When I came bact to LEGO, the PowerMiner series just published. Again I fell into LEGO due to PowerMiners. Then I was interested in trains. I made this drill train by the concept of tunnel boring machine (TBM).
This one is constructed on a LEGO RC train base. Your can operate it with LEGO RC remote controller. The huge drill is driven by a LEGO M-motor. It runs clockwise or conter-clockwise dependingon the direction(forward or backward) of the train. Check this. http://www.youtube.com/watch?v=NF-XAuQA8mQ