  We use high order linked cluster series to investigate the hard core boson
model on the triangular lattice, at zero temperature. Our expansions, in powers
of the hopping parameter $t$, probe the spatially ordered `solid' phase and the
transition to a uniform superfluid phase. At the commensurate fillings $n=1/3,
2/3$ we locate a quantum phase transition point at $(t/V)_c\simeq 0.208(1)$, in
good agreement with recent Monte Carlo studies. At half-filling ($n=1/2$) we
find evidence for a solid phase, which persists to $t/V\simeq 0.06$.
