Overview
Report 1
Introduction
The objective of our design is to optimize mass and robot speed while maintaining structural rigidity. To optimize mass, we plan to use “Finite Element Analysis” to gain the most effective mass per leg while maintaining rigidity. Moreover, we plan to utilize one motor that will reduce our mass by over 100g (motor + battery pack). In addition, to maximize speed we plan to increase the amount of distance covered by the robot in one single rotation while keeping the number of rotations per second high. A transmission will be the means of accomplishing such. Through using a low gear ratio, we can allow the output RPM to increase. Additionally, covering enough distance per rotation will be a large factor thus, using a large leg length and arc length will ensure we improve distance per rotation. Finally, reducing slip between the gears is crucial to ensure proper propulsion.
Possible Deigns
Result
We decided to use the bevel/shaft design as it lends the lowest weight, high speeds, and high structural integrity. Moreover, we chose the pie leg design as it optimizes speed and has high structural integrity without being heavy. These factors are beneficial as it can allow us to spot reduce mass in the leg without comprising structural integrity. Finally, we chose the servo trap door due to quick release speed, incredibly low weight, and simplicity in the design.
While any of our transmission designs would lead to roughly the same speed, the bevel gear/shaft design allows for the lowest weight, marginally, while being very creative. However, this idea can be iterated in a few ways. The first being by adding a hole into the midshaft to lighten it. Due to stiffness being a factor of cross-sectional area moment, rather than weight, we can even further reduce weight allowing our robot to be quicker. Finally gear ratios can be tweaked greatly to get a proper balance of torque and linear velocity to avoid any slipping. While this will be an effective design, an uncertainty in our calculation is if each leg will only receive half the power as 2 legs are splitting the motor. While this wouldn’t make our robot exponentially slower, we should expect our robot to perform at half the speed we calculated, thus we should plan to use even lower gear ratios.
The pie leg is our most effective leg choice. As shown in the FEA simulations it experiences the least amount of deformation and stress. Furthermore, it is as quick as the J hook which is ideal. Finally, to lighten our part while maintaining structural integrity, we strategically added slits into the pie which there is low stress concentration, to reduce 3D print times and lightweight our robot further.
Report 2
Introduction
Our team aimed to design a robot which maximizes speed, optimizes mass, prioritizes creativity, with sufficient build quality while staying within the 90-degree rule constraints and robot size constraints. Our strategy to maximize speed is to maximize the number of rotations per second and minimize mass. To minimize mass, we opted for a single motor. To mitigate the speed reduction from using one motor, we ensured to utilize a transmission consisting of spur and bevel gears to increase output velocity over torque to ensure no speed losses. Furthermore, to minimize weight further we favored lightweight materials (e.g., cardboard, PLA shafts over metal, and the use of hot glue and tape over heavier fasteners), along with chassis and leg cutouts. Finally, to introduce creativity and increase speed, instead of utilizing a traditional pie leg, we designed a flexible unfolding wheel that abides by the 90-degree rule. This leg provides high traction due to the grippy flexible filament and 4 times the speed output of a traditional pie leg. Ultimately these strategies led to a high speed and creative robot which optimizes mass.
Final Design