Mechanical design minor project

Product Design Specification

Design Problem

  • The design should eliminate the need of foot controlled pedals to actuate the master cylinder.

  • There is need for light weight master cylinder with reduced effort required to actuate the valve.

  • Most master cylinders and reservoir mechanism make use of complicated and expensive components and thus making it an expensive device.

Constraints

  • The design must fit on the existing infrastructure, framework or design of the clutching mechanism.

  • The design should make use of tools and components that are readily available on shelf or components that are easy to find.

  • The design should be light and can be operated by hand of the driver amongst other hand operated controls.

  • The design of the master cylinder should be easily controlled by hand of the driver while still steering.

  • The master cylinder should be readily and easily actuated throughout all driving conditions.

Criteria

The design concepts will be rated between 1 and 10 with the highest value representing best design criteria. The ratings will be based on the following criteria:

  • The easy of actuating the clutching mechanism. The easier it is to actuate the mechanism, the better.

  • The weight of the over mechanism. Since the design is geared towards a light weight master cylinder, thus the design will be such that, the lighter the device, the better.

  • The design concept should be suitable for underlying clutch systems already existing. The more compatible it is, the more desirable it gets.

  • The cost of designing the system should be at the minimal and should be low as compared to the existing clutching mechanism. Therefore, the lower the cost, the more desirable the design is.

  • The concept should be easily operated by hand without compromising the safety of the driver while driving.

  • The design should also be reliable in performing the task it is designed for. Clutching failures can cause detrimental safety issues and reliability should be focused in concepts.

Concepts

Concept 1: Mechanically Actuated

This concept consist of a horizontal arrangement of the master cylinder mechanism with the actuation by a hand lever situated near the steering. The actuation consists of a lever that pushes the push rod thus pushing the piston subsequently. The piston is reduced in size so as to minimize on the effort required for actuation.

A return spring is used to return the piston back to position after actuation. The spring tension should be appropriate so as to reduce cases of excessive energy required for returning the piston.

An illustration of the system is as shown in the figure below.

mechanical design minor project

Figure 1: Concept 1

Concept 2: Spring Actuated

This concepts consists of two tensioned springs on each sides of the piston. Actuation of the master cylinder piston is entirely done by proper tensioning and release of the springs. The springs are controlled by spring tensioner controls that are connected to a lever mechanism that can be controlled by driver`s hands. When one spring is tensioned, the other one is released and vice versa depending on the type of actuation required. Therefore, this system can be regarded as self-actuating with the control only dedicated to the driver.

The figure below is an illustration of the concept.

mechanical design minor project 1

Figure 2: Concept 2

Concept 3: Pneumatically Actuated

In this concept, the actuation of the master cylinder is entirely by pneumatic control. Compressed air is used to actuate the mechanism. Compressed air is controlled by use of a control valve. The valve is thus controlled by a lever that is located near the steering and thus the driver can control the actuation of the master cylinder by use of a hand lever. This mechanism requires the least effort as compared to the other designs. A return spring is used to re-position the piston back in position after actuation process.

The figure below illustrates the concept.

mechanical design minor project 2

Figure 3: Concept 3

Concept 4: Hydraulic fluid optimization

This concept is entirely design with regards to optimizing the use of the hydraulic fluid used in load transmission. The concept working mechanism is similar to that of the mechanically actuated concept but has incorporated the use of equalization port that ensured maximum use of the hydraulic fluid. Actuated is by use of a mechanical level that can be controlled by the drivers hand just like the gear selection lever in most vehicles.

The figure below illustrates the concept.

mechanical design minor project 3

Figure 4: Concept 4

Evaluation and selection

The three concepts were evaluated based on the criteria discussed in the criteria section of this report. The weighting of each criteria were as discussed below.

  • Ease of actuation (20%).

  • Weight of the mechanism (15%).

  • Suitability (15%).

  • Cost (20%).

  • Reliability (30%).

Table 1: Concept Evaluation Table.

Ease of actuation (20%)

Weight (15%)

Suitability (15%)

Cost (20%)

Reliability (30%)

Total Score

Concept 1

Shifting of a lever

Relatively heavy

Suitable to existing framework

Relatively reliable.

Concept 2

Shifting of a light lever

Very light.

Suitable

All materials readily available

Springs rarely fail if well tensioned.

Concept 3

Pressing a knob

Requires more components

Fits existing framework

Most components off-shelf

Pneumatic systems prone to leakage

Concept 4

Shifting of a lever

Relatively fewer components

Suits existing framework

Requires more components to manufacture

Relatively reliable.

Concept selection

Based on the above evaluation (table 1), concept 3 is the most suitable concept with the highest score in all the criteria. The concept according to the total scores is rated the highest with a score of 9.0/10.

Detailed illustration

Manufacturing Techniques

Manufacturing of the design in concept three requires three dedicated lines. A line to manufacture the master cylinder housing, a dedicated line for manufacturing tension springs as well as another line for manufacturing reservoir.

The control valves, spring retainers and pistons are available on shelf and can be outsourced from existing manufacturers or distributors.

Assembling of the device is easy and can be done in a production line with specific tasks at each stage. The number of units manufactured depends on the type of manufacturing employed. Automatic systems such as robots should be employed to increases the manufacturing output, efficiency and accuracy in dimensions.

Works Cited

Sugihara, Masami, et al. «Clutch master cylinder.» U.S. Patent No. 4,716,733. 5 Jan. 1988.

Montanari, M., et al. «Control and performance evaluation of a clutch servo system with hydraulic actuation.» Control Engineering Practice 12.11 (2004): 1369-1379.

Sturm, Gary L. «Hydraulic actuator for clutch assemblies.» U.S. Patent No. 5,224,906. 6 Jul. 1993.