Westonbirt Arboretum, near Tetbury in Gloucestershire, is famed for its autumn colours. But here, as anywhere else, trees sometimes have to be removed, be it because of old age or damage. And at this point, there is usually a need to remove the stump as well.
At Westonbirt, staff use a tractor-mounted stump grinder but the choice on the market is huge. There are hand-held models, pedestrian-operated push machines, self-propelled units, tracked machines and even radio- controlled versions.
Conditions on the day of the test were dry and sunny.
This machine puts a staggering amount of power into the front to rip off between an inch and two inches with each slew. The Predator is capable of devouring tough old stumps, but it also leaves the neatest pile of waste imaginable.
The minute the 75R arrives on a small trailer, we recognise this machine is distinctly different from anything else we have seen. For starters, considering it's a 75hp stump grinder, it is surprisingly compact. It's a main selling feature.
The 75R is refined, has smooth lines and it is uncluttered by the tangle of hydraulic hoses we would normally expect on a machine this size. Then there's the cutting head wheel - it isn't round. And the teeth are different from what we are used to.
The unusually shaped wheel is designed to enable the engine to pick up speed between hits, ensuring maximum torque as the next teeth hit the stump.
The concept works extremely well, but this is a completely new approach to wheel design and from our testing we are unable to say whether this unusual configuration of wheel has any effect on the long-term running of the engine and other component parts.
What we are sure about, however, is the teeth. We love them. On the cutter wheel there are two front-leading teeth, a few side teeth and two teeth on the back side. They fit into a notch in the wheel and require one screw to hold the assembly firmly in place. Just one screw means that broken, damaged or worn teeth can be whipped out and replaced in less than a minute.
With its tracks tucked under the body of the machine, the 75R is gently led down the ramp of the trailer. It only takes a minute to unload and as soon as it is on the ground the tracks are extended. Then it's off across the glade at a belting pace.
At 75hp, the 75R is the largest grinder in the Predator range. It's also the newest. The "R" stands for radio-controlled. Standing at a safe distance and with a view from any angle desired, the operator only needs to tweak the paddle levers on the remote to move the machine left or right, adjust the track width or move the cutter arm. Flick the toggle switch across and the variable two-speed runs from "tortoise" to "hare" and back again.
Measuring just 89cm with the tracks retracted, there should be no problem accessing awkward sites such as rear gardens. With the tracks extended to 118cm, stability is provided for negotiating rough terrain and slopes.
All our testers are impressed with the ease of positioning to get the kit ready for work. "It's easy to manoeuvre into position - it's so compact it is easy to get all round the stump," says Townsend.
Movements are made even easier with the quality remote-control system behind this machine. This is a proportional control and the difference is felt immediately. Some radio-controlled units are either on or they are off. With this one the further you push the paddle, the faster the function works. It's a nice feature, very controllable, and impresses Litten.
"The controls are really good. Usually radio controls are all or nothing, but this one is really touch-sensitive and it makes a world of difference. It's just like using the hydraulic levers on the tractor," he enthuses.
Jones comments: "The controls are easy to use and sensitive. It's easy to move the machine around and from an operation point of view the remote allows you to have full view of the grinding rather than having to stand at the rear or side of the machine."
If the remote is damaged or lost, the machine can still be controlled via levers accessed via the rear door. It is even clever enough to change frequency if it finds something else being operated on the same wavelength nearby. This means there is no fear of children accidentally taking control of the stump grinder if they are playing with remote control toys nearby.
Another big selling point on this machine is the engine. This is a four-cylinder Hatz Silent Pack engine and it's quiet. It's also very torquey - there's the bottom end torque that you need with stump grinding, but it also has a torque that keeps the machine going when it's down in a hole filled with loads of chips. The hydraulic motors are by Parker.
"It's quiet," notes Townsend. "When it does a sweep and it starts to labour, it simply backs off. It all happens very quickly, in seconds."
"I can't believe how quiet it is," comments Litten. "Yet it has plenty of power for its size. It would be good for clearance operations. I'm impressed."
We also love the no-stress device on the 75R. It works on hydraulic pressure. When the wheel gets up to a certain pressure, the arm will actually back out of the stump by a few centimetres to take away the resistance and let the wheel speed build up again quickly.
The arm goes down that little bit further than competitor machines - down to 68cm below ground. On completing grinding, a neat pile of chips next to the hole is ready to be raked in as backfill.
"It's grinding, but it's not throwing the material all over," confirms Townsend.
"We've had some shockers on demo - machines that throw the stuff miles," laughs Litten. "But with this the guarding stays on the ground to contain the debris. It's a nice machine. I like it."
Maintenance consists of oil checks and greasing of three nipples - two on the linkage and one on the head - though later machines are now being fitted with worry-free non-greasable bearings on the head. Predator Manufacturing believes these sealed bearings will be good for 5,000 hours. And emptying an air filter has never been this easy - simply unscrew the opaque dome on the top and tip out the debris.
The 75hp Predator is also available in a manual version.
THE REVIEW PANEL
Ben Jones, arboreta specialist, Westonbirt Arboretum
Justin Litten, arboreta specialist, Westonbirt Arboretum
Richard Townsend, arboreta specialist, Westonbirt Arboretum