I did my homework - much easier than I expected - which is usually a bad sign for me.
For critical buckling load,
For 1.5" x 0.035thick, 6061-T6 Al, cylinder, simply supported,
Area moment of inertia = 0.043 in4
Young's Modulus = 1.00E+07 psi
L = 109 in.
Fcr = 359.2 lbf
Good thing there...