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About MidiFlex

History

The idea of MidiFlex was born from the Silva Nova planting machine. This machine was made to provide terrain ready for immediate planting. In order to do this the disc trenchers were mounted in front of the bogie and during scarifying, the bogie wheels ran over the ridge and the soil was thereby ready for immediate planting.

After Silva Nova there was still interest from employers and entrepreneurs to develop the machine further. This led to the following specification for the new machine.

It should be possible to mount the unit in front of the bogie wheels on a medium-sized forwarder and work with the disc trenching technique.

  • The device should work at a continuous forward speed and make a "reversed ridge" in front of the bogie wheels. The ridge should be compressed by the wheels and thereby prepared for planting.
  • The biological results should be prioritized, with good planting spots and very little unnecessary impact on the soil.
  • It should be possible to adapt the trenchers to low impact for less energy consumption and smaller machines.
  • Based on this, the idea of a parallel arm and continuous measuring of the ground pressure was born.

A first prototype was developed and tested on a forwarder smaller than usually used for scarifying. Almost immediately, it was clear that the idea was good, but it needed more sophisticated hydraulics and control systems than was used at the time.

After these prototypes, the project grinded to a halt, mostly due to lack of time. Eventually, we at Alftaprodukter were asked to take over and finish the product.

In late summer 2008, we started working on the hydraulics. Several proportional valves are used to regulate the hydraulics and different cylinders. At the same time, we searched for a new control system. Eventually, we choose an IQAN system from Parker with a modern display to present the different data. Our intention was to be able to test the machine before the season was over.

Time began to run out, but by the end of October, the machine left the workshop. We were lucky to have a local entrepreneur who was willing to test the machine on some sites he had marked for this occasion.

Working method

MidiFlex works with two disc trenchers mounted on each side of the forwarder, in front of the bogie wheels.

The driver very easily chooses an appropriate working width, disc angle and ground pressure for the terrain that is to be processed. It is also possible to adjust the speed of the rotation of the discs which follows the machine´s speed forward. These parameters can also easily be adjusted by the driver during ongoing work. The machine has several sensors that inform the system of speed, position of the arms, disc angle, ground pressure and so on.

A fixed value is continuously calculated in the system, depending on chosen ground pressure, position of the arm, etc. This value is transformed into a force that, through the hydraulics, aims to keep the turnable holder against the frame in its original position. If the force on the disc exceeds this value, for example when it runs in to an obstacle, the position of the arm will be changed. The system then compensates by reducing the force on the ground. This makes the disc more or less "float" over instead of moving the obstacle. If the obstacle is too big, the system commands the arm to lift over it instead of "floating".

Regardless of the height position of the trenchers the pressure on the ground is continuous due to a number of cylinders that control the arms. The pressure on the ground is variable from floating to a ground pressure of about one ton.

The right and left arms are functionally separated, which enables the machine to handle one-sided obstacles. By using the joystick, the driver can easily lift one or both arms when, for example, passing a ditch or any other large obstacle. The arms are automatically lifted when reversing the machine. 

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