Group 5 - Motorized Scooter (Goped)/Gate 2

Gate 2

Project Management: Preliminary Project Review

Cause for Corrective Action

Overall, the proposed plan worked well, however there were some complications that led to the group having to rethink our process and come up with new solutions. Our plan was to “work from the front of the scooter to the back, [while] separating parts, and taking dimensions”. The first issue that arose was the removal of the front fork and steering assembly. Without first being able to assess the necessary tools that would be provided for us in the workshop, we found that the assemblies would not be able to be removed. This was due to the fact there was not a bolt holding the fork and t-bar together, but rather a soft plastic punch. Our group was unable to remove the punch because it would have required professional disassembly and reassembly to render the product usable once again. After moving on from our issue with the front fork, disassembly closely followed the plan without issue. The next set of difficulties we encountered occurred while attempting to remove the spindle. Without prior knowledge of the relationship between the spindle and piston, the group could have run into issues with creating enough torque to remove the spindle. Our technical expert had the idea to hold the piston in place by inserting a thick piece of cord into the spark plug hole, preventing the piston from completing its cycle while the spindle rotated.

Figure 2.1- Spindle Bolt Failure

The next area of difficulty dealt with the removal of the flywheel. Our original plan was to use the spindle bolt to create a wedge and pull off the flywheel. The spindle bolt ended up being too short to make full contact with the base and was unable to provide leverage. Our next idea was to use a “flywheel puller”, which is a device that puts even pressure around the flywheel and pulls it out. Unfortunately, due to the small size of the engine, it was unable to get a proper grasp onto the flywheel and was not useful. Instead, the group came up with the idea to use a long, threaded bolt to push the flywheel off the crankshaft. Using a M6 hex-bolt, the flywheel then was removed with general ease. The final issue that the group encountered was a stripped Phillips head screw of the motor mount. After numerous attempts to remove the screw properly, we consulted with the supervising machinist in the Jarvis machine shop. The machinist advised us to use vice-grips on the head of the screw and go a half-turn at a time. In the future, the complications that we encountered can be avoided with relative ease. For example, when trying to remove the flywheel from the crankshaft, we tried several techniques before finding one that worked (i.e., the M6 hex-bolt method). However, now that we have gone through the trial and error process, we know the best and fastest way to remove the flywheel. Another way that we can over come difficulties in the future is to replace the stripped Phillips head engine mounting bolts with hex-head bolts. This will make fore quicker and easier removal due to the fact that they will be non-stripped, and that it is easier to apply usable leverage with a wrench than a screwdriver.

Product Archaeology: Product Dissection

Before assessing the ease of disassembling our product, it is necessary to create a scale in order to properly gauge level of difficulty for each step. To do this, we will employ a scale of 1 to 5 tailored to our specific application:

• 1: Extremely Simple: Requires little to no technical knowledge and is performed with ease; intuitive
• 2: Relatively Simple: Slightly more effort required but still little to no technical knowledge required
• 3: Moderate Difficulty: Some technical knowledge required, may take some effort to perform
• 4: Difficult: Requires technical know how, component may need some coercion to remove
• 5: Very Difficult: More technical than other components, may require alternative methods to go about process (brainstorming to perform process with an unconventional method).

As a whole, the disassembly of the Goped would likely rate at a 2. Although our team reached some difficulty along the way due to the lack of the proper tools required, nearly every subsystem of the Goped could have been taken apart with a socket wrench, an allen wrench, or a screwdriver.

Steps to Dissect the Product

#	Step	Tool Used	Part Removed	Process	Difficulty	Figure
1	Remove Deck	5/32" Hex Key	Goped Deck (4 Hex Screws, Bushings)	Used the hex key to remove the screws, then pulled off the deck and removed the bushings. This part is intended to be removed in order to gain access to other parts for service.	2
2	Remove Front Axle Bolt	14mm Socket Wrench	Front Axle Bolt, Front Wheel, Lock Washer	Removed the lock washer on the bolt using the socket wrench and pulled bolt out of the fitting. This part is meant to be disassembled in order to gain access to the front wheel.	1
3	Remove Bearings from Front Wheel	Hex Key (any size)	Front Wheel Bearings, Spacer	Using the hex key as leverage, the bearings can simply be popped out. There is no specific tool for this task. This part is meant to be disassembled in order to gain access to the front wheel.	1
4	Disconnect Front Brake Assembly	10mm Socket Wrench	N/A	Due to the location of the crimps holding on the brake cable, we were only able to use the socket wrench to disconnect the cable from the physical brake. The cable is still attached to the handle bar. The cable is not meant to be removed as it has a permanent cap on the end of it.	2
5	Remove Front Brake	10mm Socket Wrench	Brake Assembly	Used the same 10mm socket wrench to remove the brake from the frame. This requires the removal of one lock washer. The brakes are meant to be disassembled so that they can be serviced.	2
6	Removal of Throttle and Brake Levers	Phillips Head Screwdriver	Throttle, Brake Levers	Removed two screws to take levers off of handle bars. These parts are designed to be removed in order to tighten the cables that are attached to them.	1
7	Removal of Kill Switch	Hands	Kill Switch	Unscrewed kill switch with fingers and pulled out of socket. This part is designed to be removed so that it can be serviced in the event of the failure of the switch or the wire.	1
8	Removal of Handle Bar	Punch Tool	N/A	This part is not meant to be disassembled due to the punch connection it has. Disassembly would result in the inability to reassemble.	5
9	Remove Kick Stand	Needle Nose Pliers, Rubber Mallet	Kick Stand	Bent the spring so it would be able to slide out of its position. Then once the spring was out, used a rubber mallet to tap the kick stand out of its socket. This part is designed to be removed as not all users may prefer to use the kickstand.	3
10	Remove Fuel Tank	10mm Socket Wrench	3 bolts, Fuel Tank	Used the Socket Wrench to unscrew the bolts and remove the fuel tank. The tank at this point is still connected to the Goped via the fuel lines. This is meant to be removed for the sake of serviceability, as it may be necessary to drain the gas tank.	2
11	Disconnect Fuel Lines	Needle Nose Pliers	Fuel Lines	Used the pliers to pull of the lines from the fuel intake ports. The fuel lines are intended to be removed in case of clogging.	1
12	Remove Rear Wheel	Hands	Quick Release Bolt, Wing Nut, Rear Wheel	Loosened the quick release by hand and pulled the bolt out from the wheel. Then removed the wheel. The rear wheel is intended to be disassembled in case of failure, and is necessary to do so in order to service the engine.	2
13	Remove Bearings from Rear Wheel	Hex Key (any size)	Rear Wheel Bearings, Spacer	Repeated same procedure as with the removal of the front wheel bearings. These are designed to be removed so that they can eventually be replaced.	1
14	Remove Spark Plug	3/4" Socket Wrench	Spark Plug	Unscrewed spark plug from its socket and removed. The spark plug is intended to be removed so that it can be easily serviced or replaced.	1
15	Immobilize Piston	Thick Cord, 5mm hex key	N/A	Inserted Cord into the spark plug hole and pushed in with the hex key in order to stop the piston from moving. This would allow for the spindle to be manipulated and would allow for proper leverage to remove the spindle.	3
16	Remove Spindle	Hex Key, Hands	Spindle	Removed spindle bolt and pulled out spindle by hand. The spindle is intended to be removed in order to service the engine. Additionally, it is a common aftermarket modification to install an upgraded spindle.	2
17	Disassemble Intake	Hands	Intake Cover, Filters, Metal Grates	Unlatched the cover and removed the two foam filters followed by the metal grates. This allowed for access to the throttle assembly. The air filter is intended to be removed, as this step is necessary to service the filter itself, the carburetor, and the engine.	2
18	Remove Intake Casing	Phillips Head Screwdriver	Intake Casing	Unscrewed the intake casing and removed, allowing direct access to the throttle assembly. Removal of the intake is necessary and intended, in order to service the carburetor and engine.	1
19	Remove Throttle Assembly	Hands	Throttle Assembly	The throttle assembly was only bolted on using the screws that were also holding onto the intake casing. This allowed for the throttle assembly to be simply removed. This part is intended to be removed in order to gain access to the carburetor and engine.	1
20	Remove Intake Manifold	Phillips Head Screwdriver	Intake Manifold	Used screwdriver to remove two screws that held in the manifold. Then removed manifold by hand. This part is intended to be removed in order to gain access to the carburetor and engine.	2
21	Remove Flywheel Cover	3mm Hex Key	Fly Wheel Cover	Used hex key to remove 4 bolts that held the cover in place. Then removed cover. Removal of the flywheel cover is intended in order to gain access to the flywheel, magneto, and engine, for service.	2
22	Remove Flywheel Nut	12mm Socket Wrench	Fly Wheel Nut	Unscrewed the nut in order to allow for the removal of the flywheel. The removal of this part is necessary, and intended, in order to gain access to the engine.	1
23	Remove Engine Cowl	Hands	Engine Cowl	Pulled off the cowl by hand. Required no tools. This is intended so that the engine can be serviced.	2
24	Remove Magneto	3mm Hex Key	Magneto	Remove 2 bolts to allow for the removal of the magneto. Pull out by hand. Disassembly of the magneto is intended so that the engine can be serviced.	2
25	Remove Flywheel	M6 Hex Bolt, 10mm Socket Wrench	Fly Wheel	Used the M6 Bolt as a wedge to push the flywheel off of the crankshaft. This was finally performed after several complications. The flywheel is intended to be removed in order to gain access to the engine.	5
26	Remove Muffler	4mm Hex Key	Muffler	Unscrewed the muffler using the hex key and removed by hand. This part is intended to be disassembled so that the engine can be accessed in order to serviced.	1
27	Remove Engine From Frame	Phillips Head Screwdriver, Vice Grips	Engine	The engine was held on by 4 phillips head screws. One screw was heavily stripped and a vice grip was used to gain proper leverage to unscrew it. The engine is meant to be removed from the frame so that the internal parts can be serviced.	4
28	Remove the Cylinder Head	Allen Key	Cylinder Head	Used allen key to remove 4 bolts. The head then was able to be pulled straight off. The cylinder head is intended to be removed so that the cylinder and piston can be serviced.	2
29	Split the Case	Allen Key	N/A	Removing another 4 bolts using an allen key, the case was able to be pulled apart. The engine case is meant to be disassembled so that the inside of the case can be refinished and the crankshaft can be serviced or replaced if necessary, and the piston can be removed from the crankshaft.	2

---

Connection of Subsystems

Nearly any mechanical system that is engineered will be comprised of smaller subsystems that will need to be connected to each. How each of these subsystems interacts with each other can be extremely different, and designing a way of doing so is an engineering process within itself. Some of the ways that components can be connected include physically, by signal, by mass, or by energy. The Goped's subsystems include the following: the engine, the brake, the frame, and the steering.

The most complicated of the Goped’s subsystems is its power source: the small internal combustion engine mounted in its rear. In order to function, the engine requires air, fuel, and oil. These masses are combined in the carburetor, and are then injected into the combustion chamber, where it is compressed into a combustible mixture due to the upward propulsion of the piston. While the fuel delivery and compression is taking place, the process of ignition begins outside of the engine case with the rotation of the flywheel. This rotation interacts with the magneto, which creates the proper timing and necessary electric signal to send electricity through the spark plug. This electrical signal forces the air and fuel mixture to combust, therefore moving the piston to the bottom of the cylinder. Then, the final part of the engines combustion cycle takes place, which to rid itself of exhaust gasses. While this cycle is taking place, the crankshaft is rotating along its axis due to its physical

Figure 2.2: Zenoah G23LH Engine

connection to the piston. The rear wheel, which is physically connected to the crankshaft, then exerts torque against the ground in order to propel the Goped.

To slow down the Goped, the engineers who designed it employed a rim brake design, similar to what is seen on many bicycles. The brake’s main components are a single pivot, side-pull caliper, the brake lever (both of which are mounted to the frame with fasteners), and the brake cable. The rider sends a signal and energy into the brake lever to activate the braking system. This results in a tension in the brake line, which simultaneously signals the caliper to squeeze closed, and provides the energy to do so. When the caliper closes, it applies pressure to the front wheel in order to slow it down.

The braking system utilizes a hand lever to active the caliper. This is an advantageous method of implementation which leads to positive societal impacts. For example, in order for the alternative, a foot brake, to work more effort is required by the user to operate. This is because throw off the user’s balance which can be dangerous. Moreover, the deck has strips of grip tape on it which could make moving the user’s foot along the board more difficult. This could impede the user’s ability to stop in the event of an emergency. From a performance aspect, a foot pedal is also inferior to a hand brake in that its mounting location on the board could potentially lead to the brake cable becoming twisted around the T-bar. Economically, this system is better than its only logical alternative which is a drum brake system because drum brakes involve more mechanical parts and movement. This would increase the manufacturing and purchase costs.

Figure 2.3: The Goped's Brake Caliper

Steering the Goped is also much like a bicycle. The frame, to which the handlebars are attached, passes through an outer pipe with bearings inside it, which keeps the frame aligned when the handlebars are turned. The turning of the handlebars is a result of human signal and energy, much like with the brake lever. The force exerted from the rider results in an unbalanced moment, which steers the Goped.

The handlebar, which creates the cross in the T-bar structure, is connected to the frame by a set of braces holding the bar in place while it goes through a bearing that is connected to the frame. This system of connections provides a stable structure so that the user can balance himself while riding the Goped, while simultaneously providing an intuitive steering system. This implied simplicity results in a higher level of safety in comparison to any alternative methods. Also, directly connecting the steering system to the wheel vial physical connection is the least expensive way to implement a steering system on the Goped.

The fourth subsystem of the Goped is the frame. The user interacts with the frame when he stands on the deck, which is secured to the frame by a set of physical fasteners. This load that the rider applies to the deck results in support reaction by the frame, thereby provide the user with a safe and stable ride. The ride is made more comfortable with the aid of bushings or dampeners which reduce vibration. Additionally, the frame provides an identical function where ever all other subsystems are connected to it. All other subsystems are mounted and connected to the frame. They are connected as such because the frame is designed to provide a stable support for each component where they can easily and safely carry out their function. For example, the engine is mounted on the rear of the frame.

From a societal standpoint, this allows the highest level of safety for the user, as there is a significantly smaller chance that any piece engine would touch the user during operation. Additionally, the mounting position creates a low center of gravity which provides better stability. Economically, this is also the most cost effective way to mount the engine. This is because mounting the engine in the back requires the least amount of parts due to its direct connection to the drive wheel. This eliminates the need for a drivetrain. This setup provides the best performance and ease of use.