Note: This is an ongoing project that will be updated as significant progress is made in the future
Project Overview
Worcester Polytechnic Institute has a combat robotics club that primarily competes in the 3 lb category, otherwise known as Beetleweight. WPI competes in competitions like the National Havoc Robot League (NHRL) and Granite State Combat Robot League (GSCRL). Since January 2025 I have been designing and competing with my own Beetleweight called Thimbleberry.
Thimbleberry is a 2-wheel drive robot with directly driven motors and uses a vertical spinner in the form of a bar as a weapon.
The body of Thimbleberry’s chassis is made out of TPU, a flexible 3D printing filament that is strong due to its elastic properties. There are carbon fiber plates at the top and bottom of the chassis that stiffens the TPU body, making it very strong.
Electrically, I used a custom Printed Circuit Board called a Power Distribution Board (PD Board) to optimize electrical space by reducing the size of power wiring. This is not a very traditional route in combat robotics due to more troubleshooting in the beginning stages of wiring.
For Version 1 of Thimbleberry, I ran 2 separate boards on different halves of the Chassis that connect to each other via wires.
The Thimbleberry weapon assembly is supported by 2 pocketed “uprights”. These uprights are strong and serve to mount all of the moving parts in my weapon assembly, like the weapon motor and the weapon itself. I used UHMW for the uprights due to its strength and stiffness.
The weapon for Thimbleberry V1 was 5.9” in diameter and was driven by a 35 mm brushless motor and a 3/8” XL Belt. I designed the weapon for the largest possible force by making it out of AR500 Steel and adding a counterweight in the back to make the center of mass as close to the axis of rotation as possible.
V1 Competition Results
In late September of 2024, Thimbleberry competed in a local Beetleweight competition that was run in Fitchburg, MA. Thimbleberry was able to get a single match in against a Hammer-saw robot, which uses saws to cut robots in a hammer-like movement. Thimbleberry lost that match, unfortunately, but taught me many things that I need to improve on moving forward.
Top-Plate Damage from Match
Version 2 Revisions
After going through the first design cycle of Thimbleberry, there were many aspects of the robot that I could improve drastically. So I hit the ground running with many improvements. Some of the biggest changes that I made with Version 2 were redesigning the weapon entirely, decreasing from 2 to 1 PD Board, downsizing the weapon motor, interfacing the uprights into the Chassis body, and increasing electronics space. I hope with these changes my robot will be more successful at future competitions.
