In this paper we study a Fermi–Ulam model where a pingpong ball bounces elastically against a periodically oscillating platform in a gravity field. We assume that the platform motion
$f(t)$
is 1-periodic and piecewise
$C^3$
with a singularity,
$\dot {f}(0+)\ne \dot {f}(1-)$
. If the second derivative
$\ddot {f}(t)$
of the platform motion is either always positive or always less than
$-g$
, where g is the gravitational constant, then the escaping orbits constitute a null set and the system is recurrent. However, under these assumptions, escaping orbits co-exist with bounded orbits at arbitrarily high energy levels.