As self-propelled sprayers go, there aren’t that many different configurations on offer. Most are somewhat bug-like, with large bodies, spindly legs and huge wings.

Challenger’s RoGator looks little different, although it’s unusual in having a distinctly streamlined appearance.

What chiefly sets it apart, says Challenger, is the single-beam chassis which allows operators to alter the machine’s height and adjust track width hydraulically.

Challenger has a lot of experience in the sprayer market. More than 600 RoGators are sold in the USA every year, and the unusual-looking SprayCoupe has been in production for more than 45 years. The current Rogator 418 and 618 are available with Chafer spraypacks in the UK and have been fitted with Knight kit in the past.

The RoGator 600, however, involved a clean-sheet approach to self-propelled sprayer design, says Agco design engineer Joris Hiddema.

Powered by a Sisu block, it shares the same cab as the company’s MT Series tractors, as well as a 40kph hydrostatic transmission designed to operate in a similar fashion to the CVTs used in Agco’s Vario-equipped tractor. The new RoGator adopts the same single-beam chassis for each of its three models.

“We didn’t want a heavy machine, but we did want to distribute the weight evenly,” says Mr Hiddema. “It was also important to keep width to a minimum of 2.55m for transport.

“The tank and driveline components are all positioned between the front and rear axle, meaning the centre of gravity is always in the middle of the machine regardless of what tank size is fitted.”

Working height control

“While many operators need high ground clearance for certain crop stages, it’s often only for a short period of time, leaving the machine operating at a height that can be unstable for the rest of the time,” explains Mr Hiddema.

“Having variable ground clearance means operators can alter the working height of the machine by 45cm from the standard 75cm up to a maximum of 120cm as and when it’s needed.”

Because of the hydro-mechanical setup, it’s also been possible for Challenger to add car-like electronic stability programme (ESP) for stability on- and off-road.

For its size, the RoGator 600 is surprisingly nimble, with a 4.75m turning circle made possible by three steering options – two-wheel, four-wheel and crab-steer. When four-wheel steer is engaged, there’s a +/-4% buffer before the wheels start to move to avoid veering off into the crop. Then, as speed increases above 15kph, the rear axle will gradually return to the central position.

There are three models in the 600 Series: The 175hp RoGator 635, available with 3500- and 4000-litre tanks; the 645 with 208hp under the bonnet and either 3500- or 4000-litre tanks and the range-topping 236hp 655, with 3500-, 5000- and 6000-litre tank options.

To meet Tier 3B emissions legislation, the Rogator will adopt SCR and AdBlue technology come 2011, like the higher-hp Massey Ferguson and Valtra tractors. Standard Pommier aluminium booms come in 24-36m widths, however UK customers can opt for Chafer booms up to 40m.

Fully independent suspension

“We wanted to produce a sprayer that’s capable of spraying at 20kph,” says Mr Hiddema. “For this, we had to make sure both boom and wheel suspension systems were enough to cope.”

To achieve this, each wheel has independent, hydro-pneumatic suspension attached to double wishbones and shock absorbers mounted to the chassis in a rail formation. This allows the whole arrangement to move in and out depending on track width, as well as up and down when the working height is altered.

With high-capacity sprayers (and, in fact, any sprayer) boom stability is crucial, says Mr Hiddema.

“Not only does boom suspension maintain accurate application rates, but it extends the life of the boom itself.”

The boom mounting arm, which is connected to the single chassis in front of the rear axle itself, uses a single-
parallelogram design with a pendulum-type mounting. This results in a 3D movement claimed to stabilise both horizontal and vertical motion, as well as yaw, when the boom moves to and from the main frame (which can cause the edges of the boom to flex forwards and backwards).

High capacity spraying

The tank, made from 12mm thick polyethylene, is sculpted to maintain a low centre of gravity, regardless of how much it has in it. It also means there’s always 50:50 weight distribution between front and rear axles, even when the boom is unfolded.

The self-priming centrifugal pump has a filling capacity of 800 litres/min and produces an output of 784 litres/min at 2 bar and 167 litres/min at 8.3 bar. Challenger has opted for a new plumbing system which uses 45mm diameter pipework throughout joined by Banjo fittings, meaning fewer bends and no flexi-hoses. A touchpad allows operators to enter filling modes electronically.

To increase cycle times, the huge 60-litre pre-mix hopper can deal with an impressive 200 litres/min, as well as being able to handle 30kg/min of soluble products. The hopper height can be adjusted to suit preferred loading heights thanks to gas struts.

In the cab

Having the same cab as the Challenger MT crawlers (except the one-piece door opens the other way) means operators get the most spacious sprayer cab on the market, claims the company.

Those familiar with the Challenger tractor layout will feel at home in the RoGator cab – a right-hand armrest houses a multi-function joystick with boom-control functions and transmission settings, as well as proportional speed control in common with other hydrostatic systems.

An Isobus-compliant 7in screen displays engine speed, chassis and transmission settings, while an additional Topcon terminal provides spraying functions and, with GPS, offers auto-section boom control as well as mapping functions, too.