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Continental nations,—a remark which also applies to the excellent method of extracting large quantities by means of Timber-Slides. Sledging is done either by woodmen alone, or also by horses, mules, and oxen.
There are various kinds of sleds or sledges, but they all consist of (1) two runners or long horizontal pieces of wood, often shod with iron, which in the case of handsleds run up into bent points in front, that are grasped firmly by the man dragging the sled; (2) cross-pieces binding the runners, and serving as benches upon which to rest the timber; and (3) a brake or drag to regulate the speed, the most powerful brake being the strong hooked point of an iron bar worked by the leverage of a long arm, the handle of which remains always in the grip of the sledger (it is usually fastened on the left-hand side of the sledge). Hand-sleds are only used for the conveyance of comparatively light loads of wood, like firewood
billets, light pit-props, and timber of small dimensions cut into comparatively short lengths (Fig. 254). For such sledding by woodmen the sledge-tracks are made from 4 to 6 ft. in breadth, and with a constant gradient not under 7 nor above 25 per cent (1 in 14, and 1 in 4). According to Gayer, the usual load consists in Germany of from 55 to 70 cub. ft. of light coniferous wood, and a sledder working on a sledding track having a favourable and constant gradient can convey from about 108 to 180 cub. ft. of wood per diem to a distance of 14 miles (3 kilometres), or from 350 to 425 cub. ft. for the half of that distance; but either a low or a high gradient, or a frequent change of gradient, prevents such good results.
The larger sledges used for dragging long logs by horses, mules, or oxen are heavier in construction. They consist of a front sledge and a hind sled, in order to keep the ends of the logs from trailing along the ground and cutting up the earthwork. In some parts of the Black Forest large single sledges are often loaded with from 1050 to 1100 cub. ft. of Spruce or Silver Fir wood cut up into fuel-billet lengths.
Sledging operations for extracting heavy timber mostly take place only while
the ground is covered with snow, so that it is a method that can only be applicable to localities having severer winters than are usual throughout the greater part of Britain. But sledging can also be done during the summer months if the track is specially prepared (Fig. 255) by corduroying it through laving round poles on the
Timber Sledging-track for Summer use, in Bavarian Alps. ground, or split poles with the smooth side uppermost, so as to minimise the friction. These cross-pieces have to be fenced in with poles as flange-like sideguards, in order to prevent the sledge gliding off the track. They are, in fact, just like rude railway tracks, but the corduroy sleepers are smooth and round on the top so as to offer a minimum of friction, while the sleds run over these crosspieces in place of along the guard-line of parallel poles. The corduroyed cross
pieces must not be farther apart than will adnit of the sledge always resting on two-i.e., will prevent any portion of the sledge touching the ground—anil not farther apart than about 2 ft. when the sleds are to be worked by men, as they must have good foot-hold to keep their loaded sled under control. According to Gayer, the preparation of such summer sledging-tracks made with Silver Fir and Beech for the extraction of firewood at Hochwald, near Barr, in Alsace, over a total distance amounting with ramifications to 12} miles, cost a little over £33 a mile, or 4}d. a yard, and the sledding-track lasted ten years, while the cost of slelging came to about 38. 6d. to 48. per cord or cubic fathom of 216 cub. ft. of stacked wood.
3. Timber-Slides for the shooting-down of timber, to be carried by its own weight, are a branch of transport widely and cheaply practised throughout all the mountainous tracts of Central Europe. Its advantages are greatest where the timber-slide can be made to terminate at any river or good water-way, which can be used for floating to some favourable mart or to large saw-yards, whence further transport of the sawn timber is favourable by road, rail, river, or sea.
There are different forms of timber-slides, constructed either of wood or of earthwork; but the leading principle is, in either kind, that a good bed should be prepared, down which the timber can glide with it minimum of friction, while side-guards protect the logs or fuel-billets from springing out of the slide.
(1) Road or Earthwork Timber-Slides are an excellent means of transporting large quantities of long timber from mountain forests, when the horizontal projection of the pathways and side-roads has taken place in long sweeping curves, round which long coniferous logs can easily glide. They can be made about 5 to 8 ft. broad, and in much the same manner as has already been sketched for constructing sledging-1 racks for summer use (Fig. 255). The best gradient for laying out the roadway may vary from 9 to over 15 per cent (1 in 11 to over 1 in 61), according to the use to be made of the slide. A fall of 8 to 10 per cent (1 in 12 to 1 in 10) is enough for winter-slides with snow, while at least 15 per cent (1 in 6]) is requireil for shooting the logs in summer (Schuberg; though according to Gaver, 8 to 12 per cent (1 12} to 1 in 8) are needed for sliding down on snow in winter, and 12 to 18 per cent (1 in 8 to 1 in 5) for shooting logs in summer). In either case, however, the greatest gradient is given at the top end to start the logs on their downward course, and the lowest gradient is at the lower end wliere the slide terminates.
The leading principle is to have broad, sweeping curves, and to avoid as much as possible any sharp turns and -udden changes in the general direction which the logs must follow. Often, however, sharp turns and suilden changes in direction are unavoidable, and they are then arranged for in the manner indicated in Fig. 256. Here the stem sliding down in the direction ab bumps against the bundle of faggots fixed as a buffer, rolls over into the lower track diverging at a very acute angle, and continues its way slowly in the new direction mn.
In mountain tracts, transport by roadway timber-slides deserves far more attention than has hitherto been given to it. It wastes no timber; and it is economical, as from 1000 to 1300 logs can daily be shot down a slide nearly 1} miles long,—while the roadway can also be used for sledging. It therefore offers particular advantages in localities where carting is impossible (Gayer).
The logs should be launched butt-end foremost into the slide, after the points have been adzed or rounded with the axe to ensure their gliding smoothly over the cross-pieces or sleepers corduroyed at short intervals across the track. As may be seen in Fig. 256, where the logs are not likely to run out of the track on the upper side, a flange-pole is then only needed on the lower side ; but, otherwise, guardpoles have to be fixed along both sides of the slide.
Operations of this description require to be conducted with something like military precision and good organisation in order to prevent accidents. Before timber is launched at the upper end, a bugle or horn signal is given, which is repeated down the line by men stationed at different points, and then passed up again, to ensure that the slide is clear, before the log leaves the top. Its arrival, at the depôt below is indicated by another preconcerted signal being passed up the line; and so on with each log.
If the slide be no longer required, when all the timber from the fall has been transported, the logs used in the corduroying and fencing-in of the roadway can also be slid down, commencing at the top.
(2) Wooden timber-slides are constructed more or less semicircularly of 6 or 8 logs or poles of from 4 to 12 in. in diameter. The two lowest of these form the base of the slide, the whole breadth of which usually varies from about 2 to 5 ft. So far as possible the slide rests on the ground; but wherever required to maintain the gradient, it is raised to the necessary height by trestling sections of logs to form suitable supports. The slides intended for transport of large logs of timber
must of course be constructed more solidly than those required only for fuel billets. That shown in Fig. 257 is a slide for long logs in the Triftenthal, North Tyrol.
The gradient is a very important matter in constructing wooden timber-slides. With too low a gradient they are practically useless, while too high a gradient is apt to induce such a velocity as to cause the timber to spring out of the trough. But the gradients permissible, and also those that may prove best, vary between wide limits, accoriling to the circumstances of each case. Thus dry slides, used only in summer, need a gradient of 20 to 25 per cent (1 in 5 to 1 in 4), and even up to 40 per cent (1 in 2}) is not excessive for fuel-billets and small log-sections ; while for long heavy logs from 15 to 20 per cent (1 in 51 to 1 in 5) is ample. But when transport is to be on a snow-slide during winter, the best gradients are from 6 to 12 per cent (1 in 16 to 1 in 81) for small log-sections and fuel-billets, and from 3 to 6 per cent (1 in 33 to 1 in 17) for long logs. Where the gradient is below about 6 per cent (or 1 in 16 to 17), long logs can only be shot down when the slide is watered during frosty weather, and thus made into an ice-slide. Men are then required to water the slide constantly. As the showting of the logs is then dependent on the frost, work is often, especially when warmer weather comes in spring, confined to the cold night-time, in place of during the day. In the damp climate of the Highlands of Scotland the slide might generally be used during wet weather, when a gradient about half-way between the two extremes for
summer and winter slides would probably suit best. Wherever a high gradient is unavoidable in any particular part of the slide, it should be followed by a short horizontal stretch, or by a slight rise, in order to check any tendency to excessive velocity in the timber. The velocity may also be checked by means of a brake or drag (Fig. 258), consisting of two poles fixed at their upper ends, but with their lower ends resting loosely in the slide, between which the logs have to pass on
their downward Fig. 257.
passage ; and
ing ground on Wooden Timber-Slide.
issuing from the
slide. Wooden timber-slides cost a good deal more to make and maintain than roadway-slides, and they do not last so long. Much wood is used in making them; the timber sometimes gets badly shaken and split; and the slides usually begin to need repairs in 3 or 4 years' time. They seldom last more than from about 6 years to 8 at most, or about 7 on the average ; and a considerable proportion of the logs then forming the slide are unfit for anything but fuel.
Flumes or Water-Shoots.-In California, throughout the Rocky Mountain tracts, enormous quantities of timber are conveyed for immense distances in flumes