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Title:
TWO-WHEELER FRAME STRUCTURE
Document Type and Number:
WIPO Patent Application WO/2008/087661
Kind Code:
A1
Abstract:
A two-wheeler frame structure having enhanced strength, comprising a crosspiece (130) attached to a head tube (135) is described. The head tube (135) is attached to a main tube (200), which in turn is attached to an engine mounting arrangement (225) with a wide base. Rear shock absorber mounting brackets (230)- are attached to the upper tubes (210), which are further attached to the main tube (200). The shock absorber mounting brackets (230) have a cutout (310) with side supports (320, 325) for receiving top end of the shock absorber (305). The side tubes (205), having portions (235, 240) with different cross sections, are attached to the upper tubes (210) at one end and to swing arm pivot tube (215) at the other end. One of the portions (235, 240) of the side tube (205) extends below chain line (220) and has a cross section different than that of the other portion. The upper tubes (210) are attached to a pillion handle mounting bracket (405) that is supported by a male bracket (405) from the bottom.

Inventors:
RAGHAVAN, Venkatesan (Tvs Motor Company Limited, Jayalakshmi Estate24 , Haddows Road, Chennai 6, 60000, IN)
BHUSAM, Syamalarao (Tvs Motor Company Limited, Jayalakshmi Estate24 , Haddows Road, Chennai 6, 60000, IN)
BALAGURU, Sridhar (Tvs Motor Company Limited, Jayalakshmi Estate24 , Haddows Road, Chennai 6, 60000, IN)
Application Number:
IN2008/000030
Publication Date:
July 24, 2008
Filing Date:
January 18, 2008
Export Citation:
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Assignee:
TVS MOTOR COMPANY LIMITED (Jayalakshmi Estate, 24 Haddows Road, Chennai 6, 60000, IN)
RAGHAVAN, Venkatesan (Tvs Motor Company Limited, Jayalakshmi Estate24 , Haddows Road, Chennai 6, 60000, IN)
BHUSAM, Syamalarao (Tvs Motor Company Limited, Jayalakshmi Estate24 , Haddows Road, Chennai 6, 60000, IN)
BALAGURU, Sridhar (Tvs Motor Company Limited, Jayalakshmi Estate24 , Haddows Road, Chennai 6, 60000, IN)
International Classes:
B62K11/04; B62K19/02; B62K25/04; B62K25/28
Foreign References:
FR2549795A1
FR2369147A1
EP0826584A2
US20050029032A1
Attorney, Agent or Firm:
VARADHACHARI, Lakshmikumaran et al. (Lakshmikumaran & Sridharan Advocates, B6/10 Safdarjung Enclave, New Delhi 9, 110 02, IN)
Download PDF:
Claims:
IAVe claim

1. A frame structure 100 for a two-wheeled vehicle, said frame structure 100 comprising a head tube 135, a main tube 200 having one end attached to said head tube 135, an engine mounting arrangement 225 attached to another end of said main tube 200, one or more swing arms 330 attached to said engine mounting arrangement 225 with the help of a swing arm pivot tube 215, one or more upper tubes 210 attached to said main tube 200, one or more rear shock absorber mounting brackets 230 attached to said upper tubes 210, one or more rear shock absorbers 305 attached to said rear shock absorber mounting brackets 230 at one end and to said swing arms 330 at the other end, one or more side tubes 205 attached to said upper tubes 210 at one end and to said swing arm pivot tube 215 at the other end, a pillion handle mounting bracket 405 attached to said upper tubes 210, characterized in that: said side tube 205 has a first portion 235 and a second portion 240, said first portion 235 extending below chain line 220 and having a cross section different from that of said second portion 240.

2. The frame structure 100 as claimed in claim 1, wherein said first portion 235 of said side tube 205 is attached to said swing arm pivot tube 215 and said second portion 240 of said side tube 205 is attached to said upper tube 210. 3. The frame structure 100 as claimed in claim 1, wherein said first portion 235 of said side tube 205 has a rectangular cross section and said second portion 240 of said side tube 205 has a circular cross section.

4. A frame structure 100 for a two-wheeled vehicle, particularly for a motorcycle, said frame structure 100 comprising a head tube 135, a main tube 200 having one end attached to said head tube 135, an engine mounting arrangement 225 attached to other end of said main tube 200, one or more swing arms 330 attached to said engine mounting arrangement 225 with the help of a swing arm pivot tube 215, one or more upper tubes 210 attached to said main tube 200, one or more rear shock absorber mounting brackets 230 attached to said upper tubes 210, one or more rear shock absorbers 305 attached to said rear shock absorber mounting

brackets 230 at one end and to said swing arms 330 at the other end, one or more side tubes 205 attached to said upper tubes 210 at one end and to said swing arm pivot tube 215 at the other end, a pillion handle mounting bracket 405 attached to said upper tubes 210, characterized in that: said rear shock absorber mounting bracket 230 has a cutout 310 for receiving a top end of said rear shock absorber 305, wherein a pair of supports 320, 325 is provided on both sides of said cutout 310 for supporting the attachment of the said top end of said rear shock absorber 305 in said cutout 310. 5. The frame structure 100 for a two-wheeled vehicle as claimed in claim 4, wherein said rear shock absorber mounting bracket 230 is a simply supported bracket. 6. The frame structure 100 for a two-wheeled vehicle as claimed in claim 4, wherein said rear shock absorber 305 is clamped to said cutout 310 of said rear shock absorber mounting bracket 230. 7. The frame structure 100 as claimed in claim 1 or 4 further comprising a male bracket 410 supporting said pillion handle mounting bracket 405 from bottom.

8. The frame structure 100 as claimed in claim 7, wherein said pillion handle mounting bracket 405 is made blind shelled by using said male bracket 410.

9. The frame structure 100 as claimed in claim 1 or 4, wherein said engine mounting arrangement 225 has a lower portion wider than an upper portion to accommodate a wide center stand 510.

10. The frame structure 100 for a two-wheeled vehicle as claimed in claim 9, wherein said engine mounting arrangement 225 comprises a pair of vertical brackets positioned opposite to each other. 11. The frame structure 100 as claimed in claim 1 or 4 further comprising a crosspiece

130 attached to said head tube 135 for supporting a front license plate mounting bracket 115, a head tube cover 110 and one or more electrical units. 12. The frame structure 100 for a two-wheeled vehicle as claimed in claim 11, wherein said crosspiece 130 is welded to said head tube 135.

13. The frame structure 100 for a two- wheeled vehicle as claimed in claim 11, wherein said electrical units include a horn 120 and a regulator 125.

14. A frame structure 100 for a two-wheeled vehicle, particularly for a motorcycle, said frame structure 100 comprising a head tube 135, a main tube 200 having one end attached to said head tube 135, an engine mounting arrangement 225 attached to other end of said main tube 200, one or more swing arms 330 attached to said engine mounting arrangement 225 with the help of a swing arm pivot tube 215, one or more upper tubes 210 attached to said main tube 200, one or more rear shock absorber mounting brackets 230 attached to said upper tubes 210, one or more rear shock absorbers 305 attached to said rear shock absorber mounting brackets 230 at one end and to said swing arms 330 at the other end, one or more side tubes 205 attached to said upper tubes 210 at one end and to said swing arm pivot tube 215 at the other end, a pillion handle mounting bracket 405 attached to said upper tubes 210, characterized in that: said side tube 205 having a first portion 235 and a second portion 240, said first portion 235 extending below chain line 220 and having a cross section different than that of said second portion 240; said rear shock absorber mounting bracket 230 having a cutout 310 for receiving a top end of said rear shock absorber 305, wherein a pair of supports 320, 325 is provided on both sides of said cutout 310 for supporting attachment of said top end of said rear shock absorber 305 in said cutout 310; a male bracket 410 supporting said pillion handle mounting bracket 405 from the bottom; said engine mounting arrangement 225 having a lower portion wider than an upper portion to accommodate a wider center stand 510; and a crosspiece 130 attached to said head tube 135 for supporting a front license plate mounting bracket 115, a head tube cover 110 and one or more electrical units.

Description:

TWO-WHEELER FRAME STRUCTURE

TECHNICAL FIELD

The present subject matter, in general, relates to a two wheeled vehicle and in particular relates to a frame structure for a two wheeled vehicle.

BACKGROUND

Generally, a frame structure for a two-wheeled vehicle is designed to act as a base onto which various components are attached. The frame structure minimizes the damages occurring to the vehicle in case of an accident or a collision. Normally, in a two- wheeler, the frame structure provides support to most components like the engine, the seats, the suspension system, and other electrical components like battery. The frame structure for the two-wheeler is usually manufactured from metal tubes that are suitably joined together to provide locations to accommodate the components.

The frame structure of the two-wheeler must meet international standards for performance and safety. The stiffness or strength of the frame structure defines the reliability of the two-wheeler. The stiffness of the frame structure plays an important role in the overall design characteristics of the two-wheeler. The overall stiffness is affected by various factors such as variations in mounting the engine and the number of loose parts. A decreased number of loose parts in the frame structure provide better stability to the two- wheeler. Moreover, a vibration resistant frame structure ensures reduced noise and provides a comfortable ride to the rider.

SUMMARY

The subject matter described herein discloses a frame structure for a two wheeler vehicle. The frame structure comprises a head tube, a main tube attached to the head tube, an engine mounting arrangement attached to the main tube, and one or more swing arms attached to the engine mounting arrangement with the help of a swing arm pivot tube.

Further, one or more upper tubes are attached on each side of the main tube, one or more

rear shock absorber mounting brackets are attached to the upper tubes, one or more rear shock absorbers are attached to the rear shock absorber mounting brackets at one end and to the swing arms at the other end. The frame structure also comprises one or more side tubes attached to the upper tubes at one end and to the swing arm pivot tube at the other end, a pillion handle mounting bracket attached to the upper tubes.

In an embodiment of the subject matter described herein, a crosspiece is attached to the head tube and supports a front license plate mounting bracket, a head tube cover and one or more electrical units like a horn and a regulator.

In another embodiment, the side tubes of the frame structure have a first portion and a second portion. The first portion extends below a chain line and has a cross section that is different from that of the second portion.

In yet another embodiment, each of the rear shock absorber mounting brackets has a cutout for receiving the top end of the rear shock absorber. A pair of supports is provided on both sides of the cutout for supporting attachment of the top end of the rear shock absorber in the cutouts.

In yet another embodiment, a male bracket is provided at the bottom of the pillion handle mounting bracket for supporting the pillion handle mounting bracket.

In yet another embodiment, the engine mounting arrangement has a wider base to accommodate a wider center stand. The subject matter disclosed herein is related to a two wheeler frame structure which possesses improved quality, at a lower cost, and provides enhanced safety. More specifically, the frame structure possesses advantages such as reduced number of loose parts, dust and vibration resistant, enhanced reliability, stiffness, strength and better clearance. These and other features, aspects, and advantages of the present subject matter will become better understood with reference to the following description and appended claims. This Summary is provided to introduce a selection of concepts in a simplified form. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features, aspects, and advantages of the subject matter will become better understood with regard to the following description, appended claims, and accompanying drawings where:

Fig. 1 illustrates a partial side view of a frame structure of a two-wheeled vehicle in accordance with one embodiment of the present subject matter.

Fig. 2 illustrates a partial side view of the frame structure, depicting metal tubes joined together to form the frame structure, in accordance with another embodiment of the present subject matter.

Fig. 3a and Fig. 3b illustrate partial views of the frame structure of a two-wheeled vehicle in accordance with yet another embodiment of the present subject matter.

Fig. 4 illustrates a partial side view of the rear part of the frame structure of a two- wheeled vehicle in accordance with yet another embodiment of the present subject matter.

Fig. 5a and Fig. 5b illustrate a partial side view and a part sectional rear view of the frame structure of a two-wheeled vehicle respectively in accordance with yet another embodiment of the present subject matter.

Fig. 6 illustrates a side view of the frame structure of a two-wheeled vehicle in accordance with yet another embodiment of the present subject matter.

Fig. 7 illustrates a part sectional side view of a motorcycle adapted to incorporate the frame structure of Fig. 6.

DETAILED DESCRIPTION

Typically, a frame structure for a two wheeler comprises a sub-frame and a main frame. The sub-frame is attached to the main frame using fasteners and holds components like a head tube cover, a front license plate mounting bracket and electrical units like a horn and a regulator. However, this arrangement leads to increased number of loose parts.

Furthermore, the main frame comprises a head tube, a main tube having one end attached to the head tube and an engine mounting arrangement attached to the other end of the main tube. One or more swing arms are attached to the engine mounting arrangement with the help of a swing arm pivot tube. The frame structure further comprises one or more upper tubes attached to the main tube. One or more rear shock absorber mounting brackets are attached to the upper tubes. Rear shock absorbers are attached to the rear shock absorber mounting brackets at one end and to the swing arms at the other end. Conventionally, the rear shock absorber mounting brackets are added to provide additional support to the rear shock absorbers. A pillion handle mounting bracket is attached to the upper tubes. The top of the pillion handle mounting bracket is supported by the upper tubes whereas the bottom is an open shell. Hence no support is provided for the pillion handle mounting bracket of conventional frame structures, thereby leading to vibrations in the pillion handle mounting bracket. One or more side tubes are attached to the upper tubes at one end and to the engine mounting arrangement at the other end. The attachment of the side tubes to the engine mounting arrangement defines the stiffness of the frame structure. The side tubes can be attached to the engine mounting arrangement above or below the chain line. However, attaching the side tubes below the chain line may lead to the brushing of the side tube on the left hand side with the chain while driving. Generally, to avoid the contact of the left hand side tube with the chain, the side tubes are attached to the engine mounting arrangement at a location above the chain line. Alternately, the side tubes extend below the chain line via utilization of alternate sleeker raw material in left hand side tube or by bashing the left hand side tube with reinforcements. The subject matter disclosed herein is a two wheeler frame structure which overcomes the foregoing and other drawbacks and possesses improved quality, reduced cost, and enhanced safety. More specifically, the frame structure possesses various advantageous features such as minimum number of loose parts, improved resistance towards dust and vibration, enhanced reliability, stiffness, strength and better clearance of the side tube from the chain line.

In accordance with one embodiment of the present subject matter, a frame structure for a two-wheeled vehicle, particularly for a motorcycle is described. The frame structure comprises a head tube, a main tube having one end attached to the head tube, an engine mounting arrangement attached to other end of the main tube and one or more swing arms attached to the engine mounting arrangement with the help of a swing arm pivot tube. Also present are one or more upper tubes attached to the main tube, one or more rear shock absorber mounting brackets attached to the upper tubes, and one or more rear shock absorbers attached to the rear shock absorber mounting brackets at one end and to the swing arms at the other end. Additionally, the frame structure comprises one or more side tubes attached to the upper tubes at one end and to the swing arm pivot tube at the other end, and a pillion handle mounting bracket attached to the upper tubes. Furthermore, the side tube has a first portion and a second portion such that the first portion extends a below chain line and has a cross section different than that of the second portion. In accordance with aforementioned embodiment, the frame structure has the first portion of the side tube attached to the swing arm pivot tube and the second portion of the side tube attached to the upper tube. In addition, the first portion of the side tube has a rectangular cross section and the second portion of the side tube has a circular cross section. In accordance with yet another embodiment of the present subject matter, the frame structure comprises a head tube, a main tube having one end attached to the head tube, an engine mounting arrangement attached to other end of the main tube and one or more swing arms attached to the engine mounting arrangement with the help of a swing arm pivot tube. The frame structure further comprises one or more upper tubes attached to the main tube, one or more rear shock absorber mounting brackets attached to the upper tubes, and one or more rear shock absorbers attached to the rear shock absorber mounting brackets at one end and to the swing arms at the other end. One or more side tubes are attached to the upper tubes at one end and to the swing arm pivot tube at the other end. Also, a pillion handle mounting bracket is attached to the upper tubes. The rear shock absorber mounting bracket is provided with a cutout for receiving the top end of the rear

shock absorber, such that a pair of supports provided on both sides of the cutout, support the attachment of the top end of the rear shock absorber in the cutout.

According to one aspect of the frame structure for a two-wheeled vehicle described herein, the rear shock absorber mounting bracket is a simply supported bracket. Alternatively, the rear shock absorber is clamped in the cutout of the rear shock absorber mounting bracket.

In one embodiment of the present subject matter, the frame structure further comprises a male bracket for supporting the pillion handle mounting bracket at the bottom. The pillion handle mounting bracket, in one embodiment, is made blind shelled by using the male bracket.

The frame structure, in one embodiment, has the engine mounting arrangement with a lower portion wider than an upper portion to accommodate a wide center stand. Furthermore, the engine mounting arrangement comprises a pair of vertical brackets positioned opposite to each other. The frame structure of the preceding embodiments further comprises a crosspiece attached to the head tube for supporting a front license plate mounting bracket, a head tube cover, and one or more electrical units such as a horn or regulator. The crosspiece is welded to the head tube.

In accordance with yet another embodiment of the present subject matter the frame structure comprising a head tube, a main tube having one end attached to the head tube, an engine mounting arrangement attached to other end of the main tube and one or more swing arms attached to the engine mounting arrangement with the help of a swing arm pivot tube is described. Additionally, one or more upper tubes are attached to the main tube, one or more rear shock absorber mounting brackets are attached to the upper tubes and one or more rear shock absorbers are attached to the rear shock absorber mounting brackets at one end and to the swing arms at the other end The frame structure also comprises one or more side tubes attached to the upper tubes at one end and to the swing arm pivot tube at the other end and a pillion handle mounting bracket attached to the upper tubes. The side tube has a first portion and a second portion. The first portion

extends below the chain line and has a cross section different than that of the second portion. Moreover, the rear shock absorber mounting bracket has a cutout for receiving a top end of the rear shock absorber. A pair of support is provided on both sides of the cutout for supporting attachment of the top end of the rear shock absorber in the cutout. A male bracket is provided for supporting the pillion handle mounting bracket from the bottom. The engine mounting arrangement is provided with a lower portion that is wider when compared with the upper portion in order to accommodate a wider center stand. A crosspiece is attached to the head tube for supporting a front license plate mounting bracket, a head tube cover and one or more electrical components.

While aspects of the described system and the method for improving the performance of the frame structure can be implemented in any number of different mechanical systems, environments, and/or configurations, embodiments discussed herein are described in the context of the following exemplary system architecture(s) and method(s).

Fig. 1 illustrates a partial side view of a frame structure 100 of a two-wheeled vehicle in accordance with one embodiment of the present subject matter. For instance, and by no way of limitation, the two-wheeled vehicle can be a step-thru motorcycle. The frame structure 100 is designed so as to possess suitable specifications in conformity with the principles of the present subject matter. The frame structure 100 comprises a plurality of parts coupled to each other, thereby providing support to the components of the motorcycle. For example, and by no way of limitation, the frame structure 100 comprises a main frame 105, a head tube cover 110, a front license plate mounting bracket 115, a horn 120, a regulator 125 and a crosspiece 130.

A plurality of loose parts of the frame structure 100 may be held together by a suitable assembly in conformity with the present subject matter. By way of example, and in no way limiting the scope of the present subject matter, some of the loose parts of the frame structure 100, such as the head tube cover 110, the front license plate mounting bracket 115 and the electrical units like the horn 120 and the regulator 125 are held together via the crosspiece 130 so as to form an assemblage.

The crosspiece 130 is welded to a head tube 135 of the main frame 105 and the loose parts of the frame structure 100 are attached to the crosspiece 130 by a fastening means. In the present embodiments, the fastening means include nuts and bolts.

From the design and implementation standpoint, the aforementioned selection vis- a-vis the assemblage and specifications thereof, the aggregate number of loose parts therein, the total number of parts constituting the frame structure 100 suggested herein are merely illustrative of the present subject matter and in no way limit the scope of the present subject matter. Various modifications to the aforementioned embodiment may be readily known to persons of ordinary skill in the art having the benefit of the disclosure. Fig. 2 illustrates a partial side view of the frame structure 100 of a two- wheeled vehicle in accordance with another embodiment of the present subject matter depicting metal tubes joined together to form the frame structure 100. As shown herein, the frame structure 100 comprises a plurality of tubes, enumerated herein as a main tube 200, side tubes 205, and upper tubes 210. The side tubes 205 are provided on both sides of the two- wheeled vehicle. The first end of each side tube 205 is attached to the upper tube 210. The second end of each side tube 205 is attached to an engine mounting arrangement 225 by means of a swing-arm pivot tube 215 and extends below a chain line 220 of the two- wheeled vehicle.

The side tube 205 substantially comprises a plurality of portions having suitable specifications thereby enhancing the strength and stiffness of the frame structure 100 and providing better clearance between the side tube 205 and the chain line 220.

More specifically, the side tube 205 includes a first portion 235 and a second portion 240 having heterogeneous specifications. For instance, and by no way of limitation, the side tube 205 possesses the following specifications: the cross section of the first portion 235 is rectangular; the cross section of the second portion 240 is circular; a first end of the side tube 205 is suitably coupled to the upper tube 210, whereas the second end of the side tube 205 is suitably coupled to the swing-arm pivot tube 215. It must be noted that the side tube 205 directly connects the swing-arm pivot tube 215 below the chain line 220 and the region of the upper tube 210 is associated with a rear shock absorber mounting bracket 230.

Owing to the fact that the cross section of the side tube 205 is transformed from a circular cross section to a rectangular cross section moving from the second portion 240 to the first portion 235, a better clearance of the side tube 205 with respect to the chain line

220 is achieved. As a consequence, the use of different raw materials for left and right side tubes 205 or reinforcement can be eliminated.

The frame structure of Fig. 2 can be embodied in many other ways as would be clear to a person skilled in the art. For example, the side tube 205 may be suitably coupled to two or more parts of the frame structure 100 at both ends. Similarly, the side tube 205 may comprise two or more portions possessing heterogeneous specifications. Referring to Fig. 3a and Fig. 3b, partial views of the frame structure 100 of a two- wheeled vehicle have been illustrated in accordance with yet another embodiment of the present subject matter. The frame structure 100 of the present embodiment comprises a simply supported rear shock absorber mounting bracket 230 with cutouts 310 and a pair of side supports 320 and 325. Fig. 3a illustrates a partial bottom view of the frame structure 100 depicting the side supports 320 and 325 and the cutouts 310 in the rear shock absorber mounting bracket 230. Fig. 3b illustrates a partial side view of the frame structure 100 depicting the rear shock absorber mounting bracket 230 for mounting top end of a rear shock absorber 305.

As shown in Figs. 3a and 3b, the rear shock absorber mounting bracket 230 is attached to the upper tube 210 and the side tube 205. The shock absorber mounting bracket 300 has a box-type construction with a cutout 310 at the center for mounting the rear shock absorber 305. A pair of side supports 320 and 325 on each side of the cutout 310 provides additional support to the attachment of the shock absorber 305 in the cutout 310 of the rear shock absorber mounting bracket 230. The bottom end of the shock absorber 305 is attached to a swing arm 330 and moves resiliently with the movement of the swing arm 330. The configuration of the rear shock absorber mounting bracket 230 suggested herein facilitates dust prevention and imparts additional strength to the frame structure 100.

Fig. 4 illustrates a partial side view of the frame structure 100 of a two-wheeled vehicle in accordance with yet another embodiment of the present subject matter. As

shown herein the frame structure 100 comprises a pair of upper tubes 210 and a pillion handle mounting bracket 405. The pillion handle mounting bracket 405 is a U-shaped bracket and is attached to the upper tubes 210. The pillion handle mounting bracket 405 is made blind shelled by utilizing a suitable technique in accordance with the principles of the present subject matter. For example, and by no way of limitation, a male bracket 410 is used herein so as to support the pillion handle mounting bracket 405 from the bottom. The provision of the male bracket 410 at the bottom of the pillion handle mounting bracket 405 provides resistance to vibrations occurring in the pillion handle mounting bracket 405. Fig. 5a and Fig. 5b illustrate a partial side view and a part sectional rear view of the frame structure 100 of a two-wheeled vehicle respectively in accordance with yet another embodiment of the present subject matter. As shown herein, the frame structure 100 comprises an engine mounting arrangement 225, a center stand 510. The engine mounting arrangement 225 comprises a pair of engine mounting brackets 500 and a base 515. The engine mounting brackets 500 are provided on both sides of the main tube 200 and the base 515 supports the engine mounting brackets 500. The engine mounting brackets 500 are designed in such a way that the lower portion of the engine mounting arrangement 225 is wider than the upper portion. The increased distance between the engine mounting brackets 500 from bottom enables mounting of a wide center stand 510. Fig. 6 illustrates a side view of the frame structure 100 of a two-wheeled vehicle in accordance with yet another embodiment of the present subject matter. The frame structure 100 of the present embodiment comprises a head tube 135, a main tube 200 having one end attached to the head tube 135, an engine mounting arrangement 225 attached to the other end of the main tube 200, one or more swing arms 330 attached to the engine mounting arrangement 225 with the help of a swing arm pivot tube 215. The frame structure 100 further comprises one or more upper tubes 210 attached on each side of the main tube 200, one or more rear shock absorber mounting brackets 230 attached to the upper tubes 210, one or more side tubes 205 attached to the upper tubes 210 at one end and to the swing arm pivot tube 215 at the other end, a pillion handle mounting bracket 405 attached to the upper tubes 210.

The frame structure further comprises a crosspiece 130 attached to the head tube 135. The crosspiece 130 is welded to the head tube 200 from front and supports a front license plate mounting bracket, a head tube cover and electrical units like horn, regulator. The side tubes 205 of the frame structure 100 extend below the chain line. Each of the side tubes has a rectangular first portion 235 and a circular second portion 240. A shock absorber mounting bracket 230 is attached to each of the upper tubes 210. The shock absorber mounting bracket 230 has a box-type construction with a cutout 310 at the center. A pair of side supports 320 and 325 is provided on each side of the cutout 310. A male bracket 410 is provided at the bottom of the pillion handle mounting bracket 405 making pillion handle mounting bracket 405 blind shelled and thereby reducing the vibrations occurring in the pillion handle mounting bracket 405. The engine mounting arrangement 225 of the frame structure 100 has a wider base 515 to accommodate a wider center stand 510.

Fig. 7 illustrates a part sectional side view of a motorcycle adapted to incorporate the frame structure of Fig. 6. As shown in the figure, the cross piece 130 is welded to the head tube 135. The side tube 205, having two portions with different cross sections, extends from the upper tube 210 to the engine mounting arrangement 225. The shock absorber mounting bracket 230 is a simply supported bracket and is attached to the upper tube 210 as well as to the upper portion of the side tube 205.

Although the subject matter has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternate embodiments of the subject matter, will become apparent to persons skilled in the art upon reference to the description of the subject matter. It is therefore contemplated that such modifications can be made without departing from the spirit or scope of the present subject matter as defined.




 
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