Trends in tractors

Tractor development in recent years has been heavily influenced by exhaust gas legislation. "Common Rail" injection, four-valve technology, turbochargers, "intercooler" and electronic engine control are the pillars of engine technology for diesel units that comply with the V emissions level currently valid in the EU, in order to meet performance, consumption and emissions requirements.

In power classes from 56 to 560 kW, diesel oxidation catalyst (DOC), diesel particulate filter (DPF) and selective catalytic reduction (SCR) exhaust gas aftertreatment systems are also indispensable, supplemented in some cases by exhaust gas recirculation (EGR). Many manufacturers have already approved their emission level V units for the use of HVO (Hydrotreated Vegetable Oil).

With the CO2 problem, attention has shifted to combustion engines for alternative fuels. Cummins was the first manufacturer to announce a multi-fuel engine platform (diesel/HVO, methane and hydrogen) with the "Fuel-Agnostic X6" 15-cylinder unit (14,9 L displacement) in early 2022. The basis for This is a standardized basic engine system that can be combined with various cylinder head modules. FPT is following a similar path with the XC13 (6 cylinders, 12,9 l displacement), which was launched a year ago as a “single base multi-fuel engine”. The new Cursor-X concept also aims to feature a modular system with header modules for diesel/HVO, methane, hydrogen and other renewable fuels.

AGCO Power also announced a new engine platform with the CORE series. The first representative was the CORE 75 with 6 cylinders and 7,5 l displacement, which is used in the new Fendt 700 Gen7 tractor series and can also be operated with HVO. In the future, this platform should also be developed to allow the use of other alternative fuels, depending on market developments. With CORE 50 destined for the new Fendt 600 Vario series, the next engine model is already in the starting blocks. With a maximum power of 224 hp (including DynamicPower), the 200 hp mark is clearly broken for the first time in tractors by this 4-cylinder engine with a displacement of 5,0 l - at a nominal speed of just 1.900 rpm.

In addition to Cummins and FPT, other non-highway engine manufacturers working on H2 combustion engines include Deutz, JCB and Liebherr. This approach is also currently considered the most economical and viable solution in the commercial vehicle industry to achieve CO2 reductions with carbon-free hydrogen in the short and medium term. However, the prerequisite for this is always that it comes from environmentally friendly sources. Hydrogen can be transported in vehicles – like methane – in gaseous form in pressurized containers or in liquid form in insulated tanks. The engine technologies for these two energy sources are also similar (Otto process or High Pressure Direct Injection - HPDI).

Gas engines entering agriculture thanks to LNG?

New Holland has benefited from the many years of experience of its sister company Iveco/FPT and in 2022 was the first manufacturer to launch a mass-produced tractor with a gas engine, the T6.180 Methane Power. Methane is transported here in gaseous form as CNG (Compressed Natural Gas) in pressurized vessels. As the energy density of CNG per liter of tank volume is only about one-fifth that of diesel, the operating times of such vehicles are generally limited. The relationship is much better with cryogenic liquid LNG, which is why it has been used in long-distance road transport for years. In tractors, LNG has hardly been a problem until now because the usual vacuum-insulated cylindrical tanks are difficult to integrate into the cramped installation space and because larger quantities of boil-off gas can be produced due to the longer service lives involved.

With the T7.270 Methane Power LNG, New Holland now presents a gas tractor with LNG tanks designed to avoid these problems. Thanks to a special double-wall technology, vacuum-insulated LNG tanks do not need to have a cylindrical shape and can consequently be better adapted to the typical space conditions of tractors - similar to diesel tanks. The T7.270 LNG can therefore transport 200 kg of methane, which is around seven times more than the approximately 30 kg of the T6.180 Methane Power (based on the integrated CNG tanks). New Holland combats the problem of evaporated gas with a “cryogenic cooler” that constantly keeps methane below minus 162°C and therefore in a liquid state. The energy required for the electrically driven refrigerator is minimal and comes from a battery that can be charged via an external power source or the integrated IC generator (boiling gas operation). This means that LNG gas engineering Innovative concepts can now also become a valid propulsion option in agriculture, combined with the opportunity to use your own biogas (bio-LNG) as a fuel for vehicles in CO2-neutral systems.

Battery-powered electrical systems are gaining ground

Battery technology is constantly developing and in recent years, gravimetric and volumetric energy densities (Wh/kg or Wh/l) have been steadily increasing. From today's perspective, however, batteries will probably always remain relatively large and heavy, which is why vehicles equipped with them are mainly suitable for light and moderately heavy-duty applications or for periodic recurring jobs where there is sufficient time for intermediate charges. In agriculture, these conditions exist for smaller tractors, among others, which are now gradually coming onto the market.

Starting this year, Rigitrac has been building the SKE 40 Electric compact tractor (continuous traction drive/peak power 40/64 kW, battery capacity 50 kWh) in small series. The Fendt e107 V Vario narrow track tractor (continuous/peak power 55/66 kW, battery capacity 100 kWh) and the New Holland T4 Electric Power (continuous/peak power 55/89 kW, battery capacity 110 kWh) were announced for 2024. Charging capacities with alternating current (AC) are 22 kW for the three models, and those with direct current (DC) between 80 and 100 kW.

Fuel cell units are still in their infancy

Fuel cell drives also count as electrical systems. Here, however, the electricity does not come from the socket, but is first generated from the hydrogen in the vehicle. Since fuel cells cannot react quickly to load changes and the ideal efficiency is in the medium load range, they are always combined with buffer batteries when driving vehicles. In most cases, the fuel cell is the main element and the battery is the additional element that covers load peaks and can store braking energy. However, the fuel cell can also be used to extend the range of battery-powered electric vehicles.

Current prototypes and studies are available from Fendt, among others. The HELIOS (electric hydrogen powered tractor system) developed as part of the H2Agrar research project operates with a 100 kW fuel cell and a 25 kWh buffer battery. This means that it can be attributed to the concept of “fuel cell as main drive”. Five high-pressure tanks mounted above the cabin roof can transport a total of 21 kg of hydrogen (700 bar). Being able to carry enough energy for the required operating times/ranges is also a major challenge for fuel cell vehicles in general.

In the DLG competition "AgriFuture Concept Winner 2023", Fendt also presented a study of a mobile fuel cell that can generate electricity from green methanol to continuously recharge the battery of the Fendt e107 V Vario. Liquid methanol is transported in a 60-liter fuel tank and does not need to be pressurized or cooled. The fuel cell has a power of 15 kW and can generate around 100 kWh of electrical energy from 60 liters of methanol. This allows you to double the operating time of the e107 V Vario battery-powered electric tractor for low/medium workloads. The fuel cell module is connected to the front or rear lifter and the electrical connection is established using an AEF plug. This solution corresponds to the concept “fuel cell as a range extender”.

Hybridization: solution for medium and large tractors?

CNH presents the Steyr Hybrid CVT, a modular hybrid concept for standard medium and large tractors. The prototype presented is based on a series production model in the entry class with 6 cylinders (power 180 HP, wheelbase < 2,8 m), but the diesel engine used here produces 260 HP. The familiar continuous hydrostatic-mechanical transmission is adopted in a 1:1 ratio of the original. Completely new, on the other hand, is the front axle support with independent spring-mounted suspension and two integrated electric motors. The generator is driven by the diesel engine via a transmission stage and transmits the generated electrical energy (up to 75 kW) to the electric motor via the power electronics. This converts electrical energy back into mechanical energy, which is fed via a two-stage reducer to the ring gear of the front axle differential. However, the front axle can still be driven mechanically via a classic multi-plate clutch. In the electrical sector, there are also SuperCaps (electrostatic energy storage devices that can capture and release a lot of energy in a short time, but can only store a small amount of energy), a braking resistor and a high voltage AEF. socket at the front and back.

These components and the serial-parallel hybrid structure enable numerous functions that are new to tractors. These include the variable and actively controlled forward movement of the front axle (E-direction), the electrical boost function for rapid acceleration during transport (E-boost), the compensation of load peaks (E-torque fill), purely diesel -electric driving during light work and rapid id direction changes at low engine speeds in each case (E-CVT/E-shuttle mode), together with brake retarder with continuous power of 20 kW (E-braking). Other functions include variable distribution of torque between the axles (torque vectoring E) and the supply of electrical power of up to 75 kW to implements (implement E).

Evolutionary development for gearboxes

CNH's hybrid concept fits into the trend towards holistic propulsion concepts that go beyond previous diesel engine gearbox systems to enable new functions. Previous examples include Fendt's VarioDrive gearbox/all-wheel drive concept and John Deere's eAutoPowr gearbox, with electromechanical power splitting and the option of current output for implements.

Fendt first introduced VarioDrive in 2015 for the 1000 series and has since successively moved this concept to lower performance classes. Following the 900 and 700 series, tension-free all-wheel drive, which is permanently engaged up to 25 km/h, was also introduced in the new 600-cylinder 4 Vario series.

John Deere has been installing eAutoPowr on the top model 8R410, for which there was previously no continuously variable transmission option, since 2022.

New stepped and continuously variable gearboxes have not been announced in the last two years, but there have been additional interesting developments. Claas also uses ZF's Eccom 5.5 continuously variable gearbox, which was introduced along with a new pump transfer case for the previous XERION series (4200/4500/5000) for the 2023 model year, in the new XERION series models 12 (maximum power up to 653 HP). However, due to the high torques of the 15,6-liter six-cylinder unit with a turbo compound from Mercedes-Benz, a “high transmission stage” is integrated into the pump gearbox. This allows gearbox input torques to be reduced and engine outputs to be transmitted at higher speeds.

At Agritechnica, Claas will also introduce a new front loader mode for the Arion 500 and 600 tractor models with their own continuously variable gearboxes (EQ200/EQ220). This allows torque/thrust control via the accelerator pedal when hitting bulk material or manure piles, as is the case with wheel loaders or telescopic loaders with hydrodynamic torque converters. This should make filling front loader attachments easier and more convenient.

Chassis technology is being adapted

Chassis technology is becoming more important as the power and weight of large tractors increase. Therefore, Claas has developed new triangular track drives for the 12-series XERION series, which are built in-house. This design was necessary because the new flagships are also equipped with Ackermann steering and not the articulated steering usual in this performance class. The large drive wheel of the track drives, together with the two deflection rollers, is mounted on a main frame that can oscillate +/- 10°. The boogie suspension of the two intermediate rollers is integrated into a separate swing arm, which is damped by rubber elements.

In Europe, the 12 series models are offered exclusively with track drives, also called TERRATRAC. For markets with less stringent width requirements, tractors are also available with wheeled chassis. Dual tires with dimensions 800/70R42 and consequently an external diameter of 2,15 m can be fitted here, which is not yet offered by “articulated competitors”.

Case IH, a pioneer in 4-track undercarriage and triangular tracks on large tractors, has also stepped up its efforts. To apply the maximum power of 778 HP of the new flagship Quadtrac 715 (6-cylinder engine with 15,9 l displacement and 2-stage turbocharging) to the ground, the track drives were lengthened by 10 cm and the wheel diameter driving force was increased to more than 100 cm. They can now also be ordered with PowerFlex undercarriage suspension, which not only provides more comfort but also better ground tracking. Previously, spring-mounted triangular track drives were only available for large combines, but not for heavy tractors.

Tire pressure adjustment systems (Central Tire Inflation System - CTIS) are increasingly offered from the factory by tractor manufacturers. These include integrated solutions and those with externally routed lines. Due to the increasing importance of stub axles worldwide (among other things as a result of mechanical weed control), Fendt has adapted the "VarioFlex Duals" system with a 3 m stub axle and a double wheel hub, which has already been proven abroad, for an approved external width < 2,55 m for Europe. The use of wheel weights and the integrated VarioGrip tire pressure adjustment system remains possible.

Continuous development of comfort functions

Many manufacturers have introduced new and in some cases larger cabs with digital operating and display systems for their tractor series in recent years (examples: FendtONE operating concept or Massey Ferguson 8S cab). In the recent past, however, the development of cabs and operating systems has tended to occur in the “evolutionary” area.

Case IH presents “Adaptive 360° Work Lighting”, a lighting system that provides homogeneous lighting around the tractor without increasing the number of headlights. An important element are the folding supports at the front, halfway into the cabin. The settings for the headlights mounted on these, together with those on the rear fenders, can be made from the cabin and then saved. Memorized implements/working widths can be accessed via the "auto implement" mode in the tractor control panel lighting menu. For ISOBUS implements, this is carried out automatically during coupling. Consequently, there is no longer a need to choose between constantly re-adjusting work lights and a single compromise configuration for multiple units.

Previous cruise control systems are mainly controlled according to the speed of the wheels and therefore the theoretical driving speed. Slip (positive or negative) caused by tensile strength or rising/falling is generally not taken into account. Fendt now bases the "Real Speed ​​Cruise Control" function on actual driving speeds recorded via GPS or radar sensors, thus improving SET speed compliance. This is advantageous, among other things, when applying fertilizers and crop protection agents.

With ErgoSteer, Fendt also introduces joystick steering on the left armrest - in addition to the steering wheel. This can also be used to change the direction of travel and activate lane guidance. Self-centering allows you to always drive in a straight line with precision and the steering sensitivity can be set individually on the tractor control panel. An interesting aspect here is: ErgoSteer can be adapted to all tractors with FendtONE.

In current tractors, traction force is normally controlled through the lower arms. Raising or lowering the 3-point hitch often causes the position of the tillage implements to no longer be parallel to the ground, which can have a negative effect on the quality of work. To optimize this, Claas now also includes the hydraulic upper arm in the 3-point multidimensional control. To determine the position, height measuring sensors are mounted on the implement at the front and rear, which transmit signals to the tractor's electronic control system. These signals are converted into a control setting for the upper arm length via an additional hydraulic control unit, resulting in automatic adjustment of the implement's longitudinal tilt.

Autonomy presents new challenges

Automatic steering systems and programming options for recurring operating sequences, for example on the headland, have been available on tractors for years. The next step now is to try to “autonomize” the tractor implements. Depending on the level of autonomy, the driver may only need to monitor work processes; in extreme cases, he/she should no longer be needed. Several manufacturers are therefore presenting systems for transferring fully autonomous vehicles or for monitoring the quality of work. An example of this is the Krone/Lemken Vehicle Transport System (VTS) for the autonomous Process Engineering Unit (VTE). A drawbar allows the vehicle and its implements to be moved to the field by a “normal” tractor. The steering strategy is adapted to the speed so that it is stable at high speeds and follows closely through curves/entrances. The service brake of the autonomous towing vehicle, which is considered a towed vehicle on the road when using the new VTS system, is actuated through a standard 2-driver air brake system.

New Holland is taking a slightly different approach with the T4 Electric Power battery-powered tractor, introducing interesting range and safety features that could already be beneficial for practical use in the near future. Camera systems mounted on the cab roof and front of the hood allow, for example, a 360° panoramic view of the tractor that can be transmitted to the cab control panel, recognition of rear-mounted implements for simplified hitching and automatic transmission Power take-off disconnection if people get too close to the power take-off shaft.

In addition, there are the functions "Route Mode" (the tractor follows a defined driving sequence, for example in orchards), "Invisible Bucket" (improved vision during front loader work by "editing" the implements on the control panel from the cabin) and "Follow me". The “Follow Me” mode should be particularly interesting for jobs in which the driver has to constantly get up and down to move the vehicle forward a few meters, as is the case, for example, when manually harvesting vegetables or assembling fences. To do this, the driver must activate the mode on the tractor's control panel and then go to the tractor's front detection area for “identification”. The tractor then follows just that person. Additionally, there is a gesture control system that allows the tractor to receive driving instructions through hand signals.

By Roger J. Stirnimann, professor at the School of Agricultural, Forestry and Food Sciences (Zollikofen, Switzerland)