vp_const&var.py

g = 9.8 #G force
M1 = 2 #bar 1 mass in kg
M2 = 1 #bar 2 mass in kg
d = 0.05 # thickness of each bar
gap = 2*d # distance between two parts of upper, U-shaped assembly
L1 = 0.5 # physical length of upper assembly; distance between axles
L1display = L1+d # show upper assembly a bit longer than physical, to overlap axle
L2 = 1 # physical length of lower bar
L2display = L2+d/2 # show lower bar a bit longer than physical, to overlap axle

# Coefficients used in Lagrangian calculation
# https://en.wikipedia.org/wiki/Lagrangian_mechanics#Two-body_central_force_problem
A = (1/4)*M1*L1**2+(1/12)*M1*L1**2+M2*L1**2
B = (1/2)*M2*L1*L2
C = g*L1*(M1/2+M2)
D = M2*L1*L2/2
E = (1/12)*M2*L2**2+(1/4)*M2*L2**2
F = g*L2*M2/2

hpedestal = 1.3*(L1+L2) # height of pedestal
wpedestal = 0.1 # width of pedestal
tbase = 0.05 # thickness of base
wbase = 8*gap # width of base
offset = 2*gap # from center of pedestal to center of U-shaped upper assembly
pedestal_top = vec(0,hpedestal/2,0) # top of inner bar of U-shaped upper assembly

theta1 = 1.3*pi/2 # initial upper angle (from vertical)
theta1dot = 0 # initial rate of change of theta1
theta2 = 0 # initial lower angle (from vertical)
theta2dot = 0 # initial rate of change of theta2