Introducing Puca, a 4WD Drum Spinner!

A near-final render of Puca with a mockup decal I wasn’t able to get made in time for its debut event


Puca is my take on an uber-competitive try-hard Beetleweight. Those of you familiar with my Hobbyweight Son of Kram will notice that’s nearly identical in everything except size! (And of course the drum isn’t a stack, but more on that later). Due to SOK’s success in previous event, it seemed like a good place to start. The entire robot was then designed with the mindset of “What if took all of the effort I put into Kelpie/other flippers and instead put it into a weapon type that’s actually competitive just for funsies?”. The result is this zippy 4wd drum spinner with a 13oz weapon!

The Name

In Celtic mythology, Pucas are shapeshifting horses similar to Kelpies that are entirely black with gold eyes. While Kelpies trick people into riding them so that they can drown and devour them, Pucas are much more playful and mischievous, only tricking people into riding them so that can thrash them around and mess with them for fun. Given that this robot is a LOT more “murder-ey” than Kelpie, my beetles should probably switch names. Oh well, can’t go back now 😛

Electronic Components

Weapon Motor: Leopard 2845-2250kv brushless inrunner
Drive: FingerTech Mega Spark Gearboxes with their matching Brushless 1806 2300kv motors
Drive/Weapon ESC: Diatone Mamba 55A 128K BLHeli_32 4-in-1 ESC
Receiver: FlySky 4ch AFHDS 2A Mini Receiver
Battery Eliminator Circuit:  DYS UBEC 3A
Battery: CNHL 6s 650mAh LiPO

Bot Construction

The construction style and materials of Puca are exactly like Son of Kram. The bot’s main frame rails are chonky UHMW with carbon fiber top/bottom plates. Puca even has SOK’s classic and iconic side “pickles” to protect the wheels (except black of course!). So far, they seem to be just as tanky!

The weapon is where things start to deviate from SOK. Instead of a “stack” style of disks bolted together, Puca has a solid billet 4130 drum with anodized 6061 endcaps for the bearings to press into. Then the drum was painted gold and the caps anodized black to match the robot’s color scheme. The drum’s effective diameter is about 2″ and it’s 4 1/8″ long.

For drive, I’m powering the back wheels directly with the Mega Sparks and then running belts to the front. The wheels themselves are cut from raw sheets of Gum Rubber I got from McMaster and cut with a holesaw into ~2 1/8″ disks. The wheels are then mounted to my Mega Smol Hubs.

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