1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I Rolling Pendulum

  1. Dec 10, 2016 #1
    (This is NOT a homework problem. It's an engineering problem I'm trying to crack.)

    A wheel with a rubber tire (friction) can roll on a suspended rail. Attached to it is a pendulum that's rigidly mounted on the axle of the wheel with a mass that can hand down and swing. (The wheel's rotation and the pendulum's are coupled.)

    The system swings freely and due to the energy lost to rolling resistance of the tire against the rail ( F = N*Crr ), the system's amplitude decreases over time.

    I am trying to find the dynamical equations of motion of this system.

    d (theta)/dt = alpha

    d(alpha)/dt = f(Crr,M,L,R,m,...)

    Can anyone help me? I know the equation for the normal force on the wheel axle is given by something like:

    N - M*g - m*v^2/L cos(theta) = 0, where
    N = normal force
    M is the total mass of the system
    m is the effective mass of the pendulum portion
    v is the velodity of the COM of the pendulum portion
    theta is the angle of the pendulum to the vertical
    Crr is the coeff of rolling resistance of the tire
  2. jcsd
  3. Dec 10, 2016 #2


    User Avatar
    Science Advisor
    Gold Member

    Small amplitude or large amplitude of swing ?
  4. Dec 10, 2016 #3
    Large amplitude. -pi/2 to +pi/2

    I don't want the solution. I want to understand the governing equations.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted