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RoMeLa | CIVT: Cam-based Infinitely Variable Transmission
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Cam-based Infinitely Variable Transmission

Researcher(s): Derek Lahr

The Cam-based Function Generating Transmission is a novel mechanism that takes two inputs, an angular rotational input and a ‘gear ratio’ selection, and outputs an angular rotation with a variable speed ratio. This transmission has unique characteristics such as generating specific functional speed ratio outputs including dwells, for a constant velocity input.

Mechanical Goals and Objectives

    • Design synthesis and optimization

    • Efficiency and durability testing

    • Adaptation of CIVT to automobiles

    • Control methods for and implementation in a wind turbine

Current work on the CIVT focuses on the design, fabrication, and testing of several prototypes. The goal of which is to increase the power throughput density of the transmission through optimization processes, advanced manufacturing techniques, and the implementation of novel mechanisms. Future work will focus on configuring and adapting the transmission to several applications, including automobiles, human powered vehicles, and renewable power generation facilities.

Operation Concepts

The CIVT mechanism receives a rotational input through the input shaft, which drives two sun pulleys through one-way clutches. Each sun gear is connected to two planet pulleys mounted upon a carrier. Each planet gear drives one follower assembly. As the follower moves outward, it causes the carrier to rotate faster then the sun gear, with the amount of speed increase being determined by the particular profile of the cam and the planet to sun pulley ratio.


  • Lahr, D. and Hong, D. W., “Contact Stress Reduction Mechanisms for the Cam-based Infinitely Variable Transmission”, 31st ASME Mechanisms and Robotics Conference, Las Vegas, Nevada, September 4-7, 2007.

  • Lahr, D. F. and Hong, D. W., “The Operation and Kinematic Analysis of a Novel Cam-Based Infinitely Variable Transmission”, 30th ASME Mechanisms and Robotics Conference, Philadelphia, Pennsylvania, September 10-13, 2006.

  • Lahr, D., and Hong, D. W., “The Operation and Kinematic Knalysis of a Novel Cam-based Infinitely Variable Transmission”, ASME Journal of Machine Design, 2008.

  • Lahr, D. and Hong, D., “Dimensional Synthesis of a Cam-Based Infinitely Variable Transmission Using Genetic Algorithms”, US-Korea Conference on Science, Technology and Entrepreneurship (UKC2007), Mechanical Engineering & Robotics Symposium, Washington DC, August 9-12, 2007.