Group 10 2011 Gate 4: Product Explanation

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Critical Project Review

Cause for Corrective Action

On this particular gate we faced challenges due to the fact that we had time off for break and each group member went home. This meant that we did not have as much time to work on the engine as on previous gates. To compensate for the lost time, tasks were delegated to each group member to complete during break before classes resumed. These included design revisions and formatting the wiki page so that once the engine was completely reassembled, all that needed to be done was copy the information over to the page. Then as soon as all of the group had returned to school, we immediately began the reassembly process at the first available office hours. This ensured that there would be enough time to thoroughly document the reassembly process. We are still having some communication issues do the travelling of some members during weekends which we plan an addressing in our next meeting. We intend to reinforce out initial guidelines of the project planning in order to make sure that those who are not at school when work needs to be completed have the necessary tools to do so.

Product Explanation

Ease Of Reassembly

When reassembling a product as complex as a motorbike engine, it is important to understand the difficulty associated with each step of the reassembly process. Some parts cannot replaced intuitively and require specialized tools or procedures that must be followed to avoid permanent damage or failure. Therefore, a scale has been devised relatively by comparing an example of each level of difficulty.

Value Rating Case
1 Very easy Tools not typically needed.
2 Easy Basic tools required, but in a basic use.
3 Intermediate Basic tools required, physically hard to complete.
4 Moderately hard Tools necessary, physically hard to complete, and weight of error is greater.
5 Hard Complex tools required, physically difficult to complete, experience

most likely required, and errors are irreversible.

Product Reassembly

Lower Crankcase

Process Tool(s) Used Number of Fasteners Difficulty Rating Picture
Press oil filter back into the lower crankcase. By Hand 1
Fasten oil pan to lower crankcase. 10 mm Socket Drive 14 Bolts 2
Slip shifter drum into lower crankcase, By Hand 1
Press shift drum bearing onto shift drum. By Hand, finished with Rubber Mallet 3
Slide shift fork shaft into lower crankcase while positioning the right, center, and left shift forks on the shaft. By Hand 1
Fasten both shift drum bearing plates to lower crankcase. 10 mm Socket Drive 2 Bolts 2
Insert gear shift spindle into the lower crankcase. By Hand 1
Attach gear shift pedal link to gear shift spindle. By Hand, finish with Rubber Mallet 3
Push shifter cam onto shift drum bearing. By Hand 1
Fasten shifter cam to to shift drum bearing. 6 mm Allen Wrench 1 Bolt 2
Place stopper arm over the shifter cam and fasten to lower crankcase. Flathead Screwdriver and 10 mm Socket Drive 1 Bolt 3
Place main shaft and counter shaft into lower crankcase, carefully aligning shifter forks. By Hand 3
Fasten oil pump to the lower crank case. 10 mm Socket Drive 3 Bolts 2
IMG 0804.jpg
Fasten oil pump sprocket onto oil pump. 10 mm Socket Drive 1 Bolt 2
IMG 0809.jpg
Place clutch outer onto mainshaft. By Hand 1
IMG 0820.jpg
Press clutch bearing onto main gear shaft. By Hand 1
IMG 0821.jpg
Slide clutch pressure plate through clutch discs. By Hand 1
IMG 0811.jpg
Slide disc and pressure plate assembly into clutch outer. By Hand 1
IMG 0822.jpg
Slide clutch springs onto clutch pressure plate. By Hand 1
IMG 0823.jpg
Slide clutch center lock nut onto the main shaft. By Hand 1
IMG 0824.jpg
Fasten clutch lifter plate to clutch pressure plate. 10 mm Socket Drive 4 Bolts 3
IMG 0827.jpg

Upper Crankcase

Process Tool(s) Used Number of Fasteners Difficulty Rating Picture
Slot pistons into each cylinder in the upper crankcase. By Hand 1
IMG 0835.jpg
Place crankshaft onto upper crankcase. By Hand 1
IMG 0836.jpg
Fasten connecting rod bearing caps onto connecting rods. 10 mm Socket Drive 8 Nuts 2
IMG 0838.jpg
Place assembled upper crankcase onto assembled lower crankcase. By Hand 1
IMG 0840.jpg
Fasten upper crankcase to lower crankcase. 10 mm Socket Drive 2 Bolts 2
IMG 0845.jpg
Slide clutch lifter arm into crankcase cover. By Hand 1
IMG 0849.jpg
Fasten right crankcase cover onto crankcase. 10 mm Socket Drive 10 Bolts 2
IMG 0846.jpg
Push timing sprocket onto crankshaft. By Hand 1
IMG 0850.jpg

Cylinder Head

Process Tool(s) Used Number of Fasteners Difficulty Rating Picture
Lower cylinder head onto upper crankcase. By Hand 1
IMG 0851.jpg
Fasten cylinder head to upper crankcase. 10 mm Socket Drive and 11 mm Allen Wrench 12 Bolts 2
IMG 0857.jpg
Position timing chain on crankshaft. By Hand 1
IMG 0852.jpg
Place camshafts into cylinder head and underneath timing chain. By Hand 1
IMG 0853.jpg
Fasten timing chain sprocket onto crankshaft. 10 mm Socket Driver 1 Bolt 2
IMG 0854.jpg
Fasten drive sprocket cover cover to crankcase. 10 mm Socket Driver 8 Bolts 2
IMG 0855.jpg
Fasten cam chain tensioner to upper crankcase. 10 mm Socket Driver 2 Bolts 2
IMG 0856.jpg
Slot spark plugs into cylinder head. By Hand 1
IMG 0859.jpg
Fasten camshaft covers to cylinder head. 10 mm Socket Driver 20 bolts 2
IMG 0861.jpg
Place valve cover and gasket onto cylinder head. By Hand 1
IMG 0864.jpg
Fasten valve cover to cylinder head. 10 mm Socket Driver 6 Bolts 2
IMG 0865.jpg
Place thermostat into thermostat housing. By Hand 1
IMG 0866.jpg
Fasten thermostat housing cover to cylinder head. 8 mm Socket Driver 3 Bolts 2
IMG 0867.jpg

Peripherals and Intake System

Process Tool(s) Used Number of Fasteners Difficulty Rating Picture
Fasten starter motor to lower crankcase. 8 mm Socket Driver 2 Bolts 2
IMG 0869.jpg
Fasten alternator to lower crankcase. 10 mm Socket Driver 9 Bolts 2
Fasten coolant pipe to upper crankcase. 10 mm Socket Driver 2 Bolts 2
IMG 0870.jpg
Insert Diaphragm/Vacuum piston into each carburetor. By Hand 1
IMG 0815.jpg
Fasten vacuum chamber covers to each carburetor. Philips-Head Screw Driver 12 Screws 2
IMG 0817.jpg
Press all four carburetors together. By Hand 1
IMG 0818.jpg
Fasten carburetors to air chamber. Philips-Head Screwdriver 8 Screws 2
IMG 0844.jpg
Fasten carburetor assembly to air cleaner base. Philips-Head Screwdriver 3 Screws 2
IMG 0848.jpg
Fasten air cleaner housing cover to air cleaner base. Philips-Head Screwdriver 7 Screws 2
Attach air-box assembly to cylinder head. By Hand 1

Original Product Assembly

The CBR600F2 would have been originally assembled at one of Honda\'s plants utilizing a combination of mechanized assembly lines and hands on human operators. The assembly would be similar to our process with respect to the order that each subsystem is completed. The transmission would be completed first, with machines to press fit the gears onto their respective shafts. Workers would then place the gears and crankshaft into the upper crankcase while the rest of the transmission is being assembled in the lower crankcase. When each crankcase is completed, they are bolted together on the assembly line and are fed the pistons and connecting rods. Machines would be used to press fit the piston pin and piston rings onto the piston. At this point the finished clutch assembly would be mounted to the crankshaft and then the finished cylinder head assembly would be mounted to the crankcase. The cylinder head would be assembled separately due to the complexity, number, and tolerances of the parts associated. This also applies to the carburetors, which would be mounted as an assembly to the cylinder head. Finally, the airbox would be mounted onto the carburetors and the engine would be complete and ready for installation on the frame of the bike.

Reassembly vs. Disassembly

Almost all of the steps taken to reassemble the CBR600f2 engine are the same as the steps taken in disassembly with a few exceptions. Most of the steps simply require the user to reverse the disassembly process by fastening the necessary bolts, nuts, and screws, or pressing the part back into place instead of pulling it out. However, in our particular case we took some steps in reassembling the upper and lower crankcases that were not identical to the dissection process. Instead of working from the upper crankcase down to the lower crankcase, we began by assembling the transmission in the lower crankcase as per instructions out of the service manual. Due to this reversal of mounting order, the two crankcases needed to be assembled separately and then mated together. This proved somewhat difficult since the pistons needed to be held into the cylinders while the entire assembly was lifted and placed onto the lower crankcase. Complications also arose in attaching the connecting rods to the crankshaft due to the pistons already being inside the cylinders. This meant that we had limited control over the movement of the connecting rods, which ultimately required much force to cooperate. From this experience we deduced that in the future, reassembly should more closely mimic disassembly in that all of the components of the transmission should be placed back into the upper crankcase initially.

Design Revisions

Mild Hybrid

In vehicles today, hybrid drivetrains are used to both increase efficiency and increase performance. For this engine, the alternator could be replaced with a brushless DC electric motor of similar dimensions connected to the crankshaft. This would create a series hybrid engine, where the electric motor could assist the gasoline engine by providing torque at low speeds, improving acceleration and reducing the power needed from the gasoline engine to achieve acceptable acceleration values. A brushless DC motor with a diameter of 6.5 cm, similar in size to the alternator, could provide about 1 N-m of torque at low speed*, compared to the maximum torque of the gasoline engine of 64 N-m at a much higher engine speed of 10500 rpm[1]. Also, the electric motor would allow the gasoline engine to turn off when the motorcycle is stopped, and would smoothly restart the engine when needed to move. These two improvements would lead to the motorcycle using less fuel to accomplish the same tasks, reducing emissions, an environmental factor, and reducing the cost of operation, an economic factor.

The electric motor would also be performing the role of the alternator by generating electricity. At higher speeds when the electric motor is less effective, it could be generating electricity from the movement of the crankshaft. Also, the electric motor would assist with braking and generate electricity in this manner as well. However, to perform this role effectively, the motorcycle would need increased power storage capabilities, so more efficient batteries such as lithium ion batteries would be needed to store a sufficient amount of power in a similar space as the normal motorcycle battery. This would increase cost of production of the vehicle which would have to be offset by the increased performance or this improvement would not be economically viable.

Brushless DC electric motors are also complex and need computers to regulate them. When this engine was in use in the early 1990s, such complex electronic control units were very expensive and not very accessible or reliable. However, modern computers for engine regulation are sufficiently complex and would be relatively inexpensive. The cost of this required modification should then be greatly offset by the reduced cost of operation. Because the electric motor would be similar in size to the alternator, and placed in a similar position, the user should see little or no cosmetic difference in the overall engine. However, motorcycles already have much higher fuel economies than conventional cars, so consumers may not be drawn toward a more efficient motorcycle if the cost is too much of an increase over other motorcycles of similar performance. Also, motorcycles are very good at squeezing through traffic, and so they are not stopped as frequently as conventional cars, so consumers may not see the benefit of having an engine that turns off when stopped. Overall, this improvement would only be viable if the creator was able to market it in a way that convinced consumers that the performance improvements would benefit them greatly in certain common situations.

Flex-Fuel Capability

One type of flex-fuel vehicle is a vehicle designed to run off of both gasoline in traditional mixtures of up to 20% ethanol, and with gasoline-ethanol mixtures containing between 85% and 100% ethanol, depending on the country. In the United States, particularly in the mid-west where corn is grown, gasoline-ethanol mixtures of 85% ethanol, also known as E85, can be as much as 15% less expensive than traditional gasoline, containing about 10-20% ethanol[2]. In Brazil, the difference is even greater, as gasoline is imported and highly taxed while ethanol is produced from sugar cane grown in the country. For these reasons, it would be of great economic benefit for the engine of a motorcycle to be able to run on mixtures containing high amounts of ethanol.

The properties of ethanol make this slightly more limiting. Ethanol has a slightly lower energy density than gasoline, so if the price difference in fuels is small, an amount of gasoline may still provide more travel distance than an amount of E85 of the same price. In the United States, ethanol fuel is not as widely marketed outside of the mid-west, either, so most consumers would not see a benefit. However, the cost of converting an engine to be able to run on ethanol is quite low, and as this would allow marketing to much larger audiences in certain regions, such as Brazil, it would be quite beneficial to the producer of the motorcycle to consider this global factor.

Because ethanol is more corrosive than gasoline to certain engine components, specifically those made of rubber, steps must be taken to allow an engine to run off of higher percentage mixtures of ethanol. Also, ethanol can be compressed much more than gasoline before it begins to auto-ignite, so if the engine has a good computer control unit and flexible compression ratios, then the losses due to lower energy density are off-set by the higher and more efficient compression ratios. However, as this engine still uses carburetors and is not as advanced as modern engines when it comes to computer control, it will be assumed that the increased cost of changing how the engine operates on different fuels is too great to consider. However, even without those changes, conversion to allow the vehicle to run on higher percentage ethanol mixtures would still benefit the user in that in some areas the fuel is much cheaper, an economic factor, and the ethanol is produced from plants and not drilled from beneath the earth, so there is a much lower net release of carbon into the atmosphere, an environmental factor. Such changes can be accomplished for only a few hundred dollars*, replacing seals and allowing the engine to intake more fuel, a cost greatly offset by allowing for marketing the motorcycle as more environmentally friendly and by opening up new markets[3].

Variable Valve Timing

Generally, valve timing is any mechanism or method that can alter the shape or timing of a valve lift event within an internal combustion engine. More specifically, Honda implemented their own system of valve timing called VTEC, which stands for Variable Valve Timing Engine Control. The purpose of VTEC is to improve the volumetric efficiency of a four-stroke internal combustion engine by using two camshaft profiles and electronically selecting between the profiles.

The VTEC system provides the engine with multiple camshaft profiles optimized for both low and high RPM operations. In basic form, the single cam profile of a conventional engine is replaced with two profiles: one optimized for low-RPM stability and fuel efficiency, and the other designed to maximize high-RPM power output. It provides improved engine characteristics with respect to all of the design factors. The CBR600F2 was not originally developed with variable valve timing as it had not been implemented on motorcycle until 1999. However, VTEC would be a smart system to add to the engine due to its improved power, fuel economy, and emissions. Societal benefits include increased comfort for the user, as idle characteristics would be improved as well as low end torque. Also, power would increase while broadening the effective power range. This results in more usable power for the rider with a greater top end speed.

Environmental concerns would be met, as the different profiles used on the camshaft would optimize fuel consumption. The most efficient amount of air and fuel for every range of engine speed is utilized resulting in the most complete burn possible. Thus minimizing harmful emissions and fuel needed for each cycle.

There would be an added cost due to the extra parts an assembly, as well as the need to use an ECU. However, even the simplest use of valve timing would bring improvements that would justify these increases. The marketing used to sell the bike could highlight the great efficiency of the engine which could ultimately result on more potential buyers[4].