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

  

 

• These buses have a greater number of seats for a given overall length than a single Decker but stability is not so high as for the single Decker.

4.Split‐level bus

 

• An intermediate solution between the two is the split‐level layout.This layout has more seats than a single Decker and more stability than the double Decker.
• However, owing to the small number of variations that can be made from this basic design, it has not been widely accepted.

5.Two‐level single Decker

 

• Two‐level single Decker has been used for luxury coaches.
• This layout provides good forward visibility for all passengers, good luggage space and easy installation of an under‐floor or rear engine.
• Again this type is only made for special orders, as it is not easy to make derivations from the same body shell.

6.Articulated bus

  

• ‘Articulated Vehicle/Bus’ means a vehicle which consists of two or more rigid sections which articulate relative to each other; the passenger compartments of each section is interconnected by an articulate section allowing free movement of passengers between them.
• Bodies for very large coaches or in particular, city buses are often made in two parts because of axle load limitations. The rear portion is articulated to the main vehicle by a covered pivot allowing easy access between the two sections.
•  A bi‐articulated bus or double articulated bus is an extension of an articulated bus in that it has three passenger compartment sections instead of two.
• This also involves the addition of an extra axle. Due to the extended length, bi‐articulated buses tend to be used on high frequency core routes or bus rapid transit schemes rather than conventional bus routes.

Bus body Regulations:

Classification of buses:

Buses are categorized into four Types,
namely,
 
1) Type I
2) Type II
3) Type III
4) Type IV

Type I

•  Vehicles are the medium and high capacity vehicles designed and constructed for urban and sub urban / city transport with area for standing passengers. 

Type II

•  Vehicles are those designed and constructed for inter-urban/inter-city transport without specified area for standing passengers 

Type III

•  Vehicles are those designed and constructed for long distance passenger transport, exclusively designed for comfort of seated passengers and not intended for carrying standing passengers.

Type IV

‘Type IV’ Vehicles are those designed and constructed for special purpose use such as the following :-
 (1) School Bus: means vehicles designed and constructed specially for schools, college, and other educational Institutions.
 (2) Sleeper Coaches: means vehicles designed and constructed specially berth to accommodate sleeping passengers.
 (3) Tourist Bus: means vehicles designed and constructed for the purpose of transportation of passengers as tourists and may be classified in any one Type of comfort levels. 

•  Non Deluxe Bus(NDX) means bus designed for basic minimum comfort level.

•  Semi Deluxe Bus(SDX) means a bus designed for a slightly higher comfort level and with provision for ergonomically designed seats.

•  Deluxe Bus(DLX) means a bus designed for a high comfort level and individual seats and adjustable seat backs, improved ventilation and pleasing interiors.

•  A.C. Deluxe Bus(ACX) means a Deluxe Bus which is air conditioned.

 Number of Service Doors

Minimum dimensions of Service Doors

 

Window:

• The window panes shall be of sliding type for all buses except ACX buses.
•  However, in ACX buses the provision for adequate ventilation in case of A.C. failure shall be made.
•  The minimum width of the window aperture (clear vision zone) shall be 550 mm.
•  The minimum height of the sliding part of the window aperture (clear vision zone) shall be 550mm

Emergency Exits:

•  At least one emergency exit shall be situated on the opposite side of the service door.
•  In case of more than one emergency exit, one of the emergency exit shall be situated in the front half of the vehicle, opposite to the service door and the second emergency exit shall be either on the rear half or at the rear side of the bus.

 Minimum dimensions of the emergency exits:

Steps:

 CONSTRUCTIONAL DETAILS:

1.Frame construction
2.Double skin construction

1.FRAME CONSTRUCTION:

The design of bus body is based on the use of a light metal frame, braced by stressed metal panels.
The main framing is of light members of thin gauge material formed by folding, pressing, stretch forming, rolling, extrusion and connected by gussets generally riveted to the structure framework which is applied to the inside face of the framing.


 Sequence of Bus body building operation:

•  Chassis Preparation
•  Side and front framing
•  Roof framing and rear end
•  Truss panel riveted
•  General inspection
•  Roof panels
•  Paneling and moulding
•  final finish

1.Chassis Preparation:

The floor frame is placed in position, holding down and fixed with bolts or rivets and all parts of the chassis are painted.

2.Side and front framing:

The body side framing and front end is assembled.Truss panels bolted into position, the body lined up with the waist rail and the lower bolts tightened.

3.Roof framing and rear end:

The body ends and roof framing are positioned and fixed, the wheel boxes and entrance steps installed.

4.Truss panel riveted:

Truss panels between the waist rail and seat rail over the wheel arches are riveted into position.

5.General inspection:

General inspection of finished framing to ensure all structural bolts are tight and truss panels securely riveted.

6.Roof panels:

 
Roof panels are fixed and riveted.

7.Paneling and moulding:

  8.final finish:

 2.DOUBLE SKIN CONSTRUCTION DETAILS:

• Normally inner skin will take part in load carrying ,Outer skin will be fixed in such a way that it can be replaced easily.

   (a)Interior paneling:

• This is the paneling done in side the vehicle. 
• The paneling inside the body gives comfort to the passengers.
• The factors to be considered during paneling are safety, easy maintenance, easy cleaning. 
• Decorated laminated sheet are used for this. When laminated sheet and aluminium and stainless steel are combined give the good look.
• GRPF (glass reinforced plastic fiber) can also be used for this purpose. 
• Floor side panel and roof has to be thermal insulated or sprayed.

 (b) Exterior paneling:

• The paneling done on the exterior is called as exterior paneling. 
• This is also called as skin of the vehicle.
• This does not take any load.
• This is done by galvanized steel sheet coated with zinc coating.
• The galvanized steel sheet is welded or riveted to form panel.
• The body paneling is done by two ways.
• Small panels are attached together according to the requirement.
• To make a single big panel for the whole length.
• Steel sheets are used in the uneven surface. This increase the beauty.
• To avoid corrosion, leak and vibration, the panel should be made with plastic trim fillet. 
• The normally used material for exterior paneling is aluminium.

TYPES OF METAL SECTION USED: 

a. Channel Section -Good resistance to bending

b. Tabular Section-Good resistance to Torsion

c. Box Section-Good resistance to both Bending and Torsion

CHASSIS AND BODY BUILDING TECHNIQUES:

• The basic under structure is fabricated out of thin mild steel cold rolled channel sections fully galvanized for corrosion protection.
• The structure is provided with cross members and outriggers at specified intervals so that they will form complete ring frames along with body side pillars and roof sticks.
• Pillars and roof sticks are made of sheet metal pressed sections.
• Pillars are bolted to the sole bar of the under structure and the roof ticks are connected to the pillar by stiff pressed steel corner brackets and the joining of them done using solid rivets 
• All inner panels and wheel arch truss panels are of sheet metal and solid steel riveted to the pillars and longitudinals.
• All outer panels and roof panels are of aluminium and pop riveted. 

CONVENTIONAL TYPE CONSTRUCTION:

                                                                                                                                                                               

(It also called as “Separate body and chassis type”, “Orthodox type”)

• The body and chassis will be as separate unit. 
• Bolts are used to join the body and chassis together.
• The separate part of body will be placed over the top of the chassis.
• A rubber block will be placed in between these two parts to avoid the vibration.
• The conventional type building involves in building up of a ladder type frame with two long side members interconnected by cross members at intervals.
• The units like engine, gear box, radiator, axles, steering wheel, fuel tank are mounted on the frame.
• The whole body and passenger load is transmitted to the chassis by means of spring.
• Chassis should be built strong so that it can withstand the weight of the body.

• The basic under body structure is fabricated only thin mild steel cold rolled channel sections
• It is fully galvanized for corrosion protection
• It is provided with cross members and out riggers at specified intervals.
• The pillar and roof shocks are made of sheet steel.
• Pillars are bolted to the sole bar of the under structure.
• The roof sticks are connected to the pillars by stiff pressed steel corner brackets and joined by solid rivets.
• All the inner panels and wheel arch truss panels are sheet steel and solid steel riveted to the pillars.
• All the outer panels and roof panels are pop riveted.         

Advantage:

1.This is used in heavy vehicle.
2.This is of simple construction.
3.The change of designing and the alteration of frame length is easy.
4.Servicing is easy in case of any damage.
5.There is no need for more expenditure for preventing corrosion.

Disadvantage:

1.The weight of the frame is more, due to this the vehicle speed is decreased. More fuel is also required.
2.Since the floor height is more, the centre of gravity from the ground will also be more. Due to this, the stability will be decreased.

                                                     

CONSTRUCTION OF INTEGRAL BUS BODY(MONOCOQUE / UNIBODY) :

• Monocoque, meaning 'single shell' in French, is a construction technique that utilizes the external skin to support some or most of the load. The technique may also be called structural skin or stressed skin.
• The semi-monocoque is a hybrid of a mutually reinforcing tensile shell and compressive structure.
• Unitary body / unit body - uses a system of box sections,bulkheads and tubes to provide most of the strength of the vehicle,to which the stressed skin adds relatively little strength or stiffness.
• In integral bus construction, a base structure is formed with 4 long Side members, cross members, outriggers and wheel arch supports.
• Units like engine , gear box, axles etc are mounted on the flexible Under structure, which is fabricated by welding.
• These under structures are painted with suitable colors to prevent corrosion .
• The body pillars which are ring frames are attached to the two extreme Side members called sole bars by bolting.
• The panelling is done as per specifications to give good integral Structure.
• The under and body structure act as a single structure to carry the Load.Thus for a given load the integral structure will withstand more stress which indicates that every member of the structure is sharing the load.

  

DESIGN OF INTEGRAL BUS:

 Chassis under structure 

• Unit weights like engine, gear box, radiator,steering box, batteries and fuel tank acting as point loads at the mounting points.
•  Weight of under stucture considered as uniformly distributed load. 
• Considering the vertical and lateral bending,moment is calculated and a section required to carry the weights is decided allowing for a reservefactor depending on the road conditions.

       Chassis body structure 

• Body weight considered as uniformly distributed load. 
• Payload considered as uniformly distributed load
• Considering bending , torsion and combination of both, the body structure is designed allowing for a
  reserve factor depending in the road conditions.

Advantages:

1.Light in weight compared with conventional type of body construction. so fuel consumption is less.
2.Easy entry/ exit and lower floor height is to be achieved.
3.Greater strength.
4.Free from squeaks and rattles caused by the working of bolted joints which are absent in this construction.
5.Reduction in heat in the driver and passenger area.
6.Low noise and vibration level.
7.Lowered wind screen level and better visibility for driver.
8.Assembling of component is easy.
9.Mainly this type is used in car construction.

Disadvantages:

1.when a car is involved in an accident, it is more expensive to repair the large panel sections.
2.There is a greater liability of injury to the driver.
3.It is more expensive to introduce changes in body styling to keep abreast of the times.
4.Initial cost is more.
5.Thick gauge material should be used.
6.More cost to avoid corrosion.

FLOOR HEIGHT: 

• The floor should be placed as low as possible so that distance of centre of gravity of bus from road surface is small. 
• The stability of the bus gets increased.
• It gives easy entry to the bus.
• It is easy to place luggage in bus. 
• Due to the lower height, the Bus design is more complicated in separate chassis and body construction.
• Considering floor level, the chassis frame are made specially shaped.
• If an integral body is used, low floor level becomes much easier to design.
• Large number of passengers can be seated in the bus.

ENGINE LOCATION: 

 According to location of engine, there are five types as given in figure.
a)Engine behind front axle.
b)Engine above front axle.
c)Engine in front of front axle.
d)Engine at rear.
e)Under – floor engine.

• Advantages of different engine locations are to improve visibility (i.e.) forward and side visibility. 
• Reducing extra placing space of engine. 
• It improves space for passenger in bus.

ENTRANCE AND EXIT LOCATION: 

• Generally in all types of buses, back side door is for entrance. 
• Front side door (nearer to driver) is exit.
• In city bus, back and front door are as usual. But middle door is for easy exit for more number of passengers at a time.
• In city bus, the door width is more.
• In sub – urban bus, the entrance is at the middle and exit is at the front.
• In long distance bus, the back door is for entrance and front door is for exit. 
• In long distance bus, the door size (i.e.) width of the door is less.

SEATING DIMENSIONS:

If the seat is comfortable, the journey may be a pleasure trip ,But it will be a trouble some, tiring, agony, if the seat is uncomfortable. The design of seat is designed to the structure of human. Passenger seat is designed for comfort and also described according to distance between the consecutive seats.

Seats are manufactured by the materials
a)Natural rubber latex
b)Cold – cure polyester (or) urethane
c)Hot – cure foams (or) chip forms.

• In passenger seat, the seating angle ranges from 50 to 100 
• In push back seating, the seating angle is included to 60deg