Claims:
We claim:
1. An internal combustion engine assembly (200) for a vehicle (100), said internal combustion engine assembly (200) comprising:
a crankshaft (215) rotatably supported by a crankcase (205) of said engine assembly (200), said engine assembly (200) includes a gear set comprising a first gear (225) and a second gear (300), said second gear (300) having a diameter (D1) substantially greater than a diameter (D2) of said first gear (225), said first gear (225) is functionally coupled to said crankshaft (215) and said second gear (300) is functionally coupled to said first gear (225), said second gear (300) includes a body portion (305) and plurality of teeth (310) annularly disposed about the body portion (305), and said second gear (300) is having density substantially lesser than density of said first gear (225).
2. The internal combustion engine assembly (200) as claimed in claim 1, wherein said second gear (300) is made of a non-metallic material.
3. The internal combustion engine assembly (200) as claimed in claim 1, wherein said plurality of teeth (310) having a first width (W1), in axial direction, in the range of 1.5 to 2 times of a second width (W2), in axial direction, of said body portion (305).
4. The internal combustion engine assembly (200) as claimed in claim 1, wherein said plurality of teeth (310) includes a teeth-center (310C) taken in an axial direction (A-A’), and said teeth-center (310C) is disposed at an axial offset from a body center (305C) of said body portion (305) taken in said axial direction (A-A’).
5. The internal combustion engine assembly (200) as claimed in claim 1, wherein said engine assembly (200) includes a clutch housing (235) capable of accommodating one or more clutch plates, wherein said clutch housing (235) is having a face portion (235A) provided with a dent portion (235D) extending along an outer periphery of said face portion (235A) and at least a portion of said plurality of teeth (310) axially facing said face portion (235A) is accommodated by said dent portion (235D) of said clutch housing (235).
6. The internal combustion engine assembly (200) as claimed in claim 1, wherein said plurality of teeth (310) are having a first end portion (311), said first end portion (311) is in line with a first axial surface (305A) of the of the body portion (305) and a second end portion (312) of the plurality of teeth (310) are extending beyond a second axial surface (305B) of the second gear (300) when viewed in radial direction of said second gear (300).
7. The internal combustion engine assembly (200) as claimed in claim 1, wherein said second gear (300) is injection-molded and said second gear (300) is capable of providing a backlash in a range of 25 to 125 micron.
8. The internal combustion engine assembly (200) as claimed in claim 1, wherein said plurality of teeth (310) includes a module in a range of 1.75 to f3 for individual strength of said teeth (310).
9. The internal combustion engine assembly (200) as claimed in claim 1, wherein said plurality of teeth (310) is provided with a pressure angle (PA) to be in a range of 15-30 degrees.
10. The internal combustion engine assembly (200) as claimed in claim 1, wherein said plurality of teeth (310) is provided with a pressure angle (PA) to a module ratio in a range of 6 to 15.
, Description:TECHNICAL FIELD
[0001] The present subject matter relates generally to an internal combustion engine for a motor vehicle, and more particularly and not exclusively to a gear set for the internal combustion engine.
BACKGROUND
[0002] Generally, a frame assembly acts as skeleton and a structural member for a vehicle. An engine assembly is either fixedly mounted or is swingably mounted to the frame assembly of the vehicle. In case of an internal combustion (IC) engine, there are one or more cylinder bore(s), where combustion happens. The IC engine has a piston(s) slidable inside the cylinder bore(s). Further, there are various parts including crankshaft, connecting rod(s), camshaft(s), and gears. The combustion of air fuel mixture inside the cylinder bore results in the reciprocating motion of the piston. The reciprocating motion of the piston in the cylinder bore is converted into a rotational motion of the crankshaft.
[0003] The rotational motion from the crankshaft is transferred to one or more wheels of the motor vehicle. The rotation of the one or more wheels results in motion of the vehicle. Generally, the IC engine is desired to be capable of providing power and torque depending on user requirement.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] The detailed description of the present subject matter is described with reference to the accompanying figures. Same numbers are used throughout the drawings to reference like features and components.
[0005] Fig. 1 illustrates a right side view of an exemplary two-wheeled motor vehicle, in accordance with an embodiment of the present subject matter.
[0006] Fig. 2 (a) illustrates a front perspective view of an exemplary engine, in accordance with an embodiment of the present subject matter.
[0007] Fig. 2 (b) illustrates a perceptive view of a gear, in accordance with the embodiment of the present subject matter as depicted in Fig. 2 (a).
[0008] Fig. 2 (c) illustrates an exploded view of a clutch housing employed with the gear, in accordance with an embodiment of the present subject matter as depicted in Fig. 2 (a).
[0009] Fig. 3 (a) illustrates a side view of a gear set, in accordance with an embodiment of the present subject matter.
[00010] Fig. 3 (b) illustrates an enlarged view of a portion of the gear set, in accordance with an embodiment as depicted in Fig. 3 (a).
DETAILED DESCRIPTION
[0001] In the last few decades, the small vehicles automobile industry that includes two-wheelers and three-wheelers has shown a remarkable growth and development, in terms of technology as well as sales. Due to consistent advancement in technology, especially the two-wheelers have succeeded in maintaining their popularity among different sections of society. Different sections of society, based on their requirement, utilize the two-wheeled vehicles for various purposes, such as a recreational activity, a means of transportation, and for sports activities. As a result, it becomes pertinent for the two-wheeler automobile industry to constantly develop and modify the components of the two-wheeled vehicles to suit requirements of different riders.
[0002] In accordance with the same ideology, various types of engine performance improvements are being made to provide improved performance and fuel efficiency. Moreover, there is a continuous research happening in improving the fuel economy of the vehicle, which is a desired feature by the customer. At the same time, performance in another characteristic that is to be retained while improving the fuel economy of the vehicle.
[00011] Generally, two-wheeled vehicles are provided with the internal combustion engine that is one of the heaviest components of the vehicle. Moreover, hybrid-type vehicles also accommodate an electric motor that further adds weight to the vehicle. Generally, the vehicle includes plurality of rotating components that are generally made of metal. For example, in the internal combustion engine, the chemical energy, which is the fuel mixed with air, is converted into heat energy due to combustion that is used of rotating the various gears and shafts made of metal. The reciprocal movement of the piston of the engine is converted into a rotational motion of the crankshaft. Therefore, the engine also includes various rotating members for transferring the power or torque.
[00012] The engine which is the power generation unit of the vehicle includes plurality of the gears that includes gears with larger diameter like the primary driven gear, when compared with the primary drive. The driven gear has higher mass and therefore requires higher inertia. Therefore, effort required for rotation of the larger diameter gears like the primary driven gear, which acts as load on the primary drive gear. This results in loss of energy that is generated by the crankshaft. This affects the torque and power being transferred to at least one wheel connected to the IC engine. Also, the metal gears with large diameter make the engine heavier. This further increase the weight of the vehicle, which acts as load on the engine. This higher weight affects the performance of the engine, which consumes higher energy generated by the engine.
[00013] Moreover, the metal gears when engage or during rotational operation produce higher noise, which is undesirable. Further, the metal gears require machining and heat processing. In addition to need for machining and heat processing, the process results in wastage of metal. Furthermore, the metal gears requiring heat treatment is time consuming. Thus, the metal gears are difficult and costly to manufacture due to the multiple stages of manufacturing and also the process is costly due to the aforementioned reasons.
[00014] To this end, conventionally polymer gears are known to have lower weight. However, the gears made of polymer or the like will easily deform and chip off or brake, when operated with fast rotating and high torque generating applications like internal combustion engine.
[00015] Thus, the challenge is to address the aforementioned and other problems in the prior art Also, the system should be capable of providing low noise. The gear should be rigid, high wear resistance and should be capable of being coupled to a metallic gear like the primary drive. Further, the gear should be easy to manufacture incurring less number of post processing stages.
[00016] Hence, an objective of the present subject matter is to provide a gear set having at least two gears. The at least two gears includes a first gear made of rigid material like metal and a second gear working in conjunction with the first gear, wherein the second gear is having low inertia and is preferably made of a non-metallic material.
[00017] It is an aspect of the present subject matter that the second gear is preferably having a diameter greater than a diameter of the first gear, wherein the second gear is larger in size but at the same time is having a lower inertia. Thus, it is an advantage of the present subject matter that the second gear diameter is retained and the weight of the second gear is reduced. The second gear is having a density substantially lesser than density of said first gear. It is an additional advantage that the weight of the system in which the gear set is deployed is also reduced.
[00018] The second gear is preferably made of polymer or fiber reinforced polymer or a combination deepening on the application. For example, the gear can be deployed in the engine that produces higher torques that requires higher structural rigidity.
[00019] The second gear includes a base portion and a peripheral portion including plurality of tooth disposed annularly about the base portion forming a circular/disc shape structure that is capable of working in conjunction with the first gear.
[00020] In one implementation, the gear set is deployed in an internal combustion engine. The engine assembly includes a crankcase having at least two portions. The crankcase includes plurality of apertures and grooves that are capable of rotatably supporting various parts of the engine assembly. Also, the crankcase supports various parts rotatably supported thereof including a crankshaft that is connected to a piston. The crankshaft is connected to a first gear, and preferably the first gear is directly mounted to the crankshaft. The first gear is functionally coupled to a secondary gear that is rotatably supported by the crankcase. In one implementation, the secondary gear is coupled to the clutch housing of the clutch assembly. The first gear and the secondary gear form a gear set made of dissimilar materials that provide reduced weight and inertia.
[00021] It is another aspect of the present subject matter that the tooth of the second gear is provided with a width greater than a width of the body portion. It is an aspect of the present subject matter that the secondary gear is injection-molded The secondary gear that is injection-molded enables ease of provision of the different widths for the second gear without the need for machining or other post processing.
[00022] It is yet another aspect of the present subject matter that the width of the tooth is approximately one and a half times the width of the body portion. Thus, the second gear of the present subject matter provides a lightweight and compact structure that is having low material and inertia. At the same time, the teeth being provided with greater width, the required amount of flexural strength to sustain the force/torque transmitted form the first gear that is connected the crankshaft.
[00023] It is an advantage of the present subject matter that the gear set having low inertia thereby providing a faster response. This in effect improves the performance of the engine/vehicle. Moreover, the present subject matter enables provision of a ratio of the width of the tooth to the width of the body portion to be greater than 1. Preferably as per an embodiment, the ratio is in the range of 1.5 to 2 times to attain the desired flexural strength and the compact profile deepening on the application.
[00024] It is another aspect of the present subject matter that the gear (second gear) is provided with a module greater than 1. Preferably, the second gear is capable of having a module in the range of 2.5 to 3.5. Therefore, the module provides the gear with teeth with the required flexural strength and rigidity. Furthermore, the second gear provides desired dampening features that is capable of dampen/reduce any vibrations generated during operation of the engine.
[00025] Also, the second gear includes a cylindrical sleeve disposed at a center thereof that is axially extending outward from the body portion, wherein the gear is mounted to the shaft. In one implementation, the cylindrical sleeve is provided with a metal pinion that is capable of rigidly securing the gear to the corresponding shaft thereof. The cylindrical sleeve is also integrally formed with the gear.
[00026] In one implementation, the gear of the present subject matter, referred to as second gear, is coupled/affixed to the clutch housing of the engine assembly whereby the first gear directly transfers the force and torque to the clutch assembly through the second gear.
[00027] It is yet another aspect of the present subject matter that the gear can be compact packaged. For example, the second gear enables compact packaging of the engine assembly. The teeth can be disposed at an axial offset from a center of body portion or in line with the center. This provides the freedom to provide the teeth according to the assembly requirements without any post processing. In one implementation, the teeth are disposed at an axial offset with respect to the body portion thereby providing a flat surface on the one side thereby enabling compact packaging of the components being disposed adjacent to the flat surface.
[00028] Further, it is an additional feature of the present subject matter that the second gear can be deployed in engine or the like that operate at high temperatures reaching 150 degrees centigrade. Therefore, the gear of the present subject matter provides a low thermal expansion coefficient thereby maintain the required clearances. It is an advantage that the gear set retains required clearance and gear jamming is reduced/ eliminated.
[00029] Furthermore, it is yet another additional aspect that the gear is provided with a higher pressure angle. The pressure angle taken between the tooth profile and a radial line passing through a pitch point of the teeth defines the profile of the face of the teeth. Preferably the pressure angle is provided in the range of 15-30 degrees. Thus, the teeth are provided with sufficient thickness to maintain sufficient flexural strength and rigidity.
[00030] Also, the pressure angle to module ratio is provided in the range of 6 to 15 for desired flexural strength and rigidity.
[00031] It is a feature of the present subject matter that the driven gear is capable of absorbing vibrations or impacts caused by speed variations and torque fluctuations, especially in case of engine assembly. This reduces noise between the gears and the overall noise from the IC engine is reduced.
[00032] An object of the present invention is to provide the gear for an engine, having high reliability, tenacity, and accuracy, which is capable of being manufactured at low cost.
[00033] The aforesaid and other advantages of the present subject matter would be described in detail in conjunction with the figures in the following description.
[00034] Arrows wherever provided in the top right corner of figure(s) in the drawings depicts direction with respect to the vehicle, wherein an arrow F denotes front direction, an arrow R indicates rear direction, an arrow UP denotes upward direction, an arrow DW denotes downward direction, an arrow RH denotes right side, and an arrow LH denotes left side.
[00035] Fig. 1 (a) illustrates a right side view of an exemplary two-wheeled saddle-ride type vehicle, in accordance with an embodiment of present subject matter. The vehicle 100 has a frame assembly 105, which acts as the skeleton for bearing the loads. The frame assembly105 extends from a front portion F towards a rear portion R of the vehicle 100, which is substantially along a longitudinal axis of the vehicle 100. A handle bar assembly 110 is rotatably disposed through a head tube 105A of the frame assembly 105. The handle bar assembly110 is connected to a front wheel 115 through one or more front suspension(s) 120. A front fender 125 is mounted to the one or more front suspension(s) 120 and covers at least a portion of the front wheel 115. A swing arm 160 is swingably connected to the frame assembly 105. A rear wheel 130 is rotatably supported by the swing arm 160. A rear fender 135 is disposed upwardly of the rear wheel 130 and is covering at least a portion of the rear wheel 130. One or more rear suspension(s) 140, which connect the swing arm 160 to the frame assembly 105, enable to sustain both the radial and axial forces occurring due to rear wheel 130 reaction. In one embodiment, a mono-shock suspension is used. A seat assembly 145 is mounted to the frame assembly 105. A fuel tank 150 is disposed at an anterior portion of the seat assembly 145.
[00036] An engine assembly 200 is disposed substantially below the fuel tank 150 and in the front portion F of the frame assembly 105. The engine assembly 200 is coupled to a starting mechanism for cranking, a transmission system (not shown) for transferring the power to the rear wheel 130, and an air-fuel supply means. Further, a carburetor or a fuel injection system or the like (not shown), which act as the air-fuel supply means, supplies air-fuel mixture to the engine assembly 200. A muffler assembly 155 is mounted to the vehicle that transfers exhaust gases into atmosphere.
[00037] The handle bar assembly 110 includes a handle bar, an instrument cluster, handle grips and one or more levers. The vehicle 100 has various electrical loads including a headlamp 165, a tail lamp 170. Also, the vehicle 100 includes other electrical, electronic, and mechanical systems like an anti-brake system, a synchronous braking system, a vehicle control system, a vehicle diagnostics system. Further, plurality of body panels including a side panel 175A and a tail cover panel 175B are mounted to the frame assembly 105covering at least a portion of the frame assembly 105.
[00038] Fig. 2 (a) depicts a left side perspective view of the engine assembly, in accordance with an embodiment of the present subject matter. The engine assembly 200 includes a crankcase 205 having at least two portions. In the present embodiment, the crankcase 205 includes a right crankcase and a left crankcase. The crankcase 205 includes plurality of apertures and grooves that are capable of rotatably supporting various parts of the engine assembly 200. Also, the crankcase 205 supports a cylinder body 210, and a cylinder head (not shown).
[00039] The various parts rotatably supported by the crankcase 205 include a crankshaft 215 that is connected to a piston 220. The piston 220 has reciprocating motion within the cylinder body. The reciprocating motion of the piston 220 is converted into rotational motion of the crankshaft 215. In one embodiment, the crankshaft 215 is connected to a first gear 225. In a preferred implementation, the first gear 225 is directly mounted to one end portion of the crankshaft 215. The first gear 225 is coupled to a second gear 300 that is rotatably supported by the crankcase 205. In one implementation, the second gear 300 is coupled to the clutch housing 235 of the clutch assembly 240 is capable of accommodating one or more clutch plates. It is an aspect of the present subject matter that the second gear 300 is preferably having a diameter D1 greater than a diameter D2 of the first gear 225 (shown in Fig. 3 (a)), wherein the second gear is larger in size but at the same time is having a lower inertia. The first gear 225 and the second gear 300 form a gear set made of dissimilar materials, wherein the first gear 225 is preferably made of having density similar to or same as the density metal and the second gear 300 is preferably made of material having a density similar to or same as density of polymers. Further, the engine assembly 200 includes a crankcase cover 245 disposed on lateral side enclosing the components disposed thereof. For example, the crankcase cover 245 disposed on the left side LH encloses a magneto or an integrated starter generator (ISG) disposed thereof. Similarly, a crankcase cover is also disposed on the right side RH to cover/enclose the gear set and other components.
[00040] Fig. 2 (b) depicts a perspective view of the primary driven, in accordance with the embodiment of the Fig. 2 (a). The second gear 300 is made of a non-metallic material like polymer. The second gear 300 includes a body portion 305 and plurality of teeth 310 disposed annularly about the body portion 305. The plurality of teeth 310 are provided with a width W1 greater than a width of the body portion 305, which is the rest of the second gear 300. The width W1 of the teeth is hereafter referred to as first width W1 and the width W2 of the body portion is hereinafter referred to as second width W2. The second gear 300 that is preferably made of polymer by injection-molding provides an advantage that the second gear 300 can have a desired width or profile without the need for machining or other post processing. The second width W2 of the body portion 305 and the first width W1 of the teeth 310 is the thickness taken in axial direction, which is along axis A-A’ (shown in Fig. 2 (b)) of the primary driven 300.
[00041] The first width W1 of the teeth 310 is approximately one and a half times the second width W2 of the body portion 305 in the present implementation. The second gear 300 of the present subject matter provides a lightweight and compact member that is having low inertia as the weight of the gear is less when compared with a metallic gear with similar volume. At the same time, the profile of the second gear 300 provides the flexural strength to sustain the force/torque transmitted form the first gear 225, which is preferably a primary drive. Additionally, the low inertia of the second gear 300 provides faster response thereby the effect can be seen in the performance of the vehicle 100 as the clutch housing 235 is functionally coupled to at least one wheel of vehicle 100. Moreover, the ratio of the first width W1 to the second width W2 can be maintained to be greater than 1. However, the ratio can be maintained in the range of 1.5 to 2 to attain the desired flexural strength and the compact profile.
[00042] Further, the second gear 300 is provided with a module in the range of 1.75 to 3 for individual strength thereof. This provides the second gear 300 to have less number of teeth but provides the required flexural strength and rigidity to the second gear 300 that is required to be engaging with the high speed and high torque generating first gear 225 that is made of metal. Furthermore, the second gear 300 with the module in the range of 1.75 to 3 provides a damping feature to the teeth 310. Therefore, the second gear 300 attains the desired dampening features at the same time reduces/eliminates any vibrations generated during operation. Also, the second gear 300 includes a cylindrical sleeve 315 disposed at the center thereof and is preferably axially extending outward from the body portion 305. The cylindrical sleeve 315 is provided with a metal pinion 325 that is capable of rigidly securing the second gear 300 to the corresponding shaft thereof. Also, the cylindrical sleeve 315 is integrally formed with the gear 300. Further, the second gear 300 includes plurality of apertures 320 provided about the body portion 305.
[00043] Fig. 2 (c) depicts an exploded view of the clutch housing, in accordance with the embodiment as depicted in Fig. 2 (a). The second gear 300 is coupled/affixed to the clutch housing 235. The clutch housing 235 includes a cylindrical portion with opening on one axial end and the other axial end is provided with a mounting portion/face portion 235A for supporting the second gear 300. The clutch housing 235 includes plurality of bosses 235B provided on the mounting portion/face portion 235A, wherein the bosses 235B are extending in an axial direction A-A’. The second gear 300 includes plurality of apertures 320 provided about the body portion 305 of the second gear 300. The apertures 320 are provided so as to align with the bosses 235B provided on the clutch housing 235. One or more bushes 250 are disposed between the second gear 300 and the clutch housing 235. The bushes 250 act as damping members during sudden transfer of forces from the second gear 300 and the clutch assembly 240. Further, a plate member 255 is disposed abutting the primary driven from outer axial side. In the present implementation, the second gear 300 is riveted to the clutch housing 235 through one or more riveting member 260 so as to rigidly retain the assembly.
[00044] Further, the clutch housing 235 includes a dent portion 235D, extending along an outer periphery, provided annularly at the outer most periphery of the clutch housing 235. The second gear 300 is adapted to have the teeth 310 disposed offset OS to the center of body portion 305 thereof, wherein the offset OS is depicted between the center of the teeth 310C and the center of the body, referred to as body center 305C. The teeth 310 are preferably disposed at an axial offset so that the teeth 310 extend asymmetrically towards one axial side of the body portion 305. The plurality of teeth 310 includes a teeth-center 310C taken in an axial direction A-A’, and a teeth-center 310C is disposed at an axial offset from a body center 305C of the body portion 305 taken in axial direction A-A’, as depicted in Fig. 2 (b). Therefore, a first end portion 311 of the teeth 310 are in line with a first axial side/axial surface 305A of the of the body portion 305 of the primary driven 300 and a second end portion 312 of the teeth 310 are extending beyond a second axial side 305B of the second gear 300, when viewed in a radial direction. The second end portion 312 of the teeth 310 extending beyond the second axial side 305B, which abuts the clutch housing 235, is accommodated by the dent portion 235D formed on the clutch housing 235. Thus, the second gear 300 of the present subject provides a compact clutch housing assembly as the first axial side 305A of the second gear 300 can have a flat side profile excluding the cylindrical sleeve 315, whereby the components disposed adjacent to the second gear 300 can be compactly packaged. Moreover, the teeth 310 can have the desired width to withstand the forces acting thereon. Preferably, a ratio of the width (which is the face width) of the teeth 310 to the width of the body portion 305 is maintained in the range of 1.5 to 2 times depending on the engine capacity and the material used for the primary driven gear. Moreover, the second gear 300 that enables in having higher face width provides lower contact stress thereby improving the life of the gear. The width referred above is the thickness at the particular region measured in the axial direction A-A’. The terms ‘axial side’ and ‘axial surface’ are interchangeably used.
[00045] Further, the gear set that includes the first gear 225 and the second gear 300 is provided with a back lash in the range of 25 – 125 microns. The back lash BL is depicted in the enlarged view of the gear set that is depicted in Fig. 3 (b), wherein the gear set is depicted in Fig. 3 (a). The backlash BL is the play provided between the gears. The second gear 300 of the present subject matter enables provision of low back lash as the primary driven gear produces low chattering noise as the primary driven is capable of dampening any noise and vibrations. Also, the backlash in the range of 25-125 micron enables the individual teeth of the teeth 310 to be stub with the required amount of base that enables in withstanding any forces acting thereon from the first gear 225.
[00046] Further, the second gear 300 is preferably made of a polymer or the like material having a thermal expansion coefficient being low. Therefore, the second gear 300 enables in having the back lash in the above defined range as the clearance between the gear set is maintained.
[00047] Furthermore, the second gear 300 is provided with a lower pressure angle PA so that the face of the teeth thereof is provided with sufficient thickness to maintain sufficient flexural strength and rigidity. The pressure angle PA taken between the tooth profile and a radial line RL passing through a pitch point P of the teeth is preferably in the range of 15-30 degrees. The pressure angle PA is measured between the radial line RL and a tangent line TL drawing at the pitch point P. The tooth profile mentioned herein is the angle made by the face of the teeth, which can be defined from a tangent drawn at the pitch point of the tooth. The pressure angle PA enables the gear to have required flexural strength and the contact ratio between the gears can be kept sufficient enough to transfer the torque or power generated from the first gear 225 to the second gear 300.
[00048] It is to be understood that the aspects of the embodiments are not necessarily limited to the features described herein. 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, the present disclosure may be practiced other than as specifically described.

List of reference signs:

100 vehicle
105 frame assembly
105A head tube
110 handlebar assembly
115 front wheel
120 front suspension
125 front fender
130 rear wheel
135 rear fender
140 rear suspension
145 seat assembly
150 fuel tank
155 muffler assembly
160 swing arm
165 headlamp
170 tail lamp
175A side panel
175B cover panel
200 engine assembly
205 crankcase
210 cylinder body
215 crankshaft
220 piston
225 first gear
235 clutch housing
235A/235B boss
240 clutch assembly
245 crankcase cover
250 bush
300 second gear
305 body portion
310 teeth
315 sleeve
320 apertures
325 pinion
W1 first width
W2 second width
D1/D2 diameter