<https://dfi.org/2021/02/09/differential-acting-hammer/#webpage>
<http://schema.org/description>
"A fluid -powered hammer in which fluid lifts the ram on the up stroke and is exhausted into and combined with additional fluid entering over the piston to take advantage of differential piston areas to accelerate the ram and to act in concert with gravity"
<https://dfi.org/2021/02/09/differential-acting-hammer/>