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.
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
List price TBA (prototype)
Tel Spectrum Plant - 0845 345 4866
Tested This Issue
Carlton SP7015 TRX
The Review Panel
Dan Goulbourne, trainee arborist, Westonbirt Arboretum
Andrew Jane, operations support officer, Westonbirt Arboretum