Ribbot is WPI’s 250lb robot that competes on Discovery channel on the TV show “BattleBots.” This robot sets itself apart from the competition by being a modular robot. Most robots only have one weapon type. Ribbot on the other hand, currently has 2 main modules that allow us to configure our robot to specially counter our opponents. I was in charge of front end attachments for our vert module, electronics enclosures, frog head mounting, and manufacturing. I started working with the team in 2019 and am still an active member.

Ribbot V2 with the undercutter module installed.

 

Tune into Discovery Channel starting January 6th, 2022 to watch Ribbot compete on BattleBots! More pictures of Ribbot’s fights will be posted after the respective episodes have aired on TV.

Ribbot V2 with the vertical spinner module installed.

The vertical spinner module (left) and the undercutter module (right) spin on different axes, providing options for how we want to approach our opponent. Each module uses the exact same mounting system: interfacing geometry between the module and the chassis and four 1” bolts. 

One of the front attachments I designed (shown above) is our sprung-down wedgelet system. Wedgelets are intended to serve as a ramp that an opposing bot would slide up so that they are getting hit when a vertical spinner impactor is hitting a robot upward, launching them into the air. These wedgelets also are sprung down using torsion springs, providing ~5lbs of down-force at the tip. Adding springs forces the tip to stay down while driving so that we are always scraping the floor. This is important because if the tip isn’t ground scraping, we have no chance of getting underneath our opponent. The wedgelet (in red) is laser cut AR500 steel and has a bushing pressed into a bore. That bushing is sandwiched between two nylon washers and rests on top of a steel sleeve in between an aluminum wedgelet mount. A shoulder bolt constrains the entire assembly and is in compression for added rigidity of the assembly. The aluminum surrounding the wedgelet that serves as the mount is intended to yield before the wedgelet itself in case they get hit. This failure point was made on purpose so that if they do get hit by an opponent, the wedgelet gets ripped off and the module remains undamaged.  

The graphic above displays why being able to get underneath an opponent allows us to hit them upward. If we assume that the energy transfer is the same between the two hits, the opposing robot is more likely to take more damage if they are also falling after a hit rather than sliding backwards across the floor.

Wedgelet mounts for days! These are a two operation part that I got cycle time down to about 7minutes total.

A few parts I made at school for Ribbot V2. Components include: drive rails, front/back plates, gearboxes, and post processing uprights.

There is nothing more satisfying than nailing a tolerance on a large billet part.

Ribbot’s undercutter module with 3d printed battery enclosures that I designed (in light green). These enclosures are printed out of an ultra flexible TPU material that helps shock mount our batteries so that they are less likely to get damaged during combat. Each case holds several batteries and a custom PCB for power distribution. 

Careful! Ribbot runs the highest voltage at BattleBots: 250volts. 

The battery enclosures and PD boards make the wiring very clean and modular. 

 

Shown on the top plate are our new frog head mounts. They have built in break points using slots in the print so that in the event we land upside down, the mounts will flex away with our vacuum formed head. This ensures that the frog head does not hinder our driving capability. 

This is Ribbot in raw stock form. So much material to remove!

This custom receiver case I designed allows the antenna to stick out above our top plate just enough so that we wouldn’t run into any connection issues. It also doubles as a protective case and shock mount.

Ribbot V1.2 launching Beta into the air.

Ribbot pulls off the upset of the season, defeating MIT’s robot “Uppercut.”

Ribbot V1.2 posing for a glamor shot with the vertical spinner module.

In Ribbot’s first season, we consistently were stripping out the key connecting the motor shaft to our Apex gearboxes. In order to solve this problem, I wire EDM cut these custom keys out of 4140 steel that replace the key and interface into the slots of the gearbox mating connection. In order for the connection to break, you need to break friction due to the clamping force of the shaft collar, and the spoked-key adapter. In Season 5 of BattleBots, our drive keys didn’t strip out once!

The custom spoked-key adapter slid into the Apex gearbox. First try on the slip fit tolerance!

The wire EDM Making first contact with the steel stock, look at that arcing!

Key profile straight off of the wire. The part is removed from the stock using a hacksaw and is then filed down. Each run of the EDM yielded enough stock length for 3 keys. The length of the part didn’t need tight tolerances so I cut each part off with a hack saw.

These support blocks that we refer to as “feet” are meant to transfer the reaction forces from when we strike an opponent with our vertical spinner module into the floor. This helps alleviate the stress on the shaft, module, and drive shafts.

Feet mounted on the bottom of the vertical spinner module.

After BattleBots banned our foam frog head for making too much of a mess, we vacuum formed our own heads using a custom vacuum former and 1/16” HDPE. Switching to plastic heads saved over 20lbs of weight, allowing for us to get much more serious with our weapon power.

A fun shot of Ribbot’s components pre-assembly.