Memento Mori: a 1lb Antweight Combat Robot

A few weeks ago, I had the idea to create a nice, spooky, Halloween themed combat robot to add to my collection. Since the competitions I go to have pits to eliminate enemy bots, I decided that a skull grabber would be a fun challenge to undergo. And thus, Memento Mori was born. This is a relatively oversimplified bot, but I wanted to make something that would be simple to work on; additionally, due to the more "relaxed" nature of the ants at my competitions, I don't need to worry as much about the "inefficient" design of my bot, and could indulge in the fun aspects of it (such as putting a life size 3D printed skull on it). I'll share with you my process of creating the spookiest antweight to date, as well as some possible upgrade paths for it.

These are only the absolute basics for the 'bot. Some materials were chosen based on what I had on hand. Possible upgrades for materials, and additional tools required, will be listed at the end!

Supplies:

1x Controller/Receiver combo (if you don't have one already, I suggest the FlySky FS-i6. It's a great combat controller, and has a lot of programmability to it at a relatively cheap price point)

2x 50:1 Fingertech motors

2x TinyESC's

2x 2" Lite Flite wheels (can be swapped for Fingertech wheels)

2x Dale Hubs (can be swapped for Fingertech hubs)

1x 2s 300mAh battery

1x uBEC

1x Fingertech power switch

1x Spool of your spookiest color filament (a strong filament is suggested, such as Onyx, Nylon, or PETG. If none of these are available, ABS or PLA+ will work, or PLA if you're desperate)

2x Red LED's

1x Resistor (roughly 650Ω is appropriate)

You will also need some wire for your motors, zip ties, heat shrink, and wire shroud.

Tools:

If you have access to CAD to model a cut for your servo, then that would be the best thing to use. Otherwise, you will need a dremel (or similar tool) to cut into the 3D printed skull tab. Additionally, you will need

1x Soldering iron, with solder

1x Hot glue gun, with hot glue

1x Wire strippers

As mentioned before, one of the recommended plastics is recommended for this build, but just about anything will work if you aren't planning for rigorous combat. For my proof of concept, I have printed my components out of PLA (my printer was unfortunately not running at 100%, and thus I needed something that would be easy to print/modify). When printing, try to utilize your printer setting to your advantage: a skull with 100% infill is extremely unnecessary, as are supports for it, due to the sliced top on the skull. I've attached both the .stl files for direct printing, as well as the CAD files, in case you wish to modify components. For best results, try to maximize your wall thicknesses around the printed components, whilst minimizing infill percentage. This will give you the optimal strength and weight for your given material.

This step is mostly going to be a matter of following the diagram, and, if you have experience in combat robotics, using a bit of common sense. I'll supply some commentary on choices made, but leave most of the instructions to the diagram shown. Unfortunately, I grew up learning STEM, none of which had any artistic skills really involved; as such, you'll have to excuse my horrendous drawing, which may be more frightening than the robot itself.

The general concept is this: power flows from the battery to the power switch, which then branches off to the resistor, UBEC, and Tiny ESC's. From the resistor runs the power indicating LED's (the light up eyes of the skull), and the negative goes back to common ground for the battery. The UBEC powers the receiver, and the negative of it goes back to common ground for the battery. The Tiny ESC's flow power to the motors, and normally to the receiver, but not in our case; THE RED WIRE FLOWING TO THE RECEIVER FROM THE TINY ESC'S MUST BE CLIPPED AS SHOWN OR ELSE YOU COULD SHORT THE RECEIVER OR ANOTHER CRITICAL COMPONENT. The negatives from the Tiny ESC's run back to the common ground for the battery.

It is recommended that you do a few things: firstly, give yourself ample length of wire to run into the skull for your wires, that way they don't pop out/become disconnected. Second, wire shroud of some sort is recommended to wrap the wires going to the skull for a couple of reasons; the first, it'll keep them tidy and protected, and if you get matching shroud, it sort of looks like a spine! The third recommendation is that you put heat shrink around all soldered connections, to keep them from shorting the robot out; the last thing you want is a LiPo fire!

A lot of the components get placed exactly where you would expect in the robot; the motors go in the rear of the chassis in the openings made for them, the battery goes into the battery cubby in front of the motors, the switch fits in the square slot in front of the battery, the receiver cables stick out the big square hole in the top place, and the rest of the wire/components fill the rest of the space in the chassis. If you're worried about space, some components can be placed into the skull, just be sure that there is ample wire available so nothing pops out! This is the route I took, again, due to printer issues; as such, I don't have many photos of the wiring assembly. Sorry!

The entire top panel is held on via zip ties and duct tape on my robot, mostly out of the convenience and speed available for my competition. This isn't necessarily recommended, due to how the robot is built, but it is an option. Instead, I recommend proper fasteners and standoffs in the holes/spaces that are printed.

To hold the skull to the servo horn, hot glue is recommended. This is an easy solution that will hold well enough for some light duty fun. If you want to be able to remove the servo horn, drill/dremel a hole in the back of the tab where it lines up with the servo horn screw.

To attach the servo, there are holes with which the servo front lines up with. A zip tie will work to hold the parts together, or you can use tiny fasteners. Your choice!

Congratulations! You've completed the build. As previously mentioned, it's a relatively simple build, with a very fun end result. For further iterations, the possible ideas could be used to make the robot more robust/combat ready:

• A linkage setup from the servo to the skull, to provide better shock mounting of the system, as well as an overall stronger lift/clamp hold
• More fastener positions to hold the top panel on better
• A servo mount inside the chassis, as opposed to the top panel
• A way to mount a stronger wedge
• A lower wedge, to ensure an easier "bite"
• If you really want a competitive design, a smaller skull would be more reasonable, or simply remove the skull aspect (but honestly, what's the fun in that?)

Again, this is just the first iteration of the design! Check back for future iterations, where I update the robot with better fittings and an overall stronger design.