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Y Link Final Report 2009

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Senior design final report, currently building phase of the project

Senior design final report, currently building phase of the project

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    Y Link Final Report 2009 Y Link Final Report 2009 Document Transcript

    • 2009 UNC Charlotte Mechanical Engineering Matthew Etter Jesse Parnell Faculty Mentor – Dr. Ahmed Soliman [Y-LINK PROJECT – SENIOR DESIGN DOCUMENTATION] Date Revision Author Comments 2009-12-11 REV. A Matthew Etter Original
    • UNC Charlotte Senior Design Rev. A Y-Link Project Table of Contents 1 Overview of this Document .................................................................................................... 3 2 Overview of the Y-Link Control Arm Project ........................................................................ 4 3 Project Requirements .............................................................................................................. 4 3.1 Major Requirements ......................................................................................................... 4 3.1.1 Increase in Ride Comfort .......................................................................................... 4 3.1.2 Increase in Suspension Articulation.......................................................................... 6 3.1.3 Increase Ground Clearance ....................................................................................... 7 3.2 Minor Requirements ......................................................................................................... 8 3.2.1 Adjustability of the new design ................................................................................ 8 3.2.2 Allowance for factory components (bolt on design)................................................. 8 4 System Design ........................................................................................................................ 8 4.1 Bent Y-Link Design ......................................................................................................... 8 4.1.1 The Y-Link.............................................................................................................. 10 4.1.1.1 Y-Link Design Overview ................................................................................ 10 4.1.1.2 Y-Link Design Details ..................................................................................... 10 4.1.1.3 Joint Selection.................................................................................................. 12 4.1.2 The Cross Member .................................................................................................. 12 4.1.2.1 Cross Member Design Overview .................................................................... 13 4.1.2.2 Cross Member Design Details ......................................................................... 13 4.2 Alternative Designs ........................................................................................................ 14 5 Design Calculations .............................................................................................................. 15 5.1 Strength of Design.......................................................................................................... 15 5.2 Stability .......................................................................................................................... 17 6 Legalities of Suspension Alteration ...................................................................................... 17 7 Implementation ..................................................................................................................... 18 7.1 Budget ............................................................................................................................ 18 7.2 Manufacture ................................................................................................................... 19 7.3 Installation ...................................................................................................................... 21 8 Works Cited .......................................................................................................................... 23 9 Appendix A – Accelerometer Data Sheet ............................................................................. 24 10 Appendix B – Engineering Drawings ................................................................................... 25 11 Appendix C – Cover Letter ................................................................................................... 31 12 Appendix D – Statement of Work ........................................................................................ 32 13 Appendix D – Project Capabilities and Requirements ......................................................... 33 2
    • UNC Charlotte Senior Design Rev. A Y-Link Project 1 Overview of this Document The goal of the Y-Link Control Arm project (henceforth referred to as the Y-Link project) is to increase the ride comfort and off road capability of the 1984-2001 Jeep Cherokee vehicles. The goal will be met through changes in the Lower Control Arms (LCA) and the transmission supporting cross member designs. (Parnell, Y-Link Statement of Work 2009) With the addition of aftermarket lift springs the short factory design of the LCA on the Cherokees have a tendency to rotate down as lift height increases thus increasing the angle off of the ideal horizontal position. This off-horizontal position creates a resultant force being transferred into the chassis of the vehicle, decreasing the effectiveness of the suspension when road impacts are encountered. This results in a harsh ride for the driver. An illustration of the problem is seen in Figure 1: Figure 1: An illustration to show the effects of a steep angle in the LCA. The longer LCA decreases the off-horizontal angle as well as increases vertical movement. The tendency for the axle to travel rearward as the suspension unloads also creates a problem as the suspension binds the vehicle’s steering and track bar. The LCA also rotates upward in relation to the axle and contacts the lower coil spring pad creating another problem. These issues cause a lack of downward wheel travel, also known as droop. With limited droop a four wheel drive vehicle is less able to keep downward force on all wheels and forward motion in difficult terrain is negatively affected. With standard differentials power is transmitted to the wheel that is providing least resistance and thus power is no longer effectively transmitted to the ground. Therefore wheel spin is the result eliminating forward progress. 3
    • UNC Charlotte Senior Design Rev. A Y-Link Project The implementation of a longer LCA with a necessary new rear attachment point will decrease the off-horizontal angle while minimizing horizontal travel in the front axle. Therefore, ride quality would increase due to a decrease in forces directed into the LCA. The minimization of horizontal axle movement relative to the chassis will eliminate the binding issues which currently affect axle droop. The project can be broken down into two main areas: Y-Link arms and a cross member. The new cross member will provide the pivot points for the new arms and will also support the transmission due to its rearward placement. The design was created using industry standard materials and load ratings were calculated based upon a factor of safety of at least two. Once the load rating for the Y-Link arms had been determined, the new cross member was designed in a similar fashion. Given a maximum load rating for the system, a maximum bump height was determined for the vehicle while in two wheel drive. 2 Overview of the Y-Link Control Arm Project The Y-Link project addresses issues with the factory 1984-2001 Jeep Cherokee LCA when used in conjunction with an aftermarket suspension lift. The factory LCA negatively impacts ride quality and off road performance when a longer than factory spring is installed. After implementation of the design the ride quality and suspension articulation will be compared to the suspension which utilizes the factory LCA. This document illustrates the methods used to determine ride quality, suspension articulation and the design of the new system which include long control arms and a new transmission cross member. 3 Project Requirements In order to evaluate the success of the Y-Link project, a list of requirements was established. The requirements list will compare with the end result of the project to ensure the goals have been met. The project Capabilities and Requirements document can be found in Appendix D 3.1 Major Requirements Major requirements are the goals set forth that can be quantified in the end product. These are the main consideration during the design phase. 3.1.1 Increase in Ride Comfort The ride quality of the test vehicle, a 1991 Jeep Cherokee fitted with 4.5 inch lift springs and factory lower control arms, was analyzed using an LIS331DL accelerometer from STMicroelectronics, secured in the passenger cabin, over standardized bumps. The data sheet for the accelerometer can be found in Appendix A. To minimize the effects of gravity and any misalignment of the accelerometer the magnitude of the three axes were used after being passed through a high pass filter. The test procedure went as follows: 1. Vehicle speed was set to 25 mph 2. 2x4 (1.5x3.5 actual) inch blocks were used as a standard bump 4
    • UNC Charlotte Senior Design Rev. A Y-Link Project 3. Tire pressures were set to 35 psi 4. Accelerometer sampling rate was 20 Hz The test was conducted in a local parking lot with impacts on the front wheel. The driver’s front wheel was driven over a wooden block to replicate a bump on an otherwise smooth parking lot. The data was recorded and another run was compared with the front driver’s side wheel with two stacked wooden blocks. Finally, a third run was performed with each front wheel contacting one wooden block. The data collected over the three trials was centered over the peak acceleration so that the three distinct runs could be compared. The graph of this data is shown below in Figure 2: Figure 2: Preliminary accelerometer data from ride harshness test shows that the harshest impact was from 2 stacked 2x4 inch blocks on one wheel. The accelerometer data was centered upon the spike of each run and the magnitude of the total acceleration was used to minimize any error from accelerometer misalignment. Finally, the high pass filter feature was used to negate the effects of gravity. With the data collected the most extreme impact from the test was found to be just over 1 gravitational constant. One of the primary goals of the project is to lessen the severity of the impact after the new equipment is installed by reducing the off-horizontal angle of the LCA. 5
    • UNC Charlotte Senior Design Rev. A Y-Link Project 3.1.2 Increase in Suspension Articulation A common measure for the articulation of a suspension is the Ramp Travel Index (RTI). The basis for the measurement is to navigate a vehicle up a standardized ramp of 20 degrees until the lack of droop in the front wheels pulls a wheel off of the ground. Just before a wheel leaves the ground the distance that the vehicle traveled up the ramp is recorded. This is put into the RTI equation, Equation (1): (1) where; is the vehicle’s score, is the distance traveled up the ramp without lifting a wheel and is the length of the wheel base of the vehicle. (Medina 2009) The RTI number is essentially the vehicle ability to traverse uneven terrain off road. A low RTI score implies difficulty in maintaining traction over difficult obstacles. The basic layout of the test can be seen below in Figure 3: Figure 3: The test vehicle during a RTI evaluation at Tarheel 4WD in Charlotte, NC. The wheel in the foreground illustrates a lack of droop which causes the driver’s side rear wheel to come off of the ground and lose traction. The black RTI scoring ramp can be seen in the background under the driver’s side front tire. As a vehicle climbs the RTI ramp the front suspension is forced to articulate until the suspension extends to its maximum vertical travel. Any lack of travel can be caused by shock absorbers which have reached the end of their stroke, brake lines or binding suspension components. The 6
    • UNC Charlotte Senior Design Rev. A Y-Link Project brakes lines on the test vehicle are long aftermarket units and the shocks were disconnected to check for stroke. The shock proved to be near the end of its useful length but was not considered a limiting factor in the system. The binding suspension components due to the short LCA were to blame for the test run. After the inspection of the test vehicle’s suspension was completed the numbers for the trial were processed. The test run on the 20 degree ramp at Tarheel 4WD in Charlotte, NC provided the results for the test vehicle which is seen below in Table 1: Table 1: The preliminary RTI score of the test vehicle proved to be a 647.4 on a 20 degree ramp. Ramp Vehicle Lift/Type Wheel Base (in) Distance up ramp (in) RTI Score Type 1991 20° 4.5"/Factory LCA 100.4 65 647.4104 Cherokee While the score of 647 is considered fair to good in the industry, a goal of the project is to increase articulation (RTI score) 50 points through the reduction of horizontal binding in the front axle. 3.1.3 Increase Ground Clearance Ground clearance is one of the primary concerns when building an off road vehicle. The ability to pass over obstacles without getting hung up is a goal that will be kept in mind in the design of the Y-Link project. The current design can be seen in Figure 4: Figure 4: The current cross member is shown with red arrows and the limiting factor on the underbody of the test vehicle is highlighted on the current cross member with orange. The current clearance of the cross member is 15.125 inches from the ground. 7
    • UNC Charlotte Senior Design Rev. A Y-Link Project Figure 3 shows where ground clearance will be increased (highlighted in orange). Low ground clearance is a common problem when traversing off road resulting in immobile vehicles. A major goal in the project is a cross member with increased ground clearance for easy travel over obstacles. The construction of the factory design was based on the use of very thin sheet metal. For this reason Jeep engineers were required to use a box structure to get the strength out of the metal. 3.2 Minor Requirements Minor requirements are the goals set forth which need to be in the end product to create a smooth transition to the new system. These are features which are not improved but are required for the design. 3.2.1 Adjustability of the new design Adjustment of the new control arm system is required for alignment issues to provide a safe, stable vehicle. The new design should allow adjustment for the longitudinal location of the axle for proper steering geometry. The control arm should also allow adjustment to caster for vehicle tracking. Each adjustment should have 1 inch of travel such that factory alignment specifications can be assimilated. 3.2.2 Allowance for factory components (bolt on design) As this system is to be bolted on with minor cutting and drilling and no requirement to weld, the final design should have the ability to be bolted on to a factory Jeep Cherokee between the years of 1984-2001 with no other modifications. The factory exhaust system as well as the factory transmission mounts need to be retained for a satisfactory result. Also, factory attachment points on the axle will be utilized in the new Y-Link project. 4 System Design In order to properly meet the requirements set forth in this document as well as the Capabilities and Requirements document the Y-Link project could have taken several different paths. (Parnell, Y-Link Requirements 2009) Each design idea brought unique advantages to the work space but the bent Y-Link design proved to be the best decision. 4.1 Bent Y-Link Design The bent Y-Link design addressed the issues listed in the requirements with the simplicity and ease of manufacture. The design features 2 Y-Link control arms attached to a cross member to retain the front axle. The layout of the design can be seen below in Figure 5: 8
    • UNC Charlotte Senior Design Rev. A Y-Link Project Figure 5: The Y-Linked project design in its entirety. The design utilizes 2 Y-Link control arms and a newly design cross member to help locate the front axle. The cross member supports the control arms and the transmission. The design can be broken down into two main elements: the Y-Link and the cross member. The system will require Cold Rolled Steel (CRS) 1020 Drawn Over Mandrel (DOM) steel, 0.25 inch thick CRS plate and a variety of joints and bushing which will be sourced from outside vendors. A bill of materials can be seen below: Table 2: Bill of Materials (BOM) for the Y-Link project. This is a complete listing of parts needed to complete the project. UNC Charlotte Senior Design Project : Y-Link Project Bill of Materials for End Project 2009-10-08, Rev A Assembly Component Item Qty Price per Total Source Cross Member Main Frame 48.0"x48.0"x0.25" 1020 CRS 1 $114.24 $114.24 Metals Depot Cross Member LCA Bracket Prefabricated LCA Bracket 2 $15.00 $30.00 Poly Performance Cross Member Hardware 1/2" - 2 UNF Bolts (Grade 8) 6 $1.13 $6.78 McMaster Carr Cross Member Total $151.02 Lower Link Tubing 3.0'x0.25"x35" 1026 DOM 3 $13.50 $40.50 Poly Performance Lower Link Front/Rear Joint 2.5" Johnny Joint_1.25-12 Thread 2 $39.95 $79.90 Currie Enterprises Lower Link Tube Insert/Jam Nut 1.25"-12 Round Threaded Bung - RH with Jam Nut 2 $25.00 $50.00 Currie Enterprises Lower Link UCA Bracket 8.0"x8.0"x0.25" 1020 CRS 2 $26.18 $52.36 Metals Depot Lower Link LCA Rear Bolt 9/16"-3.5" UNF Bolt (Grade 8) 1 $1.56 $1.56 McMaster Carr Lower Link LCA Front Bolt 9/16"-4.0" UNF Bolt (Grade 8) 1 $1.95 $1.95 McMaster Carr Lower Link Hardware 9/16" UNF Nut (Grade 8) (Nylon Locknut) 2 $0.58 $1.16 McMaster Carr (1) Lower Link $227.44 Upper Link Tubing 2.0'x0.25"x35" 1020 DOM 2 $13.50 $27.00 Poly Performance Upper Link Rear Joint 2.0" Forged Rubber End 1 $39.00 $39.00 Rusty's Off-road Upper Link Front Bracket 12.0"x12.0"x0.25" 1020 CRS 1 $20.46 $20.46 McMaster Carr Upper Link Tube Insert/Jam Nut 1.25"-12 Round Threaded Bung - RH with Jam Nut 1 $25.00 $25.00 Currie Enterprises Upper Link UCA Front/Rear Bolt 9/16"-3.0" UNF Bolt (Grade 8) 2 $1.56 $3.12 McMaster Carr Upper Link Hardware 9/16" UNF Nut (Grade 8) (Nylon Locknut) 2 $0.58 $1.16 McMaster Carr (1) Upper Link $115.74 9
    • UNC Charlotte Senior Design Rev. A Y-Link Project 4.1.1 The Y-Link A pair of Y-Links is used to make the connection between the axle and the chassis of the test vehicle. They will replace the factory upper and lower control arms. Grade 8 hardware is used throughout the assembly with a minimal bolt diameter of ½ inch. This results in a minimum single-shear strength of 22,000 lbf in the hardware for the system. The hardware in the system does not present a yielding concern.(Potter 2009) 4.1.1.1 Y-Link Design Overview The upgrade from the factory control arms will be the new Y-Link control arm. It can be seen in Figure 6: Figure 6: The Y-Link Subassembly which is one of two connections between the chassis and the front axle. The replacement of the upper and lower control arms with a single Y-Link proves to be a simple design which will allow for flexibility and adjustment as stated in the requirements. It has several advantages over the factory style arm: 1. Longer arms create advantages a. Lower off-horizontal angle increase’s ride quality b. Longer radius of travel decreases longitudinal movement to reduce binding in the steering and other suspension components to improve articulation 2. Curved arm increases ground clearance over a more traditional straight LCA 3. The adjustable threaded links allow for alignment corrections once installed 4. Bolt on design 5. Quite simple design and easy to manufacture 4.1.1.2 Y-Link Design Details The approach to the design of the Y-Link control arms was based on material selection and research of existing commercially available equipment. The decision was made to use DOM 10
    • UNC Charlotte Senior Design Rev. A Y-Link Project 1020 steel tubing which describes the manufacture process of the material which eliminates the seam commonly found in rolled tubing. The joints for the Y-Link are as described in the BOM seen above and are designed for chassis linkages. Using dimensions which fit the test vehicle, the SolidWorks solid model was formed using the material selection as described. The resulting solid model was processed in the SolidWorks Simulation software. The procedure was performed on the lower link due to its curved nature which normally creates curved beam stresses not found in straight designs. This resulted in a load on each arm at 2,500 lbf with a safety factor of two. The results can be seen below in Figure 7: Figure 7: The results of the Y-Link analysis. A load of 2,500 lbf is handled with a safety factor of two. To verify that the curved element did cause increased stresses, the SolidWorks Simulation software was once again used to highlight potential problems. The results can be seen below in Figure 8: 11
    • UNC Charlotte Senior Design Rev. A Y-Link Project Figure 8: The stress concentrations in the curved lower link of the Y-Link. Curved beam theory would predict that the highest stresses could be found on the inner portion of the radius. The design includes the upper link attachments which act as gussets. For this reason, the highest stress concentration can be found on the inner region of the arm opposite of the thinnest section of the gusset. Though the stress is high in this region, it was calculated that each of the two arms could handle 2,500 lbf with a safety factor of two. Further analysis of this number can be found in the design portion of this document. 4.1.1.3 Joint Selection The Currie Johnny Joints chosen for the Y-Link project were selected because of their relatively high 30 degree range of motion compared to a more conventional heim joint which offers limited flexibility at only 22 degrees. The housing materials for the selected joint are of superior strength due to their forged construction and a quiet ride because of the polyurethane bushings. Conventional heim joints typically have excessive play and lack a bushing resulting in loud operation. (Currie Enterprises 2009) 4.1.2 The Cross Member The cross member is a necessary portion of the design. It attaches the Y-Links to the chassis of the test vehicle. Due to the length of the control arms, the transmission cross member was an ideal place for attachment. 12
    • UNC Charlotte Senior Design Rev. A Y-Link Project 4.1.2.1 Cross Member Design Overview With the critical loads determined in the Y-Link portion of the system, the cross member was designed for similar loads in addition to the weight of the transmission. It is wider (front to back) than the factory design to provide enough structure for the support of the transmission and the Y- Link control arms and encompasses a third mounting bolt on both sides to fix the cross member securely to the frame. The factory frame possesses a hole in this location with a thick metal insert capable of holding threads. The design can be seen below in Figure 9: Figure 9: The top view of the cross member design. The vertical ribbing allows for added strength, the round holes allow for water drainage and the semi-circular cutout allows for front driveshaft travel. Note the angled attachment points for the Y-Link arms which add triangulation and strength to the design. 4.1.2.2 Cross Member Design Details During the design of the cross member, torque from the transmission was considered negligible because of the mount’s rubber composition and the outward placement of motor mounts. Therefore the cross member was designed to withstand loads of 2,500 lbf from each control arm and a 50 lbf load was placed over the transmission mount to help promote any potential failures in the design during analysis. Vertical ribbing was required to provide the strength and because of the possibility of water pooling on the inner areas of the cross member, drain holes were incorporated. A small relief had to be implemented to allow for the front drive shaft. Finally, the Y-Link mounts are angled to point the new arms directly at the existing axle mounts and add triangulation for strength and stability. The isometric view, loads and safety factor can be seen in Figure 10: 13
    • UNC Charlotte Senior Design Rev. A Y-Link Project Figure 10: The results of the strength analysis for the cross member. The cross member is designed to withstand 5,000 lbf total from the front axle with a safety factor of two. For the maximum rated load from the Y-Links of 5,000 lbf the factory of safety for the cross member is two. The design is strong, improves ground clearance, clears all existing systems on the test vehicle and provides a suitable foundation to anchor the front axle. 4.2 Alternative Designs Alternative designs that were considered during the design phase of the project include: 1. Drop brackets a. Cheap and easy b. Ground clearance greatly decreased 2. Longer upper and lower control arms with stock mounts a. Slightly increase articulation and improve ride quality b. Complex design and only marginal benefits. 3. Straight Y-Link arms with a cross member a. All the benefits of the bent Y-Link except ground clearance b. Ground clearance is negatively affected The design selected addresses all the requirements set forth in the Capabilities and Requirements document and is a simple design which aides in the manufacturing process. 14
    • UNC Charlotte Senior Design Rev. A Y-Link Project 5 Design Calculations 5.1 Strength of Design The current approach to creating ratings for the equipment is based on four main points: 1. The factor of safety (2) 2. The weight over the front axle 3. Bump height 4. Driving force of the vehicle The Capabilities and Requirements document states that a safety factor of 2.0 will be established with the design. Thus the design is rated, based on this safety factor and the strength of the design. The test vehicle has a curb weight of 3,100 pounds and an estimated 60/40 front to rear weight ratio. (Wikipedia 2009) This results in 930 lbf load over each front tire. In order to overcome obstacles while traveling off road, (slow speeds) a sum of the forces was taken at the point where the front tires contact a bump. This can be seen below in Figure 11: Figure 11: The Free Body Diagram (FBD) of the tire just as the wheel is leaving contact with the ground. The calculation of the force in the control arm is based on the angle associated with Figure 11 as well as the bump height and is as seen below in Equation (2): ( ) where; is the force in the control arm, is the weight over the front wheel and is the angle between the axle to bump line and the horizontal 15
    • UNC Charlotte Senior Design Rev. A Y-Link Project By graphing the force as a function of angle along with a factor of safety, a region of safe two wheel drive travel can be determined. This force is applied to one Y-Link arm in Figure 12: 2700 2500 Force as a Function of Bump Height Pushing Force (lbf) 2300 Maximum Thrust From Rear Wheels 2100 Safe Limit 1900 1700 1500 8 8.5 9 9.5 10 10.5 11 Bump Height (Inches) Figure 12: Force in one Y-Link arm as a function of angle between bump contact and axle centerline. This calculation assumes a rigid suspension. The horizontal red line is the 2,500 lbf which the system can handle with a factor of safety of two. The red line shown in Figure 13 is the force at which the system is rated with a safety factor of 2. The green line is the ability of the vehicle to drive itself forward given the maximum amount of torque possible if 100% efficiently transferred to the ground. The sweeping blue line is the curve which describes the changing forces required to push the front wheel over the given obstacle as a function of step height. As Figure 12 illustrates the force which the system can exert on the front axle to overcome an obstacle it should be noted that this force is based upon the following assumptions: 1. Navigation of off road vehicles is “slow” where momentum is small 2. Zero tire deflection 3. The vehicle suspension is rigid. That is, it does not unload the front springs when the rear wheels begin to drive the vehicle forward. 4. The 60/40 weight distribution is correct even with any payload over the rear tires 5. The test vehicle can actually exert the force to the ground required and no wheel slip 6. The front wheels provide no propulsion 16
    • UNC Charlotte Senior Design Rev. A Y-Link Project 7. Both rear wheels are driving while only one front wheel makes contact with the bump In reality the assumptions are conservative measures. When the tires on the front axle deflect, the moment arm which the weight of the front vehicle acts upon is reduced. Also, the vehicle does not have a rigid suspension. During trial runs the front of the test vehicle unloaded the front suspension reducing the weight over the front tires. This would consequently reduce the required force in the front Y-Links. The assumption that the test vehicle can provide the driving force without wheel slip is also very conservative from a safety standpoint. In reality the vehicle’s force to the ground through the rear wheels is determined by Equation (3): ( ) where; is the force which the rear wheels can provide, is the maximum torque output of the rear wheels, is the gear ratio of 1st gear, is the gear ratio of the rear axle and is the radius of the rear tire. With a maximum output of 220 lb-ft, a first gear ratio of 2.804:1, a rear axle ratio of 4.11:1 and a tire radius of 1.333 feet the maximum force to the ground was found to be 1,900 lbf. (Jeep Horizons 2005) During slow driving where momentum of the vehicle is near negligible this is the maximum force from the rear tires is the maximum force that can be exerted on the front arms. This value falls well below the rated load of 2,500lbf and adds to the factor of safety for the system. Furthermore, the rated torque output of the engine for the test vehicle is at 4,000 RPM which is above the stall torque of the torque converter. An occurrence of negligence would be the only foreseeable circumstance where engine speed would be adequate to create such torque. Such events would be considered an accident. 5.2 Stability During the design phase of this project stability for the test vehicle was a concern but there will be no change in ride height of the vehicle and spring rates will remain unchanged. The lateral movement of the axle with a longer control arm can also be considered a concern. With the installation of a longer set of control arms the axle will have more freedom to walk side to side with respect to the chassis. However the existence and understanding that the new set up will retain the factory track bar, which limits lateral movement of the front axle, eliminates concern. The sole purpose of the track bar is to ensure that the axle remains fixed along the axis of the wheels. 6 Legalities of Suspension Alteration Much effort was placed on locating any information which would lead to Department Of Transportation (DOT) approval. After significant research a direct contact with the DOT was established and it was determined that there are no road standards in the state of North Carolina. 17
    • UNC Charlotte Senior Design Rev. A Y-Link Project (Dona 2009) The initial idea of building the system to suit a specific bump at speed was put to rest. A phone interview with BDS Suspension Company, a manufacturer of suspension equipment which is sold nationwide, stated that the company sells only DOT approved brake lines. The suspension systems sold by BDS do not feature DOT approval. (Bob 2009) A call to Inspector Hunts at the Rowan County License and Theft office stated there is no law regarding suspension changes and that any changes made to a vehicle’s suspension is the liability of the vehicle owner. (Hunts 2009) Since this phone interview approaches toward a DOT approval have ceased. 7 Implementation The implementation of the Y-Link project will require the design finalization and purchase phase followed with manufacture of the system and finally installation. 7.1 Budget The budget for the Y-Link project is as seen below in Table 3: Table 3: The Budget for the Y-Link project UNC Charlotte Senior Design Project : Y-Link Project Bill of Materials for End 2009-10-08, Rev A Category/Item Qty Price Per Total Components Cross Member 1 $151.02 $151.02 Lower Link 2 $227.44 $454.87 Upper Link 2 $115.74 $231.47 Materials/Tools MIG Welding Gas 1 $45.00 $45.00 Spool of Wire 1 $5.40 $5.40 Other Consumables 1 $25.00 $25.00 Components and Materials/Tools Total $912.76 Labor Hours Rate Total Student time (est) 150 $100.00 $15,000.00 Mentor time (est) Dr. Ahmed Soliman 6 $150.00 $900.00 Total labor $15,900.00 Total Components, Materials/Tools, Labor $16,812.76 18
    • UNC Charlotte Senior Design Rev. A Y-Link Project Table 3 is the estimated budget for completion of the Y-Link project. The hourly rate is a fictitious term used to put value you on the time and effort put into the project by the personnel involved in the design and manufacture of the system. Consumables are to include any grinding wheels, flap disks, marking paint, tape, cutting oil, etc. 7.2 Manufacture The manufacture of the Y-Link System will begin with the construction of the cross member. The purpose of completing the cross member first is simple: without the cross member the control arms have no attachment point. Furthermore dimensions can be confirmed for a final time before the manufacture of the Y-Links during the prototype phase. Enlarged versions of the engineering drawings can be seen in Appendix B. The cross member will be constructed of 0.25 inch 1020 steel plate and MIG welded together. The process will involve three stages: The main frame, the control arm mounts and the ribbing. The drawing for the cross member as planned can be seen below in Figure 14: Figure 14: The engineering drawing for the cross member as designed. 19
    • UNC Charlotte Senior Design Rev. A Y-Link Project The Y-Link portion of the design will require specialized tools. A tubing bender will be utilized to create the correct bend with a 10 inch radius. The 2 inch DOM tubing will be then cut to length as required to meet specifications and the tabs, which provide mounting for the upper links will be externally sourced from a fabrication shop with a CNC cutting device. The bottom tube will be MIG welded together and the design for the bottom tube of the Y-Link can be seen in Figure 15: Figure 15: The engineering drawing for the bottom tube of the Y-Link control arm as designed. The upper link is simply a section of material as used in the bottom tube and the upper axle mount will be constructed with the same material as the cross member. These items can be seen in Figure 16: Figure 16: The engineering drawings for the upper link and axle mount as designed. 20
    • UNC Charlotte Senior Design Rev. A Y-Link Project With all of the parts manufactured and items from the BOM (Table 2) sourced the process of MIG welding will commence to assemble the system as seen in Figure 17: Figure 17: The Y-Link project assembly drawing as designed. 7.3 Installation Prior to disassembly measurements for front axle location will be taken to ensure proper adjustment of the new system and to ensure proper steering geometry is maintained. Also, care will be taken to maintain proper pinion angle and longitudinal axle location. As an initial requirement for the project, the design will be completely bolt on. After fabrication of the system the installation for the Y-Link and cross member should only involve the following tools: 1. Drill and drill bits as needed 2. A ½ - 18 Tap to thread the existing holes in the chassis 3. General hand tools such as wrenches, hammers and jacks As stated in the Capabilities and Requirements document, the system will require no specialized tools to install. The initial phase of the installation will be the removal of the existing cross member. The installation of the newly design cross member will follow. This will require support of the transmission while the transmission mount is removed and the cross members are changed out. 21
    • UNC Charlotte Senior Design Rev. A Y-Link Project After the new cross member is installed and clearances are checked, the Y-Links will be assembled and bolted in place to secure the front axle to the cross member. Adjustment of the system through one of the many threaded adjustment points will follow. 22
    • UNC Charlotte Senior Design Rev. A Y-Link Project 8 Works Cited Bob, interview by Jesse Parnell. Technician at BDS Suspension (December 8, 2009). Currie Enterprises. Rock Jock. 2009. http://www.currieenterprises.com/cestore/johnnyjoints.aspx (accessed November 9, 2009). Dona, interview by Matthew Etter. NC DOT CONTACT US (November 13, 2009). Hunts, interview by Jesse Parnel. Inspector for Rowan County License and Theft Office (December 9th, 2009). Jeep Horizons. Jeep Cherokee (XJ) Stock Specifications. 2005. http://jeephorizons.com/tech/xjstockspecs.html (accessed November 12th, 2009). Medina, Mark I. 4Lo. 2009. http://4lo.com/calc/rticalc.htm (accessed October 28, 2009). Parnell, Jesse. "Y-Link Requirements." Capabilities and Requirements, 2009. Parnell, Jesse. "Y-Link Statement of Work." SOW, 2009. Potter, David. RockCrawler. 2009. http://www.rockcrawler.com/techreports/fasteners/index.asp (accessed December 5, 2009). STMicorelectronics. LIS331DL. 2008. http://www.st.com/stonline/products/literature/ds/13951.pdf (accessed October 26, 2009). Wikipedia. Jeep Cherokee XJ. December 2009, 2009. http://en.wikipedia.org/wiki/Jeep_Cherokee_(XJ) (accessed December 1st, 2009). 23
    • UNC Charlotte Senior Design Rev. A Y-Link Project 9 Appendix A – Accelerometer Data Sheet 24
    • UNC Charlotte Senior Design Rev. A Y-Link Project 10 Appendix B – Engineering Drawings 25
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    • UNC Charlotte Senior Design Rev. A Y-Link Project 11 Appendix C – Cover Letter 31
    • UNC Charlotte Senior Design Rev. A Y-Link Project 12 Appendix D – Statement of Work 32
    • UNC Charlotte Senior Design Rev. A Y-Link Project 13 Appendix D – Project Capabilities and Requirements 33
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