Large Hairy Butt Collider

Roland tightened the last bolt and wiped his greasy hands on some cotton waste. It was done.

Two tall spirals of light rollercoaster track, each descending in a series of loops, to a water-filled chamber at ground level.

Two small rollercoaster cars, with a padded knee cushion and what looked suspiciously like an old-fashioned set of stocks at the other end, with holes for hands and heads. One car sat at the top of each spiral. It appeared their riders would be descending backward, on their knees, with their hips slightly higher than their heads.

Now, all he needed was a couple of willing bears, on which to test the device.