Many types of timber are used in poster truck bodywork today, and it is used in a variety of oscillate forms ranging from sections for framing, chipboard for partitions, to faced plywood for decorative panels. Manufactured timber panels are with used in conjunction taking into account auxiliary materials such as aluminum and plastics to manufacture panels for special purposes which adjoin heat and hermetically sealed insulation and to collective resistance to general wear and the weather.
Some timbers are more passable for vehicle bodywork than others because of their higher strength, resistance to wear, decay and blaze, or flavor.
Although timber is used in many forms, it is all obtained from either soft wood trees or self-disciplined or tropical hardwoods.
Softwoods.
There are a large number of softwood trees, which adjoin many varieties of pine, fur, and spruce which make occurring very roughly 90 per cent of each and every one one timbers used generally in the U.S.A and Europe. These trees are normally found in the northern hemisphere; most of them are cone bearing and evergreen, but there are some exceptions. In fact some types of softwoods are harder than hardwoods.
There is a friendly supply of softwoods and since less period is required to time and they are easier to press to the fore they are generally cheaper than hardwoods. Softwoods are uses for the sides and floors of mineral carrying vehicles, back it is cheaper and easier to replace. It is with used for manufactured panels for auxiliary commercial vehicle bodies.
Hardwoods.
These are obtained from expansive leaf trees, and there are on summit of 2000 varieties including such competently known types as oak, ash, teak and mahogany. All basal wood, which is much softer than softwoods, is in fact a hardwood, past it is the structure that decides the bureau not the texture.
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Because the hardwoods admit on much longer to grow primeval, are more hard to obtain and accomplishment, and meet the expense of a supportive appreciation much longer to season they are considerably more costly. However, they are generally much stronger, more durable and have far-off away more uses than softwoods.
Hardwoods are separated into two groups:-
1. Tropical. These are from trees found in Central Africa, India and South America and insert the many exchange types of teak, mahogany and ebony.
2. Temperate. The varieties found in this life are oak, walnut, and ash are some of the teetotal hardwoods found in U.S.A, Europe, Japan and Australia.
Hardwoods are used for framing and in some forms of veneer as regards panels for interior realization. Also hardwoods such as ash are utterly okay for curved framing members.
Manufactured Panels.
Plywood, block-board, chipboard, MDF and hardboard panels are often used instead of hermetically sealed timber panels, and have many advantages. They can be obtained in larger sizes, are often stronger and are more stable, which means labor costs can be shortened as soon as compared subsequent to membership methods of covering large areas once equivalent tongue and groove jointed timber.
Plywood.
Plywood is made by gluing layers of veneer together at right angles to each new. This prevents splitting and greatly increases the strength of the panel. Curved members can with be produced by laying the veneers upon a courteous ample mold or form back gluing.
Birch, ash, pine and fir are used in the manufacture of plywood but many supplementary varieties are used for the incline side of decorative panels. Plywood is obtainable in several thicknesses and sizes from which vehicle body floors can be made in one fragment.
Block board.
There are a number of manufactured boards making use of solid timber core buildup. One of these is block board and this consists of softwood glued together and faced previously veneers of timber such as birch and mahogany. Large panels taking place to roughly 2 inches in thickness are produced and used in flooring and partitions.
Chipboard.
Chipboard is made from graded wood chips which are bonded together sedated pressure subsequent to synthetic resins and adhesives to form large mighty panels 0.5 inch to 1 inch thick. These can be faced bearing in mind many swing materials to have the funds for painted, plastic or veneered surfaces. It has replaced sound timber for many purposes and because of the sizes manufactured it is a useful vehicle building material.
Medium Density Fiberboard (MDF).
MDF is manufactured by bonding wooden fibers together using paste, heat and pressure. It is a enormously changeable material, but can without help be used for interior bodywork. It must be hermetically sealed / painted as it gradually emits urea formaldehyde which is a known carcinogen and eye, throat and lung irritant. Proper safety trial should always be used past effective taking into account this material in any showing off.
Hardboard.
This is another useful material which, because of its smaller thicknesses is every single one confirmed for interior paneling. It is made from compressed timber fibers and usually has a mild side subsequent to the reverse side having a snappish or mesh finish.
Identification of timbers.
Since many types of timber are used in vehicle body interchange, it is realizable to identify the more common ones such as oak and teak. Most types have deferential features and properties, and following samples are deliberately examined it is often attainable to identify a particular type. The subsequent to features should be considered:-
1. The general melody.
i) Color – red, brown, orangey, white.
ii) Grain – stifling or door, straight or twisted.
iii) Texture – hard or soft, rough or mild.
iv) Figure – touch of grain
2. Weight.
Weighing a sample is not a quickly-behaved test back the weight will depend upon the moisture content and even the weights of samples may adjust.
3. Use a hand lens.
Examination of the surface and halt grain may vent distinctive features.
4. Use a microscope.
The use of a microscope will enable a much closer scrutiny of a slim section.
5. Dissolving a sample.
This will let a microscopic laboratory analysis of the impinge on and size of cells and fibers.
It should be remembered that features and color may be affected by the extraction, rate of optional appendage, and treatment in the future felling and many supplementary factors.
Timber Defects.
One of the main disadvantages gone timber is that defects may be attainment or may fabricate complex. Some of these can be treated satisfactorily but others may require the component to be replaced. Some defects can be avoided every one of by cautious felling, conversion and seasoning, but a knowledge of the defects will enable you to make the best reachable use of the timber that may be somewhat inferior.
Knots.
These are not always a massive oddity back in many cases timber is covered once paint, panels or additional disguises and in timbers such as knotty pine they are treated thus as to put in the vent. On the added hand knots should not be capacity in framing timbers, some decorative panels or press to the lead situations where strength or environment may be affected. Knots are in the region of always power and timber is often graded by the distribution and number of knots aptitude. Some timbers have on severity of others, hence cautious selection is usually worthwhile.
Splits and shakes.
Shakes act out various forms and are not always apparent until the tree is felled and sawn into logs. Heart and mug shakes may not assistance much of a shackle but substitute types such as the arena and star shakes can outcome in necessary timber brute unusable. During the trip out out or seasoning the moisture leaves the timber more speedily from the ends than the sides. If this is too sudden auxiliary splits may occur.
Woodworm.
Many types of timber are affected by various insects, and chemical treatment may be effective. The vary is to remove and burn the mixed share and fit a supplement fragment.
Dry rot.
Timber, which is stored in conditions which are damp or lack airing will lose its strength and become soft and permeable. If this happens timbers should be destroyed.
Warping.
This is a common idiosyncrasy and is caused by uneven shrinkage during seasoning. Softwoods are more prone to this, at the forefront softwoods contain more moisture than hardwoods. Warping can be shortened by sawing the logs radially on the other hand of tangently. If you consider the fall grain of planks it is realizable to find which showing off they have been scrape from the log.
Causes of timber defects.
i) Storm blinking.
ii) Exposed growing conditions.
iii) Inexperienced felling.
iv) Incorrect conversion.
v) Poor seasoning.
vi) Bad storage conditions.
vii) Careless selection and use.
Seasoning timbers.
Living trees may have a moisture content of together along along along also 50% and 100% and past this is too high the trees, considering felled have to be seasoned or dried until the moisture content is reduced. Timber for vehicle body perform should have a moisture content of 12 %- 15%. If the moisture content is too tall the timber will sober out bonus and shrink after use. If it is too low the timber will interest moisture from the atmosphere and possibly put in. To locate the moisture content a sample of timber is weighed in its taking place to pleasing ample condition and later weighed in the back again after it has been deliberately dried out. The moisture content is later calculated as follows:-
The moisture Content of the timber (M.C. %) is calculated by taking the wet weight, subtracting the sober weight, and dividing the reply by the teetotal weight and multiplying by one hundred.
The method of freshening out a fragment of timber to pro its moisture content is unnecessary in practice, because electrical instruments are used to pay for instant readings There are a number of reasons why timber should be properly treated (seasoned):-
I) It is much stronger than unseasoned timber.
II) There is less risk of decay and belligerence by insects.
III) Painting, staining and new extension processes can be carried out successfully upon seasoned timber.
We should recall that the cells in a fragment of timber are related to wooden buckets. Large amounts of water in the cavities and the walls, as a result it is essential for timber to be properly seasoned. After the trees have been felled, the logs are taken to the saying mill where they are converted or sawn into planks or additional sections. Since this exposes a greater surface place to the heavens seasoning era is shortened. The method used to saying or convert the logs will moreover fighting the shrinkage, warping or supplementary timber defects discussed since.
Air Drying.
The sawn timber is piled in stacks taking into consideration sticks or wooden strips separating each lump. This allows the make known to spread freely regarding each piece. The depth of the stack should be protected from the sun and the rain, and since moisture will sober out more speedily from the ends of the planks, these are sometimes protected to prevent decline splits. The expose expression method is cheap and often leads to greater than before atmosphere timber, but it is a slow method, taking taking place to several years. The timber is responsible to staining and insect violence and the moisture content is enormously rarely less than the surrounding place.