This page contains hi-res pictures of an RC tank I found I BiMart in Grants Pass this afternoon.  I have been buying all kinds of RC cars and tanks hoping to find something inexpensive that lends itself to making "micro" and "nano" sumo bots.  I have spend a lot of time looking and today I finally hit PAY DIRT!!!  This little tank was not on sale and still only costs $9.95 locally.  If you search for it on ebay you will find them for $6.99!  ( )  As you will see (if these pictures ever finish loading) this tank is built around two pager motors and a very high reduction gear train.  This is by far the nicest motor/gear train combination I have seen to date and it's super cheap on top of it all.  With a little hacking this would fit very nicely into a nano sumo.  Notice that the entire motor/gear train section is only about a quarter of an inch wide and very short.  Unlike other tanks I have dissected, the two sections are pretty much independent.  In case you get one of these I should mention that there are three screws on the bottom that hold it together.  Two of them are under the tracks and are not so obvious.  You will need to remove the center wheel on each side in order to get to the screws.  The wheels are held in place by a little rivet looking thing in the center and simply pull off.  It's nice that all the wheels don't have shafts going from side to side like most others I have seen.  These things are really neat !