The two-model Case IH Optum CVX range spans the power and size gap between the Puma and Magnum lines.

Three hundred horsepower to pull a trailer? That sounds excessive, but it is one of the roles envisaged for a new breed of powerful tractors that makers say are not so big as to be confined to field work.

Just as fertiliser spreading used to be the preserve of 80-100hp tractors, but is now frequently undertaken by machines in the 200hp class, so haulage and other jobs once exclusively handled by those tractors are being handed to bigger, heavier, more powerful machines.

It is a matter of convenience as much as anything. With fewer operators driving bigger tractors handling wider tillage and drilling equipment to gain economies of scale, so equipment for transport, spreading and spraying are being up-scaled to match the capabilities of those power units.

Claas Axion 870 CMatic is a new addition to the Axion 800 range with up to 295hp for pto and transport operations, and when there a major demands on the hydraulics.

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On the face of it, running a 280-320hp tractor on a trailer sounds bonkers; but if it saves running additional smaller tractors that will stand idle at others times, it begins to make sense.

Big improvements in fuel economy help ease the pain of running costs – although it should not be underestimated just how much a tractor pulling a big trailer on a long haulage job will consume compared with a truck.

And on farms where a chaser bin system has been adopted to take grain off the combine, a tractor of substance is essential to keep in charge of the field-to-road bulk shifter.

Newcomers

As established tractor ranges such as the Fendt 800 Vario and John Deere 7R have grown into the 280hp-plus sector and become more accepted by larger arable growers, so newcomers from other manufacturers have emerged for 2016 and beyond to reinforce this trend.

They offer growers a wider choice of power unit close to or breaking through the 300hp mark and with sufficient practicality in terms of size and manoeuvrability to handle big trailers, slurry or anaerobic digestate tankers, muck spreaders and similar equipment, while also being well equipped for field work.

Weight of the 280hp Fendt 828 Vario can be trimmed to less than 10t but can be ballasted to operate at 16t for heavy draft work.

This is also Fastrac 8000 territory, of course, with arguably the most comprehensive specification suited to haulage operations – suspension front and back, not just on the front axle; 70kph top speed potential; and anti-lock as part of an air over hydraulic braking system configured to EU truck specification.

ABS is an option on the two-model Optum CVX range unveiled by Case IH to span the size and power gap between the top end of the Puma line, which goes to 260hp for draft work, and the bottom end of the Magnum line-up starting at 284hp.

The similar New Holland T7 Heavy Duty with the same 288hp and 313hp peak outputs provides a stepping stone to the T8 Ultra Command and Auto Command models. At 2,995mm, its wheelbase is up 11cm – almost 4% – on the most powerful regular T7.

An increase in power to create the Claas Axion 870 CMatic takes the smaller of the two Axion ranges into this powerful-but-versatile tractor group with 280hp at the driver’s disposal for draft work and 295hp when various parameters for a higher-rising power curve are met.

A new Carraro front suspension axle trims 380kg off the tractor’s base weight and allows up to a tonne increase in maximum permissible weight.

JCB Fastrac 8310 is best-equipped for haulage operations, with axle suspension at both ends and truck-spec disc braking all round.

The same front axle has been adopted for the McCormick option arriving in due course: the X8 VT Drive unveiled at the recent Agritechnica show, in Hanover, is scheduled for commercial availability in 2017 with three models and peak power outputs of 264-310hp.

A number of features are common to all these machines, including a wheelbase around the 3m mark; 2.15m tall rear tyres – most can accommodate 900/60R42 rubber – and an infinitely variable transmission.

Diehards who prefer the hands-on management of a powershift transmission can indulge their preference with the e23 option on the John Deere 7270R and 7290R but on every other tractor CVT (continuously variable transmission) is exclusive.

While the Fendt 828 Vario and JCB Fastrac use Agco’s 0-50kph fully hydrostatic to fully mechanical transmission, the others have four-step CVTs that use no more than 50% hydrostatic drive and have four fully-mechanical drive points through the 0-40kph or 0-50kph speed ranges.

The Claas Axion 870 CMatic and McCormick X8 VT Drive employ ZF’s Terramatic with their own engine/transmission management software and control interfaces, while the John Deere has an in-house IVT and the Case IH and New Holland machines share the group hardware.

John Deere 7270R and 7290R can be had with the latest 23-speed powershift or Deere Autopowr stepless transmissions.

Engine developments

As for the power source, developments in electronic common rail fuel injection, combustion chamber design and turbocharging have enabled engineers to extract prodigious amounts of power from existing engines.

The 9.0-litre John Deere PowerTech PVX is by far the biggest engine here – lesser 7Rs use the 6.8-litre version – with a single, adjustable vane turbocharger providing variable charge pressure determined by the demands on the engine.

Similar technology is used on the 6.7-litre NEF from FPT Industrial, which in other applications is tuned to extract as little as 126hp. It is used here in the Case IH, Claas, McCormick and New Holland contenders with an electronic variable geometry turbocharger for the first time.

This minimises turbo lag to deliver a quicker response from the engine by optimising exhaust flow to encourage the turbine to spool up the compressor quickly at modest revs before easing off to avoid excessive charge pressure.

Apart from this rapid transient response, the variable geometry also maintains torque output levels across a wider range of engine speeds than a fixed turbo.

In other words, these engines will deliver plenty of grunt to pull through tough patches of soil or to climb field and road gradients.

McCormick X8 VT Drive channels up to 310hp and 1282Nm from a 6.7-litre FPT engine through a ZF Terramatic stepless transmission.

Emissions control is inevitably part of the engine story: the 6.08-litre Deutz in the Fendt employs exhaust gas recirculation, selective catalytic reduction (SCR) and a diesel particulate filter (DPF) to achieve the exceptional demands of European Stage IV/US Tier 4 Final clean-up rules.

The Deere motor adds a diesel oxidation catalyst (DOC) to this suite of technologies for good measure, while the Agco Power engine in the JCB Fastrac is still at the preceding emissions level at present, using SCR alone to reach the required standard.

With the addition of no-maintenance catalysts either side of the SCR injection module, the FPT Industrial engine achieves Stage IV/Tier 4 Final without a DPF.

Combustion efficiency keeps the particulate (soot) content of the exhaust gases at the required level while a dedicated closed-loop NOx monitoring system achieves 95% plus conversion to keep AdBlue fluid consumption as low as possible.

Engine installation varies on these tractors, being part of the Fastrac’s modular drivetrain supported by a comprehensive fabricated chassis.

The Fendt, Deere and McCormick tractors have substantial chassis frame structures to support the engine (and the transmission in the 7R’s case), while the Axion has a cast sump to bridge the transmission housing and front bolster.

Big enough for heavy cultivations but compact enough for trailer and tanker haulage – that is the formula for the New Holland T7 Heavy Duty tractors.

These arrangements lend themselves to an integrated front linkage installation, which all of these tractors get as standard, reinforcing the assumption that front-rear combination working makes a lot of sense at this power level.

It also makes it easier to disrobe the tractor of linkage-carried ballast when switching between the different roles envisaged.

Pto drive to power front-mounted equipment can be added in all instances, but only the Optum CVX and T7 Heavy Duty tractors have two-speed front pto, which allows lower, more economical engine speeds when less power-demanding implements are used up front.

Selecting the 1000E output trims engine speed from 1,890rpm to 1,585rpm, saving fuel while taking the engine closer to its 1,400rpm torque peak. Eco 1,000rpm settings for the rear pto – as on all these tractors – do much the same thing.

As, of course, does a CVT transmission when the application and load involved allow.