I have just been using the standard Tunnel x number of blocks command. So, tunnel 100 will dig out a 3 x 3 x 100 tunnel. This works perfectly when I had 4 of the things running and I hung out in the area cleaning up behind them. However, when I leave the area they all died. So, I looked up the chunk loader turtle last night and made one. But it dies when I leave the area unfortunately. Going to have to do some more research on it but I think I am going to get a quarry up and running tonight so I am not too woried about it right now. I just like to know why things don't work. I really do wish a chunk loader wasn't required in single player if you have active devices in an area.