We are team Parts And Wreck, and we have decided to iterate on Budget Extension by creating Budget Extinction! There was much discussion of pursuing an entirely new combot design, however we decided on improving our existing design. We felt that there was so much room for growth in Budget Extension, and the unfortunate battery fire of last year ended its run short. Additionally, the team is aiming to compete at both Motorama and RoboBrawl, which means that iterating on Budget Extinction will give more preparation time for Motorama than starting a robot from scratch.
Budget Extensions, the robot we are iterating on this year
We started our design cycle with evaluating the performance of Budget Extensions, our old robot. A few notable things we realized was that:
1. Our powertrain electronics were overkill
2. Our chassis can’t have any catchable edges
3. Weapon geometry can incorporate higher rake angles
4. UHMW can be incorporated into our chassis to make an effective side armor
5. Assembly was very inefficient due to excessive screws
6. Our wedgelets were not effective at all against other horizontal spinners
Weapon Assembly Exploded View
With this in mind, we swapped from a 4 motor drive to a 2 motor drive, and used the extra weight to add more structural integrity to the chassis and create an armored wedge. We also improved our weapon geometry through more FEA analysis. When reviewing our design priorities, we realized that a full-body spinner like ours with an extremely destructive weapon does not need amazing drive power, so we traded it off for a more robust frame.
We now have a 2 motor, chained drivetrain to power our 4 wheels. The back wheels are left exposed to allow us to drive while inverted. We ran multiple drivetrain stall tests with our old chassis to confirm that the 2 motor drive and our new escs will be reliable.
We expended a lot of effort in optimizing our electronics layout and packaging to make our frame smaller, coming in at a footprint of 12.5in x 10in x 1.96in excluding the wedge. This extremely small frame pushes our weapon blade height even lower than last year, which will allow us to achieve better contact with opponents.
The last major change was the chassis which had a huge upgrade. All the chassis walls in our robot were bumped up to 3/8in except for our bottom and top plate. We also added two inner walls to brace the weapon shaft. On the sides of our frame, we incorporated 3/4in UHMW on top of our aluminum to create a “composite” side armor. UHMW has excellent impact resistance and toughness properties which will allow a lot of energy to be absorbed from hits. It also has a relatively low stiffness, so it will abrade off during a hit rather than bending and transferring the force into our frame which could permanently deform our aluminum.
Overall, the team is feeling very confident and excited about the new design. The entire robot feels much more optimized, and we are hoping that this will turn out to be a very competitive combot. The goal is to finalize the design and prepare for manufacturing over this winter break, and hit the ground running at the beginning of next semester to compete at Motorama early in the semester. Look forward to our next post on how that turns out!
