Mechanical Engineering Design Project 1

Bulk Material TransportSHIFTY

(Critterus Shiftius)

MEEN 4264: Senior Design

April 28, 2005

Mitchel Smolik Eric CoxAlan Elps Lance Cross

Table of Contents

Table of Contentsii

Abstractiii

Introduction1

Objective2

Design Development3

Analysis13

Manufacturing19

Schedule22

Budget24

Conclusion25

References27

Appendix A: ASME Student Design Competition Rules28

Appendix B: Photos31

Appendix C: Hand Calculations35

Appendix D: Finite Element Analysis 41

Appendix E: Detail Drawings44

Appendix F: Procurement Packet59

Appendix G: Drive System Specifications63

Abstract

The purpose of this senior design project is to design and build a bulk material transport device that will be used to overcome a specific barrier. The American Society of Mechanical Engineers (ASME) issued this challenge to engineering students around the world. This simplifies the first phase of the project, since the problem is defined in entirety for us ASME, as part of their 2005 student design competition, specified the criteria for the design, and the obstacle to be traversed. This project commenced in May 2004 with the concept phase. Once the 3D solid computer model was completed we obtained sponsorships to fund the materials and parts. We built and tested the vehicle and made minor modifications to the original design. The design preformed well and placed 3rd in the regional ASME competition in Spring 2005.

Introduction

The purpose of this project is to design and build a bulk material transport device that will be used to overcome a specific barrier. The American Society of Mechanical Engineers (ASME) issued this challenge to engineering students around the world. This simplifies the first phase of the project, since the problem is defined in entirety for us. The design problem description is located at the ASME student design competition web site [2]. Along with the stated problem definition, there is a question and answer forum to determine other contest legalities. Figure 1, Obstacle Drawing is a visual depiction of the problem statement and directly shapes our design. A full version of these rules can be found in the Appendix A; ASME Student Design Competition Rules.

Diagram of stair obstacle course [1].

OBJECTIVE

The objective of this project is to create a vehicle to transport as much granular material (rice) over the obstacle and dump it into the container. This can be done as many times as possible within 10 minutes.

Specifications

No quantitative design specifications are given for the vehicle, except the size constraints given in the rules (25x25x30cm). Based on initial concepts, a goal is set for at least 50 lb. of rice in 10 minutes, and a minimum load per trip value is set at 17 lb. In relation to the previous, the vehicle minimum top speed is specified to be 3 in/s. The driving motor/s are expected to be capable of providing a force on the ground equal to or greater than the weight of the vehicle at the speed specification. So, should the vehicle be capable of sticking to a vertical wall, it will be able to climb it at 3 in/s.

DESIGN DEVELOPMENT

Track Design

It is important to start the project with a good foundation. It was decided early on that a tracked vehicle would provide this. The rest of the project would be based from this decision so it was critical to choose a good design early on. As can be seen by Figure 2; Track Design Progression, several concepts were evaluated before choosing the final W design. The first concept shown in the figure is a traditional tank-type tread, ruled out for the angle it would attain when climbing. The second is a movable cantilever design, capable of either spanning an extra step, or lifting the back end of the vehicle. The third is closely related to the chosen design, but is intended to climb in one direction.

Progression track designs.

Bed Slide Design

During our concept phase, this W track design accompanied a movable bed, to control the center of gravity. This would be completely necessary, since most of the weigh was at the top of the vehicle; a rollover would be unavoidable without it. Two choices were available for consideration. The first was a double slide, letting double the slide distance over the single slide option. Figure 3; Bed Slide shows the single slide that was used for this project. The decision was made that the linear distance needed would not require the more complicated, and space-hogging slide.

Bed slide mechanism.

The slide design never strayed from a gear motor-driven rack-and-pinion drive, but the details took time to develop. Initially the rack was connected to the bed, which tilted on an axis at the end of the slide rods. This meant that the pinion would separate from the rack to dump rice. We didnt think there would be too much trouble getting them to mesh when they reconnected, given the fine pitch of the teeth. But, keeping the correct backlash, and meshing and unmeshing the gears seemed risky. It was decided at some point to keep the drive motor stationary, since it would be the lowest member of the assembly. If it moved with the bed, there would likely be interference issues with other parts. Eventually, the assembly evolved to have a rack attached to the slide bearings. The current design has a motor mount spanning between the rod mounting blocks, which means the motor now lifts with the bed, slide rods, and rack. The whole top of the vehicle flips up, not only yielding a more reliable assembly, but gives easy access to the innards for a quick battery change, and makes it easier to build. This results in more weight to lift when dumping, but being able to slide the bed nearly all the way to the fulcrum makes the bed easier to dump.

Bed Design

The other major mechanical assembly was the bed itself. At first the intention was to use one large bed. However, the question and answer forum revealed the legality of assembly after the vehicle was in the starting area. Armed with this information, the design took a radical turn. The payload capacity could be doubled by utilizing slide outs that fit within the require dimension prior to starting and then be extended in the starting area. Side slide outs were not feasible due to the necessity of a complicated dumping door that folds out. To simplify this, a fore and aft approach was taken as shown by Figure 4; Bed Extension.

Bed extension mechanism.

Motors

Geared, DC motors were the only alternative considered; we didnt want to take the time, or waste the space to attempt our own gearbox. The chosen motor was a Pittman design, capable of a continuous 500 in oz of torque, as limited by the gears. Together they are capable of providing 62.5 lb at the ground. This figure is taken at the ground, not considering drivetrain losses. The same motors would be used to drive the tracks and bed slide, so that it would be necessary to carry only one spare [2].

Discussion of Current Design

Body of Report..

.

Schedule

The schedule for this project begins in May 2004. This is when it was decided to undertake the challenge and recruit the team. We scheduled tasks in categories including design concept, solid modeling, sponsorship procurement, build, and test phases, as shown in Figure 5 and Table 1. The Gannt Chart has been updated reflect the actual completion of tasks.

Schedule of Shifty Design, Fabrication and Testing

Budget

Early on in the project we knew funding would be an issue. Since the solid model was completed we used it to create a packet, which was used to sell our project to potential sponsors. The break down of sponsorship is as follows in Table 1.

Table 1Breakdown of Sponsorships

FMC

$400

Driver/PG (Anaheim Automation)

$135

Salvage Materials (CCAD)

$297

Scrap Iron (Alan Elps)

$146

Drive Motors (Click Automation)

$330

Drive Belts (Econobelt)

$60

CMT Discounts

$67

Total Donations

$1,435

Table 2 shows our parts list break down and reflects the actual project cost.

Table 2Parts List Breakdown and Actual Project Cost

20o pressure angle gear rack

$75.53

20o pressure angle spur gear material 0.667 pitch diameter

$20.63

17-4 PH Stainless Steel slide rod material

$21.93

0.25 X 1 2024 Aluminum flat bar for cross members

$17.10

Shipping cost for above items

$30.00

3 ea. Geared drive motors 36 rpm, 2.6 lb-ft continuous torque (donated)

$330.00

3 ea. 8mm HTD timing belts (donated)

$60.00

2 X 36 6061 Aluminum bar stock for wheel material (donated)

$100.00

0.1875 X 12 X 12Aluminum plate for side frame material (donated)

$20.00

0.0625 X 3 X 3 Aluminum sheet metal for bed construction (donated)

$60.00

Electrical components used from items donated by CCAD (donated)

$150.00

32 ea. Rolled Blade Abec #1 bearings for idle wheels (donated)

$50.00

Linear Actuator for tilting bed

$136.00

Switches for controlling motors

$40.00

C cell battery holders

$15.00

C cell batteries used for testing and competition

$80.00

Driver/ Pulse Generator

$135.00

Total Expenses

$1,341.00

Conclusion

After considerable time in the concept phase, an accurate parametric model was created of the W track concept with the sliding bed. Manufacturing started late in the detail design phase as drawings were produced. Many parts were made before the entire design was complete. The finished prototype performed well after several minor modifications. All original specifications were met and exceeded. This project proved the viability of our W track design combined with a controllable center of gravity for stair climbing vehicles in general. Specifically, we won 3rd place out of 37 teams competing in the ASME Region X Student Design Competition.

Lessons Learned and Future Work

The single most important advantage the competition had was power. The teams with robots carrying more rice used CTA batteries. Although their capacity is similar to an Alkaline, there are capable of providing in the range of 10 times the current without significant voltage drop.

After the fact, it appears that in a project like this should spend as much time in the concept phase as possible to ensure that the concept chosen is optimized for all given parameters. There is always pressure to stay on schedule, and to make the prototype work. But, this competition was lost in the concept phase. We could have used more, different ideas. Judging from the competition, we should have expanded the bed upward to gain more capacity. This wasnt possible for us though. The rules of the competition took shape slowly, as more questions were asked. So teams that formed or modified their concepts after they had full understanding of the rules had a distinct advantage. With the schedules of our team members, we had no time to waste arguing about the rules. Additionally, unlike many schools, we procured our own funding, which took considerable time. Regardless, we are satisfied in completing, on time, a project that met our goals and did well against the competition.

References

Grimm, T.A., 3D Printer Benchmark: North American Edition, T.A. Grimm & Associates Inc, www.tagrimm.com, June 2010.

ASME Student Design Competition , 2005, www.asme.org/students/Competitions/designcontest/2005/Design_Problem_Description.html, May 2004 April 2005.

Peel, L.D., Baur, J., Foster. D., Phillips, D., McClung, A., The effect of scaling on the performance of elastomer composite actuators, SPIE Smart Structures/NDE 2010, March 2010.

Zhou, H, Ting, K. L., Topological Synthesis of Compliant Mechanisms Using Spanning Tree Theory, ASME Journal of Mechanical Design, Vol. 127, No. 7, 2005.

Zhou, H., Ting, K. L., Shape and Size Synthesis of Compliant Mechanisms Using Wide Curve Theory, ASME Journal of Mechanical Design, Vol. 128, No. 3, 2006.

Zhou, H, Topology Optimization of Compliant Mechanisms Using Hybrid Discretization Model, ASME Journal of Mechanical Design, Vol. 132, No. 11, 2010.

J. K. Ali; "A new miniaturized fractal bandpass filter based on dual-mode microstrip square ring resonator," Systems, Signals and Devices, 2008. IEEE SSD 2008. 5th International Multi-Conference on , vol., no., pp.1-5, 20-22 July 2008.

Peel, L., Meija, J., Narvaez, B., Thompson, K., Lingala, M., Development of a Simple Morphing Wing using Elastomeric Composites as Skins and Actuators, J. Mech. Des., Vol. 131, Issue 9, doi:10.1115/1.3159043, Sep. 2009

Peel, L., Ball, C., Fabrication and Testing of a Simple Bionic Arm, ASME Conference on Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS2010), Philadelphia, PA, Sept. 2010.

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