Skidding by farm tractors at Sao hill, Southern Tanzania.

The study was conducted between September 1978 and March 1979 at the Sao Hill Forest Project, where there is an established sawmill. Since the inception of the Sao Hill terrain transport had been carried out by two Volvo TC 860 foxwarders equipped with hydraulic grapple loaders, Due to frequent breakdowns and problems of getting spare parts the forwarders have been found to be a costly means of terrain transport, and they are being replaced by farm tractors. The study was aimed at assessing the potential use of two types of farm tractors in the skidding operation: Ford County (four wheel-drive) and Ford 6600 (rear heel drive). The data obtained were for elearfelling stands of 26-28 years old Pinus Patula in which the standing volume was approximately 450 m3/ha. Time studies, productivity, costs, and tractive forces for log-length and tree-length skidding were recorded to ascertain the most suitable skidding method. The results showed that: 1. Loading was the most time consuming work-elements and that the loading time was considerably reduced when skidding tree-lengths rather than log-lengths. 2. The average productivity per effective hour and costs per cubic metre for the different skidding methods were:

                        Skidding         Average   

Tractor method skidding average Productivity Costs per distance load size per effective cubic metre (m) (m3) hour (m3/hr) (shs/m3)

Ford Country : long-length 162 2.5 6.3 19.8 tree-length 194 3.5 12.0 10.4 _____________________________________________________ Ford 6600: long-length 198 1.5 5.5 15.9 tree-length 154 1.7 9.4 9.4 Productivity decreased with increasing skidding distances while it increased with increasing load sizes, The productivity was much higher for tree-length than for log-length skidding. 3. From the tractive forces required the best and safest way of skidding loads with farm tractors was tree-lengths top foremost and suspended. 4. In terms of productivity costs, and the skidding forces required, it is most efficient to skid tree-lengths. 5. The optimum feeder road spacing in flat terrain was 280 m (range 180-430 m), while in steep terrain the optimum spacing was 195 m range 130 300 m). 6. The need for co-ordination between felling skidding and road transport operations is emphasised. 7.Ford County tractors, mounted with double drum winches skidding shield, front blade, and equipped with protective structures would be the best buy at Sao Hill for tree-length skidding.