Abstract-This paper presents a method for generating smooth, efficiently-executable trajectories for robots under contact constraints, such as those encountered in legged locomotion and object manipulation. It consists of two parts. The first is an efficient, robust method for constructing C1 interpolating paths between configuration/velocity states on implicit manifolds. The second is a robust time-scaling method that solves for a minimum-time parameterization using a novel convex programming formulation. Simulation experiments demonstrate that the method is fast, scalable to high-dimensional robots, and numerically stable on humanoid robot locomotion and object manipulation examples.