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Australian sera clearing methods

Kingscote, South Australia

The following brief account of Australian land clearing methods was written as the result of the writers visit to some of the more remote areas of Southeast Asia and Japan, where it was felt that similar techniques might be applied with success. Many of the ideas suggested may not be entirely new. However, the techniques as evolved in Australia are highly developed and have reached a high peak of efficiency. It is hoped that they may well be applied in other countries. Although the capital cost of the heavy machinery recommended is high, its efficiency, when correctly used, will demonstrate that land clearing can be economically carried out.

IN Australia, during the past 20 years, large areas of hitherto waste land have been brought under cultivation or sown to pasture. This has only been made possible by the development of now land clearing techniques. The shortage of available manpower has made it imperative that highly efficient methods be used in order to ensure profitable returns. The increasing demand for more land in the comparatively small areas that enjoy a reasonable rainfall have speeded up this work. The techniques that have been developed in Australia could have application in other countries, and the following description of some of these methods may enable those undertaking similar work elsewhere to adapt some of them to suit their own environment, and so save valuable time and effort in experimental work.

It may be thought that the use of large machinery for land clearance is uneconomical when compared with traditional methods in those countries where labor is relatively abundant. However, a comparison of costs will usually show that the reverse is the ease. It should be emphasized at the outset that it is not proposed to mechanize agriculture in thickly populated areas. But it is hoped that mechanization of land clearance itself will enable new land to be brought under cultivation quickly and economically in order that more people may be enabled to grow more by their traditional methods.

The introduction of large crawler type tractors opened up new possibilities in land clearing techniques. Land that had hitherto been covered by dense scrub (jungle) and had been considered uneconomical to clear for production by the use of the axe, or with the aid of draft animals, was now looked on in a new light. The bulldozer was an obvious means of removing trees and undergrowth and was used in earlier work. Used alone, however, the bulldozer proved costly and inefficient on all but very heavy trees, and then only when the trees covered land of high value. Other ways were then tried. The scrub roller was first used, and later what came to be known as " chaining, " and " logging. A brief description of these methods follows.

The scrub roller

This was one of the earlier machines developed for land clearance. Although it has largely been superseded, it may still have a place in lighter types of scrub, particularly where the scrub is difficult to bum, and where it is not easily crushed by a log or a chain. Scrub rollers are usually made from old steam boilers from 3 to 4 feet (90 to 120 centimeters) in diameter and from 10 to 12 feet (3 to 3.60 meters) in length. An axle from 2 ½ to 3 inches (6.5 to 7.5 centimeters) in diameter is fixed through the center of the boiler. The end of the roller through which the axle passes must of necessity be firmly reinforced. A large bearing, usually of wood, is placed on each end of the axle. On these bearings a frame is constructed, usually of native timber. The frame is so designed that timber on the frame will strike trees to be rolled before the boiler strikes them. In this way the tree is bent over, as shown in Figure 1, allowing the roller to run up it and complete the crushing operation. The roller frame may be so designed that it will pull either from the center, as in Figure 2, or one side. A frame pulled from the center is easier to construct and may be used in light short scrub. However, one pulled from the side has the advantage that the tractor operates in the area already rolled, and there is less danger to the operator from falling trees.

FIGURE 1. - Construction of scrub roller.

FIGURE: 2. - Center pull scrub roller.

Rollers may be attached to the tractor in a variety of ways. They may be attached directly to the frame. This is very convenient where the scrub is not larger than the length from the boiler to the tractor. Otherwise it is highly dangerous to the operator. Another method is to &How the front of the frame to rest on a skid. The roller is pulled by chains as in Figure 3. These chains run through a loop of chain on the front of the frame. This allows the roller to be guided. When using this method it is advantageous to counterbalance the front of the frame, in order to make the whole machine more maneuverable. This is clearly demonstrated in Figure 4, which shows the construction of a roller from the rear.

FIGURE 3. - Construction of side pull scrub roller.

FIGURE 4. - Scrub roller. Rear view.

A third and perhaps the best method of attaching the roller to the tractor is shown in Figures 1 and 5. The front of the frame is attached to a large axle supported by large waggon wheels. A pole connects this assembly to the tractor.

FIGURE 5. - Scrub roller. Rear view.

An excellent crushing effect is achieved by welding lengths of 3-inch (7.5-centimeter) angle iron to the boiler, spaced from 12 to 18 inches (30 to 45 centimeters) apart, as shown in Figure 4. This creates a chopping action which helps to prepare the scrub for later burning. It is emphasized that rollers are primarily of use in light types of scrub which are not easily crushed. However, they have one other advantage, namely, that they do not require very large tractors to pull them. Tractors from 35 to 50 draw-bar horsepower are adequate for the purpose and with these from 20 to 30 acres (8 to 12 hectares) can be rolled in a day, depending on conditions.


This is an extremely simple operation and merely involves pulling a large chain by two tractors. It may be used in light scrub that is easily crushed, and heavy trees among which there is not much undergrowth. In light scrub relatively small tractors may be used. However, experience has shown that large tractors pulling a long length of chain are more efficient and economical for large areas. The chain they pull is obviously heavier - from 1 ½ to 2 inches (38 to 50 centimeters) diameter - and this has a greater crushing effect. Moreover, large tractors may operate up to 100 yards (90 meters) apart, so that areas of up to 100 acres (40 hectares) per hour may be chained. It is indeed spectacular and impressive to see this operation performed, as it has been on large areas of scrub in South Australia.

Where trees are denser, tractors must of necessity work much closer together, perhaps 20 to 30 yards (18 to 27 meters) apart on account of the greater load. If trees are close together, this is no disadvantage as the chain is held off the ground by falling trees and so attains more leverage on the trees. Chains should be of good quality steel to avoid breakages. Larger diameter poor quality steel chain causes too much dead weight.

Although this operation is simple, it calls for skill on the part of the operators. Above all they must work as a team and be constantly aware of the difficulties of the other driver. They should attempt to keep the tractors level. If one tractor gets too far ahead it may be dangerous for the driver of the other. The noise of the tractors makes it more difficult to keep them level than may be imagined. When turning corners it is as well for the driver of the tractor on the " inside " to reverse his machine a short way in order to allow the outside machine to turn without incurring too much side thrust.

Tractors may have tree pushers or bulldozers attached. However, experience has shown that bulldozer blades tend to restrict the vision of operators and cause unnecessary weight, thus increasing maintenance costs. It has been found that, if the blade itself is removed and the frame that carries it is used alone, the frame will do the work required. This sometimes consists of giving larger trees a glancing blow when passing which allows the chain to remove them more easily. Chaining has been successfully used in timber up to 70 feet (20 meters) high.


Logging, as the term is applied in Australian land clearing, is carried out in much the same way as " chaining " except that a log is dragged at the end of the chain in order to crush trees and undergrowth. In light scrub a log may be pulled with one tractor, as in Figures 6 and 7. The log should be heavy so that it does not bump off its work. Logs should be about 2 feet (60 centimeters) in diameter and about 40 feet (12 meters) in length for one tractor operation. This calls for a tractor of the class of 70 h.p. or upward. A chain is attached to the log about 18 inches (45 centimeters) from both ends. The other end of each chain is brought to within about 6 feet (2 meters) of the tractor and a single chain is connected from there to the tractor. This allows the tractor to back and turn without fouling the chains. The chains should be cut into the logs to prevent slipping and save wear on the, chain where the log touches the ground. It is also advisable to staple the chain on to the log with large mild steel staples in order to prevent the chain slipping round on the log and so damaging it.

FIGURE 6. - Logging, using a tractor to each log.

FIGURE 7. - Logging, using a tractor to each log.

Logging is usually carried out by two tractors having a chain from each tractor directly to each end of the log. When two tractors are operating logs of about 50 feet (15 meters) in length are usually used. Considerable strain is put on the center of a log when used in heavy timber. To counteract this, chains are often used in conjunction with the log as shown in the diagram. Chains thus take the brunt of the work, allowing the log to keep the chain spread and to perform the crushing operation, as shown in Figure 8.

FIGURE 8. - Chain used to bend scrub. Log used to crush scrub.

In heavy scrub it is usually difficult to obtain good pictures of logging operations, though Figures 9, 10, 11 and 12 give some idea of what is achieved. However, very much heavier scrub than is shown in these pictures can be successfully logged if large tractors axe used. Areas of 50 acres (20 hectares) per day are cleared in heavy-type scrub, while 100 acres (40 hectares) per day are comfortably cleared in medium-type scrub. It is again advisable to use high quality steel chain for this operation. The same skills are required of the operators as for chaining if accidents are to be avoided. Chains should be of sufficient length to avoid danger from falling timber.

FIGURE 9. - Logging methods.

FIGURE 10. - Logging methods.

FIGURE 11. - Logging methods.

FIGURE 12. - Logging methods.

The high-ball

A device which has been used in very heavy scrub is the high-ball (Figure 13). It consists of a steel ball of about 7 ½ feet (2.3 meters) in diameter and weighing from 5 to 7 tons, through which is passed a heavy axle. A heavy chain is secured to each end of the axle in such a way that the ball can revolve without fouling the chain. The other end of each chain is connected to a heavy tractor, and the operation follows in much the same way as in " logging."

FIGURE 13. - The high-ball.

The object of the high-ball is to keep the chain well off the ground and so obtain a greater leverage on large trees. With this device, trees up to 100 feet (30 meters) high have been removed. The high-ball, however, has some disadvantages. The initial cost is quite high owing to the great strength that is required. Also its weight makes it difficult to transport from one area to another. Experience has shown it to be costly equipment on all but very heavy timber covering land of high production value.

Burning and clearing up

Where conditions permit, a thorough burning of areas that have been rolled, chained and logged, greatly eases subsequent operations. If possible, burning should be carried out when the optimum amount of material will bum and the right day to bum should be chosen very carefully.

The results of a good burn are Been in Figure 14. Much of the material that is left may be removed by hand. If, however, a machine must be used, a bulldozer blade with rake attached, as in Figure 15, is most convenient. Bulldozers without rakes prove costly and inefficient, because they pick up too much dirt and so make the subsequent removal of the debris more difficult.

FIGURE 14. - After a good burn.

FIGURE 15. - Bulldozer with scrub rake attached.

These same machines may be used where a burn is not possible or where the timber is required for fuel or other purposes. However, a good burn obviously reduces considerably the cost of clearing up operations.

The stump-jump plow

Land clearing as at present practiced in Australia would be impossible without the stump-jump plow. This implement was invented in Australia over one hundred years ago and has been gradually developed into the very rugged machines of today. These implements will work over country that would seem impossible to cultivate. It has been said that they will plow up anything short of railway tracks. Apart from Australia and New Zealand they have been used with success in Canada, England, Greece, Nigeria, Papua, Scotland and South Africa. However, it is probable that their contribution to the pioneering of virgin land is only in the initial stage and that, when their usefulness is realized by people of other countries, these implements will be even more widely used.

A stump-jump plow of the heavy disk type is shown at work in thick undergrowth in Figure 16. Although it is not generally recommended that this type of plowing should be attempted, the picture does show something of the possibilities of the implement. A close-up of a plow is shown in Figure 17. A careful study of this picture shows the fourth disk from the right rising over a fixed obstacle. This is made possible by the pivoting action of the arm that holds the disk. The far end of each arm is connected to a heavy tension spring, as shown in the picture. This allows each disk to rise over any obstruction that cannot be removed, while at the same time exerting great pressure on it. A good example of what can be achieved is-shown in Figure 18. The obstacles on the left of the picture would prove extremely hazardous to conventional implements, but the stump-jump plow has brought the ground to a workable state, as shown in the right of the picture.

FIGURE 16. - Heavy stump-jump disk plow in operation.

FIGURE 17. - Close-up of stump-jump disk plow.

FIGURE 18. - Before and alter stump-jump disk Plowing.

These plows are available in sizes from 4 to 8 disks. It takes approximately 5 draw-bar horsepower per disk to pull them. They may be hitched in pairs, as shown in Figure 19, for use with large tractors. An aerial view of stump-jump plows in operation is shown in Figure 20.

FIGURE 19. - Two stump-jump plows pulled by large tractor.

FIGURE 20. - Aerial view of stump-jump disk plows in operation.

Subsequent operations

As has been suggested, the heavy disk stump-jump plow removes many obstacles from the ground. An extreme case is shown in Figure 21. Many ingenious machines have been evolved for the removal of such material, but it is doubtful if their use would be justified in countries where labor is abundant. However, the use of lighter type stump-jump disk plows for subsequent cultivation is highly recommended. From then on it may be advisable for traditional methods to take over.

FIGURE 21. - After the stump-jump plow.

It cannot be too highly emphasized that the Australian stump-jump disk plow is perhaps the most valuable development of all the equipment described. Its use may open up many new areas for cultivation and pasture.



Australian £ per acre

U.S.$ per hectare

Scrub rolling (light scrub)



Chaining (light scrub - with tractors 100 yards [90 meters] apart)

0. 4.0


Chaining (heavy scrub - with tractors 30 yards [27 meters] apart)



Logging (light scrub - one tractor per log)

0. 6.0


Logging (medium scrub - two tractors per log)



Logging (heavy scrub - two tractors per log)

1. 0.0


High-ball (very heavy scrub)



Heavy disk plowing

2. 5.0


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