Presentation on theme: "timber 7. H E A D L I N Carpentry General Advantages of Timber"— Presentation transcript:
1 timber 7. H E A D L I N Carpentry General Advantages of Timber Use of Timber.Qualities of Good Timber.Defects in Timber.Methods of stacking.
2 Carpentry GeneralTimber has been in very common use for- engineering purposes since ancient times.Even today there are certain works, where timber is considered as the most ideal material.Today although materials like steel, cement, stone bricks etc. have occupied lot of field, where timber was almost used, still timber continues to be an important structural material.
3 Carpentry GeneralThere is difference between terms timber and wood. Wood includes all types of wood which may be burning wood, structural wood, furniture wood etc. But wood suitable for use as a structural material is called timber.So we can say: Wood is usually used to refer to the material in its natural state...timber refers to it after it has been modified by man. So you go to the forest to collect wood for the fire, and to the DIY store to get timber for doing up your house
4 Carpentry GeneralTimber is obtained from trees. Timber denotes structural wood. A standing living tree is known as standing timber.Rough timber.When tree has been cut and its stem and branches are roughly converted into pieces of suitable lengths.Converted timberWhen roughly converted timber is further sawn and converted into commercial size the planks, logs, battens, posts, beams, etc
6 Carpentry _Advantages of Timber It is easily available every where.Its salvage التعديل value is high.It can be easily transported by converting large pieces into smaller pieces.Working on timber is easy. Timber constructions can be easily repaired. Additions and alterations to timber structures can be easily done.It can be easily jointed.In marine works, timber is considered as an ideal material as it does not corrode. Cement and iron structures corrode in sea water, if they are not protected with special preservative.
7 Carpentry _Advantages of Timber Being light in weight, it is preferred for building works in earth quake prone regionsالمناطق المعرضة للزلازل.It is an excellent material for decorative and general use furniture. Lot of other internal decorations can be carried out with it.It can with stand, shocks better than iron and concrete.It is good insulator of electricity and heat.It is good sound absorbing material.Timber can be easily strengthened by attaching steel or other material with it.
8 Carpentry _ Use of Timber It can be said that there is no Engineering field, where timber is not used one way or the other.Uses of timber are numerous. Some of its important uses are given as follows:It is very much used for railway track sleepers.It can be used inform of piles, vertical posts, beams, doors and windows.It can also be used as members of roofing trusses.It is an important material for furniture-makingIt is used for floors, ceiling, and partition walls.
9 Carpentry _ Use of Timber It is used as form-work for cement concrete structures.It is very much used in making sports. goods, musical instruments, well curbs, agricultural implementsالعمليات التنفيذية الزراعية , etc.Packing cases are mostly made from soft timber.It is very much used for timbering the deep. Trenchesالخنادق .Railway coaches and wagonsالعربات are also made from high class timber.
12 Carpentry _ Qualities of Good Timber Following are the qualities of good timber.A good timber should be hard and durable.It should be capable of resisting the actions of fungiالفطريات , chemicals and physical agencies.The fibers of the timber should be straight and compact.The timber should be free from knotsالعقد , twists, upsets, burlsالعقد shakes, flawsالعيوب etc.Its color should be dark. It should be obtained preferably from heart wood. Color should be uniform.It should be properly seasoned.مجهز بشكل صحيحIts freshly cut surface should smell sweet.
13 Carpentry _ Qualities of Good Timber Its weight should be heavy.It should be easily workable. It should not clog يعيقthe teeth of saw and should be capable of being easily planned.Timber should be tough i.e., it should be capable of resisting shocks.It should be able to withstand the weathering affects.It should be strong enough to withstand bending, direct and shear effects efficiently.A clear ringing sound should be emitted by the timber when struck. Heavy dull sound indicates decayed timber.It should offer adequate fire resistance.It should be elastic
14 Carpentry_ Defects in Timber The defects that usually occur in the timber may be classified into two categories as follows:Defects that develop during growth of the tree.ShakesTwisted timberUpsets or ruptureKnotsWind cracksBurlsDefects that develop after felling the tree.BowCupTwistRadial shakesWaneالتضاؤلDiagonal grains القطري
15 Carpentry_ Defects in Timber 1.Defects that develop during growth of treehave been briefly discussed as follows:1.1 Shakes. This is most serious type of defect in timber. These are sort of cracks which partly or completely separate the fibers of wood. A shake is nothing, but separation of the timber along the grains. Shakes may be of several types.
16 Carpentry_ Defects in Timber Star shakesThese are radial cracks or splits that extend from bark towards the sap wood. They usually remain confined up to the plane of sap wood only. The cracks are widest at the circumference and go on narrowing as they proceed towards the Centre of the tree.
17 Carpentry_ Defects in Timber Reasons of star shake Star shakes usually develop due to fierce heat and frost When logs having this defect are sawn they usually separate out into a number of pieces and hence become useless.Star shakes
18 Carpentry_ Defects in Timber 1.1.2 Heart shakes.These splits or cracks occur in the central part of the trees. There are widest at the centre and go on narrowing as they proceed towards outside. This defect usually occurs in over-matured trees. This defect is usually caused due to shrinkage of the heart wood. Heart shakes divide the tree cross-section into several parts. Straight running heart shake is not as serious as twisted heart shake.
19 Carpentry_ Defects in Timber 1.1.3Cup shakes.This defect develops curved slit between successive annual rings. The split does not run for the full circumference of the annual rings.This defect usually develops due to 1. unequal growth.2. Another possible reason for their development may be contraction of timber under atmospheric changes together with the twisting action of strong winds.
20 Carpentry_ Defects in Timber 1.1.4Ring shakes.When cup shake defect runs for full circumference of the annual ring, it is called ring shake. It is more serious than cup shake.1.1.5 Radial shakes.They are similar to star shakes. They are numerous, fine and irregular. They usually occur when felled tree is exposed to sun for seasoning. The cracks run for a short distance from bark to-wards the centre and then follows the course of an annual ring and ultimately goes towards the pith.
21 Carpentry_ Defects in Timber 1.2 Twisted fibers.They are caused by twisting of young trees constantly in one direction under the action of strong prevalent winds. Timber with twisted fibers is unsuitable for sawing. The timber having this defect is mostly used for posts and poles in an unsawn condition
22 Carpentry_ Defects in Timber 1.3 Upsets or ruptures.اضطرابات او تمزقاتThis defect is caused due to injury suffered by wood fibers by crushing or compression. Upsets are mainly due to improper felling of tree and exposure of tree in its young age to fast blowing wind. This defect indicates change in direction of wooden fibers.
23 Carpentry_ Defects in Timber 1.4 Knots.Knots are generally developed at the bases of branches cut off from the tree. This phenomenon ultimately results in the formation of dark, hard rings, known as knots. As knots break the continuity of the wooden fibers, they form a source of weakness. The amount of weakness caused by the knot depends upon the position, size, and degree of grain distortion around it. Knot is the most commonly encountered defect of wood.
24 Carpentry_ Defects in Timber It is impossible to procure timber free of knots.Knots may be dead, live loose,or tight. Tight knots are notobjectionable unless theyare too large. Their presence ontension members is objectionable. It is very difficult to planethe timber at knots.
25 Carpentry_ Defects in Timber 1.5 Wind cracks.The outer layers of a standing tree suffer from the effect of shrinkage due to atmospheric agencies. This causes cracks on the outer surface only. These cracks are known as wind cracks.
26 Carpentry_ Defects in Timber 2. Defects that develop after felling the tree.Conversion of timber is done almost immediately after felling The tree. The defects that may develop after felling the tree and also during conversion and seasoning are the following:2.1 Bow: when planks of converted of timber shrink and bend in curved form , in the direction of length.
27 Carpentry_ Defects in Timber 2.2 Cup:this defect is indicated when wooden planks bend in curved from in transverse direction.2.3 TwistA plank which has distorted spirally along its length
28 Carpentry_ Defects in Timber Methods of stacking.Before seasoning, the timber should be stacked in yards so as to protect the timber from direct sun.Ends of logs should be protected against splitting by applying anti-Splitting compositions and stacked on foundations in closed stacks in one or more layers.
29 Carpentry_ Defects in Timber 1.One and nine method of stacking.This method of stacking timber is most suitable for moderately heavy coniferous sleepers in hot climates and for heavy timbers in moist climates.
30 Carpentry_ Defects in Timber 2. Close crib method.This method of stacking timber allows reduced air circulations and thus slows down the pace of seasoning. This method is recommended for stacking heavy structural timbers like in hot and dry localities.