 The water bucket counterweight was emptied when it reached the bottom of the vehicle, raised back to the top, and filled with water using a reciprocating water pump, so that motion could again be achieved.It has been calculated that to move a helepolis with a mass of 40000kg, a counterweight with a mass of 1000kg was needed.Originally an incendiary weapon adopted from the Greeks in 7th century AD, the Greek fire “is one of the very few contrivances whose gruesome effectiveness was noted by” many sources.