Timber COPY Flashcards
What is Timber used for?
To Build:
- Doors
- Decorative
- Ceiling and Flooring
- Form Works
- Partition Walls
Advantages of Timber
- Easily Available
- Easy Transportation and Handle
- Sound Absorption
- Decorative Purpose
- Scraps have high value
What is wood
Hard and Fibrous substance which forms a major part of the trunk and branches of a tree
Classifications of Trees
- Endogenous
- Exogenous
Examples of Endogenous Trees
Palm, Bamboo, Cane
What are Endogenous Trees?
Trees that grow endwards
How are Endogenous trees?
Fibrous Mass
What are Exogenous Trees?
Tree that grow outwards
Types of Exogenous Trees
Conifers and Deciduous
Characteristics of Conifers
- Evergreen Trees
- Pointed needle like leaves
- Distinct annual rings
- Straight and soft Fibres
- Light in color
- Resinous
- Light weight
Examples of Conifers
Chir, deodar, fir, kail pine, spruce and larch
Characteristics of Deciduous trees
- Flat and broad leaves.
- Annual rings are indistinct
- Hard wood
- non-resinous
- Dark in colour
- Heavy Weight
Examples of Deciduous Trees
Oak, teak, shishum, poplar, maple, Babul, Sal, and mahogany
Types of wood
- Soft wood
- Hard wood
Soft wood strength
Pull/Stretch : strong
Shear : Weak
Hard wood strength
Pull/Stretch : Strong
Shear : Strong
Source of Soft wood
Conifers
Source of Hard Wood
Deciduous
Annual Rings in Soft and Hard wood
Soft wood: Distinctly Visible
Hard wood: not visible
Medullary Rays and hearthwood in Soft and Hard wood
Soft wood: Cannot be distinguished
Hard wood: Can be distinguished
Conversion difficulty of Soft and Hard wood
Soft wood: Easy
Hard wood: Difficult
Growth of Soft and Hard wood
Soft wood: Faster
Hard wood: Slower
Resinous material in Soft and Hard wood
Soft wood: Exists in pores
Hard wood: Does not exist
Microstructures of Exogenous Trees
Inside to outside:
- Pith / Medulla
- Heartwood
- Sap wood
- Medullary Rings
- Cambium rings
- Bark (inner and outer)
Function of Bark
Protects the wood against mechanical damage
Function of Cambium
To grow wood cells on the inside and smaller bast cells on the outside
Function of Sapwood
The sapwood assists in the life
process of tree by storing up starch and conducting sap
Functions of Heartwood
The heart wood gives a strong and firm support to the tree
What is Heartwodd?
With the growth of tree, the cells
in the inner older portion of trunk gradually become inactive and lifeless, but do not decay.
This portion of the trunk is called heart wood.
Properties of a good wood
i. Appearance
ii. Colour
iii. Defects
iv. Durability
v. Elastic
vi. Fibers
vii. Fire resistance
viii. Hardness
ix. Mechanical wear
x. Shape **
xi. Smell
xii. Sound
xiii. Strength
xiv. Structure
xv. Toughness
xvi. Water Permeability
xvii. Weathering Effect **
xviii. Weight
xix. Working Condition
Property of good wood : Appearance
Hard and shiny
Property of good wood : Colour
Dark => Good Strength
Light => Less Strength
Dark Preferred
Property of good wood : Defects
Should be free from defects and have uniform texture
Property of good wood : Durability
Should be durable, resist fungus, physical and chemical attacks
Property of good wood : Elastic
Should be elastic
Property of good wood : Fibers
Fine straight and parallel fibers, not rough
Property of good wood : Fire resistance
Should be fire resistant
Property of good wood : Hardness
Should be very hard
Property of good wood : Mechanical wear
Should resist mechanical wear and tear and abrasions
Property of good wood : Smell
Sweet smell => Good
Unpleasant Smell => weak due to decay
Property of good wood : Sound
Ringing Sound (clear) => Good Dull Heavy Sound => Weak
Property of good wood : Strength
- Strong in direct and transverse direction
- resist slow and sudden loads
Property of good wood : Toughness
Resistant to impact load and vibrations
Property of good wood : Structure
Uniform, firm and straight fibre
Property of good wood : Water Permeability
Should be low
Property of good wood : Weight
High weight => Good strength
Property of good wood : Working Condition
Workable in ever stage
Steps in Processing of timber
i. Felling of Trees
ii. Seasoning of Timber
iii. Conversion of Timber
iv. Preservations
Factors considered during felling of trees
i. Age: 50-100 years old (mature trees)
ii. Method of felling : Above the roots
iii. Season of felling: Not in Autumn and Spring, In hilly areas in mid summer, in plain areas in winter. Sap should be less during these seasons
What happens when water content is high
in wood?
Low strength, durability and workability
More vulnerable to decay
Deformations and changes in shape
Increase in weight
Types of moisture in Timber
- Free moisture: cell cavity
- Bound Moisture: cell wall
How much percent of wood is water
> 50% w
Types of Seasoning
- Natural Seasoning
- Artificial Seasoning
Advantages and Disadvantages of Natural seasoning
Advantages:
- Cheap
- Simple
Disadvantages
- Very slow process, takes 2-4 years for 10-20% reduction of water
- Very in efficient
Types of Artificial Seasoning
i. Boiling
ii. Chemical Seasoning
iii. Electric Seasoning
iv. Kilns (chambers of ovens)
v. Water seasoning
Process in seasoning of wood by boiling
- Boil for 2-4 hours
- Sap is removed
- Size wont shrink
Process in seasoning of wood by Chemical Seasoning
- Timber in Salt solution
- Sap is removed due to difference in concentration of solution
Process in seasoning of wood by Electric Seasoning
- High frequency AC is supplied
- Heat is generated
- Rapid Process
- Costly
Process in seasoning of wood by Water Seasoning
- Timber in running water
- Due to high velocity of water, sap is removed
What is conversion of timber
Cutting and sawing of wood in different shapes and sizes
Why is Preservation of wood done?
- to increase the life of timber
- to make timber durable
- for protection from attack of white ants (termites) and other insects
Types of Preservation
- Ascu treatment
- Chemical Salts
- Coal tar
- Creosate Oil
- Oil paint
- Solignum Paint
Which salt solution is used in Chemical salt preservation of Timber
Copper sulfate
Mercuric Chloride
Sodium Fluoride
Zinc Fluoride
Which preservation method for timber is harmful and toxic?
Solignum Paint
