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| | [[Image:MB2.jpg|thumb|right|500px|Mini-Bike Side View]] | | [[Image:MB2.jpg|thumb|right|500px|Mini-Bike Side View]] |
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| − | | + | ==Introduction== |
| − | == Group Members == | + | This project is a formal reverse engineering study of a mini-bike. The project is meant to enhance the group's technical writing skills, engineering analysis, website design and teamwork.<br> |
| − | *'''Jeffrey Becker''' - Communication Liaison
| + | In order to mirror an actual engineering evaluation the project was split up into 5 gates with definite due dates and requirements, these gates are listed below with their respective subsections.<br> |
| − | *'''Stephen Harris''' - Group Leader/Wiki Manager
| + | |
| − | *'''Eric Jongsma''' - Solid Model Creator
| + | |
| − | *'''Garth Lester''' - Technical/Mechanical Expert
| + | |
| − | *'''Eddie Morales''' - Technical/Mechanical Expert
| + | |
| − | | + | |
| | ==Executive Summary== | | ==Executive Summary== |
| − | The objective of this project is to better understand the product through dismantling, modeling and reassembly. The product is a min-bike not yet out on the market. It is designed only for recreational uses. Its top speed is approximately 10 mph. It stands up well without any external support and with its wide tires and low center of gravity is very stable even at very low speeds. The throttle is in the very convenient position of the right handlebar grip. The throttle signals the fuel air mixture flow mass flow rate to increase converting chemical energy to reciprocating mechanical energy and waste thermal energy in the combustion chamber then the reciprocating mechanical energy is turned into rotational mechanical energy by the clutch and transferred through the chain to the rear axle where the rear wheel in combination with the surface it rests on turns that rotary motion into linear motion. | + | The objective of this project is to better understand the product through dismantling, modeling and reassembly. The product is a mini-bike not yet out on the market. It is designed only for recreational uses. Its top speed is approximately 10 mph. It stands up well without any external support and with its wide tires and low center of gravity is very stable even at very low speeds. The throttle is in the very convenient position of the right handlebar grip. The throttle signals the fuel air mixture flow mass flow rate to increase converting chemical energy to reciprocating mechanical energy and waste thermal energy in the combustion chamber then the reciprocating mechanical energy is turned into rotational mechanical energy by the clutch and transferred through the chain to the rear axle where the rear wheel in combination with the surface it rests on turns that rotary motion into linear motion. |
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| | -Engineering Analysis</b><br> | | -Engineering Analysis</b><br> |
| | [http://gicl.cs.drexel.edu/wiki-data/index.php?title=Group_6_-_Mini-Bike/CoPR Coordination Project Review Page] | | [http://gicl.cs.drexel.edu/wiki-data/index.php?title=Group_6_-_Mini-Bike/CoPR Coordination Project Review Page] |
| − | ==Component Summary==
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| − | Muffler:<br>
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| − | Function: To filter exhaust gasses and mute the sound of the engine.<br>
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| − | Materials: Iron or Steel.<br>
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| − | Manufacturing Processes: made from two pieces of rolled iron or steel pressed into shape and then folded together around a catalytic converter and then spot welded to give a good seal between the two halves.<br>
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| − | Dimensions: Our muffler is approximately 17cm by 8cm by 5.5cm. <br>
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| − | Other info: The muffler is not subject to forces of any significant magnitude. The only forces present would be from:<br>
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| − | • the vibration of the bike while the engine’s running <br>
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| − | • inertial forces from slowing down, speeding up or turning<br>
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| − | • the air flow through the catalytic converter<br>
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| − | None of these pose any threat to the structural integrity of the muffler. In case of a collision or another force that the muffler was not designed to deal with, it is covered with a protective cage (which we’ve treated as a separate component).
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| − | Steel was probably chosen because it has better heat resistance than aluminum, and because it is stronger. Two sheets of rolled aluminum would be pretty flimsy, while the steel gives the necessary structural support, and is still thin enough to quickly conduct heat out of the muffler to the outside air. <br>
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| − | The muffler was made in two parts so that the catalytic converter could be easily placed inside. Each half could simply be pressed from a flat sheet of steel, so no molding would be required, simplifying the manufacturing process considerably. All in all it is a simple, functional and efficient design.<br>
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| − |
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| − |
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| − | Metal Shield:<br>
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| − | Function: The metal shield acts as a physical barrier to the engine.<br>
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| − | Materials: Aluminum<br>
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| − | Manufacturing Processes: The shield is made from rolled aluminum that is then pressed into shape<br>
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| − | Dimensions: 12cm by 7cm by 5.5cm<br>
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| − | Other info: The metal shield is built to withstand forces due to vibration from the bike but otherwise is not very strong. It’s not a load bearing component, so it doesn’t need to be very strong and it’s not so brittle that vibration would pose a threat.
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| − |
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| − | Hand Brake Lever: <br>
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| − | Function: Transmits energy from user’s hand to brake cable<br>
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| − | Materials: Aluminum and plastic<br>
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| − | Manufacturing Processes: The aluminum is cast and the plastic is molded and the two parts are joined by a connecting rod around which the metal handle pivots.<br>
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| − | Dimensions: 16.5cm by 8.5 cm by 3.5cm<br>
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| − | Other info: No force applied to the hand brake lever under normal operating circumstances is enough to break it. The only times they have been known to break is during collisions, if they strike the ground or the wall.
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| − |
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| − |
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| − | Muffler Cage: <br>
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| − | Function: Protects the muffler from damage and protects hands against accidentally brushing against a hot muffler.<br>
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| − | Materials: Steel<br>
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| − | Manufacturing Processes: The steel is extruded to form wires which are then bent into the shape for the cage and painted black.
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| − | Dimensions: 18cm by 9cm by 4cm<br>
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| − | Other info: The muffler cage is built to withstand impacts as well as to protect people from the heat of the muffler. It’s cheap and simple to manufacture, but it’s effective and does exactly what it’s designed to do.
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| − |
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| − |
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| − | Left grip:<br>
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| − | Function: Covers handlebar and gives the user a place to grip. <br>
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| − | Materials: Synthetic Rubber<br>
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| − | Manufacturing Processes: Molded<br>
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| − | Dimensions: 12.5 cm long and 4.5cm in diameter<br>
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| − | Other info: The reason for using synthetic rubber for the handle is that it provides a high-friction but non-abrasive surface, ideal for gripping with the human hand. In terms of forces applied, sometimes a twisting force will pull the handle off, but in most cases a force being applied the handle simply deforms it slightly and it springs back.
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| − |
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| − | Rear Axle:<br>
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| − | Function: Connects the rear wheel to the frame and provides an axis for it to spin around.<br>
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| − | Materials: Steel<br>
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| − | Manufacturing Processes: Cut from stock by machine<br>
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| − | Dimensions: 25.5 cm long, size 15mm head.<br>
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| − | Other info: The axles carry quite a good deal of load, which is why the bolt is designed so thick. Rather than making an axle from scratch, using a long, heavy-duty bolt saves on production and design costs and as such is a good manufacturing decision.
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| − |
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| − | Timing Mechanism:<br>
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| − | Function: This records the spinning of the flywheel and sends a charge that activates the spark plug. It is used to keep the engine cycle in sync.<br>
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| − | Materials: Plastic, aluminum, synthetic rubber<br>
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| − | Manufacturing Processes: The plastic components were probably injection molded. The wires were extruded and the metal in the mechanism itself is machined from stock.<br>
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| − | Dimensions: 7cm by 5.5cm by 3.5cm<br>
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| − | Other info: The timing mechanism is well protected, but it can still be subjected to engine vibration, and, because it is so close to the engine, could also be damaged by heat. <br>
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| − | Often the timing mechanisms are mechanical, such as having a timing belt or timing chain. Having an electronic timer reduces wear and tear, but increases manufacturing costs.
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| − |
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| − | Gas tank/engine interface:<br>
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| − | Function: This is a thin metal sheet that separates the gas tank from the engine. It’s there to add another layer of protection to the gasoline in the tank and better guard it from the hot engine.<br>
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| − | Materials: Aluminum<br>
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| − | Manufacturing Processes: The aluminum is rolled and then pressed into shape<br>
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| − | Dimensions: 14cm by 10.5cm by 2cm
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| − |
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| − |
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| − | Right Handle:<br>
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| − | Function: This handle is the same as the left except that it also integrates the controls for the throttle<br>
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| − | Materials: synthetic rubber, plastic, copper<br>
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| − | Manufacturing Processes: The wires are extruded, and the throttle mechanism put together by machine, after which the injection molded handle is placed over the assembly.<br>
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| − | Dimensions: 12.5cm long and 4.5cm in diameter<br>
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| − | Other info: The right handle reuses the same mold for the left handle, and then puts that around the components that control the throttle, in an effort to make the manufacturing process more efficient.
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| − | The only significant force applied is the twisting applied to open up the throttle, which is exactly what it is designed for.
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| − |
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| − | Throttle Cable:<br>
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| − | Function: Connects the right handle to the throttle on the engine.<br>
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| − | Materials: Steel<br>
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| − | Manufacturing Processes: It is extruded in thinner wires and then twisted to form the cable.<br>
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| − | Dimensions: 110cm by .2cm in diameter<br>
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| − |
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| − | Cutoff Switch:<br>
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| − | Function: The switch is a device used to turn off the engine<br>
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| − | Materials: Plastic, synthetic rubber, copper, steel<br>
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| − | Manufacturing Processes: Any wires are extruded and coated in synthetic rubber, and then the switch itself is made from injection molded plastic<br>
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| − | Dimensions: 4.5cm by 4.5cm by 2cm
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| − |
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| − | Brake Cable:<br>
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| − | Function: Transfers energy from the brake lever to the actual brake on the rear wheel<br>
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| − | Materials: Steel<br>
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| − | Manufacturing Processes: The steel is extruded into thin wires and then twisted to from a cable<br>
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| − | Dimensions: 150cm long and .2cm in diameter<br>
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| − |
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| − | Washers:<br>
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| − | Function: Washers are generally placed on bolts to use as spacers or to diminish friction between two parts rotating on a common access<br>
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| − | Materials: Steel or Aluminum<br>
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| − | Manufacturing Processes: Washers are usually machined from stock<br>
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| − | Dimensions: There are 13 washers on the mini bike (that aren’t included in other components) that range in size from 2.1cm in diameter to .9cm
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| − |
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| − | Chain Tensioner (pulley):<br>
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| − | Function: This is a moveable pulley which is used to keep the chain taught.<br>
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| − | Materials: The outside is made of Plastic while the inside has metal washers and bearings to allow it to spin<br>
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| − | Manufacturing Processes: The washers and bearings would be machined, and the plastic is injection molded<br>
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| − | Dimensions: 3.3cm long by 4.5cm in diameter<br>
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| − | Other info: Based on observation, the pulley doesn’t turn even though it is built to. Instead the chain just glides over the pulley. This seems like bad design and energy is lost to friction.<br>
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| − |
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| − | Gasket:<br>
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| − | Function: The gaskets separate metal components and act as seals to prevent leaks. There were three gaskets that we were able to get to and two more in the engine that we could not because we didn’t have the right equipment to open it up.<br>
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| − | Materials: thin layer of aluminum or steel coated in adhesive and some kind of paper product<br>
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| − | Manufacturing Processes: the gasket is cut out of rolled metal then coated.<br>
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| − | Dimensions: The range from 11cm by 8.5cm to 5cm by 3.3cm
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| − |
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| − | Gasket (rubber):<br>
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| − | Function: Serves the same function as regular gaskets, except that the material is different<br>
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| − | Materials: Synthetic Rubber<br>
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| − | Manufacturing Processes: Injection molded<br>
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| − | Dimensions: 7cm by 75cm<br>
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| − | Other info: The rubber makes the gasket more compressible, meaning that it works better than a metal gasket when it separates two components that may move relative to each other slightly.
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| − |
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| − | Dipstick:<br>
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| − | Function: Used to measure oil level<br>
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| − | Materials: Plastic<br>
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| − | Manufacturing Processes: It was injection molded<br>
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| − | Dimensions: 6.5cm long by 2.5 cm in diameter<br>
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| − | Other info: The dipstick is not subject to much stress and as such is made from cheap plastic to save cost on materials.
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| − |
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| − | Axle Bolt Cover:<br>
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| − | Function: Protects the outside tips of the axle from damage<br>
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| − | Materials: Plastic<br>
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| − | Manufacturing Processes: Injection Molded<br>
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| − | Dimensions: 2.7cm long by 2.9cm in diameter
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| − |
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| − | Engine Spacer Plate:<br>
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| − | Function: Separates engine from frame, providing stability and countering vibration<br>r>
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| − | Materials: Steel<br>
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| − | Manufacturing Processes: Cast from a dye (could have also been rolled and cut but the edges are too smooth)<br>
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| − | Dimensions: 12.5cm by 8.4cm by.5cm<br>
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| − | Other info: The spacer plate allows for a slightly increased tolerance between the engine and the frame, thus reducing the vibration transmitted to the frame.
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| − |
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| − | Chain Cover:<br>
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| − | Function: Is bolted over the chain to keep loose articles of clothing from getting caught in the chain<br>
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| − | Materials: Plastic<br>
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| − | Manufacturing Processes: Injection Molded<br>
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| − | Dimensions: 25cm by 12.5cm by 7cm<br>
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| − | Other info: While the bike would function perfectly well without it, the chain cover shows that the engineers were thinking about possible hazards to the future users of this bike when they built it.
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| − |
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| − | Engine:<br>
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| − | Function: Contains the chemical reaction that drives the mini bike<br>
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| − | Materials: Aluminum, Plastic, and many more<br>
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| − | Manufacturing Processes: The casing for the engine was die cast (as evident from the tapered ridges) then machined where necessary until the desired result was achieved. Plastics were used to make the o-rings which were probably injection molded.<br>
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| − | Other info: The engine was designed to have a high surface area to weight ratio, in order for it to cool efficiently. An interesting thing we found was that the inside of the combustion chamber had the piston and the valves were on the same side of the chamber. This meant that there was no risk of the piston ever hitting the valves, which is a real problem with automobiles, should the timing chain get worn or break. (shown below is a piece of the casting of the engine to demonstrate the high surface area to volume ratio)
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| − |
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| − | Throttle/choke assembly:<br>
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| − | Function: Controls the oxygen and fuel reaching the engine<br>
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| − | Materials: A large variety<br>
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| − | Manufacturing Processes: most parts were made from rolled and cut aluminum, but there are many processes involved in making an assembly this complex
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| − |
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| − |
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| − | Gas Tank:<br>
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| − | Function: Holds the fuel for the mini bike<br>
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| − | Materials: Aluminum<br>
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| − | Manufacturing Processes: It’s made in much the same way as the muffler in that it started out as rolled aluminum and was cut and then pressed into two parts which were joined to make the tank.<br>
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| − | Dimensions: 25cm by 13cm by 8cm<br>
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| − | Other info: The gas tank sits directly above the engine, so gravity feeds the gas. This is a much more efficient system than cars, which require a fuel pump to get the gas from the tank to the engine. Obviously, putting a car’s gas tank over its engine would be difficult and frankly irresponsible, but with the mini bike it is actually a good solution.
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| − |
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| − | Frame:<br>
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| − | Function: Gives structure to the mini bike, and serves as an anchor for the rest of the components.<br>
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| − | Materials: Aluminum<br>
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| − | Manufacturing Processes: Much of the frame is made from tubes which are extruded, cut, bent into the proper shape and welded together. The base plate for the engine and a few other flat pieces are rolled and cut aluminum which is also welded on. Once the whole frame is together it is then painted red. <br>
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| − | Other info: There does not appear to be machining anywhere on the frame. Even the holes for bolts have a low enough tolerance that simply casting them is sufficient. This cuts down on manufacturing cost considerably
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| − | Wheels:<br>
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| − | Function: The wheels are the only points of contact with the ground (except the kick-stand) and are the means by which the spinning of the motor is transferred to horizontal movement. <br>
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| − | Materials: The wheels are alloy or aluminum with rubber tires.<br>
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| − | Manufacturing Processes: The tires and wheels would be manufactured separately and then assembled together. The tires would be injection molded plastic around fiber. The wheels could be cast and then machined as necessary.
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| − |
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| − | Starter Cover:<br>
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| − | Function: Covers the starter motor and redirects air to cool engine<br>
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| − | Materials: Aluminum<br>
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| − | Manufacturing Processes: It was rolled and pressed into its current state.<br>
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| − | Dimensions: 20.5cm by 12.5 cm by 6 cm<br>
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| − | Other info: The starter cover is an efficient deign because it is also the base for the pull cord.
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| − |
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| − | Nuts, Bolds, Screws:<br>
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| − | Function: Hold the components of the mini bike together<br>
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| − | Materials: Steel<br>
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| − | Manufacturing Processes: Machined from stock<br>
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| − | Other info: Many of the nuts and bolts used in the bike were the same size, presumably to save money when purchasing them.
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| − |
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| − | Seat:<br>
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| − | Function: Provide a place for the user to sit comfortably while making use of the mini bike.<br>
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| − | Materials: Plastic, foam, steel<br>
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| − | Manufacturing Processes: The seat is made from injection molded plastic covered with foam and stitched leather stapled to the plastic frame. There are nuts glued to the inside the plastic frame to provide lightweight threaded holes to secure the seat to the metal frame.<br>
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| − |
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| − | ==Design Revisions==
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| − | 1) The mini bike has a chain tensioner that is clearly designed to be a pulley and yet rather than rotate with the chain, it lets the chain run over it, causing wear and tear to both it and the chain. Giving the tensioner better fitting bearings could solve this problem and eliminate all the unnecessary wear and tear and wasted energy. It would mean a slight increase in the cost of the bike however, and though it might be more fuel efficient, consumers might not notice the small increase in efficiency when compared to an increase in price.<br>
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| − |
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| − | 2) Our mini bike is somewhat underpowered. One way to deal with this would be decrease the diameter of the wheels. This would give the bike a little more torque, although its top speed would be lower. The target consumers for the mini-bike are not people that want a lot of speed, because the mini-bike was never fast to begin with. However, we would be giving them a better functioning product that was less likely to stall as you try to start it up. Also, smaller diameter wheels would contain less material and therefore be less costly to produce.<br>
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| − |
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| − | 3) The electronic timing mechanism that detects the position of the flywheel and controls the firing of the piston could be replaced with a timing chain. The timing chain might not be as precise, but it will be much more cost effective, and there seems no point in having an expensive electronic timing mechanism on an otherwise practical and simple vehicle. The only difference customers would notice would be the drop in price.<br>
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| − | ==Solid Modeling==
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| − | The chosen assembly was the rear wheel assembly. It was chosen because of its central nature to the propulsion of the min-bike. Propulsion is the key feature of the mini-bike product. <br>
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| − | Ø Wheel:
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| − |
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| − | · The rim is aluminum
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| − |
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| − | · The tire is rubber and is tubeless, which means that the tire is pressed against the rim due to the air pressure in the tire
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| − |
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| − | Ø Sprocket:
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| − |
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| − | · The sprocket is made of aluminum
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| − |
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| − | · There are 70 teeth on the sprocket
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| − |
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| − | · It is mounted by 6 bolts to the rim of the wheel
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| − |
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| − | Ø Disc brake rotor:
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| − |
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| − | · Made of aluminum
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| − |
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| − | · Has holes on the contact surface to dissipate the heat of braking
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| − |
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| − | · It is mounted to the rim by means of 6 bolts
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| − |
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| − | Ø Flywheel:
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| − |
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| − | · Is mounted to the motor
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| − |
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| − | · Transfers the energy of the motor to the wheel and sprocket
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| − | ==Engineering Analysis==
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| − | 3. Problem Statement: Find out the stress on the brake cable of the mini-bike for group 6 and evaluate it with respect to the ultimate tensile strength.
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| − |
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| − | Diagram:
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| − | Assumptions: There are multiple assumptions to be made to check for failure of this system. The perpendicular distance between the forces and the hinge remain constant. The cable does not deform under stress in such a manner as to significantly reduce its cross-sectional area. The distributed load exerted by the hand is evenly distributed for the distance that it is applied. The force applied by the hand to the cable is applied over enough time so that it acts as a loading situation (gradual increase in force over time) as opposed to an impact (sudden application of force) situation.<br>
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| − | Table 4: Problem 3 Assumed Values<br>
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| − | diameter of steel wire 0.001588 m<br>
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| − | ultimate tensile strength of steel wire 760 MPa<br>
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| − | force applied by hand 67 N<br>
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| − | Distributed Force minimum perpendicular distance to fulcrum 0.0254 m<br>
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| − | Distributed force maximum perpendicular distance to fulcrum 0.1016 m<br>
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| − | Cable fulcrum perpendicular distance 0.03048 m<br>
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| − |
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| − | Sources: http://en.wikipedia.org/wiki/Tensile_strength Steel, high strength alloy ASTM A514 for the ultimate tensile strength of the wire<br>
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| − | Governing Equations:<br>
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| − | ∑▒〖M_fulcrum =0=T_cable*D_(perp cable)-F_centroid*D_(perp brake lever) 〗 such that ∑▒M_fulcrum is the sum of the moments about the hinge, T_cable is the tension force in the cable, D_(perp cable) is the perpendicular distance between the tension force in the cable and the hinge, F_centroid is the imaginary force applied at the centroid of the distributed load to represent the distributed force at a point, D_(perp brake lever) is the perpendicular distance between the hinge and the force acting at the centoid of the distributed load.<br>
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| − | F_centroid=F_hand, the force F_centroid equals the force applied by the hand F_hand<br>
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| − | Centroid=the middle of the distributed load since it is an equally distributed load.<br>
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| − | D_(perp brake lever)=centroid+minimum perpendicular distance to the fulcrum<br>
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| − | ultimate tensile force=ultimate tensile strength*Area<br>
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| − | Safety factor=(maximum load)/(applied load)<br>
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| − | Calculations:<br>
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| − | D_(perp brake lever)=centroid+minimum perpendicular distance to the fulcrum=(.1016 m-.0254 m)/2+.0254 m=.0635 m<br>
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| − | D_(perp cable)=.03048 m<br>
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| − | F_centroid=F_hand=67 N<br>
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| − | T_cable=(F_centroid*D_(perp brake lever))/D_(perp cable) =(67 N*.0635 m)/(.03048 m)=140 N<br>
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| − | ultimate tensile force=ultimate tensile strength*Area=760 MPa*(〖10〗^(6 ) Pa)/MPa*〖((.001588 m)/2)〗^2*π=1505.2 N<br>
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| − | Safety factor=(maximum load)/(applied load)=(1505.2 N)/(140 N)=10.75<br>
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| − |
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| − | Solution Check: Brake cables on bikes are not known to fail under ordinary operating conditions so the large difference between the applied force and the maximum force the cable can take is as expected.<br>
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| − |
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| − | Discussion of Results: The scenario for failure of the group 6 mini-bike was the failure of the brake cable. As shown in the calculations the ultimate tensile force that the steel cable can withstand is 1505.2 N while the ultimate tensile force the cable will experience is only 140 N. The safety factor calculated for this problem of 10.75 means that under the assumed conditions there will be no failure of the specified component in the specified way. The limitations to this solution are numerous. The assumed hand force applied is only a rough guess given some slight experimentation meaning the maximum force could be higher especially since humans have a wide range of strengths. The distance and position over which the hand force is applied in reality would vary widely for different sized hands and grips though the distance and position assumed in this problem is a pretty common one for a standard brake grip (determined though life experience on bikes with friends and family). The exact material of the cable is unknown however the steel ultimate tensile strength used is a relatively low and common one so a reasonable maximum tensile force should have been obtained. This evaluation of the ultimate tensile force applied vs the ultimate tensile force that the cable can withstand would be improved by better knowledge of the geometry of the cable at its ends.
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| − |
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| − | ==Reassembly==
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| − | 1. Cylinder head and gasket: 6 bolts, 10mm socket wrench: when tightening the head back on, a torque wrench should be used to a specific torque specified by the manufacturer. But since we did not have one, we tightened them to the best of our abilities.<br>
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| − | a. Spark plug: 19mm socket wrench<br>
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| − | b. Spark plug cover + timing mechanism: 2 - 10mm bolts for the timing mechanism: It was difficult to adjust the timing mechanism to the proper position. The mechanism itself is magnetic and it hovers over the magnetic flywheel and is held on by 2 bolts. In order to secure it, you have to hold the mechanism over the magnetic flywheel, which can be difficult.<br>
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| − | 2. Carburetor and gaskets: 2 – 8mm bolts. The carburetor slides onto 2 rails , with a gasket on the inside and the outside. Since the gaskets were specific to there respective side, it took a minute to figure out which one went where.<br>
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| − | 3. Air filter: 2 – 8mm bolts. The air filter went on the outside of the carburetor on the same rails that the carburetor slid onto.<br>
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| − | 4. Throttle assembly: This was the most difficult part of the reassembly process. This was due to the fact that there were 2 springs that attached to the motor in different points, and we referred to pictures to see where they attached.<br>
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| − | 5. Muffler and gasket: 2-8mm socket wrench: This also includes the muffler cage. One of the springs of the throttle assembly was attached to the muffler cage to keep the assembly in proper tension.<br>
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| − | 6. Starter assembly: 3-9mm socket bolts: The starter assembly goes on the opposite side of the clutch and flywheel, which turns the motor over.<br>
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| − | 7. Gas tank and shield: 10 mm , 3 bolts : The shield goes under the gas tank which keeps the heat of the engine from heating up the gas in the tank. We also had to make sure we hooked up the gas line tube from the tank to the engine.<br>
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| − | 8. Kill switch: The kill switch has 2 wires that attach to the motor at 2 different points. One is a ground that bolts directly to the engine block and the other attaches to the timing mechanism. At this point, all the components that attach to the motor are secured.<br>
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| − | 9. Rear wheel assembly: <br>
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| − | a. Sprocket: 6 bolts, 5mm hex wrench. The sprocket goes on the left side of the wheel and the bolts have to be tightened in a star pattern with a torque wrench.<br>
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| − | b. Brake rotor: 6 bolts, 5mm hex wrench. Is secured on the same way as the sprocket in a star pattern.<br>
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| − | c. There are 2 different size spacers. The larger of the 2 goes on the left side, or the drive side, while the smaller of the 2 goes on the right.<br>
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| − | d. There is a 14mm bolt that is secured on with a lock nut.<br>
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| − | 10. Steering wheel & handlebar assembly: <br>
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| − | a. A large 14mm bolt goes through the top of the assembly and is secured on by a 16 mm nut on the bottom of the headset.<br>
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| − | b. The brake lever is reattached using a 5mm hex wrench and the cable is fed through at the top of the handle.<br>
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| − | c. The throttle is attached to the right side of the handle bars and is secured using a 3mm hex wrench.<br>
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| − | d. Rear fender: There are 2 bolts with rubber washers that attach the fender on. The rubber washers go in between the mounts and the bolts to prevent chattering noise when the fender is vibrating.<br>
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| − | 11. 2 Chain Guards: the chain guards cover the path of the chain for the safety of the rider. The rear chain guard goes on first, and then the front chain guard overlaps it.<br>
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| − | 12. Seat: There are 3 – 10mm bolts that secure the seat<br>
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| − | ==Post Reassembly analysis== | + | ==Gate 4== |
| − | <b> Reassembly Process note</b> | + | -<b>Reassembly Plan</b><br> |
| − | <blockquote> All the same tools were used to reassemble the product as were used in its dissassembly</blockquote> | + | [http://gicl.cs.drexel.edu/wiki-data/index.php?title=Group_6_-_Mini-Bike/CPR Critical Project Review Page] |
| − | <b> End Result of Reassembly notes</b>
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| − | <blockquote>After Reassembly the bike no longer works. The problem with the bike appears to be related to the throttling assembly which unfortunately no longer function properly due to the fact that at one of its pivot points it is missing a piece to hold it on. To correct the problem our group suggest looping a metal ring through the throttle assembly and the pin on that pivot to prevent the throttling device form popping off.<blockquote>
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| − | <b> Product Recommendations</b>
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| − | Our main recommendation concerning the product given our trouble with the reassembly is to make the throttling assembly more robust.
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This project is a formal reverse engineering study of a mini-bike. The project is meant to enhance the group's technical writing skills, engineering analysis, website design and teamwork.
In order to mirror an actual engineering evaluation the project was split up into 5 gates with definite due dates and requirements, these gates are listed below with their respective subsections.
The objective of this project is to better understand the product through dismantling, modeling and reassembly. The product is a mini-bike not yet out on the market. It is designed only for recreational uses. Its top speed is approximately 10 mph. It stands up well without any external support and with its wide tires and low center of gravity is very stable even at very low speeds. The throttle is in the very convenient position of the right handlebar grip. The throttle signals the fuel air mixture flow mass flow rate to increase converting chemical energy to reciprocating mechanical energy and waste thermal energy in the combustion chamber then the reciprocating mechanical energy is turned into rotational mechanical energy by the clutch and transferred through the chain to the rear axle where the rear wheel in combination with the surface it rests on turns that rotary motion into linear motion.
