Well, the reason they go up the ramp is how the ramp vibrates. It actually goes back and forth, not up and down. So when it moves in the direction of the high side, the barrels tend to lose their "grip" on the ramp and then the ramp comes back toward the low side and they move a tiny bit up as it's going in the opposite direction that the barrel's inertia is taking it. Remember, it's vibrating 60 times a second, so they don't move much for each vibration.
If they ramp is vibrating too violently, they tend to bounce around more and either don't go anywhere of jump off the sides.
At 10 VAC on my true-RMS meter, the barrels have trouble getting out of the chute, they tend to stick partially tilted and the following barrel holds them in place. If they make it, they slowly make their way up the ramp. Between 11 and 11.5 volts, it works pretty well, marginally better at 11.5. At 12-12.5 and over, it's getting too wild, and by the time I get to 14.5-15, the barrels sometimes jump off the ramp sides before they get all the way up. Even if they don't jump off, they are bouncing all over the place, looks pretty comical.
