Mechanised pitting machine in the spotlight
Mechanisation of silviculture operations is the next major development phase in the forestry industry. Factors driving this development include safety concerns, ergonomic concerns coupled with the need to provide 'decent' work and the increasing difficulty being experienced by growers and contractors to find people willing to do the toughest tasks in forestry.
Jacques van der Watt (Multipit field technician) and Fanwell Buthelezi (Multipit operator).
|The Multipit in action in Iswepe.|
One of the areas that has become a focus for mechanisation is pitting. Various single head machines have been developed with a huge variation in cost and results. Some were making single pits with a pit-size of almost 1 m diameter by 1 m deep, while others made tiny pits of about 100 mm diameter by 250 mm deep.
A local company, Novelquip Forestry Pty Ltd t/a Multipit, started in 2007 with the development of pitting and planting technology. Substantial research was done to find out what the local industry required in terms of pit size and quality and cost (high productivity). It also goes without saying that the operation should be safe, ergonomically sound and environmentally friendly.
The driving force behind Multipit is Jaap Steenkamp. The initial stage of development was funded by the DTI's Sector Partnership for Industrial Innovation fund, and in 2009, the IDC became a shareholder in Multipit. Development work is time consuming and expensive.
Jaap said that initially, the planting machine was based on a telescopic mechanism that worked well, but for a limited period only, as the forces used in the pitting process exceed 1800 NM of torque, causing friction strips to grain.
So it was back to the drawing board for the Multipit team who decided to use a polar configuration, which worked well. Another decision was taken to concentrate on pitting only as this was the primary demand from the forestry industry. Earlier prototypes were able to apply fertiliser, water, pit and plant a seedling.
The Multipit technology is now being demo'd in the Highveld region and the testing of the comprehensive new planting machine will be from March 2013.
Multipit machines are available in configurations from a single head up to six heads. A four-head MP4P John Deere is currently being used by Iswepe Contractors for Mondi with good results.
A MP4P Multipit machine mounted on a John Deere 5725 tractor powered by a 65 kW engine was recently assessed by Francois Oberholzer on a flat site in Piet Retief, with some shallow drainage ditches and good, deep soils with underlying rock only in one corner. The site was free of slash and weeds (it had been burnt) and stumps were below 10 cm in height. The machine was set up to pit at two metre by three metre spacing.
Four pits were prepared every 19 seconds in good areas, while in the less favourable conditions, cycle times went up to 23 seconds. The average cycle time for a set of four pits was 21 seconds. This translated into productivity of approximately 6 000 pits in a nine-hour shift on the favourable part of the site, and around 4 800 pits per shift on the rocky shelf area.
It made 250 mm pits. The soil in the pits was loose and the sides of the pit had a rough texture, which is good for growth.
The on-board computer keeps a log of the number of pits made, as well as the number of pits that were not successfully completed. This occurs when the head strikes a rock or other obstacle and can't penetrate. The machine is programmed to make three attempts, after which it will abandon the pit and move on, logging an uncompleted pit.
According to Jaap, a single head mini-excavator based machine equipped with the Multipit electronics and head will achieve up to 1 800 ppd. He said a wheeled multi-head machine together with a single-head tracked machine would be the ideal combination to pit a compartment comprehensively to where mechanised harvesting can reach.
The machine consists of a carrier, slash reducer, frame and pitting heads, hydraulics and electronics.
The carrier of the Multipit machine is a John Deere 5725 Turbo, 65 Kw machine. Multipit also uses CLAAS as a carrier, but a customer is welcome to make his own choice of carrier within certain parameters.
The slash reducer is attached through a three-point link to the carrier. It follows the ground profile, and in the case of the heavy-duty units, the spinners (devices removing the slash) are spring-loaded to clear solid objects like rocks or stumps to prevent damage to the reducer.
The frame is constructed on the sides of the carrier to carry the heads. It is supported by a horizontal transverse beam under the carrier.
The heads consist of a hydraulic motor with a planetary gear reduction system, delivering 1 800 NM of torque. The speed is set fairly low to prevent soil from being ejected from the pit and to ensure a good tilth.
The hydraulic system consists of four independent oil lines to ensure the right quantity and pressure of oil where required.
A standard 'over the shelf' electronics system is used which ensures availability of components and ease of maintenance. The control programme is a dedicated Multipit programme and can simply be reinstalled or updated if, as and when required. The electronics control the full operation of the system.
Single-head pitting technology
The carrier for the standard Multipit head is a Volvo mini-excavator machine chosen for the best ground clearance in its class and more than adequate hydraulic delivery. It is equipped with four depth sensors and it registers the completion of a pit if the last of the four sensors records the depth to be reached.
Jaap says that Multipit takes product support seriously and will provide a comprehensive service. Machines have been designed in a maintenance- friendly manner, using components that are easily available.
Multipit rents a facility in Piet Retief and has a formal agreement with a well-known hydraulics business in Piet Retief. Carrier manufacturers have a good presence in all the forestry regions.
The Multipit team consists of Jaap Steenkamp (management and marketing), Helgaard Steenkamp (design and engineering), Thulani Femele, Kerneels Munnik and Jacques van der Watt (Technicians).
|The soil from the pit, ready for planting.||The pit made by the Multipit machine.|
Published in August 2012