This is the part I have created.
Volume: 6.33in
Surface Area: 35.11in.
Center of Mass: x = -1.5 y = 0.84 z = -0.35
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Front Post - Low friction roller
This robot is 2 wheel drive (rear wheel), so it needs a post to support its weight in the front
This post will be 3D printed. Roller bearings from a bicycle headset will be mounted to the bottom. the robot will roll on the bearings.
The post was designed with a specific length, so that the robot will be perfectly level for the sonar, and so that the line sensor will be approximately 1/8" above the surface when mounted using a 1.5" standoff (1" standoff + .5" spacer)