BASIC UTILITY VEHICLE:Brake System

Prepared by: Julian WilliamsAdvisor: Dr. Junkun MaProfessor: Dr. Cris Koutsougeras

Senior Design I (ET 493)Southeastern Louisiana UniversityDepartment of Computer Science and Industrial Technology

BASIC UTILITY VEHICLE: BRAKE SYSTEM

Team members:1. Julian Williams2. Taylor Micas3. Leigh Villemarette4. Thomas Speer

Faculty Advisor: Junkun MaDepartment of Computer Science & Industrial Technology

Abstract

The purpose of this project is to design a mechanically operated brake system for a Basic Utility Vehicle (BUV) designed to safely slow and stop a vehicle. The project will provide me with an opportunity to apply and expand my knowledge of technology and skills I obtained from my studies at Southeastern Louisiana University. This paper will explain the system I designed and how it works, the changes made in the design and why the changes were made, the components chosen and why they were chosen, the progress and current status of the project, justification that my design did use engineering methodology and that I did remain on task to deliver the tasks I promised.

Introduction

This project allowed me to have the opportunity to apply the theory that was taught in the classroom. I am approaching the final design to my own mechanically operated brake system that will work together with other components to safely stop the BUV. The decision of choosing a purely mechanical system was due to the simplicity, low-cost, easy-maintenance and to avoid the use of hydraulic system. A customized brake pedal has been designed, with the exception of finalizing dimensions, and it will allow the brake system to be linked together and transfer the foot force to the mechanical levers attached to the brakes, which apply the brakes. Originally, brake mechanisms were designed to link four drum brakes together to transfer the foot force to the drum brakes. This design was abandoned due to various advantages the direct pedal linkage design offered.

Brake Mechanism Design

The original brake mechanism design consisted of four mechanical lever drum brakes, a pedal, two brake mechanisms mounted to the frame, cable adjusters and other miscellaneous parts. There were separate mechanisms for the rear and front that is nearly identical in design. The purpose of the mechanisms was to transfer the load applied to the pedal to the four mechanical levers, which apply the brakes

by expanding the brake shoes against the drum. Figure 1 shows a 3D sketch of the mechanism.

Figure 1

Cables NutsCable Tips Shaft

The mechanism has four cable adjusters with cables running through them that are used to link the rear system together. Welded onto the center of the mechanism and would be a hollow piece that the shaft, which is welded to the frame, would be able to slide along. The primary cable would be attached to the pedal whereas the emergency cable would be attached to a separate hand lever. The left and right rear cables would be attached to the mechanical levers on the drum brakes. When the pedal is applied primary cable is pulled and the mechanism moves in the direction shown and slides along a shaft. This movement of the mechanism causes the cables attached to the brake levers to move in the same direction, thus pulling the levers to activate the brake shoes against the drum. It is important to notice that the emergency brake is missing a nut on the front face of the cable adjuster also has a spring attached to it on the back side. The purpose for not having a nut is to allow the mechanism to slide along the cable adjuster without engaging the emergency brake. The purpose of attaching a spring to the cable adjuster is to prevent any slack that would occur from the mechanism sliding over it. There are also springs attached to both sides of the mechanism to return the mechanism to its original position after the brake pedal is released. The front mechanism is identical in

design with the only difference being that there is no emergency brake cable adjuster. The front mechanism would only consist of a primary, front right and front left cable adjusters with cables running through and two return springs. This completes the description of the brake mechanism design.

The purpose for abandoning this design transpired after the frame had been cut to desired dimensions. After an inspection of the shortened frame I noticed that there was limited room because most of the frame will be bed space for the cargo. I realized that the cables would only have to travel a short distance from the pedal to the brakes. I then decided I would implement the ideas associated with the brake mechanism design into a similar design that would use the pedal as the brake mechanism and link the entire system together at the pedal. This approach would provide me with a design that was much more simple, reliable, cost effective and easier to maintain. Figure 2 on the next page shows the cut frame with the rough representation of the cable routing.

CABLE ROUTING

Rear Brake CablesFront Rear Cables

Figure 2: Brake cable routing through modified vehicle frame

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Direct Pedal Linkage Design

The direct pedal linkage design will consist of two return springs, two front cables and two rear cables with cable covers, a pivot bolt, anchor bolts, nuts and brackets to fasten to pedal to the pedal frame which will be welded to a cross member on the vehicles frame. The type of brakes used in this system also experienced a slight change, but was not due to the actual design. While designing this system the team agreed upon using a front knuckle and wheel assembly from a S-series Saturn. The wheels called for a change in the type of brakes to be used on the front axis because the assembly was for a disk brake arrangement. Therefore the front wheels were changed to mechanical disk brakes and the rear remained mechanical drum brakes.

The pedal design will serve the same purpose as the main functioning component where cables from all the brakes are tied and will be similar to the brake mechanism design, whose intention was to transfer the load applied to the pedal to the four mechanical levers, which apply the brakes. Figure 3 shows a 3D sketch of the pedal design.

Figure 3

The pedal has four cables attached to it, which link both the rear and front brakes together. The cables are fastened to the pedal with anchor bolts that allow them to rotate as the pedal is applied and released. The pedal is fastened to the pedal frame by a pivot bolt that allows the pedal to rotate as the pedal is applied and released.

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Two return springs are attached to the frame and to the bottom of the pedal in order to return the pedal to its normal position when the pedal is released. As the pedal is applied rear and front cables with move in the proper directions in order to pull the levers attached to the brakes and engage the brakes. Figure 4 shows the pedal applied to its maximum position.

Figure 4

As you can see there are many benefits this design has to offer. It is much simpler in design and has fewer components and moving parts.

Currently, I have specified rough estimates of the dimension I will be using for my pedal and are shown in Figure 5 on the following page. In order to properly finalize the dimensions of the pedal I will have to acquire all forces that will act on the pedal. This requires that I specify the exact brakes I will be using so I can determine the force required to pull the mechanical lever on the brakes, which will be provided by the brake company. Figure 6 on the following page shows the various aspects that had to be calculated and specified in order to choose the proper brakes for our vehicle.

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Figure 5

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NECESSARY CALCULATIONS

Figure 6: A table of the required calculations that needed to be specified.

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The information provided will be sent to KNOTT braking company and with the help of their design engineers, we will specify rear drum brakes and front disk brakes. After the brakes have been specified, I will be able to obtain the force required to pull the brake activating levers and thus allowing me to distinguish the tensions our brake cables will be subjected to. The tension in the cables, the force applied to the brake pedal by the driver and the spring forces will be used to conduct a static force analysis on the pedal. The force analysis on the pedal will be conducted in order to properly dimension the pedal to guarantee a quality design. Figure 7 shows a set up for the force analysis on the pedal. A proper spring will be selected after the spring force, the spring constant, the un-stretched length and stretched length are determined. A spring that has a relatively large diameter will remain horizontal to prevent any slack in the spring in its un-stretched position and is desired to ensure a quality design. The disc, drum and band brakes will be purchased from KNOTT Brake Company and are simple in design, cost effective and provide excellent braking performance for the low speeds and weight our vehicle will experience.

Figure 7

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Emergency Brake System

The competition specifications called for an emergency brake system to also be implemented into the brake system design. I chose to have an emergency brake system that will be a separate system controlled by a hand lever that will be placed next to the driver and will be composed of a band brake attached to the drive train. I decided to isolate the emergency brake system due to the fact that the competition also calls for a brake system that provides redundancy. Isolating this system ensures that if the primary brake system were to fail, there would be another option for stopping the vehicle.

Advisor/Group Collaboration

Through the semester I met with my advisor at least once a week to update him on the progress of the project as well as get any guidance I needed to deliver a quality brake system design. I also collaborated with my team members to gain insight on the various systems involved as well as offered any insight I may have had to the team for their systems. We worked closely together and helped each other throughout the entire semester.

Potential Impact

This project will show that the Southeastern Louisiana University’s Engineering Technology Program is capable of producing outstanding engineers that will be valuable in the field. Aside from providing the industry with exceptional engineers, the project itself has the potential to impact others lives. The team took on this project by entering a competition held by the Institute of Affordable Transportation. The competition tests the ability of the vehicle through various terrains as well as being evaluated for vehicle design for certain specifications including lightweight, low cost, and durability. The winning team’s design will be mass-produced in the area and impacts the lives of less fortunate individuals in rural Africa. In summary, this project will not only test the groups’ ability to design and assemble a working vehicle, it also has the possibility of positively impacting the lives of people who are in need of vehicles like this.

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Budget Justification/Component List

Component Price Description2 Drum Brakes2 Disk BrakesCablesCable CoversBracketsCustom Pedal Assembly2 Springs4 Anchor BoltsEmergency Brake Assembly

Deliverables

Throughout the semester I have remained on task with the design phase of the brake system. I have specified all components that will be used along with rough sketches and dimensions of the system I will be using. I have been in close contact with a design engineer at KNOTT Brake Company to determine the correct front disk brakes and rear drum brakes. All calculations that needed to be specified have been completed and I am waiting to hear back from my contact to get our verdict on the specific brakes we will be using. When the brakes have been specified I can further my design by conducting a force analysis on the pedal to properly dimension it. The Christmas break will be used to do the force analysis, properly dimension the pedal, create CAD drawings, send drawings to fabricator to be made, specify all required components and purchase as many components as possible. We plan to use next semester to integrate all systems into a fully functioning vehicle and also make any necessary adjustments so that the vehicle is competition ready.

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TENNATIVE TIMELINE PHASE 1BRAKE SYSTEM

Date Description Status

21-Oct-12 Remove frame from S10 at Pull-A-Part in Baton Rouge, LA. Obtain a proper engine ✔

22-Oct-12 - 27-Oct-12 Cut frame down to desired length and weigh it ✔28-Oct-12 - 3-Nov-12 Take dimensions of frame and figure out how to route cables ✔4-Nov-12 - 10-Nov-12 Make all necessary calculations (i.e. weight, deceleration, weight distribution, etc.) ✔11-Nov-12 - 17-Nov-

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Contact brake manufacturer and specify brakes to be used (could roll over to Fall Brake) Get required force to pull mechanical lever on brakes Create rough drawings of the pedal in a design program

18-Nov-12 - 24-Nov-12 Prepare for Final Presentation

25-Nov-12 - 1-Dec-12 Final Presentation

Christmas Break

Conduct a force analysis on pedal and design pedal (specify dimensions of brake pedal) Make CAD drawings of brake pedal Send drawings to fabricator to be made Figure out exact component requirements (i.e. cable length, number of brackets, etc.)

Task in process✔ Task completed

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