Fracas-2024

Thanks to JCRB Phtography for the epic shot of Fracas at Motorama!

Despite Fracas’ low visibility in the second half of 2024, developments in the machine were really important insights that were applied on Vorion and Phenomenon later on.

Post-NHRL Finals Rebuild

Fracas’ story actually begins in December of 2023. Since the NHRL Finals of 2023 were moved up to November to allow for the December All-Stars event, there was plenty of time for ideas for Fracas to be worked on. The first big upgrade was to the lifting arm assembly. A huge error on the previous design was the use of 12L14 steel which is a leaded steel designed for fast machinability but decreased strength and horrible weldability (that is to say, don’t weld it as the process releases lead). To replace this, a new shaft design was outsourced and made from 4340 steel. This new piece integrated much of the features into one piece which made assembly very straightforward. Once the sprocket was welded to the shaft, it was on to the next part: the jaws.

After seeing Red Storm resist Yahoo so well, I wanted to incorporate that into Fracas. One key feature was to make give the side armor more solid skin. The harder TPU means another weapon can’t easily cut through the guard but instead squishes the TPU and using it as a spring. Unfortunately it was a bit heavier to implement so it will be put on the backburner for now.

Another key feature was to make the jaws incredibly strong; as Kevin (builder of Red Storm) said, “you want to hit them with themselves.” By making the jaws made of the same 1/2″ AR500 material that some weapons are made from, it allows the shock to reflect back into the opposing weapon and allow for better resistance. The same strategy of welding the upper jaw gears to the jaw itself was applied and the assembly came together quickly. For the intermediary shaft, a washer was welded to a precision shaft. This allowed it to only need one screw to stay aligned and minimized any risk of a screw head interfering with the chain path.

One skill I sought to try out was flashing the Flycolor X-Cross 80A ESCs from BLHeli32 to AM32. Using this guide and the reference to the Github, it took a bit of effort to figure out how to do it, but it was possible. The general idea is you have to reflash the whole system via two tabs then reflash it with AM32. From there you tune it like any other AM32-native controller. It was an interesting exercise in understanding software and a good cost saver from having to get a whole new set of ESCs.

The last touches on the machine were pretty straightforward. After welding on a nut as a additional mounting point (steel construction makes things like that super easy), wheels were cast from Vytaflex 60. One of the first big ideas I wanted to try out was finding a replacement for the Robocore 80mm wheels I used in 2023. These wheels are exceptional and handle really well but have two key weakpoints:

Their softness means they get consumed at a faster than the Banebots wheels that came before them. This was a tradeoff for their high traction though as these wheels did an excellent job grabbing to the arena floor to the point where Vorion could even push around 45lb machines like Knock Off White once it had proper leverage.
Their cost. Due to their high traction and demand, the cost for these wheels has steadily increased over time to nearly eight times the cost of a Banebots wheel. Again, this is understandable from an effectiveness standpoint but because this could mean the wheels are consumed quickly then the cost of replacement quickly balloons to a point which hurts the budget.

These Vytaflex wheels were molded over common Vex Versahubs and sat inside the 3D printer to cure a little faster (the heated chamber helps the epoxy cure) and voila! They were much heavier and less grippy than the Robocore due to the higher hardness, but the robot was still plenty maneuverable so no issues there. I have a theory that mixing in MICA powder will soften the epoxy due to it affecting how thoroughly it cures so it could be a way to have it match the Robocore hardness level. I’m thinking the next set of these wheels will have that powder mixed in both for function and to make the appearance a bit more neutral (the beige stands out far more than the all-black wheels). After that I splashed on a quick paint job to the polycarbonate top plates and the bot was mostly ready for fights!

Motorama 2024

You can read the full event report here. Here are the main takeaways:

The lifting is great, though the weapon gearbox needs more support. Since the end isn’t being supported, the threads were the only thing keeping it together which isn’t good when you have so much torque. While Fracas is the most direct example of a lifter, this is important for the other machines too as they evolve.
The wheels were an excellent solution that just needed a bit more tweaking. Fracas didn’t drive quite as well as Vorion but it was still good enough that it was certainly worth improving on. The hubs worked as well though they need to be more encased by the epoxy since they could slowly work their way out of the epoxy. This should be fairly straightforward.
Better top armor. The polycarbonate was a liability so switching back to aluminum (or at least much thicker plastic) is good. Sportsman machines still pack a punch!

Redesign

One idea for Fracas V2 was to make the machine more low-slung by shortening height of the weapon assembly. By making everything much lower more dense I was able to steal some weight back to make the top armor steel. In theory if I want to weld deflecting plates to the top and/or add more anti-hammersaw armor I’ll be able to do so.

Unfortunately, Fracas’ development was put on pause for the rest of 2024 due to the bigger focus on Vorion and Phenomenon. Even so, read through their reviews to see how some of the ideas from Fracas transferred over! Hopefully Fracas activity will return in 2025 but it could be a little different than what we see here…

Check back in to see how Fracas grows and read through the other machines too!