So… We built a robot.

Projects, Robots
Seven of Nine Lives – prototype

I used to love robot wars when it was on TV. I always wanted to make a robot for the competition, but when I was a kid I didn’t have the technical skills or budget to make a 100kg fighting robot. I still don’t, but more recently my girlfriend and I found out that there are several weight classes of robot which people compete in the UK, one of them is the 1.5kg ‘Beetleweight’. These are much more affordable and safer than the heavier weight classes. So we immediately started planning out a design for Seven of Nine Lives.

If you have any background in physics/engineering the benifits of spinning stores of energy are obvious. The energy stored is proportional to the square of the angular speed of the blade. Effectively, you charge a battery over an hour, and then dump energy from the battery into the spinning weapon over 10sec and then you dump that energy into the other robot in ~1/1000th of a second. Even with 1.5kg robots the energy storage in the weapons can be quite amazing, many times the energy of a bullet.

Anyway, our approximate plan is for a light, small, sturdy robot with a huge bar spinning on the top. Currently we have a 3D printed draft of the design. This current prototype is the first version of the robot in which all of the components work. It drives around well and the weapon spins up.

We had a lot of problems with the drive for the weapon. This stalled the development of the rest of the robot for quite a while as we thought we had damaged the motor/esc (electronic speed controller), but it might be that we were using the wrong kind of drive belt (we used a beefy v-belt). This is next on the list of things to fix, but currently we just have the weapon directly mounted onto the motor – clearly not a good idea as the bearings inside the motor are not designed for any side loads – but as the weapon is made of hollow plastic at the moment it doesn’t seem to be an issue.

We have spent many nights researching, planning, designing, soldering, and constructing this prototype. It’s been really interesting so far, but we have a lot more work to do. After we sort out the drive for the weapon we can start working out how to make the chassis out of aluminium. It would be really interesting to numerically model the performance of the weapon, amour, and chassis but that seems to be a little out of our area of expertise. If anyone has any tips for this kind of simulation we’d be very interested. So far we have just use the simulation module in fusion 360, but it seems to be designed for static loads or resonance conditions.

Seven of Nine Lives driving around and attacking a plastic bag. If any opposing robots use plastic bags as armour they will likely be defeated.

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