Combat Robots

Like many robot builders, I've long been fascinated by Battlebots. Now I'm a part of it!

In November, 2017, I started talking to my now close friend, Daniel Parish, who had build several combat bots before with mixed success for Robogames in California. Now that he was studying at UR, he was looking for a way to compete in some east coast competitions. From that conversation, we decided to work together on a 30-pound 'bot to compete in the coming 2018 Robot Conflict event in Harrisburg PA, also known as Motorama 2018.

After weeks of multiple hours long CAD sessions, and with only about 6 weeks before the late February competition began, we began to build. Along the way, another friend joined us to help out with the construction work.

Finally, the night before the competition, we assembled most of the robot for the first time. We ended up finishing in the parking lot of our hotel at 7 am, but we managed to get to the tournament just in time to be weighed in!

Our first loss was to a horizontal spinner named Ratcatcher which tore a corner of our 1/8" aluminum base plate clean off as well as heavily bending our 1/8" steel side armor and shearing half a dozen screws off the bottom of the robot.

Then we faced off against the 2018 tournament-champion MegatRON, with a viscous vertical toothed disk weapon. It managed to knock KARMA onto its back and punch a hole clean through the bottom of the robot! We made some modifications including adding plastic wedges to try and prevent being stuck upside down or on our side, but we thought the arm would save us from being stuck on our back. This was sadly not the case...

The bot was much less impressive looking than most others there, but as my first attempt I was happy to find that it exceeded my expectations. In fact, we won our first ever fight, lost our second, and ended up winning another before eventually being knocked out by MegatRON. 2-2 isn't bad! However, the KARMA is now covered in battle scars. All of the electronics, gearboxes, motors, and the actuator survived, however, and we reused several of them in our next robot.

Conduit, a 30-pound Sportsman Combat Bot

Inspired by Breaker Box (a famous heavyweight bot), this bot is going to be a lifter powered by a full-360-rotation lifting/flipping arm, able to lift over 45 pounds with ease, and utilizing a 4-wheel drive with 3D-printed pulleys for excellent traction and maneuverability.

Above are the first complete models of this design. I went through many design iterations. Again, all CAD work is by yours truly besides those where the supplier provides the part models. Many, many hours over weeks and months of designs and revisions. All parts are modeled in their real-world materials in Fusion 360 and the model weight can be calculated to determine how much weight we had to spare.

These are some of the later but not final renders. We completed this robot in time for Motorama 2019. We ended up using polypropylene we got for free for the front, back, and drive pods, and Delrin for the top and bottom. The arms are 3/8" 7075 aircraft-grade aluminum, with a 1/4" thick mild steel angle plow.

The Combat Robotics Facebook page is amazing resource. The drive system is similar to that used successfully by another 30-lb robot, utilizing 3D printed high-torque belt pulleys with HTD timing belts. The final versions were printed in PLA.

Here is a functional 42-tooth PLA pulley and the wheel it bolts onto, a 4 inch "stealth wheel" from Andymark.

Assembled, all four wheels with pulleys are less than a pound and a half.

This lifter mechanism has the most design work of any part of the robot. Originally the plan was to use a Servocity clamp hub, but I ended up designing and machining my very own from Aluminum stock. I custom designed and CNC machined the plastic hub to fit within the lightening holes of the gear, and screw onto the hub. However, it also served to prove that sometimes you really need to keep things simple to make them work, as all of those screws sheared in our first fight! Lesson learned.

Top Kill, a 3-pound Beetleweight Combat Bot

This work-in-progress design is an effort to try and kill from above. While there are a number of potential ways to accomplish this, an overhead saw seemed like a fun way to go about it. Saw weapons are relatively rare in beetleweight robots, as the arm on the robot is an obvious weak point. However, as long as the arm can be raised out of reach of the opponent's weapon, careful driving should be able to mitigate most of the risk. The plan was to drive the 3-3/8" saw with a quadcopter motor via timing belt at about 10000 RPM.

This robot also fought at SWORD twice, and Motorama 2019 and 2020. We went with the name Top Kill for obvious reasons.

Motorama: Robot Conflict 2019

Conduit in the Pit

After completing the robot, we found we were missing a logo, so one was drawn on with Sharpie. This was the same story last year with KARMA, but this logo is very fitting.

vs. Diceratops

This was the first opponent Conduit faced. Another first-time bot, but by a seasoned competitor, this robot was a pneumatic flipper and clamp bot with a set of jaws to grab other bots.

Battle Damage

This is the inside of Conduit after its first fight! Two very apparent mistakes made evident were that the left side belt was not tensioned well, left too tight, and the lifter motor had a mounting screw loose which somehow didn't prevent it from working well at the start of the right

Conduit got two extremely unlucky matchups at Motorama 2019. First we ended up facing off against the incredibly well engineered and well driven Diceratops. Our next fight was against a Canadian reimagining of former multi-time Sportsman champion bot Nyx. This bot was dubbed Llama Sheen (a pun on La Machine) which at the 2019 tournament won second place overall for 30-pound Sportsman bots. I drove Conduit in both fights, and while losing both and being eliminated with no wins was disappointing, the robot worked great in its second fight and many first-time bot problems were ironed out after the first.

After the fight with Diceratops I was extremely concerned because I lost left side drive and use of the plow, and the fight ended with smoke seeming out of the top of the top. However, it turned out that most of the damage was due to assembly mistakes, and only one actual design issue was at fault. The left side drive belt was left too tight and not retensioned after the bot was hastily reassembled once a fresh battery was added. The added friction with 3 minutes of hard driving caused the left drive motor to overheat and one of the brushes disintegrated, causing blackening inside the motor can and all of the visible smoke. I also discovered that the clamp collar clutch mechanism I designed for the lifter did its job of saving the lifter gearbox and motor, but at the expense of itself. Instead of slipping on the shaft, all four 6-32 screws that held the gear onto the clamp sheared in half! I made the call to run the gear with key-stock in place in its keyway and simply turn down the lifter throttle signal to supply less power in hopes that the lifter would last the whole match without smoking another motor. Once available a video of the fight against Llama Sheen will be added above. Suffice it to say, I had no issues at all with the robot in that fight as far as mechanical or electrical failures. I simply had way less drive power and traction, so Conduit lost control in the fight and was judged the loser.

Top Kill was a Success!

While Conduit had some very tough matchups and was eliminated with 0 wins, Top Kill actually managed four wins before being eliminated! One of the two losses was a forfeit due to electrical issues when postponements were not allowed. Top Kill's first fight is in the video above, against a shell spinner called Mutex. Top Kill also fought and won against a famous beetle wedge-bot called Thunderchild which previously competed strongly on Bugglebots on Youtube.

Top Kill in the Pit

Prior to its first fight Top Kill rests, waiting for destruction... We entered into several fights with this black metal saw, later switching to a wood/plastic saw.

SRIMECH

Self-Righting Mechanisms are important in robot combat, so this mini "fin of shame" was added to help our bot self right if knocked on its back.

Quick Death

In its final fight against the drum spinner Mondo Bizarro, this happened in under 20 seconds. All the electronics survived, but spilled out onto the floor, making Daniel tap out.

All in all Motorama 2019 was an awesome learning experience and a ton of fun! I got to personally aid in repairing 30-pound Huge. I also shook hands with and spoke to some of the builders of Huge, Valkyrie, Tantrum, Red Devil, Sawblaze, Overhaul, and other famous bots from Battlebots and beyond!

Top Kill also went on to compete in SWORD Spring 2019, where it won the Coolest Robot award as well as taking 4th place overall, with Daniel as the driver.

Division: Super Dangerous 3lb Beetleweight

Division is the first bot I've built since graduating, and it is a serious pet project of mine. This bot is a lot of firsts for me. First bot ever under Team Just 'Cuz Robotics. First time using Topology Optimization within Fusion 360. First time CNC machining metal parts. First time using a Tormach CNC mill. First time using Fusion 360 CAM to control said mill. First ever kinetic energy weapon bot. All in all, it's been a huge learning experience and a heck of a lot of fun. There are still many improvements to do however, and its a work in progress for sure. Below are a few of the videos I've made about this bot.

Everything I've done since making Division has been documented well on my Youtube Channel!

Draconid: 12-Pound Circular Saw On Wheels

Draconid is the second robot I built entirely on my own after Division, and uses totally different manufacturing techniques from Division. Rather than using sheet-metal that I ordered already laser cut, I wanted to fabricate the entire chassis myself.

Check out these videos to hear me talking about the process of learning CNC machining and CAM.