Overview

This was my sophomore design project; to create a stairclimbing robot to retrieve an egg from the top of the staircase back down to the starting line. I was the project manager and co-lead for the chassis and drivetrain subsystem. My main contributions were designing the chassis out of U-channels, motor mounts, and drivetrain.

To keep under the $500 budget cap, the team opted to 3D print most of the components such as motor mounts, gears, and the egg grabber. This was my first engineering project and my first time using CAD software, Solidworks. I designed the motor mounts with the intent of being 3D printed. I looked at motor mounts that were commercially available and used them as the basis of my design. I also designed the gears that turn our timing belt, which we retrofitted with padded shelf liners to have more grip, which acted as our tracks. Since we were nearing our budget cap, we opted to 3D print the shaft couplers that attach our gears to the motor. I also designed the tensioner since we oversized the timing belt to ensure some leeway.

Lessons Learned

The night before our competition, we were up until 2 am assembling and fixing our robot. We tried to go up the staircase and the robot flipped over as we tried to get up a single step. This bent the left frame just slightly and the gear shaft started attached to the frame to strip our 3D printed shaft coupler since the motor shaft and gear shaft were now misaligned. This prevented our robot from moving more than an inch during the competition. 

The robot could not go up the step because our arm actuator design was flawed. The servo motor responsible to move the arm actuator up and down was not strong enough to lift the weight of the entire robot. And with the weak shaft coupler design, no power from the motor could transfer to the gears to move the timing belt.

What I learned from this was:

1. Prototype early so you can fix what's wrong before it is too late. If we prototyped early on in our design, we would've figured out that our actuator design was not sufficient and we could've changed our design.

2. Just because you can 3D print it, it doesn't mean you should. We 3D printed our shaft couplers which proved to be a wrong design decision. The couplers worked when the frame was straight. But with a bent frame, this lead to the couplers stripping from the inside face. I believe this would've been avoided, or at the very least not exaggerated, if we decided to buy metal shaft couplers instead.