Difference between revisions of "Group 31 - Honda Engine"

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==Disassembly==
 
==Disassembly==

Latest revision as of 13:38, 16 December 2009

Right side of Engine
Left side of Engine


MEMBERS:

George Alessi

Dave Chappell

Shayne Mckay

Rajdeep Roy


Contents

Executive Summary

The members of this group are students enrolled at the University at Buffalo. They are assigned to this group and this project by the requirements of the course MAE 277, Introduction to Mechanical Engineering, taught by Erich Devendorf.

The project assigned to Group 31 is to dissect, analyze, and reassemble the combustion components of an engine. The transmission components of this engine are to be dissected and analyzed by members of group 19. Research done by George Alessi based on engine numbers found on the engine prior to dissection has revealed the engine to be a 1994 Honda CBR 600 F motorbike engine.

Knowledge of engine operation and construction varies widely in this group. However through this project, the workings of this engine are to be explored and described in a way that would allow for repetition based solely on this report. This wiki page will outline the intended plan, the actual steps taken to dissect and reassemble the engine, and the analysis of Group 31.


Front of Engine
Back of Engine



The top of the engine with the valve cover, the camshaft covers and the chain taken off and the camshafts resting in place.
Top of engine with valve/camshaft covers off as well as the camshafts removed.
Intake side of engine with the valve/camshaft covers removed as well as the intake components and the transmission.
Block rotated view with Valve Cover Off
Bottom of engine with crank shaft, pistons and rods still assembled.
Process of removing the crankshaft.
Crank Shaft out of the engine separate from the rods and pistons.
Showing the bottom of the pistons. This is the top section of the bottom half of the block.
Top of engine with pistons all the way out.
Intake side of four Carburetors.
Main jet removal.


The Proposed project of group 31 is outlined below in the following links.

Work Proposal Group 31

Management Proposal Group 31

Initial Project Assessment Group 31

Planned Project Work Schedule Group 31

Causes For Corrective Action

Disassembly

DIFFICULTY SCALE

1. Light lifting force.

2. Coordinated lifting force.

3. Use of simple tools.

4. Use of tools and coordinated lifting force.

5. Assorted tool use and careful application of force and spring removal.




>Prior to dissection, the other group assigned to this engine had already disassembled much of the outer components. The components that were already removed were: the valve cover, the camshaft covers, the drive chain, the carburetor, all air intake components and the transmission components.



Removing Camshafts

DIFFICULTY = 1

Tools Needed:

  • None

>The camshafts sitting in place can be lifted out of the engine. Normally they would be held in place by the cam chain, but that had been removed prior to the start of our dissection.



Removing Crankshaft

DIFFICULTY = 3

Tools Needed:

  • 10mm Socket


>With one half of the transmission casing removed the crankshaft is fully exposed to the outside.


>8 10mm nuts, 2 per pistons need to removed to extract the crankshaft.



Removing the Pistons Assembly/Separating the Block

DIFFICULTY = 4

Tools Needed:

  • 12mm Allen Key


>The pistons can not be removed from the crankshaft side of engine.


>To get to the pistons the block needs to be separated into two pieces and removed from the middle.


>To separate the crankcase from the cylinder head (separating the block), 10 flange bolts need to be removed using a 12mm Allen key.


>The gasket separating the cylinder head from the crankcase can be removed by hand.


>To remove the cam chain tensioner can be removed by unscrewing the cap nut on the outside of the cylinder head.


>To fully separate everything two other larger flange bolts needed to be removed but no Allen key large enough was present. This was a problem, but not to the extent where it affected the analysis of the engine.


>Once separated, the pistons fall right out of the opposite side of the crankcase.


>Now, the cylinder head, crankcase, crankshaft, camshafts and the piston assembly are all individual pieces.



Dissection of Piston/Rod Assembly

DIFFICULTY = 2

Tools Needed:

  • Rubber Mallet (if necessary)


>Once out of the cylinder head there is no screw, nut or bolt holding the pieces of the piston in place. When taking out the crankshaft two nuts per rod were removed which also released the piston/rod assembly that was then only being held in by the cylinder walls.


>Pistons consist of a piston, connecting rod, two rod bolts, two connecting rod nuts, two rod bearing halves, a pin, and a two pin bearings.


Now as much of the block as was able to be taken apart was. The intake and exhaust valves were ceased in place so they could not be removed or analyzed further.



Carburetors

DIFFICULTY = 5

Tools Needed:

  • 10 mm socket and ratchet
  • 8 mm socket and ratchet
  • Phillips Head Screwdriver size 1
  • Flat Head Screwdriver size 3/16


**The center two carburetors had many stripped bolts on the casing therefore it was impossible to dissect these pieces. But all the carburetors are the same therefore it did not matter for the purpose of understanding of the part.


>The carburetors were removed from the engine prior to the start of Group 31's dissection.


>The carburetors were removed prior to dissection and consisted of 4 separate carbs connected by 2 rods.


>Remove three phillips head screws that hold the three synchronization springs in the area between the four individual carburetors.


>Separate the four carburetors by removing the two rods holding the four carbs together by unscrewing the two nuts on each end of the rods using a 10mm socket for the upper rod and an 8mm socket for the lower one.


>Using moderate force the carburetors can slide off one at a time.


>As each carb comes off, a two thrust springs pressed between two holders two on each carb need to be removed as well. Caution if not removed by hand the springs may fly off and it is very hard to find.


**Only one carb was dissected because all four are identical.


>To get the float chamber cover off the front of the carb three screws need to be removed using a phillips head screw driver.


>Next the O-ring can be removed by hand.


>Using a flat head screw driver remove the pilot screw.


>Using a phillips head screw driver remove the main jet which releases the needle jet holder.


>Using the point of a phillips head screw driver gently push the float pin out and release the float.


>Once the float is loosened the float valve with be released as well.


>Removing the vacuum chamber cover consists of removing three screws using phillips head screw driver.


>Once cover is off the spring loaded assembly consisting of the diaphragm spring, jet needle holder, o-ring, jet needle holder spring, the jet needle and a washer will all be exposed.


>Last thing to be removed in the carb is the starting enrichment valve assembly. Using a 10mm socket the valve nut can be removed revealing a spring and the starter enrichment valve.



References

1. Honda Service Manual: 91-94 CBR600F2. Honda Motor Co., LTD., 1993. PDF file.



2. "Honda CBR 600 F(2)R 1994." Motor Bikes. N.p., n.d. Web. 29 Oct. 2009. <http://www.motorbikes.be/en/Honda_CBR_600_F(2)R_1994.aspx>.



Component Summary

Part Part Number Quantity Other Parts Contained in Assembly Part Material Description
Cylinder Head 1 intake camshaft [1], exhaust camshaft [1], intake valve assembly, exhaust valve assembly, cylinder head cover breather tube [1], cylinder head bolt [1], head bolt washer [1], cylinder head cover [1], gasket [1], cam chain assembly (not dissected) [1], camshaft holder [2], 6mm bolt [2], 9mm bolt [10], 10mm washer [10], dowel pin [2], cap nut [1], sealing washer [1], cam chain tensioner slider [1] Aluminum permanent casting In an overhead cam type engine like this one, the cylinder head contains many key components as listed above. Part of the combustion chamber is in the cylinder head and the cylinder head in responsible for the entering and escaping of air, fuel and exhaust. Exhaust/inlet passages and ports inside the head, determine a major portion of the volumetric efficiency and compression ratio of an engine.
Intake Camshaft 14110-MAL-600 1 cam sprocket [1], cam sprocket bolt [2], holder [1] Steel die casting and machined Times the opening and closing of the intake valves to let the air/fuel mixture into the cylinders. This process is accomplished with the use of lobes attached to a rod with a gear on one end. The cam chain is attached to the gear which then spins the camshaft allowing the lobes to push open or keep the intake valves closed.
Exhaust Camshaft 14210-MAL-600 1 cam sprocket [1], cam sprocket bolt [2], holder [1] Steel die casting and machined Times the opening and closing of the exhaust valves to let the combustion waste products out of the cylinder/ contain the combustion. This is done using the same process as described for the intake camshaft.
Intake Valves 14711-MAL-600 8 valve lifter [8], valve shim [8], valve cotter [16], retainer [8], outer valve spring [8], inner valve spring [8], stem seal [8], inner valve seat [8], outer valve seat [8], valve guide [8] Alloy die casting Allows the air/fuel mixture to enter the combustion chamber.
Exhaust Valves 14721-MAL-600 8 valve lifter [8], valve shim [8], valve cotter [16], retainer [8], outer valve spring [8], inner valve spring [8], stem seal [8], inner valve seat [8], outer valve seat [8], valve guide [8] Alloy die casting Allows the waste exhaust gases to escape the combustion chamber.
Head Gasket 12251-MAL-601 1 none Layered Pressed Steel Separates the engine block from the cylinder head. Also creates a seal to keep oil and coolant inside the engine.
Engine Block 1 piston assembly, connecting rod assembly, crankshaft assembly, upper crank case bolt (6mm) [7], sealing washer [13], lower crankcase bolt (6mm) [14]/ (8mm) [10]/ (10mm) [1], lower crankcase [1], upper crankcase [1], oil orifice long [1]/ short [2], dowel pin [4], O-ring [1] Aluminum permanent casting The engine block contains the majority of the combustion chamber and all of its components as listed above. The block is a "container" for all of the moving parts inside of an engine.
Connecting Rods 13210-MV9-670 4 connecting rod bearing cap [8], cap nut [4], connecting rod bearing [8] Steel forged Links the crankshaft to the piston.
Connecting rod bearing 13313-MV9-630 8 none Allows the rod to rotate freely with little friction around the crankshaft while at the same time holding a firm connection.
Piston 13101-MV9-670 4 piston pin clip [8], piston pin [4], top piston ring [4], second ring [4], spacers [4], oil rings [8] Aluminum/silicon alloy permanent casting then machining The piston has many functions. It compresses the fuel and air mix before combustion, contains the combustion by moving away from it to then generate power and also to push the exhaust gases out of the combustion chamber.
Piston Rings 13011-MV9-305 8 top piston ring [4], second ring [4] Steel die casting Two rings that are secured around the top of the piston. The function of these piston rings are to seal the combustion chamber,support heat transfer from the piston to the cylinder wall and regulate the oil consumption of the engine.
Crank shaft 13300-MV9-670 1 none (as far as we took our dissection) Steel die casting and machined Attached to the connecting rod that pushes on the crank in different connection points to cause it to rotate during the combustion process. The basic function of this part is to convert the simple up and down movement of the piston/rod into rotational movement that can in turn be used to spin a series of gears until it reaches the ground through the wheels.
Carburetor 4 throttle stop screw [1], carb. insulator band screw [4], choke cable [1], throttle cable [2], carb. breather tube [2], carb. fuel tube [3], carb. insulator [4], screws [16], air chamber [1], air intake [4], O-ring [4], starting enrichment valve [2], thrust spring [3], spring seat [1], carb. connecting bolt/nut (5mm) [1/2], carb. connecting bolt/nut (6mm) [1/2], synchronization spring [4], air joint pipe [2], air vent pipe [2], fuel joint pipe [2], dowel pin (5mm) [2], dowel pin (6mm) [2], starting enrichment valve [1] Investment Casting Carburetor is simply a device with inlets for fuel and air that combine before entering the combustion chamber.


Component Summary cont.

Why were different materials selected for different components?

Different materials were selected for different components because of the different processes that each component undergoes. Some components are for aesthetic purposes and others need extreme strength because of the forces put upon them. For instance an air intake does not have much stress at all on it, there fore it can be made cheaply from plastic. But a piston is one of the key components of the engine and is continually exposed to extreme head and pressures therefore it needs to be made of a stronger material, such as a metal alloy. Other properties like the resistivity of corrosion

Does the material choice affect the manufacturing process?

Certain materials act differently when heated or deformed. Some lose strength, some remain the same and others gain rigidity and strength. For this reason there needs to be different manufacturing processes that take into account the unique properties of the material one is working with.

Does the shape affect the manufacturing process?

Shape affects the manufacturing process just as much as what material is being used. For example if you need many small to medium sized parts with specific details a good process to use is die casting. On the other hand if you needed a large, simple part that did not need to be made as much a die cast would be terribly inefficient. The cost making a die cast is expensive and only can benefit a system if the cost is the lowest possible without sacrificing quality. In this example, a large more simply shaped object such as an engine block would be much easier made in a sand cast or something similar.


Cylinder head

What forces are applied to the components?

Forces from the combustion cycle of the engine are continually being forced on the cylinder head. Friction of the valves on the actual cylinder head and the flow of intake and exhaust gases are two other forces on this component.

Why was this manufacturing process chosen?

Permanent casting was chosen because it is an way to make very detailed parts accurately. This is also a very convenient for larger pieces such as a cylinder head. Also machining is needed because

Does this component have a particular shape? Why?

This component has a specific shape so all of the smaller components contained inside of it fit precisely.

Is this component functional, cosmetic, or a combination of the two?

Mostly functional but partially cosmetic because it can be seen from the outside.

How complex is the component?

The cylinder head is pretty complex because of the parts contained inside of it. But the cylinder head itself has no moving parts but is very detailed.

Intake Camshaft/Exhaust Camshaft

What forces are applied to the components?

Forces on the lobes from the valves and the force where the cam chain is on the cam gear.

Why was this manufacturing process chosen?

Die casting was chosen because of the amount of small details that the cam has. Also machining is necessary because not all parts can be made in a casting and some secondary changes are necessary.

Does this component have a particular shape? Why?

The shape of the cam is completely functional and without it the engine would not run at all. It is a long cylinder with a cam gear on the end and lobes at specified points to control the valves. It is a cylinder because it makes it easier to rotate and keeps balance.

Is this component functional, cosmetic, or a combination of the two?

Completely functional, this part is never seen from basic use of the bike, only when the engine is taken apart.

How complex is the component?

The camshafts are complex because how exact the timing of the engine has to be. This is directly relates to the camshafts because it consists of lobes that push on the valves to open and close them. The mass and the length at virtually every point has to be perfect. Any small error could lead to catastrophic consequences for the engine.


Intake Valves/Exhaust Valves

What forces are applied to the components?

Forces from the combustion and pressure from the cylinder, along with the lobes from the camshaft are the main forces. Other smaller forces are the frictional force between the valve and the cylinder wall and the flow of exhaust/intake gases when the rush past the valve.

Why was this manufacturing process chosen?

An alloy die cast was used to make the valves because die casting is ideal for small parts that need to be made in large quantities.

Does this component have a particular shape? Why?

This component has a particular shape to fill the passage in the cylinder head when closed. Also beyond the circular flat end there is a longer rod that extends upward that can be pushed on the by the lobes of the cam.

Is this component functional, cosmetic, or a combination of the two?

These valves are completely functional because one never sees them unless a large dissasembly of the engine takes place.

How complex is the component?

Valves are simple and perform a regulated repeating function. They are a metal device used to open and close an opening to the inside of the engine. Almost horn shaped, with a flared bottom part leading to a skinny top. Typically the size of exhaust valves are slightly smaller than the intake ones because the air fuel mix needs to enter the combustion chamber faster than when exiting.

Head Gasket

What forces are applied to the components?

The squeezing force of the cylinder head and the engine block is the only measurable force being put on the head gasket.

Why was this manufacturing process chosen?

In order to function properly the head gasket needs to be thin, flexible and strong. The steel used is strong originally and by pressing the steel it makes it flexible and thin enough to fit snugly between the block and the head.

Does this component have a particular shape? Why?

The head gaskets shape is determined by the connection points between the cylinder head and the engine block are.

Is this component functional, cosmetic, or a combination of the two?

Only functional, never seen from the outside.

How complex is the component?

The head gasket is pretty simple for the function it serves and its general shape. It is a flat piece of metal that sits between the cylinder head and the engine block.

Engine Block

What forces are applied to the components?

Forces from the combustion of the fuel and air in the cylinders and the frictional forces of the piston/piston rings again the cylinder walls are the main forces.

Why was this manufacturing process chosen?

Permanent casting allows for very detailed parts to be made accurately.

Does this component have a particular shape? Why?

The engine blocks purpose is to serve as a general casing for much of the components that run the process of the engine. Every part of the engine has a purpose to hold or support something.

Is this component functional, cosmetic, or a combination of the two?

The engine block is mostly functional and partially cosmetic. This is because one can see the block but there is so much more function than the small details made to make it look nice.

How complex is the component?

The engine block is one of the simpler pieces of an engine even though many think the contrary. It just consists of four “holes” or cylinders where the piston and connecting rod sit. Other than that the only other components of it are the mounting points and the cooling system. The more complex part of the engine block does not deal with the combustion process of the engine but rather the transmission.

Connecting Rod

What forces are applied to the components?

Forces from the rod bearing and the piston are the main two forces.

Why was this manufacturing process chosen?

Connecting rods are forged because when rotating at 11000 rpms there is much stress on them. Also because of the small displacement of the our engine, when compared to the power output, the rods are smaller but need as much strength as larger ones.

Does this component have a particular shape? Why?

The rods shape is for decreasing mass, and connecting the piston and the crankshaft. Therefore the shape is designed to be relatively thin, not bulky, with holes to connect the piston and the crank.

Is this component functional, cosmetic, or a combination of the two?

Completely functional. Never seen from the outside.

How complex is the component?

The connecting rod, as its name hints is a component used to connect two other components of an engine, therefore it is not too complex by itself. It consists of just a metal rod with holes on either ends to connect to the crankshaft and piston.

Connecting Rod Bearing

What forces are applied to the components?

Forces from the crankshaft and the rod are the two main sources.

Why was this manufacturing process chosen?

Does this component have a particular shape? Why?

The bearing needs to be circular in order to rotate freely.

Is this component functional, cosmetic, or a combination of the two?

Only functional.

How complex is the component?

This is just a regular bearing consisting of two circular metal pieces and oil. The concept of a bearing is not complex.

Piston

What forces are applied to the components?

Frictional forces on the cylinder walls and forces from the combustion of the air/fuel are the main sources of force.

Why was this manufacturing process chosen?

Permanent alloy casting was chosen because it makes the part relatively strong while keeping the many details extremely accurate. Machining was necessary to fulfill the very small tolerances of length the piston has.

Does this component have a particular shape? Why?

The piston is round to fit as closely as possible to the cylinder walls to contain the explosion. Also some connecting points for the rod and also the piston is hollowed out as much as possible to decrease mass.

Is this component functional, cosmetic, or a combination of the two?

Functional, the part is rarely seen.

How complex is the component?

The piston is not complex except for the fact that the tolerance of radius and mass have small tolerances which many times causes much machining to be done after the casting is finished.

Piston Rings

What forces are applied to the components?

Frictional forces from the piston and the cylinder walls.

Why was this manufacturing process chosen?

Die casting, because of the low tolerances die casting is ideal because of the accuracy.

Does this component have a particular shape? Why?

Yes circular so it can fit around the piston and fit snugly in the cylinder wall.

Is this component functional, cosmetic, or a combination of the two?

Only functional.

How complex is the component?

Not complex at all just very exact with little error.

Crank Shaft

What forces are applied to the components?

Forces from the flywheel, cam chain and the rod/rod bearing are the sources of the forces on the crank.

Why was this manufacturing process chosen?

Die casting because of the intricate parts that are then put together to make one large complex part.

Does this component have a particular shape? Why?

Perfect shape to have a complete balance of mass. Without balance the engine can become untimed causing completely destruction of the engine.

Is this component functional, cosmetic, or a combination of the two?

Only functional.

How complex is the component?

The crankshaft is very complex. This is because on one end it has a flywheel, another has a cam gear attached to a chain and in the middle has weights and connection points where the connecting rod attaches.

Carburetor

What forces are applied to the components?

The air/fuel flowing past the valve that controls the flow is the main force inside the the carburetor.

Why was this manufacturing process chosen?

Investment casting was used because of the extreme detail of small parts that are inside of the carburetor.

Does this component have a particular shape? Why?

The shape on the inside is all there for a reason. To keep flows consistent and to have a space for all the parts to fit are the main reasons for the shape the carburetor takes.

Is this component functional, cosmetic, or a combination of the two?

Mostly functional but can be seen from the outside with simple disassembly.

How complex is the component?

The carburetor is very complex. It consists of multiple valves, many screws, rubber hoses and air chambers used for mixing of fuel and air.

**To see pictures look at dissection process above**

Design Revisions

CVT


To reduce the weight and increase the efficiency of the engine, Honda should consider the Continuous Variable Transmission (CVT) for its motorcycles. This transmission has been used for many years in snowmobiles and in recent years has been applied successfully to full size vehicles such as the Ford Escape and Nissan Altima.

A pulley based CVT replaces all the gears in a normal transmission with two pulleys connected by a chain or, more often, a rubber belt, which used to limit the torque a CVT could handle. However with new improvements in composite materials used in belts, CVTs can now handle much greater torque loads, making it a more realistic option for the Honda CBR 600 motorcycle. With a greater torque option, the motorcycle can attain greater acceleration and higher speeds.

The greatest advantage to a CVT is that it removes the need to shift. The transmission automatically adjusts to get the vehicle from rest to the maximum velocity without the need to shift. As the speed of the vehicle increases, the pulley connected to the crankshaft of the engine, called the drive pulley, contracts and causes the rotational radius to increase. While this happens, the pulley connected to the driveshaft, called the driven pulley, expands and causes the rotational radius of the belt to decrease. The end cause of these combined actions is that the transmission goes through an infinite number of “gears” until it reaches its maximum velocity or acceleration is stopped. This all occurs with little input from the operator of the vehicle.

What this new transmission system can mean for Honda motorcycles is that both racers and recreational users would no longer have to worry about shifting. This is better for a racer because they can focus on more on steering and less on shifting and managing rpm’s. For an everyday user, a CVT could greatly simplify their ride. Making the motorcycle easier to ride would entice more people to consider buying Honda’s products.

In terms of reliability and cost, a CVT will not last as long as a regular geared transmission, however may still be cheaper in the long run. The initial cost of a CVT is less than that of conventional transmission systems, using less material and being less complicated. The belt is the weakest component of a CVT and is the part most likely to fail and need regular replacement. In a well designed engine, though, the belt could be easily accessed and replaced by the user with no professional help. With easy access to parts and the problem, a CVT can prove more user friendly than a conventional transmission.


Fuel Injection


A fuel injection system on an engine controls the air fuel mixture entering the piston chamber more closely, allowing for smother operation and better efficiency. Carburetors like the ones on this Honda motor mix air and fuel before sending it into the engine. Valves in the carburetor open and close based on user input, creating a constant mixture ratio between air and fuel whose flow into the engine is the only alterable variable. Controlled by an electric system, a fuel injector changes the ratios of the air/fuel mixture based on the conditions of the engine, surroundings, and user input. This adaption can increase the ability of the air/fuel mixture to combust within the piston cylinder, making the engine more efficient and increasing combustion.

Initially this change would result in higher costs, increased weight, and more maintenance. However, over time the tradeoffs would be more beneficial. The advantages start with starting the engine, which would be more reliable, even in conditions adverse to ignition. During operation, the fuel injector system would increase fuel efficiency, a problem which affects the costs of both professional and recreational use. Along with fuel economy, fuel injectors tend to make for smoother acceleration, which would affect the comfort of racers who need to stay focused on other racers and the turns of the course, and everyday consumers who look for the best ride when buying.


Intake/Exit Ports


Most engines lose some efficiency and power in the intake and exhaust ports. The constricting nature of these components means that the engine has to work harder to draw in and push out the combustion gasses. If these ports were drilled larger and made to be more direct and accommodating to airflow, the resistance to the flow would be reduced and the efficiency and power loss could be reduced.

Successfully reducing the resistance to flow could adversely affect attaining the desired shape, size, and even weight of the engine. Modifying the engine to have straighter, bigger inlet and exit ports will take up more room, possibly making the engine too long to fit in the motorcycle frame as it currently does. Also it could require more material if the new design protrudes out of the current model.

If these problems are analyzed and worked out so that this improvement is possible, the output from this engine could be increased and done at a reduced fuel cost. An increased flow would require less energy from the rotating pistons to pull it into and push it out of the piston chamber. This would leave the engine with more power diverted to the crankshaft and to motion in the wheels. With more of the energy stored in the fuel making it to the tires, the motorcycle would require less fuel to travel the same distance and reach the same speeds.

Engineering Analysis

CONNECTING ROD

Engineering Analysis can be very useful during the design process of a component. In some cases, it can be used to analyze and determine different points of failure. Connecting rods are subject to failure under different circumstances. Thus, engineering analysis is a strong tool in the design process of the connecting rod.

The connecting rod is located between the piston and the crankshaft. There are many different circumstances that can cause a connecting rod to fail. Excessive torque applied on the connecting rods over a time can cause deformation. Excessive torque can result from an imbalance in the crankshaft and over-revving. Performance enhancers such as turbo and nitrous oxide will apply more stress on the rods as well. The bearing, which connects the rod to the crankshaft, decreases the stress on the connecting rod, and therefore must be properly lubricated. Any form of deformation on the connecting rod could result in a complete engine failure. Therefore, they must be designed to overcome all these points of failure. During the design process, all of these factors must be accounted for using engineering analysis.

Excessive Torque

Using engineering analysis, you begin with the problem statement: How much stress is needed to cause failure in the rod between the crankshaft and the piston. The rods are connected vertically from both ends, one to the crankshaft, the other to the piston. By assuming that the loads can be applied axially, the amount of stress can now be calculated. Because the rods cannot be overweight, aluminum is the ideal material for the connecting rods. Aluminum is rather lightweight and durable compared to other metal materials. Different forms of aluminum have different stress limitations.

Other assumptions that must be made are the yield strength in aluminum, thickness, lubricated bearing, and no defects in the casting of the rod. These factors are important and must be assumed during the engineering analysis of the rods. By finding the measurements of the rod, you can calculate the cross sectional area of the connecting rod. Using the cross sectional area and the stress limitation, you can calculate how much stress is needed to cause the rod to fail. As previously mentioned, the force applied to the rod can be increased by different factors such as an imbalance, over-revving and performance enhancers. (Image of connecting rod can be located in the disassembly section above)


Equations: Cross sectional area: l x w=A

S = F/A (S=stress, F=Force)


After determining the stress needed to cause failure in the rod, you can now further analyze and discuss the previously mentioned factors that can also cause failure. Ultimately, the other factors including friction and heat are direct results from excessive torque. Therefore, by using engineering analysis, you can determine the level of torque that can be applied to the connecting rod during operation.

In conclusion, the design process for the connecting rod should be carefully analyzed. Because the rod is a key component, there is no room for error. As previously mentioned, any design or manufacturing defect will cause the rod to fail, thus resulting in complete engine failure. An engineer can easily use engineering analysis to assist in the design process of the connecting rod.

Modeling

The following are the components we chose for this section:

1) Piston

The piston is one of the vital components in the engine. When the gas expands, the piston transfers force from the cylinder to the crankshaft via connecting rod. So it was good option for the group to consider modeling of the piston.

2) Gasket

The head gasket is another important component to be considered. A gasket is a type of mechanical seal, generally used to fill the space between two mating surfaces. By this, gasket helps to prevent from or into the objects that are joined, while under compression. One of the most important and desirable property of a gasket, is that it has the ability to withstand high compressive loads. These are the reasons why the group chose the gasket for solid modeling

3) Bearing

A rod bearing is a simple device that helps to reduce the friction between two moving parts. It can be a rotating or a linear movement. Plays an important role, to reduce the friction between the connecting rod and the piston.

Software

The group chose the Auto CAD 2009 version for the solid modeling of this component. This is because; it is very simple access software to use. Also the new features in the 2009 version make the work easier to work on the modeling of the components.

Piston

http://i593.photobucket.com/albums/tt16/gaalessi/Piston.jpg

Head Gasket

http://i593.photobucket.com/albums/tt16/gaalessi/HeadGasket.jpg

Bearing

http://i593.photobucket.com/albums/tt16/gaalessi/HeadGasket.jpg

Re-Assembly

DIFFICULTY SCALE

1. Light compression force.

2. Use of simple tools.

3. Use of tools and coordinated compression force.

4. Assorted tool use and careful application of force and spring compression.

Piston/Rod/Crankshaft assembled out of engine



>Prior to dissection, the other group assigned to this engine had already assembled the transmission and it was ready for us to continue with the Piston/Rod/Crankshaft assembly. When we completed our reassembly they continued to assemble the valve cover, the camshaft covers, the drive chain, the carburetor, and all air intake components.



Reassemble Piston/Rod/Crankshaft assembly


DIFFICULTY = 2

Tools Needed:

  • Rubber Mallet (if necessary)
  • Flat Head Screwdriver size 3/16


o Each Piston was reattached to a rod by a cylindrical bearing, held in place by a small ring key.

o The four Piston/Rod assemblies were inserted Rod first into the lower half of the disassembled block of the engine via the exposed piston chamber.

o For the Piston heads to fit into the Piston Chamber the Piston Rings must be compressed. This required the use of screwdrivers to accomplish.

o Inverting the bottom half of the block containing the Piston/Rod assemblies, the Crankshaft was placed onto the rods and secured in place by two rod bolts. A 10 mm socket is needed to tighten the 8 nuts.

o The orientation of the Pistons must be correct before the Rods are secured to the Crankshaft. This is done by making sure the “in” side of the Piston head faces the intake port.



Reassemble block


DIFFICULTY = 3

Tools Needed:

  • 12mm Allen Key


o Position the bottom of the block so that the Crankshaft is facing down and the Piston Heads are exposed. Place the Gasket on the exposed surface of the head so that all openings match up.

o Place the upper portion of the block on the Gasket, making sure all openings line up. Hold the two halves together and secure them with the 12 Flange Bolts using a 12 mm Allen key

o Replace the Cam Chain Tensioner by placing it into position with the bolt going through the opening in the cylinder head wall. Secure with a cap nut on the exterior of the Head.



Camshafts


DIFFICULTY = 1

Tools Needed:

  • None


o We placed the Camshafts back into position as we found them.



Carburetor


DIFFICULTY = 4

Tools Needed:

  • 10 mm socket and ratchet
  • 8 mm socket and ratchet
  • Phillips Head Screwdriver size 1
  • Flat Head Screwdriver size 3/16


--> The interior components of the Carburetors need to be replaced, this includes:

o Starting Enrichment Assembly. Beginning with the starting enrichment valve, place the valve spring on the valve and cover with the valve nut using a 10 mm socket. The whole assembly screws into the side or the carburetor. Repeat this for each carburetor.

o Replace the the diaphragm spring, jet needle holder, o-ring, jet needle holder spring, the jet needle and washer, all which go inside the vacuum chamber. Finish by replacing the Cover and securing it with three screws using a Phillips head screwdriver.


o In the float chamber, the float valve has to be replaced first. Once the float valve is in place the float can be placed into position, secure the float using the float pin.


>Replace the Needle Jet Holder into the largest of the openings. Using a Philips head screwdriver screw the Main Jet into the Needle Jet Holder.

>Screw the Pilot Screw into its position using a Flat Head screwdriver.

>Replace the Float Chamber cover and secure with three screws using a Phillips head screwdriver.


o Two rods slide through all the Carburetors, and are secured by a nut on each end. Slide the Carburetors onto the rods until all four are in place. Secure the nuts with a 10 mm socket.

o Replace the synchronization springs that go between the Carburetors. A Phillips head screwdriver is needed to tighten them, one spring goes in each gap between the Carburetors.

o Place the rubber seals on the exhaust valves of the Carburetors. Tighten the eight clamps using a Phillips head screwdriver.


Completed assembly minus the Crankshaft cover
Camshafts in position


Differences between Disassembly and Reassembly



Our reassembly was much shorter than our disassembly. This was because our members doing the actual reassembly work were already familiar with the components and procedures involved in this engine. That is opposed to disassembly, which was the first time anyone had actually seen the interior workings of the engine.

In the procedure, we found that many of the steps could be followed in reverse, with minimal complications. However in several instances, we were confronted with problems we did not have to account for during dissection. The first occurred when we tried to place the piston/rod assemblies into the block. The piston rings expanded to a radius larger than that of the piston chamber and had to be manually compressed in order to get them into the chamber. This required two members, and the use of a flat head screwdriver to hold the piston rings once they had been compressed by hand. To make the operation simpler one ring was compressed at a time, and the pistons were pushed into the chamber one ring at a time.

To find the correct tools to use we only had to consult our disassembly notes, and no additions were needed. The only instance of an extra tool being needed was in the case of the piston rings. However, the screwdriver used was already required for other assemblies and was readily available. We attribute this to the use of mainly bolts and screws to secure the components of this engine together. These require the same tools and skills for insertion and removal, which potentially saved us much time.

Another process that differed from the disassembly was the putting the carburetor back together. The reassembly part which was a challenge was when the two inner springs had to be put back in place. To do this simultaneously, the carburetors had to be pressed together and the spring be put in place; this took much trial and error. To finally accomplish this for each carburetor, the spring had to be compressed and slid into place as the valve was opened. Other than that the carburetor was a simple reassembly. With our product back to the configuration it was given to us, it still is unable to operate as intended. It is still lacking many critical parts such as a fuel tank, battery, throttle for user input, and an exhaust to manage waste products.