Group 37 - Beginner Dirt Bike

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The beginner dirt bike


Management Proposal

Project Leader: Thomas Heyden
Oversight and coordination of team efforts, communication with the instructors, and call a close to the project when delivery is reached.

  • extensive mechanical background - machinist/fabricator for past 6 years
  • solidworks experience
  • good editor (quick to grasp where improvements can be made)


  • poor writing skills
  • limited ability to delegate (tend to want to do everything)

Project Developer: Brian Morgan
Organization of the work of the team in a presentable format. Outline status through meetings and call for needed information.

Suspension and Solid Modeling Lead: Olivier Le Meur
Develop and implement the plan for the suspension analysis. Organization of the efforts of the suspension analysis. To oversee and aid in the solid modeling of the project.

Brake Lead: Steve Dibble
Develop and implement the plan for the brake analysis. Organization of the efforts on the brake analysis.

General Meeting
We will be meeting Mondays at 2:00pm in the lower common section of Knox Hall. At these meetings we will review our progress, and organize our efforts for the week.

Work Proposal

The reverse engineering process will begin with the dissection of the breaks and shock absorbers of the mini dirt bike. The first step will involve removing these components from the vehicle. Photos should be taken during each step of the removal and dissection of components to aid in reassembly.
For the breaks, the linkage connecting the levers/actuators will be removed first, and then the wheel will be removed from the frame by removing the axle. The linkage will require an open ended wrench to loosen the cable tentioner. The axle nuts will require a wrench on both ends of the axle to remove the axle.
The front and rear shock absorbers will then be removed. The fasteners at either end of the rear shock absorber use a cotter pin to prevent them from coming loose. These pins will require a set of pliers to remove. Then a wrench on either end of the fastener will be required to remove it from the upper connection point of the rear shock. The front shock absorbers are clamped and bolted in place. A socket wrench can be used to loosen the clamp but the bolt at the top of may be larger than a standard set of sockets will include. A larger adjustable wrench may be required to remove it. As this bolt is removed caution should be taken due to the possibility of releasing pressure inside the shock as well as spilling hydraulic oil contained inside. Once these components are removed from the bike, dissection of their individual components will begin.
Unfortunately the rear shock does not appear to be serviceable and may be impossible to disassemble without permanent damage. The collars holding the main spring appear to be welded in place.
The front shocks have an allen headed plug located in the lower section that should be used to drain the hydraulic oil before dis-assembly. Caution should also be taken at this point to prevent spilling of oil and potential release of spring pressure. After this is removed the shock should be able to be separated into two pieces. There is a seal between the two cylinders that make up the main body of the shock. This may require a pair of snap ring pliers to be removed. The internal components should be exposed for analyzing at this point.
Once the axle is removed from the wheel, and the wheel removed from the front fork, the outer cover of the drum break should pull off to reveal the internal pieces. The pieces inside the drum should be able to be removed with either a socket wrench or a pair of pliers.
The dissection should be complete and the process of analyzing the components can commence.

Tool list:

  • Open ended metric wrenches,
  • Metric socket wrench set
  • Large adjustable wrench
  • Needle nose pliers
  • Allen wrench set
  • Phillips head screw driver
  • Flathead screw driver

Management timeline:

General meetings will be held Mondays at 2:00 P.M. in the lower Knox common area. They will address timeless, progress, goals for the week, and set up any additional meeting times for the week.
As shown in Chart 1 we used a Gannt chart to define our time management and major deadlines.

Title: Group 37 Management Timeline
Chart 1: Time management tool and major deadlines.

Initial Product Assessment

Brakes: Drum Brake

  1. What is the intended use of the product?
    Used to apply a force that will oppose rotation of a wheel.
  2. Is this product for home or professional use?
    This product in particular is intended for a home/recreational use, but the design is basic and can be used in a variety of professional applications.
  3. What are the different functions of the product?
    Brakes are designed with one intended fonction(function), stopping or slowing a vehicle. You can also use them to restrain the vehicle from starting to move again.
  4. How do you think the product works?
    The customer pull on the brake lever witch actions the brake with a cable system.The brakes open and apply a force against the wheel which with frictions slows or stops. The consumer activates the brake with a cable system. The brake shoes, which are fixed to the frame to prevent rotation, are forced against the inside of the break drum to apply a frictional force that opposes the rotation of the drum.
  5. What types of energy are used?
    This product uses mechanical energy. There is frictions between the brakes and the wheel
  6. How are these different types of energies transformed and modified?
    The customer use mechanical energy to action the brakes. Then the kinetic energy lost by the wheel is usually transformed into heat by friction.
  7. Is the product currently functioning?
    Slowing a vehicle by friction is currently functioning and is the more common brake system in the world. Yes, there does not appear to be any problems with the operation of this component.
  8. How well does it run?
    It run pretty well as far as it is the more common brake system in the world. The wheel turns smoothly when the break is released and stops quietly after it is applied.
  9. If there are any problems, where do you think they are coming from?
    No noticeable flaws in function. The brakes get used after a while because of friction. So sometimes you need to change it.
  10. How complex is the product?
    Brakes should be considered rather simple. It is simple because it use only mechanical energy and the design is easy to understand.
  11. How many components are used?
    There is two primary components, the wheel and the brakes. Generally the brakes are in two parts. Then there is few additional components as the axle wheel, an arm actionable by a cable and seals. The main components of a drum break system are the shoes and the drum.
  12. For the individual components how complex are they?
    The brakes are a simple mechanical device on the bike. They are triggered by user input on a handle which creates tension on a cable. As the the cable tenses it will compress the cylinder causing the drums to meet the wheel, which creates friction and slows the wheels revolutions. This slows the forward motion. (we don't need to explain how it works here)
  13. What materials are used in the product?
    Most of the brake supplier these days uses some type of ceramic-based friction material. Most of the other parts are in steel. There is plastic for the seals and fat to oil the axle.
  14. What materials are clearly visible?
    The materials which are clearly visible are steel. The brakes are encased in the wheel drum. There is also a steel tensioner cable between the handlebar and the brake.
  15. Based on previous answers to the above questions, what materials do you think are not visible but present?
    A cylinder is in the drum. There are also tensioner springs in the drum. Abrasive pads serve to create the friction.
  16. If you had to use this product, would you be happy with it?
    No, I would be disappointed in performance when compared to system that uses a hydraulic piston and rotor.
  17. Is the product comfortable to use?
    Comfort is not really applicable for the brakes. Yes, the lever action multiplies the force exerted by the user so less effort is required to stop the vehicle.
  18. Is the product easy to use?
    Very easy, just pull on the brake lever.
  19. Does the product require regular maintenance? If so is the product easy to service?
    Not regularly, but maintenance is required. Yes, regular maintenance is required. The cable connecting the lever on the handle bars to the break assembly requires occasional lubrication. The shoes inside the break drum are a regularly replaceable item.
  20. What other alternatives to your product are there? How do these alternatives compare?
    One alternative is using disk brakes instead of drums, disk brakes work a little bit better, are easier to service/maintain but are more expensive.
  21. What are the differences in cost?
    There difference in cost will vary, but disk brakes are more.
  22. What are the advantages?
    The advantage to drum brakes is that it is a compact, neat setup with no parts that could be damaged by an outside source.
  23. What are the disadvantages?
    The disadvantage to drum brakes is that they are harder to service when necessary.

Suspension and shock absorber:

  1. What is the intended use of the product?
  2. Is this product for home or professional use?
  3. What are the different functions of the product?
  4. How do you think the product works?
  5. What types of energy are used?
  6. How are these different types of energies transformed and modified?
  7. Is the product currently functioning?
  8. How well does it run?
  9. If there are any problems, where do you think they are coming from?
    For the suspension, low hydraulic pressure and bent components could cause problems with the suspension. Otherwise, for the shock absorber, the shaft could present problems if it was bent, or if the spring lost its elasticity it could reduce the effectiveness of the shock absorber.
  10. How complex is the product?
    The suspension are simple. It is comprised of an hydraulic cylinder and a shaft. The shock absorber is a simple design. A shaft surrounded by a spring.
  11. How many components are used?
    For the suspensions, there are the connection pins, connecting the shaft and the cylinder to the frame, the shaft and the cylinder. For the shock absorber there are 3 Components used: connection pins, the spring, and the shaft.
  12. For the individual components how complex are they?
    Each component is simple. The spring is a simple machine in itself. The shaft is a metal rod. The pins are simple metal pins connecting the shock absorber to the frame.
  13. What materials are used in the product?
    Metals make up the components and hydraulic fluid is the medium for transferring the work.
  14. What materials are clearly visible?
    The metal shaft, connection pins, and cylinder.
  15. Based on previous answers to the above questions, what materials do you think are not visible but present?
    The hydraulic fluid must be present.
  16. If you had to use this product, would you be happy with it?
    Suspension components make bumpy roads feel much more comfortable. Without an in-depth analysis of the effectiveness of this specific type of suspension I would have to say that I am unsure. Whereas, with the shock absorber, I would have to do a more detailed analysis of the effectiveness under loading to evaluate whether I would be satisfied.
  17. Is the product comfortable to use?
    This product is intended to make the person riding the bike more comfortable.
  18. Is the product easy to use?
    It does the work for you, very easy.
  19. Does the product require regular maintenance? If so is the product easy to service?
    The suspension requires very little maintenance if any.
  20. What other alternatives to your product are there? How do these alternatives compare?
    There are alternatives such as air suspension, however I have not ever really seen this done.
  21. What are the differences in cost?
    The air suspension is close to double the cost.
  22. What are the advantages?
    The main advantage of the suspension system is a much smoother ride.
  23. What are the disadvantages?

Product disassembly

In this section we will describe the desassembly procedure. Each procedure will be given a difficulty rating. The difficulty scale will range from one to five. A rating of one will represent an operation that could be completed easily on a first attempt. A rating of five may takes several attempts to complete correctly.

Causes for corrective action

Our team's management plan has functioned well. The communication of our goals that need to be met by the individual members were well organized. The efforts of the team improved the final product from each member. Despite the overall success of our plan, improvement does needs to be made in the balance of effort required from each member. This will be remedied with greater detail of individual goals that more equally match the difficulty goals for the other members.

Front brake removal

  1. Remove brake cable: Difficulty 2
    This can be done with your hands, it is only finger tight. The Figure 1 shows the assembly. Figure 2 shows the guard being pulled away from the assembly.
    Figure 1: Handle assembly
    Figure 2: Handle with guard slide away

    Figure 3 shows the handle in misalignment which locks the cable in. Rotate the slotted bolt and slotted jam until they are aligned with the slot on the lever assembly as shown in Figure 4. The cable can then be removed through the exposed slot.

    Figure 3: Handle slotted bolt not aligned
    Figure 4: Handle with slots in alignment

    When the slots are aligned pull the cable out. The next step is to remove the cable clamp on the right front fork, as shown in Figure 5. This is held on with an 8 mm bolt.

    Figure 5: Removing the cable clip on the front fork

    The next step is to remove the cable from the drum lever arm as shown in Figure 6. Figure 7 shows the joint connecting the cable to the brake. A 10 mm wrench is used to disconnect it and then it can be pulled out.

    Figure 6: Removing cable from brake
    Figure 7: Cable connected to drum brake

  2. Remove Wheel and Brake: Difficulty 1
    The axle assembly is joined with a 13 mm bolt and a 14 mm nut. When removing these the spacer must be constrained. Figure 8 shows the bolt being removed and the spacer being constrained. Figure 9 shows the front wheel free from the front forks with the brake hub removed displaying the brakes. Once the wheel is removed the brake easily slips out of the hub.
    Figure 8: Removing rear wheel
    Figure 9: Brake removed

Rear Wheel Removal

  1. Remove brake linkage: Difficulty 2
    Remove the cotter pin holding the linkage to the brake pedal shown in Figure 10. Then remove the cotter pin that constrains the nut in Figure 11 to remove the linkage from the rear wheel.
    Figure 10: Rear wheel brake linkage
    Figure 11: Nut retaining pin

    The linkage is connected to the brake by a 13mm nut and to the frame be a 16mm bolt and a 17mm castle nut.

  2. Remove the axle: Difficulty 3
    Remove the 17mm rear axle nut. Then hold the rear wheel spacer while removing the 15mm bolt used for the rear axle.
    Figure 12: Supporting the wheel spacer

Rear Shock Removal

Difficulty: 4

Figure 13: Rear shock assembly

Remove the cotter pin that retains the 14mm castle nut at the top of the shock. Remove the 13mm bolt and 14mm nut that attach the shock to the frame.

Remove cotter pin at bottom of the shock. Remove pin that attaches the shock to the frame. This is shown in Figure 13.

Figure 14: Rear shock assembly
Figure 15: Rear shock assembly

Front Shock Removal

Difficulty: 2
The top bolts shown in Figure 16 are 19 mm. The fork clamps shown in Figure 17 are 10 mm. After removing the top bolts and loosening the clamps the front shocks can be pulled out. Further disassembly of the shocks could result in permanent damage to them.

Figure 16: Top bolts in front shocks
Figure 17: Front fork clamps

Product Documentation and Analysis

Cause for corrective action

Due to the loss of a team member, Brian Morgan, our management plan required some alteration. Thus the responsibility of formatting the wiki has been passed to the remaining members. The decrease in our group size has cause us to focus on the brake components while the suspension will no longer be analyzed. The brakes have been chosen instead of the suspension because the brake components provided more opportunities for analysis.

Component Summary for front brakes

Component Picture Component's fonction Material Manufacturing process
1 brake hub

Functional and cosmetic but not complex component

Figure 18: Brake Hub and bushing
Keeps the components together in the correct orientation Aluminum

Aluminum was chosen for it's low weight and adequate strength The material choice did not affect the manufacturing process

Die cast plus additional machining

Die casting was chosen for it's ability to produce complex shapes with good surface finishes. The additional machining is required for higher precision in some ares and threads that are not possible to complete in the casting process.

1 bushing

Functional and not complex component

Provide rear resistance between the hub and the axle Steel

Chosen for high wear resistance.


Turning was chosen for it's high precision and quality surface finish

2 brake shoes

Functional and not complex component

Figure 19: Brake Shoes and abrasive pads
Provide shape and support for abrasive pads Aluminum

Aluminum was chosen for it's low weight and adequate strength The material choice did not affect the manufacturing process

Sand cast

Sand casting is a good manufacturing process for this component because it is a symmetric shape with many complex features that does not require much precision

2 abrasive pads

Functional and not complex component

Transfer force from brake shoes to brake drum with an appropriate frictional coefficient Organic

Organic has a better frictional coefficient with acceptable wear resistance


Molding was chosen because of the component's material properties

1 lever

Functional and not complex component

Figure 20: Lever
Transform linear force from the cable in a torque on the actuator Steel

Steel was chosen for its strength but did not affect the manufacturing process

Stamped and bended

Stamping and bending was chosen for speed and low cost

2 springs

Functional and not complex component

Figure 21: Springs
Return brake shoes to a clearance location from the drum Steel

Steel was chosen for its ductility which is affected by the manufacturing process

Bended wire

Because it is the cheapest and easiest way to make a spring

1 actuator

Functional and also the most complex but steel a simple component

Figure 22: Actuator
Transfer force from the lever to open the brake shoes Steel

Steel was chosen for its strength but did not affect the manufacturing process


Machined because of higher precision and good surface finish required

1 bolt
Figure 23: Bolt, washer and wing nut
Combine to fasten lever arm to actuator Steel Machined
1 washer Stamped
1 wing nut Stamped and machined

Design Revisions

1st design revision

The bar that connects to the rear brake hub and the frame could be removed. The function of this component is to keep the brake hub from rotating relative to the frame. This could be replaced by a similar system to the front fork. A block could be fixed to the rear swing arm that would mate with a similar slot to the front break hub. This design change would allow the same hub mold to be used for the front and rear break hubs. The ability to use the same component in more than one location will reduce cost of production by eliminating the need for additional tooling. This may reduce the weight of the bike as well.

2nd design revision

The linkage that connects the brake pedal to the lever arm (Figure 20) can be replaced with a cable system similar to the front system. This revision will allow the drive chain tension to be adjusted without making any additional adjustments to the brake system. The current system would require an adjustment of the brakes for any repositioning of the rear wheel. This will also allow the front brake hub to be used in the rear without any modifications. (if design revision 1 were also implemented)

3rd design revision

The cable tensioner (Figure 7) for the front break cable would benefit from a dimension change. The threaded area used for adjustment is excessively long. Although this does provide for increased adjustability it makes disassembly and service more difficult. The decreased length would also decrease the cost and weight of the component.

Solid Modeled Assembly

Because of our reduction in team members, we had no choice but to focus on either the brakes or the suspension for solid modeling. Because we did our component summary on front brake, it made sense to model the front brake and its components. These are really different components with various manufacturing process that make the solid modeling more interesting. Also modeling these components permitted us to better understand how these components are manufactured and figure out the different steps and processes involve in manufacturing.

As for our CAD package we chose CATIA V5 which is a DASSAULT System solution for product design and innovation. Our choice was determined based on experience with this software and also because of easy access to CATIA V5 student version.

Solid model of front brake's components

Figure 24: Brake Hub and bushing models
Figure 25: Brake hub model
Figure 26: Brake shoes model
Figure 27: Abrasive pad model
Figure 28: Lever model
Figure 29: Springs model
Figure 30: Actuator model
Figure 31: Bolt model
Figure 32: Washer model
Figure 33: Wing nut model

Assembly and exploded assembly

Figure 34: Front view of the assembly model
Figure 35: Back view of the assembly model
Figure 36: Exploded view of the assembly model

Engineering Analysis

Figure 35: Force Diagram

A key component of the brake system that could be analyzed in the design and testing stages of the design process is the brake pedal. The forces applied to the brakes can vary greatly depending on the decisions made during the design of this component. The ratio of length between the foot pad from its hinge location and the linkage connection from the hinge location will affect how much force will be applied to brakes. Using the equation of torque is equal to the force applied, multiplied by the distance from the point of interest, and using the hinge location as our point of interest, the forces that are transfered throughout the brake system can be easily estimated. The frictional forces associated with the hinge locations should be negligible due to their small size relative to size of the forces calculated. The approach to begin this analysis should begin with a few assumptions about how much force will be required by the brakes to stop the bike from it's maximum intended velocity. This force required by the brakes will help dictate how much mechanical advantage should be produced by the pedal.
An appropriate input force from the user can then be
assumed to finalize the levers dimensions.

Figure 36: Pedal Dimensions

Product reassembly

Front shock assembly

The front shocks slide through the lower clamp and bolt to the upper fork support. Care should be taken during this step to replace the shocks in the correct orientation. The shocks are not completely symmetrical and the shock with the brake cable clamp should be inserted on the left side of the bike (from the riders perspective). The lobes through which the axle passes should face the front of the bike. Be sure to insert the axle before tightening the bolts at the top of each shock and the lower clamp bolts. This will hold the shocks in the correct orientation during the tightening process.

Figure 37: Front shock absorber reassembly

Rear shock assembly

The rear shock should be oriented so that the end with smaller diameter shaft (visible through the coils of the spring) is attached to the frame, while the opposite end is attached to the rear swing arm. The end attached to the frame is bolted with a castle nut and cotter pin. The end attached to the swing arm is attached with a pin that is then retained with a cotter pin.

Figure 38: Rear shock absorber reassembly

Rear Wheel

Replace the rear brake into the hub of the rear wheel. Be sure that the drive sprocket is in place as well. Place the rear wheel into the rear swing arm with the brake oriented toward the right of the bike (from the riders perspective). Before replacing the axle, the wheel spacer should be located in between the brake and the swing arm. The axle should then be replaced by inserting it through the chain tensioner in the swing arm, then the wheel spacer, then the brake/wheel, and continue on through the chain tensioner on the opposite side of the swing arm.

Figure 39: Rear wheel reassembly

Rear Brake Linkages

The rear brake should be rotated so that the cast arm is directed toward the ground (when bike is resting on it's wheels). One end of the linkage bar that keeps the brake from rotating can then be inserted in between the it's mating tabs, located on the frame. This can be loosely bolted into place. Then rotate the brake until the linkage aligns with the cast arm. Bolt these ends together and replace the cotter pin. now tighten the opposite end and replace it's cotter pin.

Figure 40: Anti-rotational linkage (frame attachment)
Figure 42: Anti-rotational linkage (brake attachment)
Figure 41: Anti-rotational linkage

Front Wheel

Orient the front wheel so that the brake is on the left side of the bike (from the riders position). Rotate the brake / wheel until the slot on the outer surface of the brake aligns with the corresponding tab that protrudes from the fork assembly. Place wheel in between the front forks and align the center of the wheel with the axle holes on the forks. Replace the axle while holding the wheel spacer in between the brake and the fork.

Figure 43: Front Wheel Assembly (Right side view)
Figure 44: Front Wheel Assembly (Right side view)

Front Brake Linkage

Attach the cable end to the brake itself. Then thread cable adjuster into the hub. Loosely attach cable clamp around cable. Attach the opposite end of the cable to the brake lever located on the handle bars.

Figure 45: Front Linkage Assembly
Figure 46: Front Brake Lever

Corrective action needed

There are still several corrective actions to bring to our product after its final reassembly.
The first one, and may be the most important, is to refill the suspension with fluid. During its disassembly, we purged the fluid by removing its drain plug. But to fill in the shock we need to open the top, an operation that appeared impossible during the disassembly of the shock absorber. Luckily, the purge was operated only the right shock absorber.
Then, to perfect the reassembly, the brakes will require some adjustments. These should be done during a driving test.
The rest of the product is perfectly reassembled.

Differences between disassembly and reassembly processes

The tools used during disassembly and reassembly were exactly the same , however reassembly needed more attention. The reassembly of the brakes, for example, need some adjustments that we did not have to worry about during the disassembly process. Moreover, during reassembly, some parts had to be fitted together with the proper orientation. The orientations were easy to deal with thanks to the pictures we took during disassembly.