3 lbs Battlebot

3 Lbs Battlebot Intro to robotics club

Design

Our team overestimated how bad other team's weapons would be. We severely prioritized armor and protection over the weapon. We choose to do a wedge prioritizing armor while having a small spinning drum weapon. The bot would have four wheels driven by two brushless motors. We were the only team using brushless drive motors. Theoretically, with our 2.375in wheels, we could move at around 20 feet/second. This gave us an incredible advantage in maneuverability and torque. All design was done in a few days in Solidworks.

Construction

Machining

Our frame was made from a singular block of aluminum. This was much stronger in our analysis tests than multiple pieces bolted or welded together. The block started at over 10 pounds and ended up at 1.3. We had to add many lightening holes to meet our 3-pound limit.

We started by cutting the raw stock out on the horizontal bandsaw. This would give us a frame 'blank'. The cut took around 45 minutes.

After this, it was roughly brought to square on manual mills.

I had to pay special attention to the sequence of operations for the CNC. Some walls were incredibly thin and would want to bend. The first operation roughed out the bulk of the interior while there was still support on all sides.

Initial Roughing. Done with a .75in tool

The internal tolerances were not critical so I added a 0.5-degree draft on the walls to allow for easier machining. I was hoping that by doing the internal roughing in the first operation that all internal stresses would have been released for subsequent operations where precision mattered.

First two operations. Top and bottom completed

The bottom had an extra 0.125 in left to add rigidity for the roughing. This flip allowed me to also cut the ortho-grid with a shorter tool.

Frame completely machined. The bearing pockets were held to within -0.001 of an inch for a hot-cold fit. The total weight came to 1.3 pounds where the cad estimated 1.1 pounds. We are not sure where this difference came from as all fillets, drafts, and holes were modeled. Fillets were modeled to reflect what each cutter could do.

Lathe parts

Doing 4 wheel drive with two motors, we decided to use O-Rings as belts. Because of this, we needed custom pulleys. I programmed these custom pulleys and axles on the CNC lathe.

Pulleys were cut on a Tormach Lathe. Grooving was done with a threading tool

Assembly

Assembled Bot

-Drum Spinner

-Powered by two brushless motors. Theoretically could spin to 15,000 RPM in under a second. The weapon could dent soda cans and mulch 3d prints

-Drive ESC

-4 in 1 ESC for weight savings

-Drive Motors

-2313 Motors at 1300KV. These were extremely powerful. Power was transmitted through O-Rings to the wheels.

-Frame

-Mono-block aluminum. Solidworks tests showed that it could survive a 500lb/ft impact anywhere without permanent deformation. (Drop Test Simulations)

Final Bot

Decalled and painted

Drive Testing

Initial Weapon Testing

Competition

We scored 5th place only due to a broken radio. We went on to beat the winning team in after competition non-official matches. We were the only team to suffer no long term damage.

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