Group 21 - Beginner Cruiser Motorcycle
Introduction
We are a group of five students in MAE 277, Intro to Mechanical Engineering. This semester we have been given a reverse engineering project based on an assigned product. Through detailed dissection, analysis, and reassembly we have put together this report in summary of our work with the Beginner Cruiser Motorcycle. This bike is as small, gas powered, cruiser inspired, recreational motorcycle.
Group Info
Ryan Boyle: Communication, CAD Lead:
-Allows communication between TA’s and group via email.
-Person who will make CAD drawings for the project.
Carl Eckhardt: Master Wiki Designer, Communication:
-In charge of editing information, and translating information to wiki.
Dylan La Lone: Project Manager, Technical Lead:
-Person who assigns group work, and keeps everyone on track.
Josh Bryant: Technical Expert, Wiki:
-Answers assembly/disassembly questions, under any means necessary including online references.
Greg Gasiorczyk: Technical Lead, Technical Expert, CAD:
-In charge of takedown, and reassembly.
-Keeps track of all parts, and keeps team on track during lab time.
- Members will be able to assist other responsibilities if circumstances require. Those roles are italicized. The description is only stated with the Role if it is the main role of the individual.
Request for Proposal
Tools:
- Socket/ Ratchet Set
- Allen Key Set
- Philips and Flat Head Screw Drivers
- Needle Nose Pliers
- Chanel Lock Wrench
- Needle Nose Pliers
- Philips and Flat Head Screw Drivers
- Allen Key Set
Capabilities:
Ryan Boyle
His experience with disassembling things is limited. He’s taken apart bicycles and small electronics, but never anything like a cruiser motorcycle, so has almost no knowledge about what is to be expected with this project. Ryan is not that good with computers beyond basic computing skills. Also, he has never made a wiki. Overall, he doesn't have much experience with any of these things.
Carl Eckhardt
Carl has a little experience with taking gas engines and bikes apart. He mostly took apart and put back together R/C cars when he was younger. He does have some experience with Wiki’s from a required project he had to do in his senior year of high school.
Dylan La Lone
Dylan has experience with small gas engines, carpentry, bicycles, paintball guns, and his dirt bike. He has taken apart and reassembled a go cart engine as well as a chainsaw engine, and worked on his dirt bike. He is fairly good with computers, but is new to using Wiki’s.
Josh Bryant
When he was young he used to build model cars but doesn’t feel that those skills will useful with a real reverse engineering situation. Outside of that he has very little experience with disassembling machines.
Josh’s computer skills are slightly above average for today’s college student but no exceptional skill and mostly good with Macs. In terms of Wiki’s, he uses wiki pages for reference regularly but has never put one together nor added to one in any way.
Greg Gasiorczyk
Greg has experience when it comes to small engines and cruiser motorcycles. He has held an internship at Jiffy-tite, and has learned the process needed to keep projects on track, and the need of properly storing components to assure a quick reassembly. He is a little rusty when it comes to any CAD software, but can quickly pick it back up if needed. Greg has no experience when it comes to Wiki.
Time and Management Proposal:
Groups 21 and 22 are sharing the Beginner Motorcycle Cruiser, so we have planned to divide some of the dissection between the groups, and share the remaining parts. Group 22 is taking the section of the bike from the engine back. Group 21 is taking on the front fork, suspension, and handlebars. We will meet in the middle, to share the dissection of the engine. Our goals for each stage in our dissection are to finish the separate dissections by Sunday, October 18th, and the engine dissection by Wednesday, October 28th. Some possible challenges or obstacles we have forecasted are the pull start and fly wheel, the clutch, and aligning the back wheel.
At the beginning of every week we will decide through email, when we can meet that week. Because of peoples after class work schedules, we will aim to meet one or two times through Tuesday, Wednesday, and Thursday.
Initial Product Assessment
- The intended use of our product is to provide a motorized, two wheeled platform to ride on for entertainment. Intended for home/recreational use, the Beginner Motorcycle Cruiser imitates a real motorcycle for younger and older users. Like the name suggests, it’s a simpler, easier, and safer yard, woods or off-road miniature motorcycle.
- The product runs on a gas engine: 196 cc, one cylinder, four stroke. The engine is started by pull start, not electric and runs via carburetor, not fuel injection. Inside the engine chemical energy is turned into thermal energy when the gasoline is ignited. The thermal energy is converted into kinetic energy when the piston is thrust down, and the drive shaft is spun. The drive shaft is connected to the clutch. It uses a centrifugal clutch which transfers mechanical/kinetic energy indirectly to a back larger sprocket via a chain.
- The Cruiser is currently running and operating. Every group member in groups 21 and 22 was able to ride it twice. It ran very successfully over gradual hills and bumps in the field next to Governors Dorms, as well as the two way trip up and down campus. The Cruiser consumed about ¾ of a 20oz Gatorade bottle of gasoline. There were no problems encountered during our outing.
- Compared to some of the other products available to us for MAE 277, the Cruiser probably falls above average. Compared to an actually motorcycle the Cruiser is considered fairly simple. If you divide the bike into systems, it falls into six main parts. The frame, the suspension, the engine, the clutch/sprockets, the handlebars, and then the fabrication like the fenders, fake gas tank, headlight, and big comfy leather seat.
- There are many materials that make up the Cruiser. So far we can say that several different types of metals are used. Some type of fake leather covers the seat. The tires and grips are made of rubber. There is also plastic around the cables, the kill switch, the exhaust, intake, and clutch guards, possibly the piston rings, and some other tubes and pieces on the engine.
- We would be happy with this product. It was very fun, comfortable, and easy to use. It is a 4 stroke engine so no mixing of gas and oil is necessary, and by nature the engine should be more reliable being a 4 stroke. With no gears the only two controls during operation were the gas and the brake, which makes it very easy to use. Our only complaints were the size of the large front tire which seemed week in turns, and the stoppers on the front fork that limited our turning radius without leaning. The only maintenance you could plan for is changing the oil, keeping the tires full of air, and always supplying it with gas.
- Some alternatives to the cruiser are dirt bikes, mini bikes, quads, and go-karts. All of these (excluding the mini bike) are more expensive than the cruiser. All of these pricier options are also more complex, but probably better performing. Dirt bikes and quads usually have gears which are less user friendly, but give more capability, power, and speed. Go karts are very similar to the Cruiser, but have four wheels and can hold more than one person. Mini-bikes are very similar to the Cruiser in every aspect except for the fancy fabrications, and suspension found on our product. The Cruiser is cheaper and simpler than most of its competition, but surpassed in performance.
Preliminary Product Review
Causes for Corrective Action:
-As we meet the deadline for our first major product review our group can confidently say everything has gone effectively with no issues up to this point in the process. We were successful because we set a solid foundation in gate 1 of how we were going to manage our time, work and roles during the disassembly. It contained realistic goals and tactics that were met by all members and groups involved by our deadlines.
-The disassembly of the motorbike took approximately 8 hours. We started at the front end of the bike and worked our way towards the center (engine). While disassembling the front section, group 22 was disassembling the rear of the vehicle. Once we had both reached the engine both groups worked together. We planned it this way because it was only fair that both groups get a chance with the “heart” of the bike. Also because the engine is the most complex part and combining our expertise would benefit both groups.
-The only potential problem that was of concern was sharing our product with another large group. This could easily have lead to some cooperation and communication issues. As a result of excellent collaboration no issues arose and everything went smoothly. Both groups worked on the bike simultaneously and met deadlines as a team.
-Sharing with another group was actually a positive situation as opposed to a potential problem. It acted as a support group that kept both groups on time and working efficiently. It also allowed us to combine notes, pictures and ideas incase one group forgot the size of a screw or what part was in a picture.
-Overall everything went as the group had planned. Disassembly deadlines were met with pictures and descriptions of all parts. As a group, meetings were productive and free of conflict. The project so far has proceeded very well and more smoothly than predicted, having one of the more complicated products distributed throughout the class. The bike seemed overwhelming at first to some students who have never disassembled motor vehicles prior to this class.
Procedure for Disassembly:
- difficulty ratings go from 1 to 5. 1 describes simple tasks that do not require physical effort or tedious procedure. 5 describes physically straining tasks or difficult processes that must be followed carefully.
Front End:
Tire:
- Remove axle (using 18mm socket) and nut (using 19mm socket), careful to not misplace washers. Remove tire and wheel from front fork by hand.
- Difficulty: 1
Fender:
- Remove 3 nuts with 8 mm socket from 3 bolts through fender and fender bracket, being careful not to lose washers. Bracket will fall from underneath the fender. Lift the fender out of fork by hand.
- Difficulty: 1
Gas Tank (fake):
- Remove 2 nuts with ½ inch socket from bolts welded to support arms underside the tank shell. Be careful not to lose rubber vibration reducing washers.
- Difficulty: 1
Headlight:
- Unclip white plug from engine, unscrew grounding washer (1) (at end of wire) from the engine using a Phillips head screwdriver, and slip wire out of zip ties (2).
- Remove nuts (2) and bolts (2) through bracket on back of headlight using pliers.
- Unscrew, holding screw (1), from back of light with Phillips head screwdriver, pop cover off back of light.
- Difficulty: 1
Throttle Grip:
- Remove screws (2), with Phillips head screwdriver, from plastic clamp throttle casing. Slide apart while holding throttle grip, keep both halve facing upward. Pull out small black plastic piece on top of cable. Twist the throttle grip and remove metal piece at the end of the throttle cable from white plastic.
- Difficulty: 2
Kill Switch:
- Remove screws (2), with Phillips head screwdriver, from clamping metal piece on backside of kill switch casing. Remove black wire from plug and grounding washer screw (1) with Phillips head screwdriver.
- Difficulty: 1
Handle Bar:
- Using Allen key 6mm, remove 4 screws from each other corner of handle bar bracket. Pull top half of bracket off and lift handle bar out. From the underside of the fork plate, remove the two bolts holding on the handle bar bracket (16mm socket).
- Difficulty: 1
Front Fork:
- Using a large vice grip, remove the large nut in the center of the fork plate. Using 17mm socket, remove bolts through top of plate into fork. Lift plate off center steering shaft. Remove the next 2 spacing nuts on the shaft using a vice grip. Take the last largest nut off the shaft, using a vice grip, make sure not loses the ball bearings that are held underneath this last large nut. Lean the bike back and slide the fork out of the frame.
- Difficulty: 1
Back End
- To view back have of bike dissection procedure performed by group 22 click on link above.
Engine
Clutch Cover (plastic):
- By gripping the cover firmly, bend sides out so that clips come out of holes in cover. Pull off gently.
- Difficulty: 1
Clutch:
- Using 12 mm socket, remove bolt and washer at end of drive shaft. To pull the clutch off, the chain must be removed. Find the master link, with a flat head screw driver push between pointed clips so that they spread apart. Slide past the first pin in that link. The master clip can be lifted off second pin at this time. Remove chain and slide clutch off of the drive shaft.
- Difficulty: 3
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Pull Start, Flywheel:
- Remove bolts (3) using an 8mm socket. Pull the pull start assembly off of the fly wheel cover. Make sure to remove both halves slowly from each other as coiled spring is under a lot of tension. Remove bolts (4) from fly wheel cover using a 10mm socket. While holding the flywheel firmly remove nut at center of fly wheel using 19mm socket. Pull metal outer piece and white plastic blades from flywheel.
- Difficulty: 4
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Air Filter and Cover:
- Remove wing nut on top of black plastic air filter cover, with your hand, off of the bolt running thought air filter assembly. Slide the cover up and off of the air filter. Next remove the second wing nut from above the air filter. Slide the air filter off of the long bolt. Next unscrew the two screws in the base of the air filter case with a Philips head screw driver. Slide the base of the air filter case up and off the long bolt.
- Difficulty: 2
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Gas Tank:
- Remove small wire hose clamp (1) with hands and slide hose off of gas tank fitting. Remove nuts from bolts apoxied to the tank (3) using pliers. Lift gas tank off of engine.
- Difficulty: 1
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Clutch Bracket Plate:
- Remove bolts (4) and nuts (4) using pliers and 12mm socket to remove the gold colored clutch bracket plate.
- Difficulty: 1
Heat Plate:
- Remove three bolts from the heat plate using a 10mm socket. The heat plate is located underneath the front part of the engine, along the underside of the cylinder.
- Difficulty: 1
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Exhaust:
- Remove nuts (2) from bolts (2) holding the exhaust header to the engine block, using 12mm socket. Remove screws (4) with a Philips head screw driver, from the heat shield around the muffler. Muffler and exhaust slide out of heat shield by hand.
- Difficulty: 1
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Carburetor, Throttle:
- Remove the springs (2) connecting throttle to connection rod using needle nose pliers. Using pliers remove the nut from the bolt running through the throttle assembly. Lift entire throttle assembly off of the carburetor. Remove hose clamp and rubber hose from carburetor. Remove nuts (2) holding carburetor cover and carburetor onto engine, using pliers.
- Difficulty: 2
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Magneto and Spark Plug:
- First pull rubber plug off of the spark plug by hand. Remove bolts (2) holding magneto next to flywheel using 12mm socket. Using a 13/16 socket remove the spark plug from the cylinder.
- Difficulty: 1
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Head, Head Cover, Valve Train:
- Remove bolts (4) holding down head cover using 10mm socket. Lift with hands. Remove bolts (4) holding down entire head assembly using 12mm socket. Lift off with hands. Be careful not to lose push rods. By removing the head you can access the valves and the top of the piston.
- Difficulty: 2
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Crank Cover:
- Remove bolts (6) using 10 mm socket. Using two flat head screw drivers, slowly and gently pry the cover off of the side of the engine. This action allows access to the cam, drive shaft, and lower piston assembly.
- Difficulty: 2
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COORDINATION REVIEW
Engine Component Summary
Component Summary Chart:
| Component | Number of Component | Material Used | Manufacturing Method |
|---|---|---|---|
| Engine Block | 1 | Stell | Cast and Machined |
| Clutch (shown in 3D rendering) | 1 | Steel | Cast, Machined, and Welded |
| Clutch Bracket Plate | 1 | Steel | Stamped, Bent, and Welded |
| Sprocket | 2 | Steel | Machined |
| Chain | 2 | Steel | Stamped and Machined |
| Pull Start | 1 | Plastic | Injection Molding |
| Flywheel Cover | 1 | Aluminum | Stamped |
| Flywheel | 1 | Steel | Die Casting |
| Flywheel Blades | 1 | Plastic | Injection Molding |
| Air Filter Cover | 1 | Plastic | Injection Molding |
| Air Filter Base | 1 | Plastic | Injection Molding |
| Gas Tank | 1 | Aluminum | Stamped, Fold-Clamped |
| Heat Plate | 1 | Aluminum | Stamped |
| Exhaust Cover | 1 | Aluminum | Stamped and Pressed |
| Muffler and Exhaust Pipe | 1 | Aluminum | Stamped, Pressed, and Welded |
| Throttle | 1 | Aluminum | Die Casting and Pressed |
| Carburetor Cover | 1 | Plastic | Injection Molding |
| Carburetor | 2 | Aluminum | Die Casting |
| Spark Plug | 1 | Ceramic/Resin, Steel, and Nickel | Resin Injection and Machining |
| Head Cover | 1 | Aluminum | Pressed and Stamped |
| Rocker Arm | 2 | Carbon Steel | Die Cast |
| Push Rod | 2 | Aluminum | Machined |
| Valve Spring | 2 | Steel | Oil Tempered |
| Valve | 2 | Aluminum | Machined |
| Head | 1 | Steel | Die Cast and Machined |
| Piston | 1 | Aluminum | Machined |
| Connecting Rod | 1 | Steel | Cast and Machined |
| Cam | 1 | Steel | Die Cast |
| Drive Shaft | 1 | Steel | Machined |
In-Depth Component Summary:
Engine Block:
- The outside is very rough and does not need to be precise in every place, the places that are, have been machined. Casting is used because it is efficient and quick, machining the entire engine down from a large block of metal is time consuming and inefficient. The inside is machined because it needs to be very precise for the piston and the head to fit onto. Steel is used because the block undergoes high temperature and pressure from within, while also withstanding many forces from components attached to it (including the frame) as well as moving parts inside it. The piston and drive shaft are in direct contact with the block and exert friction on the block. The components attached exert their own gravitational forces on the block. Also the momentum bike and the parts inside require the block to be strong enough to hold itself to the frame. Finally the force exerted on the block from the driveshaft, clutch, chains, tire and ultimately the ground require the block be incredibly strong.
Clutch:
- The clutch is another piece that undergoes great force, and in many places does not need to be precise. The general shape of the clutch is cast, and the inside is machined as well as the multiple holes through it. The sprocket is welded to the outer drum of the clutch. The sprocket needs to be machined separately so it cannot be part of the cast drum. The clutch is cast in steel because several large forces act on it. These forces are exists as torque and friction. The force from the engine and the force from the chain which indirectly connects to the ground are exerted on the clutch. Because of the weight of the bike and the rider the force the clutch receives from the ground, back tire, and chain is very large and must be overcome to make the bike move effectively. The inside of the clutch must expand and exert enough force on the outer drum to overcome these external forces to create a strong enough friction force to make the drum spin at the same rate as the driveshaft. The clutch would fail very quickly due to any deformation.
Clutch Bracket Plate:
- This piece holds the second sprocket which redirects the chain from the clutch to the back wheel and its sprocket. This piece undergoes very little extreme temperature exposure, but must be strong enough to hold the sprocket and the forces exerted on it. The component is stamped into several different pieces which were bent and welded. This part is thin and would be weak if it were simply cast. Deductive machining would be inefficient in time and material. This piece would be able to function fairly well under slight deformation, but its general success is crucial to the function of the bike.
Sprocket:
- The sprocket undergoes the same torque felt by the clutch from the ground and the successful movement of the bike. It is essential the sprocket is machined so that it is very precise and fits in the always fast moving chain exactly and does not slip and fail. It is machined in steel because the torque exerted on it is very strong and the parts success is crucial to the bike success.
Chain:
- The chain undergoes a very large tension created when the clutch begins to spin. Each link is the same shape and size and can have a small tolerance for imperfection so stamping is quick and the preferred choice for the small “8” shaped pieces. The small cylinders were machined because they need to be precise in diameter to fit in between the spokes of the sprocket efficiently.
Pull Start:
- The pull start undergoes a very small amount of force compared to the clutch or sprocket. There is friction force between the string and the pull start as well as torque. It does not need to be very strong but for ergonomic reasons needs to be light. Plastic is cheap and easy to mold, but is not incredibly precise. Luckily little precision is needed for this part. The failure of this part impedes the starting of the bike.
Flywheel Cover:
- The flywheel cover is a simple part that only needs to protect the flywheel and hold the pull start. Because great strength is unnecessary and aluminum is cheap and light, this component’s shape is stamped in aluminum.
Flywheel:
- The flywheel’s purpose is to be heavy and have rotational inertia or momentum giving the engine a more stead rhythm as well as conserving rotational motion. Therefore this piece needs to be heavy. Steel is heavy and easily cast, so the flywheel can be made quickly and efficiently. It does not need to be very precise so little to no machining is needed.
Flywheel Blades:
- The flywheel blades need to be very light and can be fairly week as the only force exerted on it is centripetal force and air drag. This part is attached to the flywheel and circulates air that exits the back of the flywheel cover and is blown on the engine. Plastic is molded quickly and easily, the part does not need to be extremely precise or machined.
Air Filter Cover:
- This part doesn’t need to be precise nor very strong. Its only purpose is holding the light air filter in place and keeping it clean. Air drag and gravity are the only forces on this piece. Plastic is the best choice because it is cheap and easy to mold. Its lack of strength is not a factor with this part.
Air Filter Base:
- This part doesn’t need to be precise nor very strong. Its only purpose is holding the light air filter in place and keeping it clean. Air drag and gravity are the only forces on this piece. Plastic is the best choice because it is cheap and easy to mold. Its lack of strength is not a factor with this part.
Gas Tank:
- The gas tank needs to be strong enough that it does not crack or puncture easily. It does not undergo large amounts of force besides the small fluid pressure from gravity on its inside. Aluminum is cheap and light compared to steel, but heavier and pricier than plastic. Aluminum is chosen because plastic could be puncture or cracked too easily. Steel is not chosen because unless the strength is needed, it is avoided to keep the overall bike’s weight to a minimum. Both halves of the tank were stamped and then the edges were folded around each other and clamp-pressed.
Heat Plate:
- The heat plate is constructed of aluminum because aluminum is very bad at conducting heat, it is also cheap and light which improves the overall performance and cost of the bike. The pieces shape is stamped. This piece experiences very little force, but must be constructed of metal due to extreme temperatures.
Exhaust Cover:
- The exhaust cover is constructed of aluminum because aluminum is very bad at conducting heat, it is also cheap and light which improves the overall performance and cost of the bike. The pieces shape is stamped and the holes are pressed out. This piece experiences very little force, but must be constructed of metal due to extreme temperatures.
Muffler and Exhaust Pipe:
- The exhaust pipe and muffler are constructed of aluminum because aluminum is very bad at conducting heat, it is also cheap and light which improves the overall performance and cost of the bike. The pieces shape is stamped and the holes are pressed out. The pipes are welded to each side. This piece experiences very little force, but must be constructed of metal due to extreme temperatures.
Throttle:
- The throttle is an unsymmetrically shaped hinge that from a cable controlled by hand, turns and opens a valve that controls how much air flows into the engine, and indirectly how much gas is entering the engine. This piece is a very critical part of the bike. It will run, but will not go without the throttle. This piece does not need to be strong, needs to be light, but also needs to be wear and tear resistant, because almost no deformation is allowed before it fails. It is a complicated part that has many springs, a connecting rod, idle speed screw, and governor attached to it. Because of its importance aluminum is used instead of a hard plastic. The aluminum is cast because the part has a reasonable tolerance with its general shape, while all the holes are pressed for precision.
Carburetor Cover:
- This part doesn’t need to be precise nor very strong. Its only purpose is protecting the carburetor and keeping it clean. Air drag and gravity are the only forces on this piece. Plastic is the best choice because it is cheap and easy to mold. Its lack of strength is not a factor with this part.
Carburetor:
- The carburetor is a small chamber that mixes air and fuel. There are no large forces on the carburetor so steel is unnecessary. While a plastic carburetor could work it would be hard to manufacture, the holes in this piece need to be extremely precise so that when small shafts or tubes go through or fit into them, they do not leak. A carburetor functions from pressure gradient, and without a seal this pressure would greatly decrease. Plastic cannot be machined so no holes could be drilled and all would have to be cast. Instead the carburetor is cast in aluminum and then all holes and gasket surfaces are machined.
Spark Plug:
- The spark plug is a small piece that creates a spark from electricity. The ceramic/resin material at the top is used so no electricity is conducted on the outside of the engine block. The inside of the plug is a highly insulated, highly conducting piece of nickel that runs the length of the plug to the inside of the firing chamber. The bottom piece is threaded and machined of steal which with stands the torque applies when it is threaded into the engine block.
Head Cover:
- The head cover protects the valve train, as well as containing heat and sealing the top of the head. This part is constructed in aluminum to withstand the temperature, add little weight to the bike, and be cheaper. The piece is thin and stamped with the four holes pressed out.
Rocking Arm:
- This is a crucial part that experiences two fairly large forces, one from the springs on its valve end, and another from the push rod which controls its timing. The piece is cast as it does not need to be incredibly precise. It is constantly moving and cannot deform because it will cause the bike to fail. It is cast in carbon steel which is very strong and lighter than other steels.
Push Rod:
- This part experiences a compression force when it is pushed to send its end of the rocking arm up and the valve on the other end down. It must be strong and light. If a push rod were to bend, it would throw off all the timing of the valves and when air, fuel, exhaust were entering or exiting the valves.
Valve Spring:
- The spring makes sure that the valve is shot back up and sealed tight when it needs to be as well as keeping constant force against the push rod on the other side of the rocking arm. This spring must be very strong and is made from oil-tempered steel for flexibility.
Valve:
- This must be light and heat resistant, so aluminum is used. The valve is machined because it must fit a very small tolerance so that it creates a very tight seal when it is against the hole in the head. The compression force is felt along the length of the valve from the explosion and compression below it and the force of the rocking arm above it.
Head:
- The head is constructed just like the engine block. The outside only needs to be rough in most parts while every face or place that is in contact with another part is machined for precision and tight fit. This part needs to be very strong as it has to with stand the explosion pressure created in the firing chamber.
Piston:
- The piston must fit a very very small tolerance as it must hold a very tight seal inside the cylinder. It is machined in aluminum to fit this tolerance, be light and easily moved by the explosion, as well as heat resistant. Pressure on the top of the piston is exerted by the explosion or compression of fuel and air. Force also acts on the piston from the connecting rod. This part must be constructed of higher grade aluminum because any deformation could cause the bike to fail.
Connecting Rod:
- This piece is cast in steal as it experiences a lot of force from the piston above, which must be transferred to the cam and the drive shaft below. The piece is cast first, its general shape needs little precision, and second machined for the more precise fittings at the top and bottom of the connecting rod. Steel is used for its greater strength in this application. Slight deformation might be acceptable in this part, but ultimately this part cannot be altered.
Cam:
- The cam is a large heavy piece of material that acts as an off axis weight to counter balance the force of the piston and the connecting rod. This piece ultimately needs to be heavy. It is cast because it does not have a small tolerance.
Driveshaft:
- The driveshaft experiences very large forces from the engine and the clutch. The clutch and driveshaft are kind of the delegates between the power of the engine and the friction of the ground and the bikes movement. This piece must be precise and strong so it is machined in steel. The torque on it is very great so it is fairly thick.
Design Revisions
- The first component change we would make to the cruiser motorcycle would be the tires. The size of the front tire strongly affects the ability for the motorcycle to turn. Our group learned this first hand on the test drive. The turning radius of the bike is uncomfortably small and makes it difficult to maneuver. Also the bike was unstable when turning. The wide almost square profile of the tire was turned and the bike rode on the edge of the tire, along the corner if viewed from the profile. It was very unstable when leaning, which is very necessary on motorcycles and very enjoyable. The tire needs to be reduced in width and made much rounder so that equal surface area is on the ground if the bike is leaning at all.
- The steering restriction knobs on the front fork are built with good intention and along with the current fat, more square shaped front tire work well. Right now they keep the bike from turning to sharply and tipping, but at slow speeds when a larger turning radius is needed, they make it very hard to maneuver the bike. Along with a new front tire, having these knobs moved back a bit would make the bike much more user friendly.
- Another feature that we found a problem with was the exhaust. The exhaust exits under seat off to the side. It should exit out the back for realism and convenience. With the current location of the exhaust leaving so close to rider it causes unwanted smell, heat, and air pollution.
- The final change I would make is a simple one and strictly for convenience. The headlight should have an on/off switch for obvious reasons. In most cases the rider would not need the headlight on and it would conserve bulb life. The bulb could not be changed without taking the entire light assembly off the front fork. The headlight is also very large and bulky the design could be slimed down to a more reasonable size.
Solid Modeling
Assembly Front
Assembly Side
Assembly Isometric
Isometric
Isometric Bottom
Engineering Analysis
- A key component of the bike is the tires. Engineering analysis can be used to test the effect of friction on the tires. This is crucial during the design process because it will help to determine whether or not the chosen tires are suitable for the bike or not.
- In order to test the effect of friction on the tires, it must be assumed that there is no friction between the bearings and the axel. The mass on the tire from the rest of the bike must be taken into account also, so some statics will be involved. This may require equations such as ∑F=0 and ∑M=0.
- After determining the total mass on the tire, the normal force on the tire must be found. This can be easily done using the equation F=ma. For this equation it is assumed that a= 9.8 m²/s (acceleration of gravity). Simply plugging in the determined mass will give the amount of force on the tire.
- After finding the total force on the tire from the bike, the friction on the tire can be found. The force of static friction should be determined as opposed to the kinetic friction, because this way the max possible force of friction will be found. This will require the equation Fs=µsFN, where FN is the normal force on the tire and µs is the coefficient of static friction. Every surface has a different coefficient of static friction, so it will change depending on the surface the friction is being tested on. The tires should be tested on a reasonable surface with a high coefficient of static friction in order to get the highest possible force of friction on the tires. After the coefficient of static friction is determined, it can be plugged in to the equation along with the normal force to find the force of friction on the tire.
- If the tires cannot withstand the test then better tires should be used on the bike. However, if the tires do survive the test and seem to be in really good condition, then a lower quality tire may also be considered in order to cut production costs. Either way, engineering analysis can help to find whether or not the tires are suitable for the bike.
Critical Design Review
Product Reassembly
Front Reassembly
Front Fork:
- The first step of the reassembly you must slide the fork back into the frame of the bike. Then screw back on all the nuts and then tighten them to a secure level.
- Difficulty: 2
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Handle Bar:
- First attach handle bar bracket by securing the two bolts on the underside of the fork. Then slide the handle bar back in place and screw down the top of the handle bar holder with the 4 screws.
- Difficulty: 1
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Kill Switch:
- Attach black wire to plug and screw grounding washer back into place.
- Reattach clamping metal piece on backside of kill switch with 2 Phillips head screws.
- Difficulty: 2
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Throttle Grip:
- Slide grip back on to handle bar and place opposing black throttle pieces in place to be tightened. Then insert small black plastic piece at the end of the cable in place. Fasten screws in slots holding Throttle and grip together.
- Difficulty: 1
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Headlights:
- Place headlight in bracket located on top middle of front fork and slide bolts through both holes. Then tighten both nuts with wrench until light cannot be moved.
- Difficulty: 1
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Front Fender:
- Carefully place fender in place lining up fender brackets with the holder (above fender) in the middle of the front fork. Slide bolts through and tighten bolts.
- Difficulty: 2
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Gas Tank (Fake):
- Place tank on frame so the underneath bracket lines up with holes on frame. Then tighten nuts from underneath so tank holds in place.
- Difficulty: 1
Front Tire:
- Hold frame over tire and slide axle through fork, wheel and other side of fork. Tighten Nut on exiting side till wheel is secure.
- Difficulty: 2
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Engine Reassembly
Crank Cover:
- Slide the slide cover down the driveshaft, and rotate until the screw holes line up. Insert bolts (6) using 10 mm socket.
- Difficulty: 2
Head, Head Cover:
- Put push rods into their holes. Slide the head over the push rods and onto the top of the cylinder making sure all the holes line up. Insert and tighten bolts (4) holding down entire head assembly using 12mm socket. Make sure the push rods are sitting in the cups of rocker arms. Place head cover over the rocking arms. Insert and tighten bolts (4) holding down head cover using 10mm socket.
- Difficulty: 2
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Magneto and Spark Plug:
- Screw the spark plug into its hole until it is tight using a 13/16 socket. Fold a piece of paper 3 or 4 times. This is to create a spacer to make sure when you put on the magneto, it is not too close or far away from the flywheel or the magnet on it. Hold the magneto in front of its holes on the engine block. Wrap the paper around the flywheel and let the magneto stick to it via magnetism. Insert and tighten bolts (2) using 12mm socket. The magneto might need to be adjusted so that the holes line up. Remove the paper, the magneto should have about 1/32 clearance from the flywheel. Rotate the flywheel to make sure it does not come close at any point. Slide the rubber plug onto the spark plug.
- Difficulty: 3
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Carburetor, Throttle:
- Screw the throttle assembly to the engine block using a wrench. Slide the governor arm onto the plastic axle and slide the pin through it. Connect the black spring to the throttle assembly and connect the brass spring to the first hole on the governor arm using needle nose pliers. Slide the carburetor onto the two parallel bolts on the engine block, as you are sliding it on slip the connecting rod from the governor arm into the black plastic throttle control on top of the carburetor. Slide the gasket on after the carburetor, then finally the black plastic carburetor cover. Tighten nuts (2) holding carburetor cover and carburetor onto engine, using pliers.
- Difficulty: 4
Air Filter and Cover:
- Screw the two screws through the base of the air filter case with a Philips head screw driver into the top of the carburetor cover. Slide the air filter onto the base, tighten down with the first wing nut. Slide the air filter cover over the top of air filter and tighten down with second wing nut.
- Difficulty: 2
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Exhaust:
- Attach the exhaust and muffler by sliding it onto the two bolts on engine block next to the exhaust hole. Tighten nuts (2) onto bolts (2) using 12mm socket. Place the heat shield over the muffler, insert and tighten screws (4) with a Philips head screw driver.
- Difficulty: 1
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Gas Tank:
- Lower gas tank into place, and slice the rubber hose under the throttle and down to the carburetor. Slide it onto the brass fuel tube. Slide the wire clamp into place. Insert bolt next to throttle and tighten with needle nose pliers. Tighten two nuts to bolts on tank with pliers
- Difficulty: 1
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Flywheel Cover:
- Place flywheel cover over fly wheel making sure all holes line up. Insert and tighten bolts (4) using a 10mm socket.
- Difficulty: 1
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Pull-Start Assembly:
- Coil spring around inner wheel, such that the spring starts in the pre-cut groove and wraps around accordingly. Un-knot pull rope, and slide on the pull-grip, and tie off, so that it doesn’t fall off. Pull rope through hole in pull-start main housing, and then into the slot in the center wheel. Tie off rope end and fit snug inside the space allowed for the rope. Wind rope around inner wheel, then place inner wheel, with spring facing the main housing, into the main housing. Fit in the brass pins, and put in small springs which cause the brass pins to be pushed in towards the center of the wheel. Now attach the top cover to the inner wheel, using a washer and screw. Pull rope out as if you were to start up the motor, but slowly. The spring tension is now tight enough to retract, but the rope needs to be re-wound…with everything in place, wind rope using the access slack. Now pull the rope once again, the rope should retract once again…if not, repeat step 9. If a small amount of rope is left after the spring retracts, simply retie a knot to make the grip be right up against the housing, and then cut off access.
- It is not recommended to take a apart a pull start for the spring can cause injury while being wound, or if it gets released without the assembly being together. Rebuild using extreme caution.
- Screw the pull start onto the fly wheel cover with bolts (3) using 8mm socket.
- Difficult: 5
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Heat Plate:
- Hold heat plate to engine block underneath cylinder so that the three holes line up. Insert and tighten bolts (3) using a 10mm socket.
- Difficulty: 1
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Clutch Bracket Plate:
- Align holes on plate with holes in engine block. Insert and tighten bolts (4) using a 12mm socket.
- Difficulty: 1
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Clutch:
- Slide clutch onto driveshaft making sure key and groove line up. Insert and tighten bolt and washer into end of driveshaft using 12 mm socket.
- Difficulty: 3
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Final Assembly Evaluation:
- The bike ran well when we were given it and to our excitements runs again after we have disassembled it. We are also proud to say that it is faster than it was when we first tested it. After changing the max position of the throttle, and increasing the idle to just below the clutch’s engaging rpm’s we saw a noticeable increase in the bikes performance. The only negative changes to the bike after the dissection are a broken headlight bulb, and masking tape holding cables to the frame instead of the original zip tie which had to be cut. The head light bulb was probably broken when all of our disassembled pieces were moved across the shop without our knowing. While it is still intact it does not illuminate.
- All of the same tools were used in disassembling and assembling the bike. Besides substituting masking tape for the zip tie the bike is back to its original assembly.
- The reassembly of the pull start proved to be incredibly difficult, and required much more attention in putting it back together than taking it apart. The throttle and governor proved a little difficult as the idle speed was too high at first and the bike idled at rpm’s well above the clutch’s engaging speed. After finding the sweet spot right below the point of clutch engagement the problem was solved.
