Name: Adder Subtracter Built by Phoenix This is a model based on "adder" by Denis Cousineau. It has two engines that through a gearsystem drives two shafts. When engine A is running, the model spins around its axis ccw/cw. When engine B is running, the model goes forward/back. When both A and B is running in same direction ccw/cw only the right wheel is turning, and makes the model take a wide left turn. When motor A and B is running in opposit direction only the left wheel is turningm, and makes the model take a wide right turn. Does this sound strange? Make this and try. It will give you some headache when trying to program the RCX :) RCX programing tip: make Custom Blocks that contains "left turn", "right turn", "forward", "back", "wide left turn" and "wide right turn". Phoenix / F0NIX http://f0nix.i.am Norway