Semester

Spring

Date of Graduation

2020

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Kenneth Means

Committee Member

Eugene McKenzie

Committee Member

Terence Musho

Abstract

Continuously variable transmission (CVT) describes a family of transmission styles. These systems serve the same purpose as their traditional counterparts; transmitting power while offering a variable gearing ratio. The difference lies in the CVT’s ability to change ratio continuously between a minimum and maximum without halting power transfer. They offer many benefits of an automatic transmission while being significantly lighter. For this reason, CVTs are often used on Baja SAE® vehicles to control gearing ratio.

WVU’s Baja team has used mechanical CVTs for many decades. These systems are simpler in the sense that they don’t require power to operate. However, understanding the mechanical control scheme they offer can be difficult. Many teams take a trial and error approach to tuning these systems. This consists of altering components to achieve desired outputs. For a mechanically controlled system this process is time consuming and cumbersome. Data collection isn’t as effective for future vehicles because gear box ratio, and vehicle weight will disproportionally affect CVT performance.

The purpose of this research is three-fold. One: researching specific, quantifiable, CVT tuning objectives. Areas of consideration include engagement speed, shift out speed, static RPM shifting, and efficient power transfer. Second: developing a model of the CVT force balance. This model is derived from the force balance between the primary and the secondary sub-systems. Third: developing tools to aid in the tuning process. This includes a system testing setup, monitoring power, torque, and shaft speed at the primary and secondary.

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