ISSN 01 11-4743

SSOCl ATlON VoI. 13 No. 4 1991

FELLER-BUNCHER APPLICATIONS ON CABLE TERRAIN

Dallas C. Hemphill, Consultant Engineer, Eugene, Oregon, U.S.A.

INTRODUCTION Steep-Slope Quad Track The rapid transition from large to small The Allied Tree (ATH) is the timber in the Pacific Northwest of the only model in this class. Designed specifi- United States has engendered an adoption cally for steep terrain, it has an undercar- of mechanised logging systems. Feller- riage with four track-type pivoting bogies bunchers, processors, and flail delimber- with Cat D6D track components. The four debarkers are finding wide acceptance. The track pods are independently hydrostati- purpose of this Technical Release is to cally powered and the suspension system document the applications of feller- permits all four tracks to maintain contact bunchers on terrain in the with uneven ground or over obstacles. The Northwest, and to draw conclusions about upperworks are self-levelling on slopes up possible applications in New Zealand. to 70% (35'). The engine is a Caterpillar V-3208 rated at 157 kW (210 hp). The fell- Note that feller-buncher applications with ing head is equipped with either a ground-skidding systems are not addressed or a shear with up to 70cm capacity, and a in this Technical Release. maximum reach of 7.6m. Most of the small second growth timber logged b in the Northwest is Douglas & and western hemlock. Typi- cally, the average tree size is about lm3. Compared to New Zealand stands, American stands, being of natural origin, are much less homogeneous in tree size and stocking. The ground is often rather wet and undergrowth can be heavy. The Northwest has a tradition of log-length cable logging. Tree-length logging - with or without a feller-buncher - is regarded as innovative in most areas. A peculiarity of man American stands not seen in New Zear and is the incidence of large diameter (1-2m) cull logs left from earlier logging, that are still not rotted. FELLER-BUNCHER CLASSES Three main classes of feller-buncher have found application with cable logging in the Figure 1 - ATH feller-buncher works comfor- Northwest. tably in small trees on 50% slope. Levelling Dual Track

As a group, these machines have the capability to level the turntable when operating on a slope, and have an under- carriage with two tracks. So far, the 2500 Series feller- bunchers (formerly Timbco) are the only models in this class used in Northwest cable logging. These machines have 130kW (175 hp) engines and a hydrostatically- powered tractor-type tracked undercar- riage with counter-rotating capability. The upperworks can be levelled on ground u Figure 3 - Tanguay levelling tracked to 51% (27') fore-and-aft or 34% (194 feller-buncher sideways. ' The most popular &ads are 55cm saw models. Non-Levelling Tracked Many models are manufactured in this class. Most are based on a modified ex- cavator chassis, such as the Cat 227. A few, such as the Timberjack 628 (previously Koehring 628) are designed specifically as a feller-buncher. Compared to the

Figure 2 - Timberjack feller-buncher As shown in Figure 2, the small timber, well-drained soil and moderate terrain are conducive to mechanical felling. However, patches of heavy undergrowth inhibit operator visibility and old cull logs like the one in the middle foreground are a sig- nificant barrier. A recent entry in this group is the Prentice 630-FB. This machine is custom-designed as a feller-buncher, and is self-levelling on slopes up to 27% ls0).It is a 30-tonne machine of 157kW i 210 hp) with a maxi- mum reach of 8.7m. The undercarriage is D6-class. Tannuav-. makes a similar machine. To date, neither model has been Figure 4 - Excavator-based non-levelling applied on Northwest cable logging opera- feller- buncher tions, but they should be suitable. modified excavators, the custom machines Slope Capabilities typically feature heavy guarding, advanced cooling for engine and hydraulics, easy ac- Operator skill is found to be a prime deter- cess to components, a custom-designed minant of productivity for all machine boom, and a custom-designed undercar- classes. riage. Custom undercarriages are purpose- designed for longer tracks and better flota- As slopes increase, travel speeds decrease tion. for all machines, and swing speeds decrease for the non-levellin machines. Specifications vary, but as an example the Also, compared to flat- ound f! eller bunch- Timberjack 628 is a 33-tonne machine with ing, it is often desireB to swing the trees a 154kW (207 hp) engine. It is typically 180' in order to bunch them with the butts used with a 55cm saw head, and has a pointing uphill for efficient extraction, fur- reach of 8.5rn. ther reducing productivity.

APPLICATIONS ATH - On suitable soils, the machine operates well on sustained slopes of 70% General (35'). However, productivity drops off on slopes over about 40% (22') and operators ATH - Only four ATH machines have been feel that the machine is probably not com- sold. User opinion is that the concept is petitive with owersaw cutting on slopes outstanding but that additional mechanical over 50-55% 4270-29') where soils are dry. modifications are necessary to achieve ac- In wet clayey soils, the machine may be ceptable availability. All have been used in limited to 40-45% (22'-24') slopes. clearcut logging, in average tree sizes rang- ing from about less than 0.5m3 to over 2.0~3. Timberjack 2500 - On dry soils with few ground obstacles, the Timberjack is Allied has extensively modified its design regarded as competitive with powersaw since the first four units were placed in cutting on slopes up to about 40% (22'). service. Areas completely re-designed in- Where soils are moderately wet, as in much clude the frame, the trunnion area, the of New Zealand, it appears to be competi- hydraulic system, and the electrical system. tive up to about 35% ( 19') slope. The fifth machine commenced operational trials in late 1990. It uses a 71cm (28) Rotosaw head. Non-Levelling - The terrain ca ability of the non-levelling machines is a R nction of Timberjack 2500 - Numerous Timberjacks torque supplied to the undercarriage drive are used on all es of terrain in the and swing motors. Powerful, custom- Northwest, most wits tractor logging. They designed machines such as the Koehring work in a wide ran e of average tree sizes, 628 readily tackle 30-35% (17'-19') slopes from less than 0.5mg3 to about 1.5m3. They and skilled operators work them on steeper are favoured for thinning and other partial ground. There appears to be little disad- cut operations because of their high vantage on slopes under 30% (17') in not mobility and limited tail swing. The design having the levellin feature of the other is regarded as mature and reliable. classes - but only if the machine has ade- quate power. Nun-Levelling - These machines are also widely used, most with tractor logging, in a Obstacle Capabilities similar range of tree sizes to the Timber- jack. The various designs are regarded as The mobility of all three machine classes is mature and reliable. Owner opinion is that substantially impaired where there are models designed specifically as feller- numerous large cull logs. This is a primary bunchers out-perform the modified ex- determinant of setting suitability for feller cavator models in terms of both produc- bunching in the Northwest. In New tivity and availability. Zealand, this would normally be a serious consideration only where there. were one pass, and metal fatigue is likely to numerous large undecayed windfalls. The result. ATH travels over culls the best, followed by the Timbejack 2500 series. Another as ect of trees barely within the felling hea fdiameter capability can be the Heavy undergrowth significantly affects difficulty of controlling the fall adequately. productivity, because it obscures the Trees over about 40m tall, for example, are operator's vision. The ability to cope with poorly controlled even by the large ATH hea brush depends mainly on the type of machine, resulting in poor bunch integrity hea7 used, a high-speed continuously- and orientation. rotating sawhead such as the Koehring having superior clearing capability. Under- growth density would be a significant con- The oversize issue aside, for settings that sideration in some New Zealand forests, af- are otherwise suitable for feller-buncher fecting head selection more than the choice operation and tree length extraction, ex- of the base feller-buncher. perience indicates that feller-bunchers are economically competitive with powersaw Soil type and moisture significantly affect falling, in terms of stump-to-truck wood machine productivity for all classes. cost, up to a tree size of very rouphly lm3. Swampy settings are unsuitable for feller- Powersaw falling is typically favoured in buncher application. Wet clay soils are timber larger than this. operable only on gentle grades. In the Northwest, it is not unusual for feller-buncher operators to stay out of wet SYSTEM ECONOMICS llies, leaving those trees for powersaw &ers instead. The main benefit of feller bunching is to increase yarder productivity, resulting in a Tree Size lower total delivered wood cost. It should be understood that this set of economics is Selectin settings for feller bunching in for the American situation, where labour is terms oB tree size usually revolves around more expensive than in New Zealand (at the maximum diameter capability of the least NZ$25/hour including fringes and machine available. Typically, operators do benefits), capital is less expensive not feller bunch stands where more than (commercial interest rates typically 11%), 10% of the stems are larger than the head and the availability of equipment service can sever in one pass. It is preferred to and parts is normally excellent. Clearly, a have almost no stems over the head different set of economics applies in New diameter capability, because of the Zealand. problems caused by handling oversized trees. There is also a benefit in lower breakage, Oversized trees can be cut by the feller- in both falling and extraction. Wood values buncher operator who caries a powersaw are higher in the top portion of American for the purpose. This means having a high- trees than for radiata ine, so the benefit capital machine idle while he accomplishes would be smaller Por New Zealand thls task, and is therefore expensive. Alter- operators. natively, fallers can cut the oversized trees after feller bunching is finished. However, Some operators report that the advantages this can result in excessive breakage when are greatest in poorly-stocked stands, the trees hit bunches, and the trees are where bunching makes the greatest im- likely to fall out of lead for extraction. provement in extraction productivity. This circumstance does not apply to most New Some operators mechanically fell oversized Zealand stands. trees by cutting them from both sides. However, machine booms are not designed Correct bunch orientation is crucial to handle trees larger than the head can cut in achieving high extraction unit productivity. Bunch integrity is also important, especially very few New Zealand operations where for grapple logging since a bunch that the trees are small enough for feller- breaks apart is no better than not bunch- bunchers to produce wood at a lower cost ing. The best feller-buncher operators than powersaw falling. place bunches on chunks under the butt end to enable easy hooking on, and for Furthermore, much of the terrain most gapple logging they take special care to suitable for feller-bunchers is likely to be index butts and keep bunch size within tractor logged in New Zealand, whereas it grapple capabilities. might be cable logged in the United States because of the greater stress on soil protec- Grapple logging of feller-bunched wood is tion. Much of the wet, steep and/or clayed regarded as little cheaper than using terrain that normally would be cable chokers except where the terrain is well logged in New Zealand is likely to be un- suited for this system (short reaches, con- suitable for feller-buncher operation. cave slopes with good operator visibility). Some operators use radio-controlled A further limitation in some New Zealand chokers successfully in bunched wood. operations would be the difficulty of having sufficient forest available at any one loca- The landing configuration is the key to sys- tion to cable log at a rate supporting a fully tem productivity. In the United States, tree mechanised system. length system economics are favoured by mechanical processing at the landing, and Thinning might be a possible application if it is regarded as imperative to have the New Zealand companies had not already ability either to inventory trees at the road- found that cable thinning produced unac- side, or to deliver sufficient volume to the ceptably expensive wood. Even so, major landing to keep a processor occupied - say capital-intensive systems changes would be over 400m3/day. In small wood, yarder necessary, that might be logistically un- productivity is usually less than this. The feasible. favoured solutions are either to add tractor production or to extract trees to the road- One factor that would favour feller bunch- side for later processing. ing on cable ground in New Zealand is that the mechanised system has a reduced Integration of all stump-to-truck system labour requirement, and a much safer work phases is extremely important to the suc- environment. The New Zealand tradition cess of feller bunching. Successful feller- of integrated system planning and layout, buncher operation requires complex plan- considering interactions between all ning of all phases, with setting selection stump-to-truck phases, would also be con- layout being the critical foundation. All of ducive to feller-buncher application. the interactions between system com- ponents must be considered in logging The conclusion is reached that economics layout and in operational management for do not favour feller bunching for most New successful feller-buncher operation. Zealand cable logging operations. Over- seas steep-slope feller-buncher develop- ments should , however, continue to be FELLER-BUNCHER POTENTIAL monitored by the New Zealand logging in- FOR NEW ZEALAND CABLE dustry. OPERATIONS This Technical Release is the work of the author and American experience is that feller-buncher is not the result of LIRA project work. LIRA operation is economically competitive on publishes it in the interests of wider dissemination of cable ground where the avera e tree size is knowled e in the industry. LIRA takes no respon- under (very roughly) lmB . In New sibility for the accuracy of figures nor does it Zealand, with the lower labour cost and necessarily support or disagree with the opinions and higher cost of capital, and in some loca- conclusions shown. tions a remoteness from skilled service and parts, the "break-even" tree size is likely to I For further information, contact: I be much smaller than this. There may be N.Z. LOGGING INDUSTRY RESEARCH ASSOC. INC. P.O. Box 147, ROTORUA, NEW ZEALAND. 1 Fax: 1073) 462-886 Telephone 1073) 487-168 1