 to 25 tonne class, is a stability question in its own right, particularly on a slope. The lift capacity calculator runs this subtraction for any attachment on the site against a chart figure you enter.
Estimating what the timber weighs
Operators are consistently surprised by green hardwood. A stem’s mass is its volume multiplied by its green density, and a stem is close enough to a cylinder for estimating purposes.
0.785 is π divided by four. Use mid-length diameter for a tapering stem, then add an allowance for crown, bark and any soil on a root ball.
Green density varies by species, age, site and season, and there is no substitute for local knowledge of what you are cutting. As a general guide, the dense eucalypts and acacias common in Australian clearing work are much heavier green than the softwoods most brochures were photographed in, and many sit at or above the density of water. For an illustration, assume 1,100 kg per cubic metre. A 500 mm diameter stem four metres long is 0.25 × 0.785 × 4 × 1,100, or about 860 kg before the crown. Extend that to a 650 mm stem six metres long and the figure becomes 0.4225 × 0.785 × 6 × 1,100, roughly 2,190 kg, which is close to the whole of the 2,374 kg left over in the grapple-saw example above with nothing in reserve. The conservative response is to shorten the piece, not to trust the margin. The Australian hardwood guide discusses how density changes cutting force and cycle time as well as mass.
For a shear that fells whole trees, the mass includes the crown, and a spreading eucalypt crown can add a substantial fraction to the stem figure. For a root cutter, replace the cylinder with a rough estimate of the root ball volume and use a higher density to account for soil and water.
Static charts, dynamic loads
The chart assumes a load lifted slowly and held still. Forestry work is nothing like that. A tree in a shear has its centre of gravity well above the jaws and a long lever arm; when the operator slews and stops, the mass tries to keep moving, and the resulting side load on the boom and the undercarriage is higher than the static figure. A saw cut that releases suddenly, a grapple load that shifts, a stump that breaks free of its last root, and travel across uneven ground with a load suspended all add shock on top of the chart value.
There is no published multiplier that converts a static rating into a safe dynamic one, and this site will not invent one. The practical rules are to work well inside the chart, to keep the load low and close during slewing, to slew slowly with long stems, to avoid travelling with a suspended tree unless the ground is firm and level, and to treat any chart figure as a ceiling that dynamic effects erode. On a slope the chart is further reduced because the tipping line moves; a machine positioned across a batter with the load downhill has considerably less stability than the flat-ground chart implies, and a steep-slope pedestal option on a WR shear does not change the carrier’s tipping geometry.
What to ask the supplier and the carrier dealer
The attachment supplier can only assess compatibility if they know the exact carrier configuration, and the carrier dealer can only supply the correct chart if they know the exact attachment. Send both the same information: excavator make, model, year and serial; boom and stick lengths; counterweight fitted; track gauge and shoe width; dozer blade or not; quick hitch make and mass; the attachment model with every option; the species and typical stem sizes; and the working radius and slope you expect. The request for quote template gathers this on one page, and the hydraulic matching guide covers the other half of the compatibility question.
Confirm before ordering
- The lift chart used for the assessment matches the exact boom, stick, counterweight, track gauge and blade configuration of your excavator
- Whether the chart values already exclude a bucket and hitch, and what mass was assumed
- Complete attachment mass in the ordered configuration, including rotator, tiltrotator, hitch, hoses, guarding and options
- Over-side capacity at the largest working radius you expect, not at the most favourable cell
- The supplier's recommended maximum piece or stem size in your species, and how it was derived
- Whether additional counterweight is recommended for the attachment, and its effect on transport mass
- Slope limits the manufacturer or dealer applies to the chart figures
- Operator briefing on radius, slewing speed and piece length for the specific attachment
Frequently asked questions
My excavator is in the attachment's stated carrier class. Is the lift check still necessary?
Yes. The carrier class describes the mass range the attachment is designed to hang from and be driven by. It says nothing about what remains for the timber at your working radius, over the side, with your boom, stick and counterweight. Two machines in the same class can differ by more than a tonne at six metres.
Which chart row should I use, over-front or over-side?
Over-side, unless you can guarantee the load will never be slewed across the tracks. Felled trees and cut sections are almost always placed to the side, so the over-side row governs.
The grapple saw can cut 650 mm. Can the excavator hold a 650 mm log?
It can hold a short one. Mass scales with the square of diameter and directly with length, so the safe length of a 650 mm green hardwood section is set by the chart remainder, not by the bar. Cut shorter pieces rather than test the margin.
How much does a green eucalypt stem weigh?
Estimate volume as diameter squared times 0.785 times length, then multiply by a green density figure appropriate to the species. Dense Australian hardwoods are often at or above the density of water when green, so a cubic metre of stem can weigh a tonne or more before the crown is counted.
Does the chart allow for slewing and shock?
No. Charts are static ratings. Slewing, stopping, sudden release and travel over rough ground all add load. Work well inside the chart and keep long stems low and close while slewing.
Should I add counterweight to run a heavier attachment?
Sometimes it is the right answer, but it changes the chart, the transport mass and possibly the permit position for the float. Ask the carrier dealer for the chart with the additional counterweight fitted before deciding.
Get a recommendation, not just a price
Send us your excavator model, hydraulic figures, tree species and typical diameters. We will come back with a carrier-matched configuration and a written specification you can compare against any other quote.