I've been thinking along the same lines as Marvo i think you have what looks like a good design there
I tried to use SDS with homemade adaptor and it wasn't much cop, in reasonable ground it wasn't going anywhere really, whereas knocked it in with the lump hammer no problems so I think you'd have to try the SDS max which for me means buying a drill just for this purpose.
so I started to think of the slidehammer idea after seeing a video on youtube ,another version has a small pneumatic ram attached to the rod only trouble is need a compressor .
I tried to use SDS with homemade adaptor and it wasn't much cop, in reasonable ground it wasn't going anywhere really, whereas knocked it in with the lump hammer no problems so I think you'd have to try the SDS max which for me means buying a drill just for this purpose.
so I started to think of the slidehammer idea after seeing a video on youtube ,another version has a small pneumatic ram attached to the rod only trouble is need a compressor .