Upgrades to Exposure

 Our trip to Robodojo earlier this month highlighted a few issues that needed to be resolved. Most of these problems were to do with the weapon assembly, which had way too much flex and caused us to lose the weapon in our first fight. Also, the 3D printed parts were PLA at the event (uh oh) so they needed to be re-printed in TPU with a slight redesign for some parts. The fork mounts needed a way to stop the forks rotating under the robot like they did in York, and the weapon spacing needed to be increased. After looking at different companies that could print what we needed, we decided that it would be easier (and probably more cost efficient) if we bought our own 3D printer and TPU filament. This also opens up a lot of opportunities for printed antweight and beetleweight chassises. 

The first step for improving the weapon was to move the weapon bulkheads outwards and extend them backwards to the piece that separates the drive motors from the rest of the robot. We changed the mounting position of the weapon motor to be behind the weapon and inside of the bulkheads. This helped with internal space and also meant that the motor and pulley had no chance of being hit again. The battery has swapped sides and has moved up along the outside edge of the left weapon bulkhead near the link. The weapon ESC and receiver are on the right side, with the breakout cable in the centre so that all of the components make a sort of 'U' shape around the weapon 

We then printed a slighter bigger pulley and bolted it through the weapon into a piece holding two M4 nuts and pressed a 6 x 19 x 6mm bearing into each side. The increased distance between the bearings helps eliminate the flex that the weapon had in the earlier version. We have both weapons assembled like this so there is no need to take the entire weapon assembly apart for every swap. Just take the shoulder bolt out, and slide the new weapon on. Speaking of shoulder bolts, longer ones were ordered to fit the new assembly, we made a new belt to cover the extra distance.

The redesigned fork mounts and anti-horizontal wedges were printed in TPU at 30% infill. this gives them a nice amount of flex to soak up hits. After the original wheelguards got completely ripped apart at Robodojo, I was convinced that the next ones would be printed so they could be more effective. These were printed with 20% infill, but unfortunately I got the measurements wrong so I needed to print a spacer to make them fit correctly. After being screwed in, they feel very flexible and should hopefully take a few hits before breaking this time. The TPU parts also helped save some weight, meaning we can run the disk with the four 8mm mild steel forks. This configuration weighs it at about 1.499kg currently, but we are looking to save weight elsewhere to make it less stressful when weighing in. We also cut a new wooden cradle as the previous one had a bit too much wobble for my liking. To save even more weight, we rewired the electronics, removing the terminal blocks and soldering the wires properly. We replaced the single white LED with two green ones, just because it looks cool and fits the robot's theme better. However, soldering the new LEDs was quite confusing as they had green and black wires, and the black wire was positive with the green one being negative. This was just weird, as I would've expected it to be black negative and then the green positive to indicate LED colour.

Testing

We did a full test of the weapon and drive in our test box, and the results were very good. The feed angle of the forks was perfect in delivering the test chassis to both types of weapon, and the wedges exposed the weapon enough so that it wouldn't have to rely on getting underneath the opponent and could just hit it.

I am really happy to have finished this project, and can't wait to take it to another event where maybe we can win a fight!