Group 10 2011 Gate 2: Product Dissection

Preliminary Project Review

Cause for Corrective Action

The dissection process of our engine was a two-week long ordeal that included planning and execution from our original Gate 1 Work Proposal, as well as situational modifications. The Work Proposal indicated a comfortable time window in which engine dissection would ensue. All work days completed fit in this proposed time windows. Work days were often made a week in advance and were coordinated with another group that was working on the same engine. We formed a good relationship with the other group that enabled us to comfortably agree on terms for our mutual dissection. For both groups, the dissection process was documented as follows: upon the removal of any part or piece of hardware was recorded with a description including the part name, its location and the tool(s) required to remove it.

There were several challenges met during dissection. In several instances, the tool required to remove a part was not available in the Furnas lab. For example, the unfastening of the head bolts called for an 8mm Allen wrench—a substitute is not possible. Ultimately, we found the appropriate Allen wrench in the SAE work room. Additionally, the valve lifters could not be removed without a hand-lapping tool which was neither available in the Furnas lab, the SAE work room, the machine shop, or the local Walmart (despite being offered on their website). This prevented the removal of the valve assembly. A visit to a local autoparts store may yield better results.

Other problems faced were organizational in nature. One more workday was planned, but mistaking a Friday for a Thursday caused us to miss a session of TA office hours. Poor communication is at fault for this mistake. Roles assigned in Gate 1 did not take much influence in the work done. The job of Delineator: “…responsible for the clear depiction of the process and parts involved in this project, creating virtual models of the engine…” was a better description of Benjamin’s role in the dissection process rather than Johnathan’s. Group coordination and communication was monitored primarily by Frank and Nick, rather than Benjamin. However, roles were not forgotten: Frank (Technical Expert) dictated and recorded most of the physical dissection, and Nick (Communication Liaison) was the head editor of the Wiki page, and maintained contact with the instructors and the other group. Adhering to our intended roles better will have made the completion of Gate 2 more efficient as jobs would not have needed careful assigning—they would be assumed for each role.

It should also be noted that an owner’s manual for the Honda CBR600F2 was used for the dissection process. However, let it be understood that it was mainly used to ensure the correct naming of parts for a more accurate dissection description, rather than a crutch for removing components.

Product Dissection

Ease of Disassembly

When dissecting a product as complex as a motorbike engine, it is important to understand the difficulty associated with each step of the dissection process. Some parts cannot removed 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.

Dissection Process

Fuel System

Step	Disassembly Process	Tool(s) Used	Difficulty Rating	Picture
	Air box was already removed from the cylinder head when we received the engine.
1	Remove air cleaning housing cover by unfastening 6 bolts.	10 mm socket drive	2
2	Lift out air filter	By hand	1
3	Separate air box from 4 carburetors by unfastening 6 bolts.	10 mm socket drive	2
4	Remove seal between air box and carburetors.	By hand	1
5	Remove vacuum chamber covers. Include 3 screws and 1 spring per cover.	Phillips-head screwdriver	2
6	Remove diaphragm pistons from each carburetor.	By hand	1
7	Remove fuel intake lines. Each tube was press fitted around a metal line	By hand	2
8	Remove metal casing mounted opposite of the vacuum chamber covers.	Phillips-head screwdriver	2
9	Remove throttle cable.	By hand	1
10	Remove 4 nuts on each side of the carburetor.	6 mm open ended wrench	2
11	Remove carburetor connecting bolts.	By hand	2
12	Unfasten screws keeping springs under tension.	Phillips-head screwdriver	2
13	Separate each carburetor.	By hand	1

Regular maintenance calls for an air filter replacement. Therefore, disassembly up to the carburetors is permitted and intended.

Cylinder Head

Step	Disassembly Process	Tool(s) Used	Difficulty Rating	Picture
14	Remove cam chain tensioner by unfastening two bolts.	8 mm open ended wrench	2
15	Remove 2 cam gears by unfastening 2 bolts on each cam gear.	10 mm open ended wrench	3
16	Pull yellow cam chain tensioner slider out through the top of the cylinder head.	By hand	2
17	Remove intake camshaft holder by unfastening 8 bolts from the holder.	10 mm socket driver	2
18	Lift up intake camshaft to free cam chain from the cam gear.	By hand	1
19	Pull cam chain out of cylinder head.	By hand	1
20	Remove exhaust camshaft holder by unfastening 8 bolts on the holder.	10 mm socket driver	2
21	Remove exhaust cam.	By hand	1
22	Unfasten 10 head bolts.	8 mm Allen wrench	2
23	Unfasten 2 auxiliary bolts holding head to block.	10 mm Allen wrench	2
24	Lift head off of the block.	By hand	1
25	Remove 4 spark plugs.	Needle nose pliers	1
26	Remove radiator hose fitting and thermostat.	8 mm socket driver	2

The cylinder head is largely meant to remain untouched by untrained hands as cam timing is essential to engine performance. The multiple covers separating a user from the camshafts are also an indication of the intended inaccessibility of the cylinder head. However, the spark plugs are regularly replaced and are made accessible without removal of the valve cover—hardly anything needs to be removed to replace the spark plugs.

Lubrication System

Step	Disassembly Process	Tool(s) Used	Difficulty Rating	Picture
27	Remove oil pump.	By hand	1
28	Remove starter motor by unfastening 2 bolts and a cable clip.	10 mm socket driver	3
29	Remove oil pan by unfastening 14 bolts.	10 mm socket driver	2
30	Remove oil filter, which is press fitted into a slot.	By hand	1

Given that an oil change is a routine maintenance procedure, certain components of this subsystem are intended to be disassembled. A press-fitted disposable oil filter is also an indication that disassembly is intended.

Clutch

Step	Disassembly Process	Tool(s) Used	Difficulty Rating	Picture
31	Remove alternator cover by unfastening 10 bolts.	10 mm socket driver	2
32	Remove right crankcase cover by unfastening 9 bolts.	10 mm socket driver	2
33	Remove clutch lifter plate by unfastening 4 bolts.	10 mm socket driver	2
34	Remove the 4 clutch springs and the clutch center lock nut.	By hand	1
35	Remove 8 clutch disks, 8 clutch plates, clutch pressure plate, and thrust washer.	By hand	4
37	Remove clutch outer guide.	Two needle nose pliers being pulled simultaneously	4
38	Remove clutch outer.	By hand	1
39	Remove oil pump sprocket by unfastening the center bolt.	12 mm socket driver	2

The complexity of disassembly and the enclosure by a metal housing and 9 bolts is a clear indication that these components are not meant to be dissected by an untrained user. Also, since there are many components whose placement in relation to one another is crucial to product functionality, untrained tampering could be devastating to a previously functioning product.

Pistons and Crankshaft

Step	Disassembly Process	Tool(s) Used	Difficulty Rating	Picture
40	Remove upper crank case by unfastening 24 bolts.	8 and 10 mm socket drives	2
41	Remove 4 connecting rod bearing caps by unfastening 8 bolts.	10 mm socket driver	2
42	Lift crankshaft off of the block.	By hand	2
43	Remove pistons by inverting engine block and pulling them out.	By hand	3	File:Photo0125.jpg

None of these components are meant to be disassembled by anyone other than a trained mechanic. They are intentionally inaccessible, as many other components need to be removed before these are accessed. Some components are connected via specialized equipment such as a press, which an average user would not own or have the experience to operate.

Transmission

Step	Disassembly Process	Tool(s) Used	Difficulty Rating	Picture
44	Remove two shafts with gears.	By hand	1
45	Pull each gear off of the shaft by unfastening snap rings.	By hand and needle nose pliers.	4
46	Remove shift fork shaft by removing center bolt.	10 mm socket	2
47	Pull out 3 shift forks.	By hand	1
48	Remove shift drum bearing set plate by unfastening 2 bolts.	10 mm socket driver	2
49	Remove shifter cam by unfastening bolt.	6 mm Allen wrench	2
50	Push out shift drum bearing.	By hand	2
51	Push out shift drum.	By hand	2
52	Remove gear shift spindle assembly by removing bolt.	5 mm Allen wrench	2

Due to their general inaccessibility and difficulty of removal, it is clear that these components are not intended to be disassembled by untrained hands.Also, since there are many components whose placement in relation to one another is crucial to product functionality, untrained tampering could be devastating to a previously functioning product.

Connection of Subsystems

Subsystem Connections

Chart 1

Chart 1 depicts the physical connections present between the subsystems. As most of the subsystems are enclosed within the crankcase and cylinder head, or attached directly to the crankcase, most of the subsystems share a housing. Aside from that, there are chains to transfer mechanical energy, along with direct connections to rotating shafts, and pipes to allow for the flow of materials. The cams are a special case in that they make a temporary connection to the valve heads to control the opening and closing of exhaust and intake valves.

Subsystem Flows

Chart2

Chart 2 depicts the flow materials, energy, and signal throughout the subsystems of the engine. The placement of these subsystems is very dependent on the flows through them. If the cylinder head was not directly above the piston, there would be little control over where intake and exhaust gases were within the engine. Similarly, the transmission and alternator are very close to the crankshaft, allowing for fewer connections required to transfer energy, so the transfer of energy is more efficient. Similarly, the pistons are connected directly to the crankshaft to avoid any unnecessary connections that would decrease the efficiency of energy transfer. This arrangement of subsystems is very complex and the subsystems are placed where they are to reduce efficiency loss and to allow for a more compact engine.

Adjacent Subsystems

Not all subsystems can be put in a position to make the engine most compact. The air intake must be on the outside of the engine to receive air The intake and exhaust cams cannot be adjacent to the crankshaft because the cams must be near the piston head and the crankshaft must be connected to the base of the piston. The alternator cannot be adjacent to the cylinder head or carburetor, either, as any electrical discharge could cause premature ignition of fuel in these systems. Aside from these limitations, the placement of subsystems is dictated by reducing the travel of flows to increase efficiency and decreasing overall size of the engine.

The 4 Factors of Design Influence

Societal

Motorbikes are typically used in warm weather, so the design of this motorcycle engine has traits that make it more specific to use in certain geographic areas or for use at certain times of the year. Honda also knows that some people are die-hard riders and will ride in all conditions, even living in places with snowy winters. Some will take their bike out if there is a day where there are subzero temperatures outside, but the sun is out and the roads are plowed. Honda, realizing this, designed this engine to be fully functional in all weather conditions. Honda has been known for years for making some of the most long-lasting, reliable, and efficient engines on the market. This engine was no exception. The CBR600 F2, an updated version of a previous Honda model, was a top performance motorcycle of its time due to Honda’s excellence in engine development. [1]

Global

Since Honda is a Japanese company, the engine uses metric sized nuts, bolts, etc. This is not a problem because the SI measurement system is the most commonly used measurement system worldwide. Metric sized tools are easily obtained even in English-unit-using areas, giving Americans full availability to work on this engine. SI units are frequently used by engineers even in places where English units are common.

Economic

In the early 90’s America’s economy was at one of its highest points in the past few decades. People were financially ready to make extra purchases at the time of this motorcycle’s release. This fact proves that money was available to be spent, giving Honda the opportunity to make their motorcycle with pure performance in mind. They were able to set their aim at creating a powerful engine, without taking much consideration into cost. [2]

Environmental

Global warming plays a top factor in the design of anything in our world today. Although global warming is an enormous a factor now, it was not considered an issue at the time of this engine’s release because it simply was not publicly addressed until 1997. Since the idea of pollution control was not publicly addressed, motor designers did not put first priority to fuel efficiency or the release of pollutants. [3]

References

[1]http://cbrjunkie.com/600f-(hurricane)-f2-f3/cbr600f2-super-review-(the-cbr-comes-of-age)/

[2]http://www.brookings.edu/papers/2001/1102useconomics_orszag.aspx

[3]http://www.benefits-of-recycling.com/whendidglobalwarmingstart.html