The driver's seat is the component closest to the driver and the one with which they have the most contact. Yet, this component often receives little attention, both during purchase and in everyday use. Few people realize how much high-tech is inside and underneath. Our seat experts would like to point out a few things. Did you know that agricultural machinery drivers are the most likely to complain of back pain among all occupational groups (72%)?
In contrast, only 38% of the general population report suffering from back pain, but why is there such a huge difference?
Sitting for hours, sometimes in extreme vibrations on fields, farm tracks, etc., these are all reasons to utilize the potential of a modern agricultural machinery seat from Grammer, because Grammer is tirelessly researching ways to make the driver's daily work routine as relaxed and back-friendly as possible.
But what technical features do current driver’s seats offer?
Active seats intervene in the damping process through electronic control. Hydraulic and pneumatic systems are available; Grammer uses the pneumatic system.
Many different components work hand in hand to create optimal damping and suspension behavior.
Oscillations and vibrations affect the driver; these can vary greatly; depending on the surface and speed, different frequencies affect the driver.
The suspension of tractors and cabs absorbs some of these oscillations, but not all oscillations and vibrations can be eliminated; a large part reaches the driver, but the main problem lies in the large differences in these oscillations, both horizontally and vertically.
In addition, there are different rider weights and different body sizes, so everyone has a different perception of comfort and convenience.
Therefore, vibrations must be absorbed in three directions:
Vertical vibrations from top to bottom. Lateral vibrations from right to left and horizontal vibrations from back to front; each viewed in the direction of travel. The frequency of the vibrations occurring is referred to as frequency and is measured in Hertz (Hz); it indicates the vibrations per second. Depending on the use in the field or on the road, these can be high or low frequencies, ranging down to 0.4 to 18 Hz, and this is precisely where it becomes dangerous, because humans are not even consciously aware of this range – these vibrations form the resonance range of the spine. In this frequency band, the vertebrae of the spine, figuratively speaking, resonate against each other, and this can lead to increased damage to bones and cartilage. That's the medical theory.
Now the active seat controls come into play.
The interaction of the following components enables the most comprehensive suspension and damping of almost all oscillations and vibrations:
the position sensor
the accelerometer
the controller as a data center
the electro-pneumatic valve
the additional air volume
the compressor
the air bellows and the damper.
The last two are not a specific characteristic of active seats; they can also be found in conventional seats.
The position sensor and the acceleration sensor work closely together. They are located close to the seat surface because that's where they can measure the most precise values. A whopping 250 values are measured per second (!). For comparison: theoretically, the average person could only blink an eye per second. However, only the current position of the seat and the occurring acceleration forces in the vertical direction are recorded. Both measuring devices are special supplied parts that are not manufactured by the manufacturer itself. The data is transmitted in real time to the so-called controller, the seat's "data center."
The controller evaluates the supplied data and, based on specific, programmed specifications, calculates the parameters that subsequently lead to optimal damping of oscillations and vibrations. During the evaluation, the controller bases its calculations on two predefined spring curves. One curve covers low-frequency vibrations up to approximately 1.2 Hz, while all higher frequencies have their own characteristic curve. Optimal vibration damping is achieved by intelligently switching between the curves and frequency-dependent adjustment of the characteristic curve. The controller also considers the values provided by the vehicle and cabin suspension, as the seat and other vehicle suspensions communicate with each other.
The controller requires approximately 0.4 to 0.8 seconds to perform a calculation and output the corresponding commands to the electro-pneumatic control valve. The controller is also responsible for the active weight adjustment of the seat. With every change in weight, the seat adjusts itself fully automatically to the new conditions.
The interaction of all components ensures that the driver's seat is kept at a virtually constant level, regardless of the environmental conditions affecting the machine and driver.
But those aren't all the highlights of the tractor seat, because while the suspension provides a significant amount of seating comfort, it still doesn't provide all the comfort possible.
Two air cushions in the seat backrest at lumbar level provide optimal support for lordosis—the curvature of the spine in the lower part, pointing toward the abdomen. This ensures an upright sitting position.
The seating climate is optimized by seat heating, an activated carbon layer, and seat ventilation. Despite air conditioning in the cabin, fresh, cool air cannot circulate between the driver and the seat. This often leads to a damp back and buttocks. Body heat and perspiration are drawn through the fabric cover into the activated carbon layer. Due to the special properties of the activated carbon, this layer is able to temporarily store moisture. Activated carbon is very porous and therefore has a large total surface area; one gram of carbon can have a surface area of up to 2,000 m² across all pores.
Beneath the activated carbon layer is a ventilation layer. A fan draws air through this layer from the front edge of the seat to under the backrest. The airflow along the activated carbon layer dehumidifies the air; the air is finally expelled from the rear under the seat.
For cold days, the seat heating can be switched on, ensuring a pleasant seating climate even in winter.
Technical innovations that are more commonly found outside of tractor seats include the fabric upholstery and the seat design itself. Alcantara, a highly durable fabric made of extremely thin threads, is available upon request. This ensures that the fabric is soft yet extremely durable.
Grammer describes the design of the seat, and in particular the design and arrangement of the controls, as "design for use." The shape of the handles alone should inform the user which function is controlled by pressing the handle, eliminating the need to look, and preventing confusion.
But what good is a proper seat if the adjustment isn't right? So, how do I adjust the seat correctly?
- All controls in the vehicle must be accessible
- The thighs rest comfortably on the seat, but not completely, as this would interrupt the blood circulation
- The back should have constant contact with the backrest
- The spine should be adequately supported by the lumbar supports
- All dampers should be set as soft as possible without hitting the end stop
- If a headrest is available, it should be at the back of the head at eye level
We're happy to offer you a suitable active seat for your tractor. Nothing is more important than a proper seat to protect the operator's health! Ask our seat experts!