From: A Statically Unstable Passive Hopper: Design Evolution Date of download: 12/29/2017 Copyright © ASME. All rights reserved. From: A Statically Unstable Passive Hopper: Design Evolution J. Mechanisms Robotics. 2017;9(1):011016-011016-7. doi:10.1115/1.4035222 Figure Legend: Early use of leaf spring in hopper. The body frame A was a U shaped bent aluminum extrusion. Leaf spring pair B connected dual wooden legs (chopsticks) C to the frame. The tail mast D was a wooden dowel with clay adhered at top. Clamps and clay were used as adjustable masses E1–E2 (multimedia extension 5 video).