monorail yarding

7/31/2019 Monorail Yarding

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MONORAIL YARDING

One of the most recent hauling methods is by monorail transportation (Figure 25). It consistsof a self-driven wagon unit and trailer which travels unattended along a single line of rail andis automatically stopped by special stop-devices placed at any point along the track. Thewagon and trailer can transport loads up to 1.5 tons. Rail sections of 3.6 meters in length aresupported by low expanding supports to enable the vehicles to ride clear of the ground, andthese telescopic adjustable supports permit, within certain limits, the easy crossing of roughand irregular ground surfaces. On a cleared ground strip only 1.5 meters in width, the

portable rail sections 74 kilograms in weight can be easily laid and assembled by two men.On steeper slopes, the speed of the loads descending by gravity can be controlled by apower-winch, placed at the top end of the slope, which also hauls the empty trailers back. Asafety stop is provided to prevent any runaway danger of the trailers in case of a cablebreaking.

Owing to its small carrying capacity, the present models of this monorail can be used only forthe transportation of the smaller timber sizes, and it is mentioned here as a possible methodfor future pulpwood logging in the tropics.

FOREST CABLEWAYS IN SHELTERWOOD SYSTEM

Ing. Pemysl HOREK, CSc. and Ing. Pavel MAUERMendel University of Agriculture and Forestry in Brno

Forest Training Enterprise, Masaryk Forest, Ktiny, CZECH REPUBLIC

There are three objective reasons for accelerating the development of cableway skiddingtechnologies in the Czech Republic. The reasons are as follows:

1. In 2000, the total volume from felling operations exceeded 15 million m3 of rough timberfor the first time in history, but the volume of timber skidded by cableways did not exceed

300 thousand m3. The latter is only 2 percent of total felling within a terrain of gradients over


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40 percent and terrains with unsuitable carrying capacity for tractors (peatlands)representing at least 10 percent of the total forest area.

2. There are about 90 forest cableways of different types known to be in operation at thepresent time and most of them are of obsolete design. Modern cableways of domestic

production (type LARIX) are gradually beginning to win the local market.

3. The changing conditions of forest management put an even greater emphasis onenvironmentally sound logging technologies, and there is no doubt that cableway timberskidding is one of the best methods from an environmental point of view.

The changing conditions of Czech forest include the shrinking size of clear-felling elements,advocating of more environmentally sound methods of management, i.e. that theshelterwood selection is winning preference over the regeneration clear-cuts. If the naturalconditions allow, the shelterwood system can work with natural regeneration. Difficult andsteep terrain requires the use of cableway skidding. In these difficult terrains, the method ofnatural forest regeneration by means of cableways usually pays back with greater ecological

and economic effects than the method of artificial regeneration, since the clear-felling systemon steep slopes brings considerable risks for the forest environment and is more costly.However, this can be avoided by using suitable silvicultural procedures, such as strip felling(by Prof. Polansk) with a forest cableway of modern design (see Photo 1). A moderncableway must be highly mobile and quick to assemble; its efficient use engages at leastabout 50 m3 of timber in one single logging operation. Also, a standard cableway must beequipped with radio control right from the place of load fastening in the stand since this is theonly way to choose work procedures with the minimum damage to self-seeding, advancegrowth and standing trees of the parent stand.

Photo 1. Strip felling by Polansk made with the LARIX cableway

Model working procedures and necessary principles that reach the objectives of naturalregeneration of stands using LARIX cableway skidding can be demonstrated with theexample of long-term successful natural regeneration of beech stands at the Training ForestEnterprise Masaryk Forest Ktiny (TFE Ktiny) of Mendel University of Agriculture and

Forestry in Brno. The Enterprise was founded 78 years ago as a multipurpose facility servingmainly the Faculty of Forestry and Wood Technology to ensure pedagogic, research andverification requirements.


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TFE operates 10 406 ha of forests, which form a continuous complex immediately situatednorth of Brno. The forest stands are situated at altitudes ranging from 210 to 575 m. Averageannual temperature is 7.5 C, mean annual precipitation amounts to 610 mm and to merely360 mm during the growing season. Parent rock is granodiorite in the western part of theEnterprise, Devonian limestone in the central part, and Culmian greywacke in the easternpart. The topography is heavily broken with conspicuous deep valleys of the Svitava Riverand Ktinsk Brook and with numerous side valleys and glens. Slopes with gradients over 34percent take up a quarter of the Enterprise area, a good reason for being professionallyinterested in forest cableways. Diversity of natural conditions is considerable andincomparable for such a small area in the Czech Republic. Mixed stands prevail in thatregion, in which 48 percent are coniferous tree species and 52 percent are broadleaf. Maintree species are spruce, pine, larch, beech and oak. The TFE Ktiny has a long tradition inthe application of feasible methods of forest management specialized in the use of naturalregeneration. Environmentally sound forest management methods have been applied over along period, including the system of small felling areas and its forms of shelterwoodregeneration and regeneration by border felling, as well as the application of selection forestmanagement principles.

Many famous foresters have worked here, such as Leopold Grabner, Chief of the ForestDistrict, managing forests formerly owned by the family of Liechtenstein; he introduced aproject in 18481897 in which the forests were aligned and, every ten years, repeatedlytreated in five elaborates of forest management plans to the Saxonian area control systemby Cotta. Clear-cuts were gradually reduced and compartment shelterwood fellingintroduced. Great emphasis was put on all tending measures which were neglected up tothat time.

Another outstanding forester was Julius Wiehl, who devised a modern management plan atthe turn of the nineteenth and twentieth centuries, in which a system of balanced ageclasses and management by stands was introduced. Julius Wiehl adopted a shelterwood

form of the small-scale management of even-aged stands. The method augured a naturalconception of the forest that would be steadily creative and sustainable.

The foresters working with the TFE forests in modern history and today are ProfessorsKonel, Haa, Opletal, Polansk, Doleal, Vyskot, Tesa and Kantor, who contributed to thedetailed precision of a special method of beech management in a shelterwood system, i.e.regeneration of beech stands by group shelterwood felling which gradually melts into bordercutting. The method has markedly expanded in the last ten years, even in difficult terrain, asa result of the application of LARIX cableways.

Good management of beech stands at the TFE is also documented by the fact that it is the

only forest facility in the Czech Republic with the Woodmark FSC Certificate for raw andsawn timber, awarded to the facility four years ago.

The special method of beech stand regeneration and tending applied at the TFE aims at amaximum utilization of natural regeneration and increment from the release. The beechstands are regenerated at a relatively long (up to 40 years and more) regeneration period.Since the present rotation period is 130 years, the first advance growths emerge as early asat the stand age of 90 years. Therefore, it is necessary that conditions be created for the riseof self-seedlings and subsequent shelterwood felling already when implementing the lasttending measure. The stands to be regenerated are to be divided by approximately 100 to120 m by inserting cableway routes, i.e. strip clear-cuts whose width should be 4 to 5 m.

There is a principle to be observed at the measure implementation: that the entire strip widthis not cut before the proper cableway timber skidding takes place, but is only the narrowest


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slit possible to enable the operation of a cableway about 3 m wide. This is eventuallywidened to the required width of the strip felling by Polansk only after the entire loggingoperation has been accomplished. This is how trees along the line can be removed, whichwere possibly scratched while serving as fenders at skidding. Then the felled stripcutbecomes a starting point for the natural regeneration which shifts under the parent standfrom below. The logging is made in the context with shelterwood felling, the intensity ofwhich decreases from the cableway line edge into the stand inside. This shelterwoodtreatment is made along both sides of the cableway route and results in the removal ofmainly large-diameter trees with ill-shaped stems or crowns from the main stand level up toa distance of 20 to 30 m from cableway reach.

Qualitative trees with perfect crowns and good growing characteristics are left in the standfor seed. By selecting the ill-shaped large-diameter trees, we release main-level and sub-dominant trees of smaller diameter, which respond to the release with increased lightincrement on qualitative mass. Research indicates that the increment can fully compensateproduction losses often recorded at the selection of large-diameter trees. The consistent andtimely selection of large-diameter trees, together with the reduced rotation period, help to

prevent the development of red core, which can result in great economic losses.

At logging, we principally save the sub-dominant trees which influence the standmicroclimate for the sound development of advance growths. After the stand has beengradually felled and ensured, there are other fellings inserted into the original system of stripfelling, which gradually results in complete regeneration of the whole stand. The describedsystem of beech stand management is a good example of qualitative incrementmanagement, and there are a number of examples in the stands of TFE Ktiny, which provethe validity of the method described above.

As to the technical aspects of cableway skidding employed with the above-mentionedsilvicultural procedures, the LARIX forest cableways - whose technical parameters and

suitability correspond to the shelterwood system in individual selection - have beenexclusively used at TFE Ktiny over the last five years. The following technical solutions ofthe LARIX type cableways facilitate the application of environmentally sound timber skiddingin selection felling:

The driving and transport unit is the farm tractor classed from 45 to 70 kW. Skylines can do timber skidding in semi-suspension or full suspension in diverse

terrain - both in a classic way up the slope from the stand towards the skyline towerand from the tower down the slope. A possibility of timber skidding on flat groundexists for sensitive terrain, particularly in protected areas (see Scheme 1).

The LARIX cableways are designed as implements on an agricultural tractor - where

a part of the cableway is carried on the rear three-point linkage (tower and winches)and another part (drums with running line) is carried on the front three-point linkage. Thus, the cableway's weight is evenly distributed onto the two axles, which renders

the tractor with the cableway mobile even in difficult terrain. Terrain accessibility of the farm tractor with the suspended skyline is nearly identical

to that of a special forest tractor. The site for the cableway does not need any special treatment; acceptable

longitudinal and transversal terrain gradients for tractors with cableways installationare up to 15 percent.

Cableway reach is up to 600 m, carrying capacity 3 000 kg, yarding force 32 kN,weight up to 4 500 kg.

Cableways LARIX are radio-controlled from the stand, from the loading and

unloading place, which facilitates a general view of the site for the operator


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The cableway is equipped with five cables: skyline, endless line, hoist line, slack-pulling lines and straw line.

The system with endless line makes it possible that loads during transport need notbe braked by the haul-back line, and it is very simple to direct the carriage with orwithout the load. Targeted automation for hauling in or hauling back the carriage isstandard equipment.

The line can be pulled out from the carriage up to a distance of 70 m.

Scheme 1. There are four ways of using LARIX cableways as follows:

1.1 System with skyline, endless, hoist, slack-pulling lines and special carriage to hold thefully suspended load in a horizontal position.

1.2 System with skyline, endless, hoist and slack-pulling lines; direction of timber transport tothe cable tower.


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1.3 System with skyline, endless, hoist and slack-pulling lines; direction of timber transportback to the cable tower.

1.4 System with skyline, mainline and gravity carriage.


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The TFE Ktiny maintains a long tradition in the application of environmentally soundmanagement methods in forest stands by using natural regeneration. The high rating ismade possible not only on the basis of assessments made concerning existing forests inconcrete production conditions but also concerning the long life of the forest stands andcomplex evaluation of their history. Nor are decisive operations in the forest neglected, suchas logging and skidding technologies, which include forest machines, transport accessibility,forest protection, execution of hunting rights and, of course, also concerning forestmanagement itself.

Recent practical experience indicates that LARIX cableways are a good helping hand inecological and sustainable forest management because of their suitable technicalparameters (see Table 1).

Table 1. Comparison of the design parameters of Larix 550 and Larix 3T

Model LARIX 550 LARIX 3T

Engine power of the tractor 45 kW+ 70 kW+

Line capacity

Skyline 550 m / 16 mm 600 m / 18 mm

Endlessline 1400 m / 11.2 mm 1 500 m / 12.5 mm

Hoistline 200 m / 11.2 mm 200 m / 12.5 mm

Slackpulling-line 1100 m / 5 mm 600 m / 8 mmStrawline (PP-textile) ---- 1200 m / 8 mm

Line pull / speed

Skyline 40 kN / 2.2 ms-1 50 kN / 3 ms-1

Endlessline (haul-in) 20 kN / 2.2 ms-1 26 kN / 2.5 ms-1

Endlessline (haul-back) 8 kN / 5 ms-1 10 kN / 5.3 ms-1

Hoistline 25 kN / 1.5 ms-1 32 kN / 1.5 ms-1

Loading - max. recommended 2 000 kg 3 000 kg

Lateral reach 60 m 70 m

WeightTower with winches and lines 2 450 kg 3 050 kg


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Storage drums with lines 1 200 kg 1 400 kg

Tower height:

in operation 6.5 m 6.5 m

in transport 4 m 4 m

CAREFUL, QUIET TIMBER FORWARDING WITH PLASTICCHUTES

Wilfried PRLLFederal Forest Research Centre Vienna, AUSTRIA

Abstract

Although operational costs of the chute seem high, this method of operation should be usedwhen the stand, the ground and the young growth need special care, and when othermethods of extraction are impossible, or simply cannot be employed. Obtaining even just alittle free output, or perhaps none at all, is however more worthwhile than thinning in thicklypopulated spruce stands and allowing uncontrolled stands to grow with associated risks.Longer racks with larger quantities of wood than those described in the above examplewould significantly reduce the cost per cubic metre for building, installing and dismantling thechute.

As far as personnel working on the site are concerned, this was a worthwhile operation on asite that had no dangerous exhaust fumes, machine vibrations or noise.

Introduction

Timber chutes are slides constructed from synthetic materials shaped into channels thatcarry timber by using the cheapest form of energy: gravity. Their length resembles the slopeon which they are laid, but they extend the distance over which logs can travel, and reducedfriction enables quicker delivery than on an earth slide.

Slides were mentioned in history as long ago as the seventh century BC whenNebuchadnezzar II had wood slides constructed to transport cedars. In Austria a fourteenthcentury chronicle tells of specially constructed timber channels in the Tirolean Weistmerarea, and there is also an eighteenth century account of similar constructions in thePontirone Valley in Tessin, Switzerland. There are other reports of slides in Ennstal andBaden Wrttemberg, therefore, this type of timber transport can be shown to have beenused in these areas since the Middle Ages until the present.

Of course their construction and maintenance required a great deal of labour and materials,and therefore over time they were replaced by other methods of forwarding, such as forexample skyline systems.

With the arrival and manufacture of modern materials based on mineral oils, newpossibilities opened up for the construction of slides and, as early as the 1970s, the Austrian


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firm, Leykam, developed a plastic slide, known as the Leykam Log Line. This wasdemonstrated to forestry professionals in 1975 for the first time.

Technical and operational details

The Log Line is composed of a semicircular plastic channel made of polyethylene - which isa material that retains its shape, is robust and can operate over a wide temperature range,both above and below zero - all of which guarantees a long service life. At first, the systemconsisted of pipes for the main run and open sections at the delivery point.

Nowadays only open channels are used. They have an internal diameter of 350 mm andwalls 9 mm thick. Each channel has a length of 5 m and weighs 25 kg. The individual shellsare fixed together in a line of required length, using stainless steel quick couplings, which arelaid down the slope. For ergonomic reasons, and because they travel better, wood lengths of2 to 4 m are most efficient. Depending on the radius of the curves on the slide and howstraight the logs are, log lengths up to 6 m, and with a diameter of 30 cm at the wider end,can be accommodated.

Because logs can build up speed, 200 m stretches are the most practicable. The individualchannels are tied with nylon rope to neighbouring trees, stumps, etc. If none are available,stakes can be used which can be quickly cut and sharpened from treetops using a chainsaw,and driven in next to the channels. To prevent the channels from sagging, branches andbrush can be placed beneath them. To avoid the possibility of breakage, the chute shouldnot be laid over loose rocks or bumpy ground. For similar reasons corners with a narrowradius should be avoided, since there is danger that the wood could slide out of the channel.If this is unavoidable, the corners should be built with higher sides.

Depending on the weather and the condition of the wood, a minimum gradient of 15 to 25percent is required for trouble-free operation. Maximum gradient is 50 percent, whichrequires braking measures to be taken or, if possible, the chute should be laid across theslope. According to studies undertaken by Horst Tauer BSc in Ort, Gmunden, spruce withthe bark still on has a dynamic coefficient of friction of 0.22 to 0.25 in dry weather, while wetwood in wet weather has a coefficient of friction of 0.15 to 0.18. Foreign bodies introducedinto the slide during operation, such as earth or vegetation, increase these valuessignificantly.

Speeds of over 15 m per second are to be avoided for the following reasons:

The kinetic energy of the log increases quadratically with its speed. This necessitatesstrong extensions above the corners and a stable construction to cope with the

increasing centrifugal force and the force of log impacts. This results in higherconstruction costs.

At points where the terrain changes suddenly, or where the direction of travelchanges, there is a danger that pieces of wood can slide out of the chute, damagingit or the remaining stand. Reparations add to the overall costs of the operation.

It will become more difficult to gather the wood at the outlet, and timber losses willmount.

Safety is compromised and the possibility of accidents increases. Braking measures become unmanageable at high speeds.

New openings for the Log Line

Despite its success in the past, the timber chute was, as mentioned above, increasinglyovershadowed by new extraction methods. Only a few contractors or woodland owners have


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installed timber chutes in recent years, and their use continues to decline. With newharvesting technology and an increasing awareness of ecological considerations, there arehowever new areas of operation, the value of which should not be underestimated.

Recognizing this, the Technical Development Branch of the FBVA in Vienna has carried out

work studies on the Leykam Log Line to determine whether this alternative method ofextraction is worth considering on steep harvesting sites where current forwarders or cablecranes are not usable. It was difficult to find a contractor who still uses this method ofoperation, and who was prepared for this type of investigation, as well as able to fit his ownschedules to our own.

Site conditions unsuitable for forwarders or cable cranes

The operation took place on a slope of around 35 percent in Rendsina. Chalky ground of thistype with an A/C profile is loose and consequently does not provide a good grip, and in wetweather it cannot be driven over at all. Dry weather is essential for harvester operations, aswas in fact the case during this study. Even though harvester operations in these conditions

are acceptable for ecological and safety reasons, this is not the case with the forwarder.Repeatedly driving up and down the harvesting racks would leave deep tracks every 20 m.which would turn into erosion channels, resulting in humus being washed away and wouldlead to karstification. For this reason and because of difficulties in driving across the terrain(this could not be carried out economically without a full load, and also could not beperformed safely), the option of forwarding never was considered.

Skylining was also not an option, since with these low volumes of wood per stand (see Table1), the small stem diameters, with a distance of 20 m between the stands, would also havebeen uneconomical. Nor were there suitable anchor trees. For these reasons, if the standwas to be completely mechanically thinned at an acceptable cost, the only option was thechute.

Specific operational procedures after harvesting

As is the case when using a skyline after harvesting, it would be advantageous to lay outassortments of wood near the racks. However, a different approach would be for the line ofthe chute to follow the path taken by the harvester through the stand. To position the chuteto best advantage for a convenient outlet, the harvester operator must be informed of theextraction plans and bear this in mind when laying out the assortments of wood. If possible,the operator should lay the wood in a herring-bone pattern, pointing down the hill in thedirection of the chute, which would make it easier to position and place the logs in the chute.The best results may be anticipated where both the harvester and the chute are the

responsibility of the same person, i.e. where a harvesting contractor is free to choose how toinstall the Log Line and when there is only one person in charge of both operations.

The same could be said for all forwarding operations following harvesting. Harvesteroperations generally succeed under the same conditions as those that favour the Log Line.The chute is therefore easily set up in the felling direction in the rack. There is usuallyenough brush in hand after harvesting to place some under the chute as support. Generally,brush can prove something of an obstacle when walking or bringing in logs. Naturally, afterclear-fell harvesting there will not be any trees to tie the chute to and, therefore, stakes haveto be driven in. These are, as already mentioned, quickly made with a few strokes of thechainsaw from the lop and top lying nearby. If they are driven in up against the chute, thishas the advantage of giving additional stability to the chute components, which is especially

important on corners.


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Operation details

Harvesting comprised the first thinning of an even-aged spruce stand, interspersed with alittle beech, in the 20- to 40- years-age class. Because of other commitments, the harvestingoperation that preceded the extraction could not be studied. This was, however, not crucial

to the study since performance data on tracked harvesters - in this case a Neuson 11002HV- were already available, and there were no noteworthy differences between this site andother similar ones. Tree size, with a breast height diameter (bhd) of 18.9 cm, was ideal forthe Logmax 3000 head, which has a maximum delimbing diameter of 380 mm.

Table 1. Main data

RackI

RackII

RackIII

RackIV

RackV

RackVI

Total

Volume (m3) over bark 15.07 12.16 12.26 8.31 4.58 5.02 57.40

Log diameter over bark (cm) 15.27 14.68 14.22 14.94 14.17 13.38 14.59

Breast high diameter (cm) 19.96 19.06 18.36 19.46 18.28 17.07 18.70

Average log length (m) 3.98 3.84 3.82 3.70 3.77 3.80 3.84

Average log value (m3) 0.07 0.07 0.06 0.06 0.06 0.05 0.06

Extraction rack length (m) 110 113 119 119 68 45 ---

Chute length (m) 90 90 90 90 46 32 ---

Number of chute elements 20 20 20 20 10 7 ---

Chute gradient % 34 35 36 38 30 34 ---

Average distance betweenracks (m)

22 metres ---

It was not possible to do a time study on the initial construction or dismantling of the chute.The pieces of the chute were carried to the operating area individually. Frequently they areattached together in a long line in the valley and then pulled up the hill by means of a smallAckja winch. Consideration was given to pulling them up the hill on a rope behind theharvester on its first foray into the woods. The possibility of placing the logs in the chutedirectly from the harvester was also considered, an idea, which because of technical drivingconsiderations, could hardly be realized in practice.

Stakes were prepared on site in the manner described, which were then driven into theground with a metal hammer and attached to the chute with nylon rope. Operations wereeasiest with log lengths of 2 to 5 m. Seventy percent of the logs lay in the ideal 4 m range, 3

percent in the 2 m range, 19 percent in the 3 m range while only 8 percent were 5 m ormore. Average length was 3.84 m (see Table 1). A chute ideal in length and gradientresulted in an acceleration pattern, which did not require a braking area to be built.

Table 2. Output

RackI

RackII

RackIII

RackIV

RackV

RackVI

Averagem3/man

Number of operators 2 2 3 3 2 2 ---

m3 with bark/h net 2.55 2.53 2.40 1.96 1.66 2.57 2.32

m3

with bark/h withbreaks

2.04 1.73 1.99 1.57 1.42 1.92 1.81


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Piles of branches on top of the logs sometimes made it difficult to pull them out - a situationthat should have been avoided by the harvester operator. As can be seen in Table 2, two orthree men were used alternately to change the position of the slide, to drag logs towards itand to lay them in the chute with the hook.

monorail yarding

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