paper: Analysis of “a torque-actuated module” used for strafing in an H-drive.

[RyanCahoon]

Originally Posted by GeeTwo

There is no single part which experiences all three of these forces.

I apologize for having been a bit lax with the rigor of my arguments. Let me try to clean some of that up.

In my physics classes, we were always told that the first step of solving a mechanics problem is to define your system. Forces between bodies in the system are internal forces and must sum to 0, because both halves of the force pairs are included. Forces from bodies outside the system acting on those inside the system are external forces. Since the internal forces sum to 0, then the external forces make up the F_net as used to calculate Newton's 2nd law, F_net = m*a.

My interpretation of your paper was that the system being considered consists of

• the strafing module arm
• the wheel
• the gear attached to the wheel ("the driven gear")

If we take a fairly idealized version of the problem, the external interactions are the following contact and frictional forces:

• the drive axle -> the strafing module arm.
• the driving gear -> the driven gear. You label this D
• the ground -> the wheel (contact force). You label this N
• the ground -> the wheel (frictional force). You label this F

Equation 3 accounts for the last three, but not the first, unless you can present an argument that the first force is completely parallel to B.

Did I misinterpret your paper? Did you use a different system definition when doing your analysis?