[Alberta's Child]

Just to clarify that . . . the tires don't actually tip the ramp -- they just bump each other in succession and get them rolling up the ramp to tip something over the edge.

Either way, I call BS on that one.

[Yo-Yo]

The tires have a weight attached inside the tread at the top. When they get bumped, the weight falls down, rolling the tire up the ramp. Look at the horizontal position of the top of the tire at the beginning position, then look at how that same spot is actually lower even though the tire has rotated and climbed the ramp. The weight fell down inside of the tire.

You can even see one of the tires rock back and forth when the weight hits equibrilium.

Think old fashioned water wheel. The weight of the filled buckets on one side of the wheel are heavier than the empty buckets on the other side, and the wheel turns.

For this video, it does have to be a very dense weight, however.