little help here...

im in need of a fast acting several ton ram. thinking of air over hydraulic. just never used one. how do they work? does the air compressor take care of the fast acting part then you manually pump the hydro for the high pressure? does air do it all? how fast does the ram move under no load (approx)

did the search, found out some use them for their tubing benders...no details on the rams specifically though...

thanks