[mechE131]

That model is only good for a situation where the normal force is exactly opposite of the force caused by weight (mass X acceleration due to gravity) and perpendicular to the resulting force (driving forward).

In the case of a "climbing" robot, the most suitable analytical situation would assume the normal force is perpendicular to the pole the robot is latched to.

I would recommend to all students draw a diagram of all the forces on their robots before using any calculators to see if the same situation applies.