Group 17 - Beginner Dirt Bike/CR
Contents |
Component Summary
Table 2
| Component | Function | Material | Forces | Shape | Manufacturing Process | Complexity* | Picture |
|---|---|---|---|---|---|---|---|
| Handlebars (1) | Functional: provides a means for the driver to steer the bike | Steel, Rubber, and Plastic. Steel for structural integrity. Rubber for the grips for extra traction of riders hold on handlebars. Plastic used to secure brake line to hand brake. | Minimal forces applied on handlebars, normal force and tension balance gravity. | Allows for comfort for riders grip | Sand cast because shape is symmetric and relatively low precision necessary. Material has no effect. | 3 | 
|
| Chassis (1) | Functional/Cosmetic: shelters other components from environment while providing color and design to the model | Plastic for ease in fabrication/lightweight. | Minimal forces act on the chassis. Forces of tension and friction between the chassis and frame in equilibrium, keeping the chassis in place. | Necessary shape because covers frame/other components | Chassis molded for cost effectiveness and because plastic is easy to mold | 2 | 
|
| Frame (1) | Functional and Cosmetic: provides stability and shape to bike | Steel for structural integrity. | Weight of chassis-7 lb, tension and torque at joints and connections all in equilibrium | Best shape possible for rider comfort and functionality | Die casted individually, bended and welded together | 4 | 
|
| Compression (1) | Functional: absorbs shock and impact | Steel and Rubber. The spring is coated in rubber but everything in the compression system is made of steel. Also a rubber washer in place in order to prevent wear. | Forces applied from weight of frame and chassis, approximately 75 lb. | Necessary shape in order for spring to compress | Spring made by coiling, die casting used for the rest of system. Steel is malleable/ductile. | 5 | 
|
| Rear Wheel Suspension (1) | Functional: keeps wheels in place and helps with some shock absorption | Steel and Rubber. Steel for structural integrity. Rubber piece serves as a cushion for the chain, resulting in less friction and ultimately less wear. | Some weight from frame and chassis, approximately 15 lbs and additional weight when rider is added. Forces of tension, torque and joints and connections in equilibrium | Designed to keep back tire secure and provide stability | Die casting used for individual pieces, then welded together. Ductility of steel is beneficial. | 4 | 
|
| Front Wheel Suspension (1) | Functional: keeps wheel in place and helps with some shock absorption | Steel is used because of the structural integrity. Rubber washers in place to aid with shock absorption and prevent wear. | Forces on front suspension include some weight of frame. | Designed to work with steering column and keep front tire in place | Left piece die casted for precision. Circular shape allows for pressure fitting to fit perfectly with cut steel rod. | 3 | 
|
| Front Wheel Steering Column (1) | Functional: causes the tires to turn | Steel for strength and stability | Forces acting on the steering column include the weight of the handlebars, approximately 7 lb. Torque is also applied when turning. | Designed to compliment front suspension and handlebars design | Turning used to create threads, sand casting used to make plate unsmooth finish and low precision necessary, shape and material have little effect. | 4 | 
|
| Exhaust System (1) | Functional: removes exhaust from the engine | Steel for structural integrity | Minimal forces applied, air pressure from exhaust applied when in use | Shaped to help funnel exhaust away from bike | Steel tubing is heated then bent, welded to a sand casted materials | 3 | 
|
| Kick Start (1) | Functional: Start engine | Steel and Rubber. Steel for strength, rubber for traction | Minimal forces on kick start when not in use. Applied force from the rider must create enough torque to force the crank shaft to start moving the pistons, approximately 50 lb is applied on average though less is necessary. | Shape based for user ease/maximum torque generation | Long thing piece steel that was heated and bent, and welded to a sand casted pieces on either end. | 3 | 
|
| Fuel Tank (1) | Functional: provides a place for fuel storage | Plastic because lightweight, easy to form as one compound piece | Forces on the fuel tank include the weight of the fuel in the tank, approximately 6 lb. Also, there are forces between the gas tank and the frame which are in equilibrium. | Designed for helping fuel leave tank | Molded plastic, for ease | 2 | 
|
| Carburetor (1) | Functional: blends air and fuel for engine | Steel for structural integrity, filter is steel/wool mesh | Minimal forces act on the carburetor | Designed to maximize efficiency | Variety of parts casted/molded then assembled. | 5 | 
|
| Engine Block (1) | Functional: provides energy for the bike to move | Aluminum for strength | Forces acting on the engine are minimal, while forces in the engine are much more complicated. Pistons, spark plug, etc all provide internal forces. | Shaped to fit maximum number of components in small space. | Variety of pieces casted, welded and assembled. | 5+ (many internal parts) | 
|
| Gear (1) | Functional: causes rear wheel to rotate | Steel is used for its strength and ductility, high resistance to frictional wear | A contact force is applied between the gear and the chain and friction between the gear and drive shaft | Teeth to have easy transfer of chain links, gear size chosen for maximizing turn of wheel | Die casted for general shape. Teeth created by turning, and holes created by drilling. Steel is a good choice because malleability. | 4 | 
|
| Gear Chain Link (1) | Functional: connects transmission to rear wheel | Steel, for ductility and high resistance to frictional wear | There is a contact force that acts between the chain and the gear. There is also an equal tension between each of the chain links. | Chain links made to work with size of teeth on gear | Links casted and then attached together. | 3 | 
|
| Tires (2) | Functional and Cosmetic: Tires provide a means for the bike to move, but design of spokes can change | Steel and Rubber. Steel for spokes, rim, center for strength and rigidity. Rubber for tire for traction and give with uneven surfaces. | Between the two tires there is approximately 50 lb of force (assuming the kickstand is down) | Circular to help ease of motion, treads for traction control, spoke design for support | Rim die casted and adhered to spokes which were sand casted. Spokes adhered to sand casted center. | 3 | 
|
| Drum Brake (1) | Functional: Brakes are necessary for the bike to stop: Part # 6-5.5 | Aluminum and Steel. Aluminum for brake hub for its strength and light weight, while the attachment from the brake to the suspension is made of steel for its strength. | Forces acting on brake are minimal, except when brake is in use. Here, a force of friction will be applied, | Shape and size based of wheel design | Both pieces sand casted then connected with screw | 2 | 
|
| Kickstand/Pedals (1) | Functional: allows the bike to stand on its own/provides a place for riders feet to rest | Steel for strength and rigidity | The kickstand supports majority of the weight of the bike, approximately 80 lb. The pedals are securely fastened to the frame, and the forces there are in equilibrium. | Kickstand designed to support weight of bike, pedals shaped to support feet/ provide traction | Individual pieces of pedals sand casted, then welded together. Spring is made by coiling. Kickstand casted then attached with bolt | 3 | 
|
| Cables (3) | Functional: needed for brake system | Plastic covering in order to protect interior cables from environment | When the rider squeezes the brake, the cables become taught and apply a force on the brake, causing it to clamp shut. The force applied on the brake would directly result from how much force is applied by the rider. | Shaped for flexibility | Multiple wires weaved for strength, covered with insulting plastic | 2 | 
|
| Screws (67), Washers (26), Nuts (14) | Functional: keeps other components in place | Steel for structural integrity | Forces acting on these components are normal forces. | Screws shaped for stability and tight fit, washers shaped to keep connection between screw and surface tight, nuts are hexagons for ease of tightening. | Screws made by turning, washers made by die casting, nuts made by casting then bored and turned. | 2 | 
|
- *Complexity in Table 2 is measured with 1 being easy to create (simple casting) and 5 difficult to create (multiple processes necessary).
VIDEO: Removing Outer Casing of Engine Block
Design Revisions
Exhaust
The exhaust pipe on the mini bike and the covering over the exhaust pipe are both made of steel. When the bike is running, the metal on the pipe gets hot. The cover does protect the rider from some of the heat, but if the direct contact with skin was made, it could burn the rider. Since the rider would likely be using the bike for recreational purposes, the rider would not always wear appropriate clothing. Assuming the rider was wearing shorts, as many recreational riders would, the exhaust could burn him. To prevent this, the cover should have a layer of rubber over the steel to further dissipate heat. This addition to the bike would not cost much because it is not very intricate in design.
Kill switch
Another safety feature that is missing from the bike is that there is no kill switch. If the rider were to fall off of the bike while it was moving, the bike would continue to move until it fell over or crashed. If there were a kill switch connecting the bike and rider, then the engine would stop the moment the rider fell off. The kill switch would be a moderately expensive addition to the mini bike; however it would make the bike safer for the rider. Safety should be the first priority while manufacturing a product that could be potentially dangerous.
Gas gauge
A flaw in design on the mini bike is that there is no accurate way to tell how much fuel is left in the gas tank. The bike should have a gas gauge. This would be a relatively inexpensive addition to the bike, and it would assure that the rider knew how much fuel they had at all times. This would make riding the mini bike safer as well. It would be safer because the rider would not run the risk of running out of fuel while making long rides far from any fueling stations.
Solid Model
The group chose the Air-Filter for the purpose of its complexity in analysis as well as simplicity in application. The air filter is functional in directing oxygen richer air than ambient air (by filtering out unnecessary particles) to the engine intake valves. During the combustion process, the efficiency of the engine is directly tied to the heat of combustion as well as the pressure ratios. These are also tied to the air intake which is the working fluid for the compression process.
The Carburetor works with the air filter by mixing fuel in the right proportion to avoid engine flooding among other issues. This component works by injecting fuel through a jet and mixing the fuel with air in a venturi effect for high pressure combustion for the power stroke. The choice of solid modelling software was restricted to the member that had the most experience modelling in CAD. Oluwatobi hence recommended Autodesk Inventor (R) as a good choice since he learnt the skill upon that platform.
Engineering Analysis
Problem Statement
Engines with carburetors can experience engine flooding; engine flooding occurs when the fuel-air mixture is too rich to be ignited by the spark plug. In order for the fuel-air mixture to ignite properly, the combination of fuel and air must be below the upper explosive limit and above the lower explosive limit. The question being asked is: What is the maximum and minimum volume of gasoline needed to properly ignite a fuel-air mixture with 5500 mm3 of air?
Diagram of System
Figure 2
Assumptions
- Gasoline is the fuel used
- Upper explosive limit = 7.6%
- Lower explosive limit = 1.4%
- Standard Atmospheric Pressure
Temperature = 20°C
Governing Equations
- Explosive Limits = (VFUEL/VAIR)X100%
Calculations
- Upper Explosive Limit = (VFUEL/5500 mm3)X100%
- VFUEL = (7.6%/100%)X5500 mm3 = 418 mm3
- Lower Explosive Limit = (VFUEL/5500 mm3)X100%
- VFUEL = (1.4%/100%)X5500 mm3 = 77 mm3
Solution Check
If there is 5500 mm3 of air in the carburetor then 418 mm3 and 77 mm3 of gasoline are plausible values for the volume of the fuel.
Discussion
- Based on the figure, the assumptions as follows are good because although they allow for some error, the accuracy of the result is not lost.
- Since we know the dirt bike runs on gasoline we should declare that the fuel used is gasoline which allows us to get specific values for the upper and lower explosive limits. We could have done the calculations using a different fuel and got different values for the upper and lower explosive limits. These values were attained from the website www.engineeringtoolbox.com.
- Using standard atmospheric pressure and 20°C gives us an ideal conditions to calculate find the values for upper and lower explosive limits.
Applications of Engineering Analyses
In the engineering discipline the user input is necessary to continue the design process. The V model is an accepted systematic model for the systems engineering in the Department of Defeense. The lowest configuration (LCIs) items appear at the base of the V in the dual V model of systems engineering which is proven to improve output. The steps that lead to the bottom require user input which int turn requires Engineering Analysis. The FMEA can also be employed in every step of the design process. The level of quality required by the user increases as technology improves. This in turn requires that the safety analysis improves such that the user is satisfied with the product. For example, in general processes, system requirements are allocated down to subsystems from the system “design-to” (i.e., requirements) specification on the left side of the System Element V. Each Subsystem Element V begins at its requirements process, passes its “build-to” (i.e., design) spec up to the system “build-to” spec process, ends at its validation process, and returns the result to the “fabricate, assemble, code” process at the bottom of the System Element V. The subsystem requirements are allocated down to LCIs from the subsystem “design-to” specifications on the left side of the Subsystem Element V. The individual steps require analysis to proceed to the next section. The problem is defined with respect to solution methods as follows.
Bounding and defining problem context
• Solution methods and techniques
• Solution tools
• Strategies for efficient solutions
