Doc Hollizontal

3lb Horizontal Spinner for Full Combat (2024)

Doc Fully Assembled

Yee Haw baby, it's time to ride the range with this big iron! And by big iron, I mean a 400g AR500 blade painted silver to be used as a weapon in 3lb combat.

I promise this name is funny just think about it for a minute

Doc Hollizontal Overview

Doc Hollizontal came about when I was approached by some faculty members at my university about hosting a robot combat event on campus. While I already had several robots to enter into the competition, none of them were the high-energy bombastic type. I wanted to try and spark some sort of robot combat club on campus here before I left, and I figured that some extremely exciting fights with a high-energy spinner was the best shot. Since I was still finishing up my degree, the original plan was to do an extremely low-effort horizontal spinner speedbuild with a weapon powered by a brushless hubmotor. Slowly this turned into a full-fledged build as I realized it was going to cost the same to do it right as to slap it together.

Features

  • Weapon blade is 400g (1/3 of robot weight roughly)
  • 4006 brushless weapon motor
  • Carbon Fiber Nylon weapon pulleys
  • Dual weapon belts for redundancy
  • 1/2 inch Titanium weapon shaft (bought from Toby, builder of T3)
  • 4mm Machined Carbon Fiber top/bottom plates
  • 1mm Carbon Fiber battery access hatches
  • Rear forks to counteract wedges
  • Wheelguards to protect fragile wheel shafts
  • Just 'Cuz Gecko Motors (better for 4S operation)
  • 850 mah GNB 4S battery

Weapon Stack

Doc Weapon stack section view

The most interesting part of the build is the weapon stack. At the top and bottom of the stack are the carbon fiber top plates. These are each 4mm thick, CNC machined custom for me. Spanning these plates is a 1/2 inch thick titanium standoff. I call it a standoff, but it's really more of a shaft. It's precision ground, which most standoffs aren't. Attaching this to the plates are two shoulder bolts. I could have used normal bolts, but I was concerned about the threads slowly eating away at the carbon on hard hits.

At the bottom of the weapon stack is a small bronze thrust washer to reduce friction. Above this is bottom bearing plate. This is a small plate, printed from Carbon Fiber Nylon, that holds a ball bearing. It also houses a quartet of nuts which hold the spinning portion of the weapon stack together in tandem with a quartet of shoulder bolts. These bolts pass through the weapon bar and a heavily modified version of the Fingertech 60T pulley. This version has been modified to accept another ball bearing as a press-fit, holes for the four shoulder bolts, and a thicker pulley section to accept two belts for redundancy. This would also be printed from Carbon Fiber Nylon. Above this is another bronze thurst washer and a nylon spacer to reduce the amount that the weapon stack can move up/down.

Fights

It lasted so long and took so many direct hits in this fight, both from hitting the wall and from landing on the floor. The weapon motor actually disconnected from the body on that last hit (I forgot to loctite it in my rush to get FOUR bots running for this event -_-)