Getting over an obstacle

I'd like to throw this question out there for some opinions:

I'm building a robot, (actually, it's the ASME's "Mine Madness" competition, about 15"x15"x15" that will run on a set of treads. this robot has to be able to get over a barrier 7" high x 3.5" wide... I'm planning on having the treads running on an angle at the front, similar to a tank, so that when it hits the barrier, they will ride over it. i'm planning on the robot weighing no more than 20lbs. does anyone know if the treads would be a good idea - i.e. will they have enough grip to pull the robot forward over the barrier, or would they just skid?

thanks for any input

I say the biggest problem is obtaining those tracks. But its probably the only solution. Maybe a walking robot may work...

Yes, drive you robot as the tank, it make the torque stronger