cant resist poking my snout in here,the 30 was a good sized robust excavator,there was an option with the engines,you could have a ruston 5 yen or an english electric 6 ydax, when i first saw a 30 i was fascinated how the rotor-seals delivered air into the inside clutches,only one downside there were no actual digging locks fitted on them,reliance for locking and spragging were those troublesome brake bands which always got covered in grease and suchlike, happy days or what
.graham.
but if the sliding clutches or linkages underneath were worn and jumped out of drive when traveling down hill 
you'd be away and nothing to stop you. 
.
