of the pile without any other means of support or guidance being required thus the dropweight 2 39 delivers the initial impact to the top wall as illustrated 13 of the body 8 39 and thus through the strike cap piston 3a to the anvil 7 the higher peak force impact is provided by having such a gas pressure in the chamber 3 or stem length of the piston 4 that the part 5 34 of the separate body strikes the anvil 7 in steel to steel fashion alternatively the higher peak force impact may be provided by increasing the stem length of the strike cap piston 3a and providing the interior wall of the chamber 3 with a projecting part 10 39 in a similar manner to the embodiment of fig1 and 11 such that the strike cap piston hits the projecting part a disadvantage of the construction of fig1 is that the impact forces are transmitted directly to parts of the apparatus other than the separate body 8 39 in which the precompressed resilient means is incorporated this disadvantage is avoided in the embodiment of fig1 in which the separate body 8 39 serves the sole purpose of transmitting the force during impact to the pile without affecting any other part of the construction the dropweight 2 39 moves within a housing 14 from the bottom of which there extends downwardly a tubular portion having a recess 15 in which the anvil 7 is held captive.