Redesigning_the_VEX_Mecanum_Wheel.pdf - SPARK

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Redesigning the VEX Mecanum Wheel Table of Contents Introduction Background: Current Problems and Proposed Solutions: Rollers Problem Solution Dimensions of the Wheel Problem Solution Lack of Mounting Holes on the Wheel Problem Solution Design Process Final Wheel Assembly Final Product Final Render of Mecanum Printed Piece Drawing Files Future Improvements A Larger Bore for the Center Hole Utilizing Higher Traction Rollers Making a Larger Library of Sizes Closing Thoughts Redesigning the VEX Mecanum Wheel 1 Introduction For the “Make It Real” CAD Engineering Challenge this year, VEXU team SPARK decided to design a custom mecanum wheel to be a more viable design option by further optimizing the mecanum wheels from the VEX EDR product line. Background: Mecanum wheels are a widely used branch of wheels that are valued due to their ability to allow robots to traverse both forward and backward as well as side to side, a technique commonly referred to as strafing. These attributes allow highly desired versatile movement while simultaneously mitigating the additional complexity from other common strafing configurations. Mecanum wheels achieve this versatility by having their rollers angled at 45 degrees Figure 1.1 rather than having them parallel to the circumference of the wheels Figure 1.2 like the standard omni wheel. Figure 1.1 VEX EDR 4” Mecanum Wheel Figure 1.2 VEX EDR 4” Omni Wheel While mecanum wheels supplied by VEX seem like a great solution for those wanting to strafe, their current shape and structure hinder how well they perform, thus making them much less favorable for driving applications. Our goal was to design a more effective mecanum wheel which was simultaneously legal for our team to utilize on our 15” robot and more versatile for teams to use in both the competition and the skills challenge. Redesigning the VEX Mecanum Wheel 2 Current Problems and Proposed Solutions: Throughout our analysis, these were 3 specific problems which stood out to us regarding the retail mecanum wheels, as well as our solutions to them in CAD Rollers Mecanum wheel rollers require a high amount of traction and support for optimal function Problem Solution The rollers are only mounted through By supporting the roller on both ends, one hole of the custom frame, friction is reduced. resulting in additional friction due to a lack of structural support. Figure 2.1.1 Close up view of Custom Mecanum rollers supported on both ends Figure 1.3.1 Close up of VEX Mecanum rollers supported on one end The cone-like shape of the retail By using a single omni wheel roller, the mecanum wheels makes them diameter of the portion that contacts significantly less effective as the Redesigning the VEX Mecanum Wheel 3 diameter of the portion that contacts the ground is constant therefore the ground is relatively small. increasing contact. Figure 2.1.2 By using a roller with a relatively small difference in diameters results in more contact with the ground Figure 1.3.2 The difference in diameters from the end of the roller to the middle of the roller results in decreased contact with the ground ℹ The Rollers utilized on the custom mecanum are from the 3.25" omni wheels, making them easily accessible by all teams Redesigning the VEX Mecanum Wheel 4 Dimensions of the Wheel The retail mecanum wheels are only sold at a single diameter and are notably thick Problem Solution Accounting for a wheel on both sides Using thinner yet symmetrical rollers of the chassis, the wheels occupy allows for a smaller diameter and a nearly 4” of space on their own, taking thinner assembly. Resulting in a thinner up a significant portion of the chassis with additional clearance for horizontal size limit. fold-in mechanisms. Figure 2.2.1 Width of Custom Mecanum at .96 inches. Figure 1.5.1 Width of Custom Mecanum at 2.02 inches. Figure 2.2.2 Diameter of Custom Mecanum at 3.31 inches. Figure 1.5.2 Diameter of Custom Mecanum at 4.05 inches. ℹ Overall Size Reduction: 52.59% in thickness, 18.52% in diameter Redesigning the VEX Mecanum Wheel 5 Lack of Mounting Holes on the Wheel Competitive robotics teams will often use gear ratios on their mechanical systems to increase speed or torque. ⚠ When a shaft is holding both a wheel and a gear separately, there will be a slight amount of mechanical slop due to the gear and wheel not being physically connected. This can lead to drifting issues which increase chances of error during autonomous routines. Problem Solution The current retail mecanum wheel Adding holes onto the plates for gears does not have any holes for mounting and sprockets to be bolted to. accessories. Figure 1.6 Side View of VEX EDR Mecanum Figure 2.3 Side View of Custom Mecanum Wheel without mounting holes with mounting holes ℹ The hole pattern of the custom mecanum is identical to all VEX gears and sprockets Redesigning the VEX Mecanum Wheel 6 Design Process ℹ Software: Autodesk Inventor Professional 2021, 64-bit, Build 183 A 3.25” omni wheel roller assembly and VEX 0.5" spacers were used in the making of the mecanum wheel.  The frames were made by first extruding a cylinder of the desired wheel diameter, then extruding a rectangular flange with an axle hole for the roller at a 45 degree angle to the disk. Figure 2.4 The flange is at a 45 degree angle to the disk  The flange geometry was then blended into the frame using fillets, and a circular pattern function was used to give the frame a total of 16 flanges, one for each roller. Redesigning the VEX Mecanum Wheel 7 Figure 2.5 The circular pattern tool was used on the flange geometry  A series of holes are then extruded into the frame for attaching the frame to the other frame component. Figure 2.6 A series of holes are extruded to allow for the other frame to be attached and for gears and sprockets to attached to the wheel Redesigning the VEX Mecanum Wheel 8  The frame is then mirrored to get the 2 frame components for both sides of the wheel. Figure 2.7 The frame is mirrored to get components for both sides of the wheel  The frames are finalized using a mock assembly to determine the optimal positioning of the roller axle holes to ensure a snug fit for the rollers. Final Wheel Assembly A new assembly is then made by constraining the frame components and rollers together, completing the mecanum. Figure 2.8 Blown up Visual of Final Mecanum Assembly Redesigning the VEX Mecanum Wheel 9 Final Product Final Render of Mecanum Figure 2.9 Final Render of Assembled Mecanum Wheel Printed Piece Figure 2.10 Final Picture of Assembled Print Redesigning the VEX Mecanum Wheel 10 Drawing Files Figure 3.1 Drawing file of the final mecanum wheel Redesigning the VEX Mecanum Wheel 11 Figure 3.2 Drawing of the mecanum frames Redesigning the VEX Mecanum Wheel 12 Figure 3.3 Drawing of a 3.25" omni wheel roller Redesigning the VEX Mecanum Wheel 13 Future Improvements While we feel that our solutions solve some of the primary issues held by the retail mecanum wheels, there is no doubt that there are additional improvements that can be made. A Larger Bore for the Center Hole Currently, the center hole of the wheel plates only supports the VEX EDR ⅛” low strength shafts. By making the bores slightly larger, they can be compatible with various other shaft sizes. Utilizing Higher Traction Rollers Rollers with a higher traction would allow us to gain more traction with the foam tiles of the field, mitigating drifting errors during autonomous routines. This could be achieved by utilizing rubber which consists of a higher coefficient of friction. Making a Larger Library of Sizes A more diverse set of sizes could be very useful for various chassis configurations and mechanical systems, increasing the versatility of the design. Redesigning the VEX Mecanum Wheel 14 Closing Thoughts Throughout this project, we learned to utilize our knowledge of physics and design to create a heavily improved version of a pre-existing product. The user-friendly interface provided by Autodesk Inventor Professional 2021 combined with convenient tutorials provided by the Autodesk webpage allowed us to pursue our design with minimal issues. Undoubtedly, this project gave us perspective on Inventor’s capabilities, and as college students entering the world of internships and various other extra-curricular opportunities, we plan on showcasing and expanding our knowledge of Autodesk to become stronger designers through innovating and expanding upon both original and pre-existing ideas. From designing custom gears and sprockets for robots to transmissions for cars, the possibilities offered by Inventor are truly endless. We would like to thank the Autodesk team for making Inventor free for students, for without it we would have never been able to pursue such an engaging project. Redesigning the VEX Mecanum Wheel 15