a tumble dryer !
now I have a wee it of experince making one of these and i would say really
look at the examples on the net, the flat vibrating ones are the most sturdy
and much more easily constructed, using you motor with an off center spin,
don't forget you may what different gradients the first thing to work out is how you are lifting the earth, how much dump wight
it will take and to what height also worth thinking about weather you can run a dumpper underneath. I made one with old iron sides car coil springs and a good strong steel
frame to start, the fall angle is important so best to give it several possibility's.
good luck