  We present radial velocities for stars in the field of the open star clusters
Berkeley 44, Berkeley 81, and NGC 6802 from spectra obtained using the
Wisconsin-Indiana-Yale-NOAO (WIYN) 3.5 m telescope. These clusters are of
intermediate age (1-3 Gyr), located within the solar Galactocentric radius, and
have no previous radial velocity measurements. We find mean radial velocities
of -9.6 +/- 3.0 km s^-1, 48.1 +/- 2.0 km s^-1, and 12.4 +/- 2.8 km s^-1 for Be
44, Be 81, and NGC 6802, respectively. We present an analysis of radial
velocities of 134 open clusters of a wide range of ages using data obtained in
this study and the literature. Assuming the system of clusters rotates about
the Galactic center with a constant velocity, we find older clusters exhibit a
slower rotation and larger line-of-sight (LOS) velocity dispersion than younger
clusters. The gradual decrease in rotational velocity of the cluster system
with age is accompanied by a smooth increase in LOS velocity dispersion, which
we interpret as the effect of heating on the open cluster system over time.
