[Jibri Wright]

I just talked to him. He said that the centripetal force does cause the outer two wheels to lift. Its the same force that NASA is currently studying to create "artificial gravity" in space stations. Centripetal force (in the form of static frictional force in this case) pulls inward and the outer wheels are pulled out parallel two the floor. As the robot begins to pivot, the centripetal force is out of balance. If you have ever done work using vectors, you can tell that one of the outer wheels on the ground and one wheel floating is what causes this imbalance. The centripetal force in turn forces a balance by making the forces on the two outer wheels equal a.k.a. set their vectors parallel to each other.

Think of it like a spinning top. When the top isn't spun, it is laying sideways on the table right? But when you spin it, it balances on a single point that touches the table, almost as if defying gravity. The force that is causing the top to balance is the same force that is causing the outer two wheels to lift.

My mentor also said that this observation is not as observable with an FRC 6wd because the dropped wheel is not dropped enough to notice, the FRC field carpet is too high to notice, FRC robot weight normally isn't evenly distributed on both sides of the robot, etc. so its hard to notice and may not come fully off the ground, but the wheels do lift.

He also said that this only occurs when the robot is pivoting. When the robot is driving forwards or backwards, four wheels are normally touching the ground and the weight (or as you said normal force) is even on all four. One set of wheels will be off of the ground and none of the weight will be on those wheels.

To put it plainly, since the wheels are probably touching the carpet when pivoting, normal force is decreased on the outer wheels when pivoting but not because of the dropped wheel. It is because of the centripetal force acting on the robot by tangential friction. Because a lot of Newtonian mechanics use a lot of the same measurements like Newtons, seconds, meters, etc.., it isn't always easy to figure out exactly what causes what. Even so in this case, it is centripetal force. The dead giveaway is the circular motion.

Btw Ether, love the Einstein picture. I love how he's the father of quantum mechanics yet dedicated his life to proving it wrong!