Bone Dead Robotics

This year saw lots of critical changes to the weapon system and ground game ultimately locking in many of the design decisions that will transfer to the next version. While there were moments of progression for the robot against noted rivals such as Emulsifier and MegatRon, the year saw Phenomenon ultimately with one of its least successful by record with it finishing most competitions at or below 50% win rate. Even so, learning always continues!

Hubmotor Hopes

After the hubmotor was destroyed by WarHard XXL at the 2024 World Champs it was time to rebuild Phenomenon. Since the hubmotor did prove its success at the June 2024 NHRL event the goal was to reinforce it to withstand the side forces and potentially hit harder. Besides rebuilding the entire chassis, the hubmotor received two changes:

1. 5/16-18 through-bolt which axially constrains the weapon assembly. Previously this was only constrained by 1/4-20 tapped into the 6061 aluminum center shaft.
2. Weapon upgraded to 5/8″ H13 from 1/2″AR500.

Both of these changes directly tackle the issues of it being pulled away from the chassis and the blade being bent by the sideways hit. The increased weapon thickness theoretically made use of the perceived “excess” power of the hubmotor and adding more KO power to the robot.

Ground Game Startpoint

Ground game started as the same as it was in 2024 with the lifting arm and two primary forks in the front of the robot. The side bracers are still critical as their smooth edges allow the robot to glide on the arena floor. Even so, the growing length of opponents forks proved to be a point of concern from prior fights over the past years. With this thought in mind, it was time for Phenomenon’s first event of the year: Motorama!

Motorama 2025

Motorama was a harsh check on the hopeful future. From the beginning, the hubmotor was notably unreliable throughout the event. Despite promising testing, much of the night before and first day of the competition were focused on getting the hubmotor to work. Ultimately this was unsuccessful with the weapon never truly working all day.

The rest of the robot relied primarily on its strong drivetrain and for the beginning this was okay but ultimately the ground game received the most testing. The fight against Ammonoid was among the most damaging fights yet. Ammonoid’s larger weapon and longer forks meant Phenomenon was playing a difficult reach game. Later damage exposed that the worst area for grabbing was the front portions of the side rails where the horizontal wedge mounts to. This is further reinforced limited by the front bracers that normally attach to these and the top of the crossbraces. During the battle, Ammonoid’s blade was able to grab these rigid components and tilt the robot up, allowing the blade to pierce the baseplate, and the battery, and hook the crossbrace ultimately throwing the robot and nearly causing a fire. While the drivetrain was strong, it was clear that the current solution to the ground game was insufficient for the growing amount of taller vertical spinners.

Ground Game Changes

After realizing how well Overlord had drove at Motorama I was convinced the only answer for Phenomenon was to make the front as flat as possible and use UHMW outriggers for stability. The outriggers were fairly simple to make on the router and initial tests looked…phenomenal.

With all internal components, weapon, lock, and lifting arm attached the robot weighed only slightly more than half of an allowed 30lb multibot. The level of flexibility that could be provided from this combo was intoxicating but ultimately it would not matter if the primary weapon of the robot proved to be ineffective.

Hubmotor Woes

After epoxying the wires again, one of the difficulties found in the hubmotor is the precise tuning of the “clutch” ring that goes around the magnet ring. In this case, the thickness of the ring was ~1.5mm. On a 0.4mm nozzle this means it will extrude to 1.6mm in 4 perimeters (4×0.4=1.6). However, once the printer was switched to a 0.6mm nozzle for the additional strength in the larger diameter strands the printer would now overshoot to 1.8mm in 3 perimeters. This incredibly tiny difference has an immense impact on mounting as the slightly oversized ring now doesn’t easily squish in the central cavity of the hub leading to it being pushed out of the way instead of properly friction driving the surface. While this was not ultimately keeping the hubmotor from functioning it was actively affecting how smoothly everything was sitting together.

As crazy as it sounds, switching from the 200A Sequre ESC to the 120A Sequre had more consistent startup though it also suffered from higher temperature. While settings were the same, there was likely something between the two boards which also resulted in the high cogging. Previously the 80A Rhino had driven the hubmotor but due to the increased load in the wider disk it was quickly overpowered by the current draw. Even so, it still had the smoothest startup of the ESCs so far which bode poorly as the March NHRL event quickly approached.

Though the hubmotor wasn’t perfect yet, it was time to at least assemble the robot and see how it was looking. The combination of low outriggers and spring-loaded forks in the front meant the robot was at its strongest ground game level so far all while it was still underweight! There was a strong pull to keep the hubmotor in but at this rate the testing was not looking any better than it did before Motorama.

In a last ditch effort to use the hubmotor, the old 1/2″ blades were added back (with a spacer since the new hubs were designed for the 5/8″ blade) but alas it was not much better. Even so, it was within weight for anti-hammersaw armor so it was a version that will be brought for that specific use case.

In a truly last ditch effort, the old pulley system was resuscitated from the Vorion chassis and retrofitted to the new Phenomenon chassis. This is why one should design for backwards compatibility!

March 2025 NHRL

The hubmotor configuration proved to be essential in the match against Aethon. While the blade was minimally effective, the aluminum-TPU-steel sandwich was more than enough to stop their hammersaw from getting to any of the important bits.

The fight against Emulsifer was the really big moment I was looking forward to all day. Just like Ammonoid back at Motorama, Emulsifier was a tower vert much taller than Phenomenon with forks that were much longer. The primary difference going into this fight was the removal of the front bracers and the addition of the low outriggers. The central forks were the same length as those at Motorama.

This kind of control and precision was the exact thing that Phenomenon was designed for. It didn’t need the biggest weapon but when that weapon is applied well it is more than sufficient to lay the hurt on stronger machines.

The other side of that equation is all it took for Emulsifier to counter this smothering was chaotic shot that blasted the front end. The level of forces would be too much for any 30lb robot so in a sense there are few things to strengthen this area beyond keeping other robots from striking there with that much power.

On both sides of the equation, the clear takeaway is the reliability of the pulley system cannot be underestimated. There were no issues starting up the weapon or its ability to keep going after each hit. Chaining hits together was a known issue in the hubmotor at Grand Finals 2024 so seeing such a direct comparison was essential.

Nevertheless, the temptations of saving so much weight and space meant the hubmotor experimentation wasn’t done yet.

Robot Combat League Championship 2025

Despite the concerns from the hubmotor demonstrated in March, there was still the hope that one more small tweak may be all that is needed. One common suggestion heard was to increase the voltage to help with the startup torque. Alongside the robot being updated and modified to help the hubmotor, ideas for how to fit 2x 6s batteries was also being weighed as well.

After a bit of tuning, testing and tuning the hubmotor was generally working well. It was not a perfect spin-up with flawless speed, but the use of Castle ESCs seemed to make the hubmotor move a bit better than the normal aircraft-based controllers. After that the bot was packed up and carried out to sunny California!

As cool as the event was, Phenomenon’s swift execution was heart-breaking. This gif removes the long spin-up taken by the weapon to get up to speed (itself a death sentence against more aggressive machines), but does fully capture the very fine line Phenomenon walks to work.

Despite it’s very strong frame, no part of the robot is very far from taking a hit. Also, with the 2WD frame that requires very hittable parts of the chassis to act as a third point of contact, not much damage is required for the machine to have limited mobility. Even though Phenomenon could keep working, as its components are generally quite rugged, all it would take were a few quick hits like Super Obliterator’s to wreak havoc on the machine. In this case it was the wire breaking on the switch (itself a very frustrating failure) but it raised some worries for the future.

At the heart of the machine’s concerns was the hubmotor. That delayed startup and finnicky tuning inspired way too much concern in a machine that needs to be simple and rugged. While I believed the hubmotor had strong features that could be revisited with a more powerful core, the current version was grossly outclassed. Due to their size they’re a little to heavy for a balanced 12lb design but also slightly undersized for a full 30lb central weapon. With weapon reliability being more essential, the hubmotors would have to be set aside for the pulleys for now.

June 2025 NHRL

With a renewed focus on the pulleys, the struggle started to figure out the small tweaks to prepare for the event. To increase the reach of the weapon and to mitigate some of the wheelying, prototyping a more forward weapon and battery placement started. The lifter mount was also tweaked some to avoid the gradual “unscrewing” motion that was found at RCL. After a rapid week of disassembling the damaged chassis, a new Phenomenon rose with speed.

After a quick test at the Hive revealed a broken bearing (this is why you test!) and a 5/16″ through-bolt solution was added to the weapon shaft mounting the newest version of Phenomenon quickly flew together. To account for the motor cut-out the graphics were shifted up some but ultimately led to a great new look heading into the event.

The June event was on average a solid event for Phenomenon. Though a stray LED wire shorted the receiver making it lose to Red Storm, it thundered back with a win over Demon Core and made it to draw against MegatRon. Phenomenon’s greatest antagonist did win again, but Phenomenon was still largely functional after the match with weapon, drive, and lifter gearbox still unharmed. However, it was clear that Phenomenon’s weight balance issue and limited reach meant it couldn’t capitalize on MegatRon eating its own drive belt. While competent, it was not yet where it needed to be.

Though the hubmotors were no longer going to be used as part of the primary configuration of the robot, there was an idea to see if “minibots” made from the Zomboxes and hubmotors could work. As pictured it would weigh ~18lbs. If it weren’t for the exponential cost of running multibots this would be a interesting idea.

October 2025 NHRL

After a summer hiatus, it was time to prepare for the October event. After losses to Emulsifier and MegatRon earlier in the year (though more closely than prior attempts), it was time to aim for a proper golden dumpster. After finding a new drill press from Facebook with the proper speed and torque to countersink AR500, the rest of the parts were fabricated quickly. To reinforce the ground game the fork mount was welded to the top of the bracer making a 3D-welded structure that should tank most hits and avoid them flying out as they did against MegatRon. Since there were more screws and mounted on a different plane than the front it should make them highly resilient. Now that the hubmotors were retired it was time to reuse the blades. These blades were wider and harder than previous versions so reusing them was essential. By combining the diamond pattern in the blades with the belt profile new hubs were made and assembled. Old rubber wheels were retreaded with urethane to keep reusing them.

Despite the dominance at the start of the day with defeats against Touro Feather and Deadrise, it was once again electronics that failed. Despite being on its way to defeating Synthesis 30 one of the wires on the power switch failed. It seemed whatever silicon wire used had brittle copper instead of stranded silver leading it to crack on the impacts. After this simple fix it led to a strange midpoint for Phenomenon. While it technically failed, it was also not losing in instructional ways. This is the hardest method for a builder as it left so little to develop. No robot is perfect so you want to fail early and often with the hope that as you discover those you can fix it handily and thoroughly. Without much change it was back to treading water and waiting for the Finals.

December 2025 NHRL

With the exception of some cleats as a last minute drive improvement, Phenomenon was effectively the same as before. With the exception of shattering Banguela’s beater bar in highlight-worthy moment, Phenomenon revealed dark spots. Usually in a fight against horizontals Phenomenon is very well situated to counter them but its fight against Jubileu revealed something not often consider: its lifter being too powerful. The chaotic self-righting gave Jubileu an opening to a glaringly weak part of the chassis: its drive motors. Large front configurations and good driving usually hide this but in moments like these they are instant kills. These will need more protection in the future. The last fight against Termigator revealed that the forks, and Phenomenon’s overall shape, remains sensitive to drum spinners. Because the simple shape of the forks if they were caught at an angle or the blade was beat on tip speed it was over. This was the case here as one Termigator shot bending the forks led to an absolute mauling of the machine.

Reflections

Phenomenon had been a good machine, but not a great machine. If given the right field it could be competent enough to win but the “just right” pathway has become more narrow with time. V2 of Phenomenon has had an incredibly long run with crowned by a golden dumpster but never enough to overcome the same machines that defeated V1. It has served as an incredibly versatile base with it being among the foremost “lifter verts” in the class and its learnings being the baseline of other machines. However it’s clear that it’s reaching the end of its run and a new version will need to take its place.