Big capacity without compromising straw quality – that’s how Claas characterises its latest straw walker combines, the Lexion 5000 and 6000 series, introduced for the 2021 harvest.

The top two models, in particular, are reckoned to cater for large growers needing lots of harvest capacity but who also want to sell straw as a commodity in addition to grain.

“We’ve never been at this capacity level with a straw walker combine before,” emphasised product manager, Adam Hayward, at the Claas UK unveiling.

“The new 6700 has performance equivalent to our biggest previous Lexion and then we have the more powerful 6800 and 6900 on top, with up to 462hp and 507hp.

“At the same time, the highest output five-walker machine – the Lexion 5500 with up to 408hp – has a larger threshing area than the previous six-walker machines and it’s also our first five-walker on Terra Tracs.”

This is no progressive upgrade of the existing Lexion combines, but rather a substantial re-design that builds on familiar features and technologies to lift the whole package with increased threshing, separation and cleaning areas, and bigger capacity grain handling equipment.

A new threshing drum positioned behind the APS separation and crop acceleration cylinder is 26% larger than before, at 755cm diameter and lifts threshing area to 1.55sq m.

Behind it for the first time is a new grain separation finger drum of 600cm diameter, after which a beater helps transfer the straw mat on to 14% shorter four-step walkers that are no longer assisted by overhead agitation tines.

Nonetheless, total separation area is increased to get grain out of the straw more effectively, and along with the rest of crop processing system the walkers are set at a slightly shallower angle to ease the crop’s passage.

Reduced main drum concave wrap helps by smooth the path to the new separation cylinder grate as a contribution to minimised straw damage.

But when necessary an extra bar can be rolled in hydraulically ahead of the concave structure when ears are more reluctant to shed their grain and for de-awning barley.

“We think this is a good solution for those situations when a little more threshing aggression is needed but when speeding up the drum or tightening the concave clearance could cause cracked grain levels to increase,” explained Mr Hayward.

Conversely, although concave/grate adjustment for all three threshing and separation elements is synchronised with a parallel action, the rear of the main concave can be opened separately when appropriate to ease the flow path.

For easier switching between crops now that different cropping and rotations are more common, the grates beneath the APS and new separation drums, and 40% of the main concave, can be replaced through the side of the housings.

Grain cleaning is now handled by the Jet Stream system already used on the Lexion rotary separation machines, with six turbine fans on the five-walker, eight on the six-walker models venting through two straw walker steps and a long airflow equalisation channel for intensive pre-cleaning.

Fan speed and sieve adjustment is handled in the cab – along with pretty much every other setting, including the synchronised threshing and separation drums and concaves.

The operator can interrogate CEMOS Dialog system for advice on optimum settings in real-time situations, or leave it to CEMOS Automatic when this option is installed.

CEMOS Auto Threshing encompasses the pivoting concave bar, drum speed and concave adjustment while drawing on information from a grain quality camera and new more accurate Quantimeter mass flow device to automatically fine-tune settings.

When CEMOS Auto Cleaning is installed, the fan speed and upper and lower sieve settings are also automated to achieve operator-set parameters and targets.

As previously, Cruise Pilot forward speed control and Auto Slope cleaning system adjustment are included but Montana chassis levelling is said to be a couple of years off yet.

Increased output potential is matched by uprated grain handling systems, with grain tank capacities of up to 12,500 litres for the Lexion 6800 and 13,500 litres for the 6900 comfortably exceeding the 11,000 litres of the 6700 and its 670 predecessor.

Seven different auger sizes are available, with greater forward angle improving the combine driver’s view and the ability to unload with the auger 45° to the rear, enabling a tractor and trailer to tuck in behind a wide header when necessary.

The Claas Dynamic Power engine control system introduced with the new combines constantly manages power and torque output according to load while maintaining a lowly 1900 rpm crankshaft speed.

Both are intended to improve fuel economy, which Claas headquarters tests suggest can be as much as 15-20% over the previous set up.

There is also a new drive system first used on Claas Jaguar forage harvesters that couples the engine and pre-tensioned power bands more progressively and smoothly than the previous set-up.

Hydrostatic ground drive provides 30kph, or 40kph top speeds regardless of whether tracks or wheels are fitted. Wheeled models get a front axle diff lock as standard, and larger tyres up to 42in with a diameter of 2.15m can keep the combines within 3.5m overall width without unduly sacrificing surface contact area.

Operators get a little more space in the cab and a larger window into the grain tank where steps make climbing in for cleaning out an easier process.

The new CEBIS terminal introduced with the 7000 and 8000 rotary separation Lexion combines last year provides a comprehensive overview to save switching between screen views and the Field Scanner guidance option can follow tramlines as well as crop edges.

GPS Pilot and the familiar Laser Pilot – which Adam Hayward says has been retained by popular demand – are also available for the new machines.

Claas Lexion straw walker combines:

Five-walker – 1420mm wide threshing and separation systems

5300 313hp

5400 354hp

5500 Terra Trac 408hp

Six-walker – 1700mm wide threshing and separation systems

6600 354hp

6700/6700 Terra Trac 408hp

6800/6800 Terra Trac 462hp

6900/6900 Terra Trac 507hp