BODY MATERIALS, TRIM AND MECHANICS

Body materials:

1. Timber
2. Steel sheet
3. Plastic
4. GRP
 
1. Timber:

Before the introduction of plastics, timber was used in vehicle body construction, because it is readily available, easily worked and economically competitive, so far as the smaller manufacturer.
 
2. Steel sheet:

The vehicle body building industry uses many different types of steel. Low carbon steel is used for general construction members. High tensile steels are used for bolts and nuts which will be subjected to heavy load.
The steel sheet thickness various from 0.08mm to 1.5mm. This type of sheet metal is mostly used in vehicle body construction.
 
3.GRP:

It is a combination of two basic materials. One is glass fiber and other is thermoplastic resign. The resign materials are relatively low strength, brittle but when combined with glass fiber it becomes strong material.

4. Plastic:

The use of plastics for interior trim is well established, and new applications are being found for components associated with the running gear, examples including reservoirs, air cleaner housings, belt covers etc.

Corrosion and Anti-corrosion:

A vehicle body exposed to corrosion through out its life and because of the load carrying structure determines the service life of the vehicle, it is essential that it should be properly protected against such effects. 
There are three types of vehicle body corrosion.
1. Chemical corrosion
2. Electro chemical corrosion
3. Fretting corrosion

Anti-Corrosion treatment

Corrosion can be prevented by three basic methods
1. Improve materials.
2. Protective coating.
3. Correct design.

Selection of paint:

The colors for finishing the vehicle should be based on scientific principles of colouring, which can be briefly outlined as follows,

• All shades are based on three colours i.e Blue, yellow and red. The basic concepts of colour technology are as follows,

TONE: The tone of colour can be defined by its position in the spectrum. i.e Wave length

VALUE: Value can be measured by the mixture of a natural grey, value corresponds to the concept of brightness or darkness of colours

INTENSITY: Intensity is defined by the mixture of white in the colours, where full colour has no white mixed with it.

COMMERCIAL VEHICLES

Commercial vehicle bodies:

Construction details

• Aluminium is used extensively for the construction of flat platform bodies for reasons of strength, durability and lightness.
• Many of the less expensive light chassis have cheaper factory build timber or steel bodies.
• The aluminium body is used, to a greater extent, at the larger end of the range and on the more expensive type chassis.
• The floor is supported by cross bearer channels, the lipped channel or the J channel being used for most applications.
• Advantage of the J channel has is that floor fixing bolts are taken through the outstanding horizontal flange and the holes drilled to take the bolts through this flange do not weaken the channel in bending strength.

• Normal depth of a cross-bearer is 101.60mm, 76.20mm depth may be used for light duty bodies.
• Cross-bearer spacing is generally at about 558.8mm, In the case of brick lorries, cross-bearer spacing should be restricted to 457.2mm
• A special rear bearer, incorporating a shroud plate is sometimes used.
• The shroud plate allows bracket attachment to the longitudinal and also provides protection for the end of the floor planks.
• Bearers are solid riveted or bolted to the longitudinal using angle brackets or special mounting brackets.
• The cross bearers are capped longitudinally by side rave section and are bolted or solid riveted to the bearers through top and bottom flanges.  

J channel

Two types of side rave are available,one with a chock rail and one without.  

• The headboard is situated at the front of the body and behind the vehicle cab. 
• This is a structural member or assembly because it has to resist the load moving forward and crushing the cab when the vehicle brakes are applied.

• The bulkhead pillars are bolted to the longitudinal and the side or corner pillars firmly attached to the side rave using gussets.
• The head board may be 10swg sheet, but generally heavy-duty corrugated plank section is used to provide strength.

          

Types:                                 

1. Flat platform
2. Drop side
3. Fixed side

Flat platform - A flat structure consists of a floor blade with edge members and  beams which are used to mount the engine and suspension elements.

Drop side - This type of body follows the main structure of the flat platform body with an addition of timber sides and a tailboard, capable of being drop to assist in loading and unloading.

• A drop side body is a flat platform with hinged sides and tailboard, held in the upright position by fastening to short vertical pillars that are generally removable.
• The sides are normally made up by interlocking hollow plank sections . 

Tipper body - The prime requirement of any tipping body is that it shall be a rigid unit capable of withstanding the rough usage to which the type of body is subjected                                                       

Fixed bodies are made of the side which is fixed in side pillars and can be opened  only from rear tail gate for unloading and loading.

TIPPER BODY:

• A tipper body is attached to a rigid cab chassis and is used to carry a wide range of bulk products, such as gravel, sand and grain.
• It is hinged at the rear which allows the front of the truck bed to be raised and the contents set down behind / side the truck.

CLASSIFICATION:

Based on type of tipping method
    • Hydraulic
    • Electric
Based on location of tipping mechanism
    • Front end tipping
    • Under body tipping
Based on direction of unloading
   • Single way
   • Three way

Tanker body: 

Commodities carried by tanker includes fuel, oils, milk, water, varnish and edible oils etc. In the case of fuel transport, to ensure safe handling, internal baffle plates are used to cut down the surge of liquid.

USES OF TANKER BODY:
  
Used to transport goods like,detergent,varnish,edible oil,resins,fat,sugar in solution,liquid gaseous,fuel, oil, milk and water in bulk.

CLASSIFICATION OF TANKER BODY:

1.According to the type of liquid carrying:
a. water tank body
b. Fuel tank body
c. Chemical liquids tank body

2.According to the shape of the tanker body:
a. Circular (round) cross section
b. Elliptical cross section
 

3.According to bulkheads:

a. Baffled tanks
b. Un baffled tanks (smooth bore tanks)

WATER TANK BODY:

• It is mainly composed of the truck chassis, water inlet,outlet system and the water tank body.
• It is a cylindrical, horizontal tank mounted onto the truck chassis
• A water tank truck is mostly used for storing water and transporting the same to some places where there is an urgent need for water.
• A sprinkler water tank truck is used for making the city environment clean and beautiful by cleaning and watering the streets, plants, and grass.
• Water tank trucks have different volume capacity.
• The rear sprinkler, and side spraying of a water tank body are made possible with the tank's fire hose coupling, working platform, and self-discharge valve.
• A rotatable water cannon is installed on the working platform to create various spraying functions and adjustments to create mist, drizzle, moderate rain, or heavy rain depending on the different purposes and environment.
• It is made of various materials such as stainless steel,carbon steel, aluminum, and fiberglass-reinforced plastic.
• The rigid steel body is further sprayed with superior quality special paint to allow it to be more solid and safe.

FUEL TANKS:

 

FUEL TANK Truck

It is constructed in such a way to safely carry different kinds of fuel to and from its destination.

• Some fuel tank body are used to transport different grades of fuel to and from the gasoline station can be

              - insulated or non-insulated,

              - pressurized or non-pressurized,

              - single or multiple compartments.
 

Some of the materials used to build these fuel tanks include aluminum, fiberglass reinforced plastic or FRP, stainless steel, and carbon steel.

• Insulated tank is used to Minimize fuel temperature increases inside the tank, reducing fuel loss due to evaporation.
• The fuel tank body that carries these flammable gases is often pressurized and can carry around 1,000 to 3,000 gallons of this fuel at one time.
• Some fuel tanks can be compartmentalized to carry 2, 3,4, or 5 different kinds of fuel at one time in one cylindrical containment unit. 

CHEMICAL LIQUIDS TANK BODY:

• chemical liquid tank truck is designed to carry corrosive, hazardous chemical liquids .
• It is mainly composed of a chassis, tank body,discharge system, as well as some protective devices.
• The tank can be constructed of carbon steel,stainless steel, aluminum alloy, or other materials,according to the specific properties of the transporting medium.
• Some tank trucks can carry a variety of products at once due to their internal divisions in their tank,allowing for an increased number of delivery options

 CIRCULAR CROSS SECTION:

• circular cross section is readily adaptable to frame less construction.
• when a circular tank is inclined towards the rear the center of gravity can be equal to that of an elliptical tank.

ELLIPTICAL SECTION:

Elliptical tank

 

• Used for a wide range of purposes, Elliptical tanks are a popular form for tanks that hold large volumes of liquids.
• Low Center of Gravity- A tank made in an elliptical shape provides a low center of gravity when it is placed on its side.
• For holding large loads of liquids, that distribution of a  tank's contents is particularly effective at providing stability. 
• The low center of gravity also allows tanks located on truck trailers to sit lower to the ground, providing better sight lines for truck drivers.
• An elliptical tank has significantly greater capacity than a round tank with the same diameter

BULKHEADS:

•  Some large tanks are divided into several smaller tanks by bulkheads.
• Bulkheads are liquid-tight separators between compartments inside the tank   

BAFFLED TANKS:

 

• Some tanks have compartments in them that have holes.
• If the compartment walls have holes in them, they are called baffles.
• Baffles let the liquid flow through and help control the forward and backward liquid surge when the vehicle is traveling, especially at higher speeds.
• However, side to side surge can still occur which can cause a rollover.
• It is used in fuel transporters to ensure safe handling

UN-BAFFLED TANKS:

• Also known as Smooth bore tanks.
• They have nothing inside to slow down the flow of the liquid. Therefore, forward and back surge is very strong.
• Smooth bore tanks are usually transport food products,Sanitation,Corrosive liquids.

DESIGN CONSIDERATIONS:

• The security of the discharge hoses 
• Provide ample drain holes to enable the liquid to drain away rather than to remain inside the container

Selection of material for the right tank

a. When corrosive liquids are to be carried, the material must resist their corrosive action and stainless steel be used
b. To provide a none reactive surface to the load and for cleanness', metals such as zinc aluminum cadmium and copper

•  Aluminum has long been used for fabricating tankers to carry liquids such as petrol and fuel oils.
• largely on account of its weight/strength relationship which makes possible an uplift of between 5% and 8% carrying capacity when compared with a similar construction in steel

Light Commercial vehicle types:

  
The light ,four wheeled rigid commercial vehicle with an unladen weight of less than 3.05tonnes.

•  Panel vans
•  Production van

          1.Standard van
          2.Chassis cab
                 i) Tipper and drop sides
                 ii) Box van
                iii)Luton head vans
          3.Chassis dash


 Panel vans:

• GVW up to 3.5 tones.
• Tradesman for door to door and high street delivery.
• Lighter modes are based on the standard motor car under-body arrangement.
• Bodies are steel pressings with large doors to facilitate entry, exit and access for loading and unloading by one or two doors at the rear.
• Almost all are the unitary or integral construction.

Standard van:

• The standard van arrangement is used for general local delivery work and, after body shell conversions and interior fitting out, for ambulance, motor caravans and security vans.

Chassis cab:

  The chassis arrangement comes in three different versions,

 i. tipper and drop sides (A)
 ii. Box van (B)
 iii. Luton head van (C)

Chassis dash:

 

• Chassis dash arrangement is used extensively for integral body/cab “walk-through” type vans. 

Design considerations of driver’s seat:

The following points must have in mind when planning the driver’s seating position
1. The most comfortable position of the body is achieved when the bulk of the weight of the seated person is taken by the ischial bones.
2. The seat cushions should be fairly rigid and must have sufficient shock absorbing
qualities to prevent resonance of any springs that may be incorporated.
3. A good back-rest relieves the neck and shoulder muscles.
4. The angle between the seat and back-rest must be obtuse.
5. Armrests reduce tiredness.

Drivers cab design:

1. Forward control cab
2. Normal control cab

The design of the cab should ensure a degree of comfort for the group directly related to the duration of the work inside it, modern cabs in trucks are having comfortable as passenger cars.

Normal control:

• In Normal control vehicle, engine is located in front of the driver’s cab to give more cab space, less noise, heat and ease entry and exit.

Forward control:

• In forward control vehicle, engine is located either at the side or below the driver’s cab
• This type has its cab built over the engine and has the advantage of additional length available for the payload and a better angle of vision.
• Its disadvantages include less cab space for crew and engine maintenance can be more difficult unless specialized equipment is available or the cab is designed to tilt forward.
• A variation to forward control aimed at giving ease of entry and exit for door to door delivery work and more space for the crew is the semi forward control type.

BUS BODY DETAILS

Bus body

It the portion of a bus that encloses the bus’s occupant space, exclusive of the bumpers, the chassis frame any structure forward of the forward most point of the windshield mounting.

The bus body builder will build the body onto the chassis. This will involve major consideration of: 

1. Seating capacity 
2. Staircase position/design (double-decker buses) 
3. Number and position of doors 
4. usage

BUS BODY LAYOUT:

1. Entrance doorway skirt panel
 2. Skirt panel front of front N/S wheel arch
 3. Skirt panel rear of front N/S wheel arch
 4. N/S main side panel Bay1.
 5. Air filter access cap.
 6. N/S main side panel Bay2.
 7. Skirt panel.
 8. Spare wheel access flap.
 9. N/S main side panel Bay3.
10. Skirt panel front of rear N/S wheel arch.
11. N/S main side panel Bay4.

12. Rear skirt panel, N/S.
13. N/S main side panel , Bay 5.
14. Pillar capping between Bay1 & entrance door.
15. Pillar capping main pillars.
16. Roof panel Bay1.
17. Roof panel Bay 2.
18. Roof panel Bay 3.
19. Roof panel Bay 4.
20. Valance panel for spare wheel access flap.
21. Valance panel.
22. Valance panel for air filter access flap.

23. Front skirt panel O/S.
24. Main side panel below driver’s signaling window O/S.

25. O/S main side panel Bay 1.
26. Skirt panel rear of front O/S wheel arch.
27. O/S brake gear access flap.
28. Valance panel for O/S brake gear access flap.
29. Valance panel.
30. O/S main side panel Bay 2.
31. Skirt panel front of rear O/S wheel arch.
32. O/S main side panel Bay 3.
33. O/S rear skirt panel.
34. O/S main side panel Bay 4.
35. Main side panel below emergency door.

36. Emergency door main side panel.
37. Pillar capping between emergency door and Bay 4.
38. Emergency door, top rail capping.
39. Emergency door, shut pillar capping.
40. Emergency door, hinge pillar capping.
41. Water bottle flap.
42. Fuel filter flap.
43. Header tank flap.
44. Electrical flap.
45. N/S rear pillar capping.
46. O/S No 1 pillar capping.

Terminologies:

• ‘Cant rails’ are structural members that connect two body sections above the window section.

•  ‘Waist Rails’ are structural members that connect two body sections below the window section.

•  ‘Seat Rails’ are structural members running along the lateral walls and provide support for seat mounting.

CLASSIFICATION OF BUSES

Passenger carrying buses are classifies based on:

1)Distance traveled by the vehicle

2)Capacity of the vehicle

3)Shape and Style of the vehicle

1.Distance traveled by the vehicle:

1.Mini bus  2.Town bus  3.Suburban bus  4.Long Distance Coaches 5.Touring Coaches 6.Midi bus  

1. MINI BUS:

• It should have a seating capacity upto 25. 
• It built on light duty truck chassis.
• It has front mounted engine and rear axle drive.
• It has soft and comfort suspension.
• It has reasonably comfortable seat. 
• It has fairly small entry platforms.

   2.Town bus

  

•  These buses are used for a short distance of about 20kms. 
•  They are provided with large number of standing places two places, wide doors with large entry and exit platform and hard seats covered with durable plastic materials.

    3.Suburban bus 

•  These buses are used for a distance of about 40 to 50 kms. They usually have reasonably comfortable seats.
• Fairly small entry platform for the extra space can be used for luggage and extra standing passengers. 
• Usually one door is sufficient for this type of operation.

    4.Long Distance Coaches

•  These buses are used for a distance of about 200 kms and above. They have comfortable seats with under floor luggage space and roof racks for large items of luggage.

    5.Touring Coaches 

•  For longer distance touring coaches, very comfortable reclining seats are used.
• Toilets, air conditioners, TV,etc are provided.
• Additional windows in the roof are used to improve visibility for the passengers.
•  Thermal and acoustic insulation is usually elaborate and spacious luggage compartments are provided  under the floor and on the roof 

    6. Midi bus 

• A midibus is a classification of single-decker minibuses which are generally larger than a traditional minibus but smaller than a full-size single decker and can be anywhere between 8 metres and 11 metres long.

2.Based on the capacity of the vehicle

  3.Based on Shape and Style of the vehicle

 Classic type
 Single Decker
 Double Decker
 Split‐level bus
 Two‐level single Decker
 Articulated bus

1.Classic type 

 

• The Classic or normal control bus has the engine in front of the passenger carrying compartment. 
• This design, which was almost universal at one time, has practically disappeared and is mainly of historical interest.
• Low ratio of useful length to overall length.
• It also has a high tare weight and poor aerodynamic shape. 

  2.Single Decker

  

• In this type of buses engine is mounted either inside or below the driver’s cab enabling additional length available for more seats and a better angle of vision. - Such buses may have one or two doors. - Many single deck models have seating capacity of fifty two which in city buses is reduced to have more space for standing. This enable transportation of more passengers for short duration. 

• The full‐length bodywork, i.e. single deck bus or coach is almost universal today as this layout eliminates all the disadvantages of classic type.

3.Double Decker