Review: Stump grinders

How will this selection of machines cope with conditions at Westonbirt Arboretum? Sally Drury finds out.

FSI D30-470 stump grinder - image: HW
FSI D30-470 stump grinder - image: HW

Tested This Issue

FSI D30-470

Toro STX-26

Carlton SP7015 TRX

Carlton SP5014TRX

Carlton SP2010

The Review Panel

Dan Goulbourne, trainee arborist, Westonbirt Arboretum

Andrew Jane, operations support officer, Westonbirt Arboretum

Perhaps due to disease, for safety reasons or, sadly, sometimes because the site is required for development, trees need to be felled from parks, gardens and highways. In public places, leftover stumps present trip hazards. Depending on the species, unwanted regrowth or potential disease spread may also be problems. If the site is to be developed, stumps are simply in the way.

Removing stumps is most efficiently done with a stump grinder. It is a market with many players and dozens of models, from small pedestrian-operated units to huge remote-controlled machines.

In this test, at Westonbirt Arboretum, we look at a prototype from FSI, three new models from Carlton Europe and a zero-turner from Toro, a company perhaps better known for its grass-cutting equipment.

The arboretum, in a picturesque Gloucestershire landscape, is managed by the Forestry Commission and supported by the Friends of Westonbirt Arboretum. Begun by wealthy Victorian landowner Robert Halford in the 1850s, it is now internationally important and contains 14,902 labelled trees from Britain, China, North American, Japan, Chile and other temperate climates. It attracts more than 350,000 visitors a year.

On the day of the test, conditions were cloudy but dry. The temperature was around 8 degsC but felt chilly due to the wind.

FSI D30-470

We have looked at the D30-470 before. In fact, it was a year ago that we used the wheeled stump grinder to decimate the stump of a tree of heaven (Alianthus altissima) here at Westonbirt. We concluded that we would like to see a tracked version. Today, we have the opportunity to test the prototype D30-470 on tracks.

Unloading the machine and manoeuvring it to the stump, it is clear that the guts of this grinder are every bit the unit we examined last time (HW, 7 February 2014). It is powered by an uncomplaining Kubota diesel engine - 30hp and water-cooled - so it is quieter than the Toro (p41), making it suitable for use in urban areas. It also remains a solidly built machine that inspires confidence. It has an amazing sweep of 1.57m (more than 5ft) and can grind to a depth of 38cm.

As before, there is a control panel on one side of the machine. There are levers to extend the tracks, for steering, forward and reverse movement, up and down control of the grinding head and sweep control. Separate flow control on the slew means the sweep can be slowed down if required. The panel swings out to enhance the view of the grinding operation, but Jane still finds it difficult to see the wheel.

"I have to drop the head and inch forward until I can feel the stump," he says. Although he would like it to work deeper, he appreciates many of the features. "It is a robust machine. I like the Kubota engine and all the controls are where you would expect. The long nose keeps the dirt and debris away from the workstation."

Goulbourne, having worked with a tree surgeon, says: "It's happy cutting - not struggling at all. This would be a good machine for tree surgeons working in gardens. For everyday use it's brilliant."

The clutch is FSI's own design and we are told there have been no failures to date. This machine also features no-stress relief. Access to all parts and grease nipples is easy and the exhaust is positioned underneath the grinder, away from the operator.

Machine width is 800mm, allowing it to squeeze through gateways, but once on site the tracks can be extended by 400mm to increase stability. There is a spotlight to help finish work in failing winter daylight and handy lifting points in case the unit has to be hoisted onto transport or craned into position. A single lockdown point ensures that the nose remains stable during short trips between stumps.


Engine 30hp Kubota diesel, three-cylinder, water-cooled

Fuel tank 35 litres (typically 10 hours)

Cutting wheel 470mm diameter with 18 teeth

Sweep 157cm

Weight 850kg

List price TBA (prototype)

Tel Spectrum Plant - 0845 345 4866

Toro STX-26

"Toro? Don't they make mowers?" Goulbourne says what is on everyone's mind as we await the arrival of the STX-26. Can a company that has such a strong name in grass-cutting and golf course equipment produce a machine to take out tough stumps? We are pleasantly surprised.

The STX-26 is built in America. Noting that some stump grinders are overcomplicated, Toro designed this machine to be easy to use - and it certainly is. The controls are similar to those on the Toro Dingo TX. We are talking two simple levers. One is for left/right traction control along with forward, reverse and turn. The other is for sweep, lift/lower and engagement of the grinder head.

"I like the controls. They are very smooth and easy to master. If I was in the market for removing stumps in gardens, I would consider this one, relative to price," says Jane.

Goulbourne agrees: "I really like the controls. It's a manoeuvrable machine and when you get used it you should be able to hold the head wheel joystick and operate the controls to move it at the same time."

To help productivity, the STX-26 has a tracking transport speed exceeding 4mph. Even more impressive is the zero-turn capability - just as you would expect from Toro. It is a real help when moving the machine into position.

Mud and inclines are not problems. The unit's low centre of gravity and large footprint combine to give increased stability when tracking across wet and soft ground or working on sloping ground. Dimensions also mean this grinder fits through a standard 36in (91cm) gateway and neatly into a van.

The head is hydraulically driven, eliminating the need to tighten belts or replace cogged pulleys and clutches. This eliminates shock loading to the engine caused by belt slippage. The head is also offset, giving a clear view of the cutting operation as the arm makes its 119cm arc.

"It is nice to be able to stand over the machine and see the wheel working," Jane comments.

We like a lot of features about the STX-26 but there is one we would change. This grinder is powered by a petrol engine. "Get rid of the engine and give it a diesel," Jane suggests.

"It would be less noisy and less expensive to run. But Americans like their gas, don't they?"


Engine 26hp Kawasaki 730V twin cylinder

Cutting wheel 19in (48.26cm) diameter, 0.75in (19mm) thick, with 12 green teeth

Cutting depth 12.5in (31.75cm) below ground

Cutting height 35in (88.9cm) above ground

Sweep 47in (119cm)

Hydraulic flow 13.5gpm hydraulic flow to head

Weight 545kg

List price £11,700 + VAT

Tel Toro - 01279 603020

Carlton SP7015 TRX

A tracked machine from the Carlton stable, the SP7015 is a dream to manoeuvre across site. This is a go-anywhere stump grinder with four-speed ground drive system providing variable travel speeds up to 3.5mph. It also has traction control and telescoping tracks. The tracks hydraulically retract from 48in (122cm) to 35in (88.9cm) to aid movement through entrances.

Power comes from a four-cylinder turbo-charged 66hp Kubota diesel engine. This power plant has 27 per cent more torque and 10 per cent more horsepower than the previous 7015 model, while also being quieter. The engine is completely enclosed.

The four-speed control allows the operator to choose between high-speed travel models and high-torque cutting modes at the flip of a switch. When grinding, the patented turntable design comes into play to allow a giant 70in (177.8cm) sweep.

The machine's wireless remote control ensures that the operator can stand a safe distance away from the noise and dirt of the grinding head. But we find the dirt does not fly - guarding ensures that.

"There is nowhere for the dirt to go," notes Jane, moving debris from the hole so he can see the remaining stump. Of course, he wants it to go deeper. On the positive side, he appreciates the extra power. "There is plenty of power in this one, and it is cutting the stump quickly," he adds.

The SP7015 is fitted with Carlton's Razor wheel and 32 teeth. Goulbourne is impressed by the build. "This is certainly a well-engineered machine," he concludes.


Engine 66hp Kubota diesel

Cutting wheel 26.5in (67.3cm) diameter Razor wheel, 1in (25mm) thick, with 32 teeth

Cutting depth 15in (38cm) below ground

Cutting height 43in (109cm) above ground

Dimensions (LxWxH) 354cm x 89cm (122cm tracks extended) x 155cm

Weight 2,460kg

List price £42,185 + VAT

Contact Carlton Europe (a brand of Orange Plant) - 0191 236 7795

Carlton SP5014TRX

American company Carlton has been in the business of manufacturing stump grinders since 1952 and offers a wide range of units from a petrol-powered 13hp pedestrian model to a massive 250hp machine with remote control. In between, there is something for everybody.

Last autumn Orange Plant announced it had taken on the distributorship for Carlton stump grinders. Modified to comply with European legislation, the machines are marketed under the Carlton Europe brand.

The SP5014TRX is the latest stump grinder from Carlton Europe. It is superbly compact, tracked and radio remote-controlled. The unusually short track base is surprisingly stable and helps manoeuvrability - a potential benefit if working in tight spaces.

This unit employs a rubber high-track system incorporating multiple idler rollers and spring tensioning to keep the track at optimal efficiency for running and tracking. We did find some ground disturbance, but wet weather the previous few days had left the ground soft at Westonbirt.

There is a choice of engines for the SP5014TRX - either 33hp or 44hp Kubota diesels or 35hp Vanguard petrol. We use the latter.

What really impresses is the teeth. This is Carlton's Razer cutting wheel and when the teeth are in good condition they will shave off 120mm of stump in a single pass. They are aggressive. We are impressed by the arc. This machine has a cutting sweep of 50in (127cm).

If we have a complaint, it is about the guarding. "The top guard is fixed and solid, and it keeps catching on the stump," notes Jane. He admits that he is not a fan of remote-control units that use paddles. "They are either on or off," he adds.

Jane is also disappointed with the working depth. The SP5014TRX only works down to 14in (35.5cm) below ground level. That might be sufficiently deep for most needs, but not for the team at Westonbirt. They like to ensure that all the stump is removed and even trace the roots out to reduce the risks of pests, diseases and regrowth.


Engine 44hp Kubota diesel (30hp Kubota diesel or 35hp Vanguard petrol optional)

Cutting wheel 21in (53cm) diameter Razor wheel, 1.25in (31.7mm) thick, with 36 carbide-tipped Sandvik teeth

Cutting depth 14in (35.5cm) below ground

Cutting height 34in (86cm) above ground

Dimensions (LxWxH) 213x134x247cm

Weight 315kg

List price £26,495 or £28,175 with Vari-Track, both + VAT

Contact Carlton Europe (a brand of Orange Plant) - 0191 236 7795

Carlton SP2010

Pedestrian stump grinders are ideal for those needing to operate in tight spaces and this one is fitted into a neat package just 74cm in width. But what makes this wheeled model particularly nice is that moving the grinder into position is a doddle.

This pedestrian machine is self-propelled, with the hydrostatic transmission allowing infinitely variable ground speed control - no struggling to get to work.

Once we have the SP2010 lined up with the stump, we find the controls are relatively simple to master, though it takes a while to feel comfortable holding the operator presence control or dead man's handle - use the movement controls and then engage the handbrake. Goulbourne needs another hand for a moment but is soon happily swinging the head to and fro across the stump.

The fingertip controls are comfortable and efficient, and the machine feels as though it has power to spare. But the best feature for Goulbourne is the adjustable handle height. "It means you can lower the head into the ground and still be comfortable standing at the controls," he says.

The 0.5in (12.7mm) cutter wheel works well at grinding the stump. This one will work down to a depth of 24in (61cm). But the lads at Westonbirt are hard taskmasters. They still want more. "There is still stump down there," says Jane, peering into the hole.

We finish work and switch off the engine - pop! Oh yes, this stump grinder has a Kohler engine.

This is quite a heavy machine and certainly well engineered and solidly built. That gives us the confidence that it will not only do the job but should also stand the test of time working in harsh environments and being repeatedly loaded and unloaded from a trailer.


Engine 30hp Kohler Command

Cutting wheel 19in (48.26cm) diameter, 0.5in (12.7mm) thick, with 16 teeth

Cutting depth 24in (61cm) below ground

Cutting height 27in (69cm) above ground

Dimensions (LxWxH) 234x74x117cm

Weight 315kg

List price £6,995 + VAT

Contact Carlton Europe (a brand of Orange Plant) - 0191 236 7795.

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