ReboundV2 Build Log

Photo Mar 29, 11 36 40 PM

Rebound V1 began when I decided to scale up my most successful  beetleweight, Ricochet,  to the 12 lb class. 12 lbers seem to have a very good energy to weight ratio and as a result, their matches tend to be highly explosive, sending many robot upwards into the ceiling of the arena. Thus they have to be both full of energy, but also able to take a serious beating.

Version 1 began life similarly to most of my robots, through the gift of the waterjet.


About an hour of waterjetting later, and a robot started to appear! I decided to use a pretty stock drive solutions, opting for 11:1 P60 planetary gearboxes, with some 35-36 sized outrunners. This left a top speed of around 12 MPH making it extremely zippy. Drive testing revealed that overall it was rather pleasant, and after flashing SimonK firmware onto the speed controllers, was very controllable.

For weapon, I used a brushless outrunner from an electric chainsaw we had lying around (good for ~2KW of power) geared almost 1:1 with the ~3lb blade. This had a free speed of ~8000 rpm which sounded quite frightening.

The wedge was made of welded 1/8″ 4130 hardened to ~45 rc.

The robot did fairly well at Motorama at it’s debut, going 2 wins and 1 loss. It had a substantial amount of power, throwing it’s opponents into the ceiling, and even breaking the arena lights with the carcasses of the other robots. Unfortunately, it was not able to continuously handle delivering these hits. I spent so much time focusing on analyzing the weapon rails  front struts that hold the blade) that I didn’t focus on the intersection between those and the rear box part of the robot. This, coupled with the fact that’s it’s hard to safely test these large robots, made it so I only found this out at the event.

First (and best) fight:

Damage Pics:


Rebound’s blade shaped gashes in one of my first opponents.


Bent and torn 1/8″ AR400 wedge from my second opponent.

I didn’t really get any pictures of the damage on my robot (and the fights aren’t up yet) , but overall, the front part of my box twisted, leaving my robot in a very unhappy state.


The overall design was fantastic, so not much had to change. First I realized my 2KW brushless motor was a bit overkill and took up a significant amount of weight, and so I moved down to a ~1KW outrunner (PropDrive 35-36) which weighed almost 1/4″ the weight.

I also didn’t like the idea of the clamping force from my bolts (and a little bit of shear Yikes!)  so I CNCed a custom clamp hub that fit around my blade to distribute impacts.


I also beefed up the rear section with thicker aluminum, and an additional support:


Somehow the robot is now almost half a pound underweight and the next competition is in around 7 months so there’s plenty of time for improvement!

Aesthetic touches include the XT60 removable link holder, as well as some logos 🙂

Photo Mar 29, 11 36 45 PM


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