Review: Under the skin of John Deeres new 8RX four track tractor

Following its European introduction at the Agritechnica show last year, we take an in-depth look at John Deere's latest four-track, tractor model, the 8RX. James Rickard finds out more.

From the outset, in creating the 8RX, it looks as though John Deere has simply stuck a set of tracks onto a normal four wheeled tractor. But delve a little deeper and you will soon find it is an entirely different story.

Sharing only the engine, cab and bonnet with its wheeled equivalent, it is clear there has been a lot of work gone into the 8RX, creating what is effectively a brand new tractor.

The transmission casing alone is now the largest single cast piece that Deere and Company produces - this includes all of its agricultural, construction and forestry equipment.

Four models of 8RX are available from 310-410hp (rated), complementing four, twin-track 8RT and five, wheeled 8R models. Apart from the flagship 8RX 410, which is only available with the firm's e23 full powershift transmission, all other 8RX models can be specified with either e23 or its AutoPowr continuously variable transmission (CVT).

At present, the AutoPowr CVT is not rated high enough for the top model, but the electro/mechanical eAutoPowr concept as shown at Agritechnica last year, will provide an option for those that want a CVT, but in a higher powered tractor. This should be on the market in about two years' time.

Similarly, Deere's optional CommandPro joystick is only available on models fitted with CVT, which is a shame, as its configurability and usability would suit powershift models too.

Available to order now, tractors will be arriving on-farm from September. Retail price for the flagship 8RX 410, with e23 transmission and the widest tracks, is just shy of £400,000.

8RX family

8RX development

Development 1

With increased traction and reduced compaction at the heart of the development, the project took about five years to complete.

However, it was not without its challenges, as John Deere UK's tractor specialist, Christian Nightingale explains; "While we really liked the idea of a track on each corner, putting third party track units onto a tractor which is designed to be a wheeled machine can introduce a lot of challenges, particularly getting ratios right between the front and rear axle.

"Fitted incorrectly, this can create excessive track wear and put a lot of strain on the axles and driveline. At worst, this can result in broken components, which then leads to a game of who is to blame; track manufacturer, tractor manufacturer or operator?"

Development 2

"To give piece of mind and eliminate all of these associated problems, we decided to do everything in-house."

Other concepts were also looked at and tested, such as a half-track design similar to Claas, Case IH and New Holland, but these were deemed to be less effective at putting the power down, while generating more compaction, adds Mr Nightingale.

"While a wheeled tractor is the ultimate in versatility, what we really wanted was a more versatile tracked tractor in this power segment, which can turn its hand to both heavy draft cultivations and lighter-duty top work, and still have some comfort on the road."

Castings

Castings 1

From the back of the engine, all castings are bespoke to the 8RX including the massive gearbox casing and final drive. Final drive to the front is done within hubs in the track units, while final drive to the rear is done ‘inboard'. Power split is roughly 60 per cent through the rear and 40 per cent through the front.

Specially developed for the 8RX, the tractor uses a rigid front axle. Suspended axles were experimented with, but simply did not work, says Mr Nightingale. "We did not get the grip and we did not get the ride comfort.

"Instead, the movement alone of the track units, mid rollers and front axle are far beer at putting the power down and reducing compaction without front axle suspension, while four point cab suspension takes care of driver comfort."

Castings 2

As drivelines had to be level with the drive wheels, it is quite a tall tractor too. This means it has a ground clearance of 700mm, which also affords room for the front track units to effectively ‘tuck' under the tractor with steering on full lock. As a result, it actually turns tighter than a Deere 6215R.

Though exactly the same as the wheeled 8R rear-end, like the RT it has been moved backwards, to avoid trailed implements from hitting the rear track units. Apart from this, layout of the rear-end is exactly the same across all 8 Series machines.

As you can imaging, the 8RX features a lot of inherent weight. With a full 850 litre fuel tank, the 8RX will tip the scales about the 21 tonne mark. Maximum permissible weight is 24 tonnes, compared to a wheeled version's 18 tonnes. The only place to add ballast, more for balance, is the nose or front linkage. An optional 5.2 tonne capacity front linkage can be specified, built by La Forge for the 8RX.

With nothing mounted on the front, tractor weight is split 55:45 (front:rear) - with draft loads and implement weight evening it out.

Track units

Track units 1

Taking inspiration from the larger 9RX models, track design features a similar triangular layout of components.

Designed to follow contours and maintain an even footprint, all track units can oscillate back and forth by 10 degrees. In addition to this, the front axle can pivot, in the same way a wheeled front axle does, and the rear axle's mid rollers can pivot sideways by seven degrees.

Polyurethane mid rollers are the same as used on the 9RX, which require an oil check every 1,500 hours. And should they need changing, it is only eight bolts to tackle, says the manufacturer.

Eliminating any drive slip, drive to the tracks is positive with about six lugs in contact with the main drive wheel on the front tracks and about nine lugs in contact at the rear.

Keeping tracks tensioned, the same idlers as used on the narrow 9RX are employed on the 8RX. These are kept under self-regulating hydraulic tension, requiring virtually no maintenance.

Track units 2

Creating a slight climbing effect, while reducing scuffing, the front idlers of each track unit are positioned 20mm higher than the mid-rollers.

Made by Camso, belt width options include 457 or 610mm (18 or 24 inches) on the front, and 457, 610 or 762mm (18, 24 or 30 inches) at the rear. Different centres (the tractor's track width from the centre of one track to another) can also be selected from 1,930mm (76 inch) to 3,048mm (120 inch).

Our example machine featured 610mm belts on the front and 762mm on the rear, with a track width of 2,235mm (88 inch). This still keeps it under three metres wide on the road, and because it turns like a wheeled tractor, you do not need an H (track) licence. In addition, this set-up generates 4.5sq.m of contact patch and about 0.5 bar of ground pressure.

Tracks have also been engineered to withstand road speeds of 40kph, with no limit on distance at that speed, says the manufacturer.

Cab and controls

Cab and controls 1

Along with styling changes courtesy of BMW, common to all new 7R, 8R, 8RT and 8RX tractors is an all new cab.

Giving it the full Easy Rider pose, the 8RX's cab features three foot pegs; one either side of the steering column and one near the right hand door. The two towards the right of the tractor can be fully exploited with a greater amount of seat swivel, which now extends to 40 degrees to the right and 25 degrees to the left. Cleverly, when swivelling to the left, the right hand armrest swings out wide, to avoid hitting the steering column.

The ‘Ultimate-spec' seat also gets heating and ventilation, as well as a two-stage massage function. When the latter is activated, the cab is bathed in the warm glow of red lights (not true).

Control-wise, steering wheel and column, and shuttle lever have all had a slight tweak, while A-pillar display and main CommandArm stay the same. As mentioned, CommandPro joystick can be specified with AutoPowr models.

Cab and controls 2

Operationally, it is just the same as a wheeled 8R tractor, with the benefit of four-wheel drive and differential lock at your disposal - something not possible with a twin-track machine.

A new addition is the 6.5inch infotainment touchscreen, mounted in the right hand portion of the roof. Compatible with Apple and Android devices, it allows all contacts, maps and music to be displayed/played, for example.

There are also more USB ports than you can shake a stick at, scattered throughout the cab, and the removable fridge has been boosted to 11 litres.

Gaining more headroom, the air conditioning unit has been moved from within the cab roof, to underneath the cab. This also has the benefit of lowering noise levels in the cab and it is quicker to get to temperature.

Practicalities

Practicalities 1

Preventing the need to climb up the steps to open the door, the handle is now at the bottom of the door and within reach from ground level. Steps are also 25 per cent wider.

For safer maintenance, a greater number of grab rails have been included, particularly on the right hand side of the tractor.

Various lighting packages can be specified including ‘Ultimate', which adds eight extra LED lights to the middle of the tractor. In addition, strategically placed strips of LED lights are positioned around the tractor in key areas and allow safe access/exit and help with maintenance in the dark.

Practicalities 2

Keeping a smoother roof profile, three LED beacons are integrated into the cab roof. Similarly, if specified with an integrated StarFire receiver, this is also built into the right hand side of the roof, and is said to be six times faster at acquiring a signal and needs no calibration. It also cannot be stolen. However, a more traditional, centrally-positioned receiver can still be fitted.

To help with visibility, the exhaust has been slightly re-sculpted, and up to three wipers can be specified - all featuring independent control. In addition, the bonnet has been sculpted to maximise forward views, particularly down each side of the engine.

Front and rear cameras can be specified, with the ability to set various triggers. For example, the selection of reverse could trigger an image on screen of the rear facing camera.

Verdict

Fully in-house engineered 8RX looks simply like an 8R on tracks but all castings from the engine backwards are bespoke and there are gearing changes to prevent front/rear axle conflict.

With around 21 tonnes distributed over 4.5sq m of ground contact area from 610mm front and 762mm rear traction belts, ground pressure is calculated at around a lowly 0.5 bar, with additional ballast limited to the nose or front linkage to keep the front tracks delivering.

The front axle is mounted rigidly to also maintain front traction but there is still some comfort to be had from the idler and track roller set up.

In short, the 8RX is a very thoroughly engineered four-track machine offering good manoeuvrability for its size and capability.