effects improved results as compared with using the oscillating bar alone while the present invention has been described above with reference to the use of electromagnets to obtain the desired oscillation it is to be understood that any mechanical pneumatic or electromechanical means can be employed to obtain oscillation for example the flange 7 or the housing 16 fig1 3 could be attached to a driven cam mechanism or to a reciprocating pneumatic means to obtain the desired oscillation furthermore any spring means other than rubber mountings can be employed such as metal springs the rubber mountings can be intermittent or continuous throughout the length of the oscillating bar 2 in addition bars 14 and 15 can be intermittent or continuous throughout the length of the oscillating bar 2 and when intermittent can be fixed by any suitable means such as being bolted to housing 16 which bolts can extend through the rubber mountings and through a clearance hole in flange 8 if desired electromagnets 28 can be attached to the fixed bar 24 while the ferromagnetic masses are attached to the oscillating curved bar it will thus be seen that the objects set forth above among those made apparent from the preceding description are efficiently attained the curved and gas cushioning reciprocating bar of.