Wide Span CTF

What is a wide span system?

The simplest way of describing a wide span system is to imagine a tractor being cut in half from front to back, pushing the two halves apart by anything up to around 10 m and joining them together by a beam (see below). The wheel mountings are redesigned so that they can be steered in the same direction of travel as the original tractor (in addition to being provided with differential speed control) as well as at right angles to this direction to allow the machine to travel lengthways along a road or track.
Considerable work was carried out on the design and commercial development of these machines by the late David Dowler and a glimpse of his genius and firm belief in the system as a practical farmer, is documented in a history drawn together from personal anecdotes, pictures and documents.

Wide Span system

Schematic of wide span vehicle. To run on the road, the wheels are turned through ninety degrees and are then steered conventionally. The vehicle can be built on any scale. (Dowler Engineering, UK)

The most common misconception about wide span systems is that they are only suitable for large, regular-shaped and level fields. Nothing could be further from the truth, unless of course the land is so undulating that even a conventional 12 m sprayer can't be used! This animation, scaled in both dimensions and speed of operation to a 10 m span machine, shows just how flexible and manoeuvrable machines of this nature can be. Although the main constraint for these machines was associated with their capital cost, this may no longer be the case. More sophisticated control systems and novel ideas such as those being pioneered (2011) by ASA-Lift make today's designs look distinctly more affordable as well as incorporating some clever road to field mode thinking. Look at our news report from 10 July 2012 and watch this page for further information.
Economics studies carried out some years ago suggest that within a cereals rotation a minimum farm size of around 900 ha would be required, and that three multi-functional units would be needed to run the operation. If you would like more detailed information about the wide span system under development, send an email to us at info@controlledtrafficfarming.com with "wide span" in the subject line.

What are the additional benefits of wide span?

The benefits revolve around a number of features of wide span – the stability afforded by the wide track, the width which more efficiently creates non-trafficked beds of soil, full width support for implements which reduces their weight, less need to fold implements for transportation and greater flexibility in harvesting operations. In detail these benefits include:

  1. Much less land lost to wheelways compared with tractors trying to do the same thing. This means that an immediate increase in yield of around 8% is likely. The drainage around these wheelways will also be better.
  2. The potential to increase farm profit by between 35 and 60 percent in a cereals rotation.
  3. Use of only half the amount of fuel per tonne of crop stored at the farmstead compared with existing systems.
  4. Automatic field marking. This avoids under- and over-lap of all implement passes, including those carried out on grassland. The figure below shows how the system works in an irregular shaped field.
  5. A reduction in chemical use through more precise and targeted applications.
  6. The creation of a system in which organic farming can be more reliably adopted and sustained and on a wider range of soil and farm types. This is achieved through more amenable soil conditions and greater precision that allows inter-row operations to be carried out more effectively, as indicated below.
  7. Optimisation of the benefits of machine stability (it provides an ideal platform for the rapidly developing DGPS technologies), wheel and crop separation, automatic field marking and new and integrated guidance and control methods to provide millimetre precision in row operations. Such a high degree of precision means that:
    1. crop row and inter-row can be managed separately;
    2. non-selective chemicals may be applied to the inter-row when crops are present;
    3. non-chemical methods of weed control can be undertaken more effectively.
  8. Four wheel drive, four wheel crab and differential steer allow the vehicles and implement systems to be highly controlled, even on side-sloping land. Such flexibility of control also ensures that the vehicles can always be maintained precisely on the wheelways.
  9. The opportunity to completely revise cereal harvesting methods to provide the potential for added crop value, reduced weed seed return and an extended harvesting period.
  10. The ability to cut grass for conservation more quickly but with little additional investment.
  11. Maximising the in-field drying area available for making hay or haylage.
  12. The means by which grass for conservation can be quickly and efficiently removed from the field with little or no damage to the remaining sward.
Wide Span field

Illustration of field set out with a wide span vehicle and examples of turning at the headland. With chemical application booms three times the width of the base vehicle, three headland passes are required. The main body of the field is worked with pirouette turns and short index traverses being made on the centre of the three headlands.

Are wide span systems available?

Although there are no commercial units available right now (March 2013), the Danish company ASA-Lift has been working on a government sponsored project over the past few years, meaning that could be offered to vegetable growers in the near future (see our News item from 10 July 2012). The 9.6 m span machine is due to be used on the Brdr Kjeldahl farm this year and we will try and report on its use and progress. Numerous photos of its first showing can be found on Brdr Kjeldahl’s website. Of particular interest is the fact that Grimme now have a majority shareholding in ASA-Lift and have already supplied Jens Kjeldahl with a 3 m stone separator for use in his 3.2 m track gauge CTF system.
Following use of the ASA-Lift WS9600 in 2013, a selection of the videos taken have been put together in a compilation which can be viewed at:  Youtube video of ASA-Lift WS9600

Also newly developed is a machine from CTBE in Brazil who became strategic partners under a plan to support innovation in the sugar industry (PAISS). PAISS is a joint initiative funding projects that include development, production and commercialization of new industrial technologies for the processing of biomass from the sugar cane. This video shows the first roll out of the machine showing its manoeuvrability but not yet equipped with implements or harvesting equipment.

As well as the Dowler machine, there have been other attempts at commercialisation, in particular by Biovelop in Sweden and by Ashot Ashkelon who produced about ten machines in the 1980s. These had a 235 hp engine, spanned 5.8 m and provided an underbeam clearance of around 2 m. One of these is still in use in Bedfordshire, UK and is included as a Case Study below. Other developments have been a centre pivot style unit in Slovakia (see this article) and an interesting design proposed by John Foxwell for small farms, details of which are given in this article.

A shift to wide span is a dramatic change for farming and may not come about by normally accepted methods. The existing industry has to be convinced that it is both practical and economically viable before it will be persuaded to invest at the significant level required. This fact was recognised and an "initiative" was formulated to fund development of a full scale demonstration programme involving six of the European Union Member States. Funding for the Wide Span Initiative (WISE) was sought from non-specific sources and sponsors who have an interest in improving the long term economics and sustainability of farming, and particularly as they relate to soil health and environmental issues. Although this initiative has not been successful so far, the partners remain committed to seeking support and are now assessing the potential of “Crowd Funding” to develop the wide span machine for the arable sector and in particular, the design of a combinable crops harvester. If you wish to find out more, want to support this initiative or be kept informed, please contact us at info@controlledtrafficfarming.com mentioning “Wide Span” in the subject line.

Wide span case study

A wide span case study from a farm in Bedfordshire, UK, is now available on this site. The Israeli "Field Power Unit" (FPU) was first introduced in 1996 and its integration is now almost complete. The image below shows the machine direct drilling winter barley in October 2003.

Direct Drilling