Hello, Just posting a bit of an event recap/project build on how my first ever 150 gram combat robot went in it’s first tournament last Sunday. My robot named Deadline entered into the non-destructive division and somehow ended up finishing 3rd amongst the six robots.
Keen-eyed readers may notice Deadline is missing the googly-eyes in the fight videos. This was not an easy decision but to try and make the lid bulge less and make weight I swapped the lid with the googly-eyes for another with a plastic window. True to the robots name I was re-soldering most of the robots insides to remove as many connectors as I could while the first fights were already underway, I had to try and shave of 3 grams before Deadline would be allowed to compete as it was overweight with the alternative lid.
The game plan for Deadline was simple, try not to get too outclassed for the first two minutes of each fight, then once the trapdoor opens for the last minute try and bulldozer the other robot in for the instant KO. Below is the video of the first match where I identified the first issue, Deadline’s lid was still too tall in the centre so it can’t drive inverted! Fortunately my opponent Roz was kind enough to keep flipping me back upright so the battle could continue until the pit opened and we both fell in.
This recording of this fight was finished right before the pit opened and I had a miraculous comeback I swear! The rest of the video is an accurate depiction of Deadline being toyed with and carried around helplessly, but at least it could now drive inverted thanks to a hot-glue based solution to keep the centre of the lid from bulging out. My pit crew and I updated our team name to hot-glue as a result.
This fight is another example of the kindness of the community and the desire to just keep having a fun fight. My opponent (whose name I’m sorry I didn’t catch) flipped me into a helpless position position multiple times but continued to flip me right-side up again so we could continue rather than have me counted out and KOd less than a minute into the match.
The Aftermath
Since Deadline ended up fighting in the non-destructive division and was still fully functional at the end of our tournament it felt like the only right thing to do was to join in with the surviving destructive robots in their free-for-all rumble.
This bout was the biggest highlight of the next major design issue of Deadline, because it is has a square chassis if it can get stuck on its end with all four wheels spinning in the air. Fortunately the other drivers were kind enough to line up a free-hit and knock be back over so I could get back in the action.
After the fight the damage was not too bad all things considered:
- A plastic window in the lid that was hot-glued on had come off
- A rubber tire tread had been knocked off
- One O-ring had fallen off the pulley
- The left side drive motor was no longer running as smoothly as the right and driving straight forward results in a slow turn to the left.
How Deadline Was Built
Deadline has an entirely 3D-printed TPU chassis so it can take quite a bit of punishment, rather than being strong and brittle, the entire robot is meant to bend and spring back into place unharmed when it takes an impact. The chassis, servo flipper arm, front fork and plow are all entirely TPU. The only solid parts are the servo horn, motor mounting brackets, wheels, pulleys and the motors and electronics inside.
I decided I wanted my robot to be 4-wheel drive very early in the design and quickly realised that although my electronics would allow 4 gearmotors it would not fit within the 150 gram total weight budget. To get around this the front two wheels are driven using O-rings connected via a PLA 3d printed pulley on each wheel.
150 gram combat robots will commonly use the maker classic N20 micro metal gearmotor with either a 30:1 or 50:1 gear ratio. I opted for the 50:1 ratio to get a bit more pushing power and lower top speed, being my first robot the extra speed would likely just make the robot harder to drive.
As a failsafe, these motors have enough torque that the wheels will break traction and spin, rather than stall the motor and risk burning out the drive.
Deadline has a 2 cell LiPo battery intended for a racing drone which means these motors will receive up to a maximum of 8.4V at full battery charge. These motors are designed for 6V so they may not live a long life, but as is the nature of 3 minute combat robot fights, most parts are considered consumables over the long term. One set of motors made it through all 7 fights during the day and are only starting to show issues after the destructive robot free-for-all rumble.
Going Forward
All up I had an awesome day for my first ever robot fighting event, I’ll be sure to head along to the next one in roughly six weeks time and some more of the Core Electronics staff are likely to be along with me to either join Team Hot-Glue as pit crew, or with their own first robots.
If you have any questions about the design, build process, or the event please post them down below
. Thanks 
