Split Belt Machine
This split belt machine drives forward when placed on a split-belt treadmill that has both belts moving backwards at different speeds.
A 1:1 geartrain connects the two rear wheels
The rear wheels contact separate belts
A rudder between the belts keeps the cart pointed forward and the free-spinning front wheels keep the cart from tipping left/right
A 5-pound weight can be added above the rear wheels to increase traction
This fun side project was a collaboration with another biomechanics lab. We wanted to demonstrate that it was possible to extract positive mechanical work from the velocity differences of the two belts of a split-belt treadmill. If this could carry over to bipedal walking, it could mean that walking on a split-belt treadmill is easier than walking on a traditional treadmill.
After a proof-of-concept Lego cart was built, I was brought onto the project to build a more precise and efficient version of the cart in order to better demonstrate the "energy harvesting" concept. I designed the cart to be minimal, low-cost, and have as little friction loss as possible. For example, bearings on the rudder greatly reduce friction and narrow wheels offer low rolling resistance.
I also filmed and edited both videos on this page, which were posted to Twitter.
I also detailed a DIY Lego version for those who want to try it for themselves and have access to a split-belt treadmill