Thor's Battle Axe

Dr. Marc Mitchell and his colleague Dr. David Wartinger were intrigued when they started hearing from patients claiming to have passed kidney stones after riding the Magic Kingdom’s Big Thunder Mountain Railroad – so intrigued they decided to test the ride themselves. Surmising that cow and pig kidneys would be inappropriate for a family theme park, they 3-D printed artificial kidneys, loaded them with actual urine and kidney stones, stuffed them into backpacks and headed to the park. They subjected the backpacks (and themselves) to over 60 rides, letting cast members seat them whither they would, and then crunched numbers. They determined that riding near the front of the train had a passage rate of 17%, but the back of the train resulted in a passed stone 64% of the time. Then they tested other more intense rides and determined that free falls, corkscrews, and higher speeds didn’t dislodge stones. Apparently a little shake, rattle and roll is all it takes.