TECHNICAL FIELD
[0001] The present subject matter relates to an exhaust pipe and method of manufacturing the exhaust pipe for an internal combustion engine and more particularly but not exclusively to the exhaust pipe for motor vehicles.
BACKGROUND [0002] An internal combustion (IC) engine comprises a cylinder head, a cylinder block defining a combustion chamber where burning of air-fuel mixture takes place. The cylinder head comprises an intake port for supplying the air-fiiel mixture and an outlet port enables scavenging of burnt gases from the combustion chamber. Due to combustion process, the piston undergoes a translational motion that is converted into the rotational motion of the crankshaft. Generally, the combustion process results in generation of energy including heat. Thus, the exhaust gases are hot and when they travel through the exhaust system, the exhaust- system also gets heated up. Typically, heat insulators or heat guards are provided to reduce from coming in contact with the surrounding components of the vehicle, which otherwise would affect their functioning due to heat dissipation. Further, the heated exhaust system may also come in contact with the user causing inconvenience or even causing injury to the riders. Conventionally, a double pipe type exhaust pipe construction is known in the art that has hot gases flowing through the inner pipe and an outer pipe that is concentrically provided of the inner pipe helps in keeping direct transfer of heat from the inner pipe. Such, double pipe exhaust system are typically used in smaller applications like two-wheeled or three-wheeled vehicles due to the ease of design. BRIEF DESCRIPTION OF THE DRAWINGS [0003] ; The detailed description is described with reference to the accompanying figures. The same numbers are used throughout the drawings to reference like features and components.
[0004] Fig. 1 illustrates the side view of an exemplary motor vehicle. [0005] Fig. 2 illustrates the side view of an internal combustion engine with the exhaust system, in accordance with an embodiment of the present subject matter.

[0006] Fig. 3 illustrates an enlarged isometric view of exhaust system, in
accordance with an embodiment of the present subject matter.
[0007] Fig. 4 illustrates a sectional view of the exhaust pipe taken along axis
A-A\ in accordance with the embodiment of the present subject matter as
depicted in Fig. 3.
[0008] Fig. 5 illustrates another sectional view of the exhaust pipe taken along
axis of the exhaust pipe, according to the embodiment of the present subject
matter.
[0009] Fig. 6 illustrates a partial exploded view of the first cover of the engine,
in accordance with the embodiment of Fig. 2.
[00010] Fig. 7 illustrates a flow chart depicting the method of manufacturing the
exhaust pipe, in accordance with the embodiment of the present subject matter.
DETAILED DESCRIPTION [00011] Generally, in the exhaust system that consists of an exhaust pipe and muffler body, both the parts are welded to each other. In the exhaust pipe having a dual pipe structure (also known as pipe-in-pipe structure), the inner pipe carries the exhaust gases from the engine, whereas the outer pipe acts a shield to the inner pipe whereby the inner pipe temperatures that are very high do not directly reach the outer body of the exhaust pipe, which is desired as the temperature of the exhaust gases reach to about 600 degrees centigrade within the engine and when these hot gases pass through the exhaust pipe could cause serious injury to the riders or to the ancillary parts of the vehicle.
[00012] Typically, the exhaust pipe consists of bends for routing of the exhaust pipe from the cylinder body of the internal combustion engine to the muffler body, which can be disposed at a lateral side of the vehicle, at underbelly of the vehicle, or below the seat of the vehicle. Thus, the exhaust pipe is provided with bend having a suitable radius of curvature to enhance the smooth flow of the said exhaust gases. Generally, the process adopted for bending the exhaust pipe includes a set of procedures, starting from filling of sand in the annular space between the outer pipe and inner pipe to avoid the touching of the inner pipe with <■ outerpipe-mMn'e^annulaV^pa^

space. Further, the ramming of the sand ensures that the firm holding of inner pipe and outer pipe in their desired locations is attained. One end of the dual pipe structure is welded thereby closing the annular space at the respective end and other end is sealed with a removable plug. After the aforementioned steps, the dual pipe structure, with sand rammed inside the annular space, is loaded on to a pipe bending machine using a CNC (Computer Numerical Control) program to get the straight pipe-in-pipe in the desired bent form. Subsequent to which, the sand is removed by removing the plug whereby the final exhaust pipe is obtained. However, the aforementioned procedure that is conventionally used involves huge labor as well as the number of steps are higher. For example, the ramming of sand, sealing of the annular space, and subsequently bending, and then removal of the sand making it time consuming process. Moreover, this also require ample sand or the like making it expensive for accumulation, storage and use. [00013] Moreover, the conventional dual pipe structure occupies lot of space on the vehicle due to the provision of annular space between the inner pipe and the outer pipe. Due to the annular space the entire volume of the exhaust pipe is ' increasing. This typically affects the assembly and maintenance of parts that are disposed adjacent to the exhaust pipe. For example, in vehicles that have the engine assembly fixedly mounted to the frame at a front portion of the frame member, the exhaust pipe that is passing through the side of the engine assembly may foul with the detachable parts like the engine covers. Thus, the challenge is to provide an exhaust that is cost effective and time saving to manufacture while overcoming any assembly & packaging limitations.
[00014] Hence, the present subject matter provides an exhaust system that includes an exhaust pipe that is connected to an exhaust port of the IC engine. A downstream end portion of the exhaust pipe is connected to a muffler body of the vehicle. The exhaust pipe includes an inner tube and an outer tube and is provided with one or more deformed portions provided on the outer tube typically formed, by bashing or the like. This enables the outer tube .to hold the inner rube at a desired position.

[00015] A gap is provided substantially annularly between an outer periphery of the inner tube and the inner periphery of the outer tube. The gap provided substantially annularly is present at portions other than at the bashed portions. For example, at the bashed portions there is no annular gap. It is a feature that the volume of the exhaust pipe occupying on the vehicle is reduced due to the bashing portions. Improvement of few millimeters of space plays significant role on the vehicle as it reduces the interference between the adjacent parts, reduced heat dissipation to adjacent parts, and also the ground clearance can be improved. For example, in typical vehicles the exhaust pipe is one of the lower most portions of the vehicle, especially when passing below a rider footrest in such cases the deformed portion can provide improved clearance.
[00016] In one implementation, the exhaust pipe is passing adjacent to a cover of the crankcase. For example, the cover can be a clutch cover. The deformed portion is provided so as to reduce the area occupied in proximity to the fasteners whereby ease of access to the fasteners is improved. Also, the removal of the cover in axial direction (of the crankshaft) is improved.
[00017] The deformed portions are preferably disposed away from the bend portions as the deformed portions are provided to hold the inner tube in a desired location.
[00018] It is a feature that the inner tube is inserted into the outer tube and the tubes are held in place through a pseudo locking method e.g. welded at one end, in order to maintain a desired relative position of the inner tube and the outer tube. Subsequently, depending on the length of the pipe one or more bashings are provided on the outer tube such that the outer tube forms the deformed portions holding the inner tube in a desired position defining the spacing formed substantially annularly. Subsequently, the resultant exhaust pipe is processed for bending depending on the layout of the vehicle by providing bends at the desired locations.
[00019] It is a feature that the concept of configuring specific bashing on the outer tube of the exhaust pipe achieved through a pseudo locking process of manufacturing^pf-the .exhaust pipe eliminates, the need .for use ,of sand and -

laborious work of sand-ramming thereby offering an optimum process that result in structurally rigid dual pipe exhaust.
[00020] The present subject matter along with all the accompanying embodiments and their advantages would be described in greater detail in conjunction with the figures in the following paragraphs.
[00021] Fig. 1 illustrates a two-wheeled vehicle (100), which is an exemplary motor vehicle, having an IC engine (101) that is vertically disposed. Preferably, the IC engine (101) is a single-cylinder type IC engine. The two-wheeled vehicle comprises a front wheel (110), a rear wheel (103), a frame member (102), a fuel tank (121) and seat (106). The frame member (102) includes a head pipe (111), a main tube (not. shown), a down tube (not shown), and seat rails (not shown). The head pipe (111) supports a steering shaft (not shown) and two telescopic front suspension(s) (114) (only one shown) is attached to the steering shaft through a lower bracket (not shown). The two telescopic front suspension(s) (114) supports the front wheel (110). The upper portion of the front wheel (110) is covered by a front fender (115) mounted to the lower portion of the telescopic front suspension (114) at the end of the steering shaft. A handlebar (108) is fixed to upper bracket (not shown) and can rotate to both sides. A head light (109), a visor guard (not shown) and instrument cluster (not shown) is arranged on an upper portion of the head pipe (111). The down tube may be located in front of the IC engine (101) and extends slantingly downward from head pipe (111). The main tube is located above the IC engine (101) and extends rearward from head pipe (111). The IC engine (101) is mounted at the front by the down tube and connects the rear of the IC engine (101) at the rear portion of the main tube.
[00022] A fuel tank (121) is mounted on the horizontal portion of the main rube
(112). Seat rails are joined to main tube and extend rearward to support a seat
(106). A rear swing arm (not shown) is connected to the frame member (102) to
swing vertically, and a rear wheel (103) is connected to rear end of the rear swing
arm (118). Generally, the rear swing arm is supported by a mono rear suspension
(117) (as illustrated in the present embodiment) or two suspensions on either side
,,.,of, the two-wheeled vehiclg.-Atail light iiniHnot shownVis disno3cd:nUhrJaLdlQf

the two-wheeled vehicle at the rear of the seat (106). A grab rail (105) is also provided on the rear of the seat rails. The rear wheel (103) arranged below seat (106) rotates by the driving force of the IC engine (101) transmitted through a chain drive (1 16) from the IC engine (101). A rear fender (127) is disposed above the rear wheel (103).
[00023j Fig. 2 illustrates a side view of the IC engine (101) in accordance with an embodiment of the present subject matter. The IC engine (101) is made up of a cylinder head assembly (140), a cylinder block (135), a cylinder head cover (not shown) and a crankcase (160). In the depicted embodiment, the IC engine (101) is having a piston axis (P-P') that is forwardly inclined type, which can be considered as substantially vertical type engine. The crankcase (160) is made up of a left-side crankcase and a right-side crankcase (not shown). The IC engine (101) rotatably supports plurality of components including a crankshaft, plurality of gears, etc. (not shown). The vehicle (100) is provided with an intake system that includes an air-fuel mixture means (150) and an exhaust system (200). [00024] The exhaust system (200) includes an exhaust pipe (205) that is connected to an .exhaust port (145) of the cylinder head (140). An upstream end portion 210 of the exhaust pipe (205) is connected to the cylinder head (140) and a downstream end portion (211) of the exhaust pipe (205) is connected to the muffler body (130). As shown in Fig. 1, the muffler body (130) is disposed adjacent to a rear wheel (103) towards the lateral side (RH) of the vehicle (100). The IC engine (101) is disposed rearward of the front wheel (110) and is fixedly mounted to the frame member (102). Therefore, the exhaust pipe (205) forwardly sideward from the exhaust port (145) is provided on a front facing side of the cylinder head (140). The exhaust pipe (205) takes a first bend (212) subsequent to which it extends downwards and then by taking a second bend (213) the exhaust pipe (205) extends rearwards towards the muffler body (130). [00025] In the present embodiment, the exhaust pipe (205) may include one or more deformed portions and in the depicted embodiment, the exhaust pipe (205) is provided with a first deformed portion (214) and a second deformed portion ,, ,(215,). The .first deformed,portion (214) and the.second deformed portion (215) are

typically formed by bashing or the like. The exhaust pipe (205) includes inner tube (206) and an outer tube (207) (shown in Fig. 4). The outer body of the exhaust pipe (205) is the outer periphery of the outer tube (207) and the inner tube
(206) is disposed inside the outer tube (207) in a concentric manner, with a gap
provided annularly between an outer periphery of the inner tube (206) and the
inner periphery of the outer tube (207). Exhaust gasses from the IC engine (101)
are transferred to the muffler body (130) through the inner tube (206). The muffler
body (130) may include one or more catalytic converters and one or more
perforated tubes (131) (shown in Fig 5).
[00026] The outer tube (207) is bashed so as to come in contact with the outer periphery of the inner tube (206). In one implementation, the outer tube is squeezed using a jaw or the like to match with an outer diameter of the inner tube (206), whereby the outer tube (207) holds the inner tube (206) in the desired position. Fig. 3 depicts enlarged perspective view of the exhaust pipe (205) depicting the deformed portions (214, 215). As shown in Fig. 3, the outer tube
(207) is bashed to form the first deformed portion (214). In the depicted
embodiment, the first deformed portion (214) is formed on substantial lateral sides
. of the outer tube (207). The deformed portion (214) is formed as a depression (216) on the outer tube (207) that reaches the outer periphery of the inner tube (206). The deformed portion (214) includes a transition portion (217) between the depression (216) and the outer periphery of the outer tube (207). [00027] Fig. 4 depicts a sectional view of the exhaust pipe taken radially long axis A-A', in accordance with the embodiment as shown in Fig. 3. The inner tube (206) is having a substantially circular profile and the outer tube (207) is disposed around the inner tube (206), wherein a spacing (208) is formed between the outer tube (207)'and the inner tube (206) except at the deformed portions (214, 215). As shown in Fig. 4, the deformed portion (214) is formed due to a first bashed portion (220) and a second bashed portion (221) is bashed to touch the outer periphery of the inner tube (206). In the present implementation, the first deformed portion (214) is provided on first facing side(s) that is lateral facing sidefsl and the second, deformed portion (215) is provided on upward-downward _

facing side(s). The facing side(s) includes any of upward-downward side(s), lateral side(s), and angular side(s) disposed symmetrically or asymmetrically. For example, the first bashed portion (220) and the second bashed portion (221) can be asymmetric and being disposed away from an inclination with respect to lateral sides! The spacing (208) is maintained along a long axis having a first diameter
(Dl).
[00028] The deformed portion may be provided on one opposite facing sides of the outer tube (207) and another deformed portion is provided on opposite facing sides of the outer tube (207), which are at a predetermined first angle (a). The first deformed portion (214) is provided substantially on the lateral sides of the outer tube (207) and the second deformed portion (215) is formed on the upper and lower sides of the outer tube (215). Considering Fig. 2 and Fig. 5, which is a sectional view taken along the axis of the exhaust pipe (205). The first deformed portion (214) is provided on the lateral sides of the exhaust pipe (205) and the second deformed portion (215) is provided in upward-downward portion of the outer tube (207).
[00029] Further, as shown in Fig. 4, at least a perimeter of the outer tube (206) abuts or holds the inner tube (207). Around 25 to 75% of the perimeter can be adapted to be abutting the inner tube (206). The pipes are made of any known rigid material capable of withstanding high temperatures including metals. The perimeter can vary based on the requirement like material used, spacing between the outer tube (207) and the inner tube (206). Further, for each deformed portion, as shown in, the current implementation provides two contact portion(s) (240) formed by the first bashed .portion (221) and the second bashed portion (222). As shown in Fig. 4, the contact portion (240) can have a first angle (a), which represents the angular portion of the outer tube (207) that is abutting the inner tube (206). The first angle (a) is kept in the range of 60-120 degrees. However, depending on the parameters of the outer tube like the material, diameter of the outer tube, or thickness of the outer tube, the number of contact points can be varied. For example, an exhaust pipe with larger diameter may have three bashed nortion forming the deformed portion.

[00030] In addition, as per another embodiment, the deformed portions (214, 215) are disposed away from the bend portions (212, 213) with a minimum distance substantially around 10 millimeters. In the present embodiment, the deformed portions (214, 215) are provided at downstream portion of the second bend (213). Further, the deformed portions (214, 215) are selectively disposed such that the deformed portion does not come in contact with the rider's body or any other vehicular components thereby additionally offering layout & packaging flexibility. In the depicted embodiment, the second deformed portion is provided substantially below the rider footrest, which acts a barrier for the rider's foot to-come in contact with the deformed portion (215) that is hotter as it is touching the inner tube (206). Similarly, the first deformed portion (214) is provided substantially subsequent to the second bend (213) with pre-determined distance such that the first deformed portion (214) is away from the rider's foot. [00031] Further, the overall space occupied by the exhaust pipe is reduced. Especially, the exhaust pipe (205) of the present subject matter enables easy removal of a first cover (165) during the service, the first cover (165) can be a clutch cover. The first cover (165) requires removal during the servicing and replacement of components like centrifugal filter (170) provided inside the engine (101). Conventionally, in the known layout where the exhaust pipe passes adjacent to the engine (101), it makes accessing and removal of the clutch cover complex. Whereas, the present subject matter enables ease of access to the fasteners due to the deformed portion like the first deformed portion that is provided on inner lateral side because of which clearance between the exhaust pipe (205) and the first cover (165) is improved thereat. Also, the second deformed portion (215) enables ease of access to the fasteners thereby enabling ease of access and removal.
[00032] Fig. 5 depicts a sectional view of the exhaust pipe taken along axis thereof. The first bashed portion (220) and the second bashed portion (221) can be asymmetric and being disposed away from an inclination with respect to lateral sides. The spacing (208) is maintained along a long axis having a first diameter (py^r^ere^asvitherdiameter of the .exhaust: pipe (205);atthe4eformed portidn(s) ""."

(214, 215) is having a second diameter (D2), wherein the first diameter is larger than the second'diameter (D2). The difference between the first diameter (Dl) to second diameter (D2) is kept to a minimum of 10 millimeters. Further, in the present embodiment, the first deformed portion (214) and the second deformed portion (215) are disposed at a predetermined distance (L) therebetween. The pre-determined distance (L) can be in the range of 50 to 400 millimeters, wherein the range enables ease of manufacturing and. at the same time provides adequate locking of the inner tube (206) with the outer tube (207) during manufacturing process. Moreover, a substantial reduction in the pre-determined distance (L) may lead to distortion which is not desirable. Such distortion, also referred to as deformation, along the exhaust pipe (205) affects the smooth flow of exhaust gas therethrough.
[00033] Further, the deformed portion (214^ 215) are having a first width (W) taken along axis of the exhaust pipe (205), wherein the width is kept in the range of 15 to 250 millimeters depending on the holding requirement of the inner tube by the outer tubes, weight of the tubes, and other holding requirements. For example, an inner tube with a smaller diameter may require smaller width of the bashing, which is kept in the lower range of the first width (W). [00034] Further, as shown in Fig. 6, the exhaust pipe (205) is passing adjacent to a first cover (165) of the crankcase (160). The first cover (165) is a first cover in the present embodiment. The second deformed portions (214, 215) are provided so as to reduce the area occupied in proximity to the first cover (165) especially in proximity to the fasteners (not shown) whereby ease of access to the fasteners is improved. Also, the removal of the first cover (165) in substantially axial direction (of the crankshaft) is improved. The first width (W) of the deformed portion is kept at least 15 millimeters to enable accessing of fasteners as well as to reduce difficult of manufacturing. Further, the first width (W) of the bashing is provided with a maximum of around 250 millimeters to reduce any significant adverse resistance to enable heat isolation between the inner tube (206) and the outer tube (207).

[00035] Fig. 7 shows a flow chart depicting the steps for process of manufacturing of the exhaust pipe (205), in accordance with the embodiment of the present subject matter. At step 305, the inner tube (206) is inserted into the outer tube (207). The inner tube (206) and the outer tube (207) are welded at one end. Subsequently, depending on the length of the pipe one or more bashings are provided on the outer tube (207) such that the outer tube (207) forms the deformed portions (214, 215) whereby the outer tube (207) holds the inner tube (206) in a desired position defining the spacing (208). Subsequently, the resultant exhaust pipe (205) is processed for bending depending on the layout of the vehicle. These deformed portions (214, 215) provided at predetermined locations can be angularly orientated in any direction to provide better holding of the inner tube (206) by the outer tube (207). The deformed portions (214, 215) act as clamps that hold the inner tube firmly in its position whereby during bending process, the deformed portions (214, 215) hold the inner tube (206) rigidly making the process cost-effective due to elimination of sand and sand-ramming. [00036] It will be appreciated that the present subject matter and its equivalent thereof offers many advantages, including those which have been described forthwith. Many modifications and variations of the present subject matter are possible in the light of above disclosure. Therefore, within the scope of claims of the present subject matter, it may be practiced other than as specifically described.

List of reference signs:
100 vehicle 150 air-fuel supply means
101 IC engine 160 crankcase
» 102 frame member 35 165 first cover
103 rear wheel 200 exhaust system
104 tail light unit 205 exhaust pipe
105 grab rail 206 inner tube
106 seat 207 outer tube
1-107 lower bracket 40 208 spacing
108 handlebar 210 upstream end
109 head light 211 downstream end
110 . front wheel 212 first bend portion
111 head pipe 213 second bend portion
i 112 main tube 45 214 first deformed portion
114 front suspension 215 second deformed portion
115 front fender 216 depression
116 chain drive 217 transition portion
117 rear suspension 220 first based portion
I 118 swing arm 50 221 second bashed portion
119 front brake 240 contact portion
121 fuel tank Dl first diameter
122 rear brake D2 second diameter
125 visor guard L pre-deterrnined distance
i 126 seat rails 55 W first width
127 rear fender a first angle
130 muffler body
131 perforated tube
135 cylinder body
> 140 cylinder head

We Claim:
1. An exhaust system (200) for an internal combustion engine (101), said
exhaust system (200) connecting said internal combustion engine (101) to a
muffler body (101), said exhaust system (200) comprising:
an exhaust pipe (205) including an inner tube (206) and an outer tube (207),
and said outer tube (207) disposed concentrically about said inner tube (206),
wherein
at least a portion of said outer tube (207) includes one or more deformed
portion(s) (214, 215) abutting said inner tube (206) thereat.
2. The exhaust system. (200) as claimed in claim 1, wherein said deformed portion(s) (214, 215) of the outer tube (207) abuts an outer periphery of said inner tube (206) thereby securely holding the inner tube (206).
3. The exhaust pipe (200) as claimed in claim 1, wherein said exhaust pipe (205) includes one or more bend portion(s) (212, 213), and said deformed portion(s) (214, 215) being disposed away from the bent portion(s) (212, 213).
4. The exhaust system (200) as claimed in claim 1, wherein said exhaust pipe (205). is secured to said internal combustion engine (101) fixedly mounted to a frame member (105), said exhaust pipe (205) extending forwardly sideward and then rearward towards a muffler body (130) forming a first bend portion (212) and a second bend portion (213), and said exhaust pipe (205) includes a first deformed portion (214) provided subsequent to said second bend portion (213).
5. The exhaust system (200) as claimed in claim 1 or 4, wherein said exhaust pipe (205) includes a second deformed portion (215) provided subsequent to the first deformed portion (214) in a downstream direction.
6. The exhaust system (200) as claimed in claim 53 wherein said first deformed portion (214) and said second deformed portion (215) are provided substantially adjacent to a first cover (165) of said internal combustion engine (101).
7. The exhaust system (200) as claimed in claim 5, wherein said first deformed portion (214) and said second deformed portion (215) provided subsequent to said first deformed portion (214) are disposed apart at a predetermined distance (L)
;ranging in the range ;of 50;to 400 rriillimctcrs; - ,: Or w "r -i - .It

8. The exhaust system (200) as claimed in claim 1, wherein said one or more deformed portion(s) (214, 215) are having a first width (W) taken along an axis of said exhaust pipe, wherein the first width (W) is in the range of 15 to 250 millimeters.
9. The exhaust system (200) as claimed in claim 1, wherein said deformed portion(s) (214, 215) includes one or more contact portion(s) (240) formed by one or more bashed portion(s-) (221, 222).
10. The exhaust system (200) as claimed in claim, wherein said contact portion(s) (240) forms about 25% to 75% of the entire perimeter of the outer tube (207), and said contact portion (240) formed by the outer tube (207) abutting the inner tube (206) is defined by a first angle (a) in the range of range of 60-120 degrees.
11. The exhaust system (200) as claimed in claim 1, wherein said first deformed portion (214) is provided about a first facing side(s) and said second deformed portion (215) are provided on a second- facing side(s) of the outer tube (207), wherein said first facing side(s) and said second facing side(s) includes upward-downward side(s), lateral side(s), and angular side(s) disposed in any one of symmetric, and asymmetric profile.
12. An exhaust system (200) for an internal combustion engine (101), said internal combustion engine (101) connected to a frame member 0) sa'd exhaust system (200) comprising:
a muffler body (130); and
an exhaust pipe (205) extending forwardly sideward forming a first bend portion (212) and then rearward, from said internal combustion engine (101), towards said muffler body (130) forming a second bend portion (213), wherein
said exhaust pipe (205) includes a at least a portion of said outer tube (207) includes one or more deformed portion(s) (214, 215) abutting said inner tube (206) thereat, and a first deformed portion (214) of said one or more deformed portion(s) (214, 215) is provided subsequent to said second bend portion (213).
13. An exhaust pipe (205) capable of working in conjunction with an exhaust
_systemv,said.exhaust,pipe (205) comprising:-: • .-••-; ■: jr- ;.; ;.

an inner tube (206); and
and an outer tube (207) disposed concentrically about said inner tube (206), wherein
at least a portion of said outer tube (207) includes one or more deformed portion(s) (214, 215) abutting said inner tube (206) thereat. 14. A method for manufacturing an exhaust pipe (205), said method comprising the steps of:
inserting an inner tube (206) into an outer tube (207); securing the inner tube (206) and the outer tube (207) at one end; providing one or more deformed portions (214, 215) on said outer tube (207) for holding the inner tube (206) in a desired position; and bending of the resultant exhaust pipe (205).