Continuously Variable Transmission Nick Lovria Matthew Rogers Bret Brinkmann September 22, 2003 Engineering Graphics Communications

What is a CVT? A continually changing pulley ratio to maintain or soften the transition between changing gear ratios. This application will be aimed at car enthusiasts who have or wish to install a centrifugal supercharger on their car and maximize the potential of that supercharger.

Why use a CVT? Centrifugal superchargers only operate at full capabilities when the engine is at full throttle. To enable a supercharger to operate at full capacity at a fraction of full throttle, but still not overpower itself when the engine is at full throttle, a CVT is used. A CVT varies its gear ratio with the speed of the engine.

Maximize Power Compressor maps relate compressor wheel speed, pressure ratio, and mass air flow to each other. The CVT allows more than twice the air flow at less than half the engine speed with out worrying about surge. Controlling the compressor speed allows for maximum adiabatic efficiency over a broader range of engine speed.

Design Criteria Small and compact design (Most important) To be incorporated into or on the front of the supercharger High durability Used at very high RPM and possibly in extreme racing Easy maintainability C’mon, the car owners have enough to worry about already!

Styles of CVT Half Toroidal V-Groove 1:1 gear ratio high Contact points Half Torodial Half Toroidal Two shapes that look like an imploded Hershey Kiss and two oval balls that rock back and forth between the varying radii of the imploded Hershey Kiss. V-Groove A belt that travels along a cone causing a variation in the drive ratio. “V-Groove” Low High

Analysis of Design The Half Toroidal CVT satisfies the criteria mentioned earlier Advantages Compact in theory Able to be housed easily within a shell Ease of operation and maintenance Drawbacks Tighter tolerances Meticulous machining

The Design To Supercharger From Engine

Operation/Installation A readjustment in mounting the current supercharger is necessary. Once the supercharger is repositioned then the CVT is simply mounted between the supercharger and the pulley. Input desired boost, pulley and gear ratios. Boost can be changed on the fly at any time.

Cost Analysis Expense Amount ($) Materials $100 Production $25,000 Per Unit Cost Breakdown Materials $100 Production $25,000 Labor $400 Tooling $50,000 Shipping $30 Per Unit* Manufacturer $615 Per Unit* MSRP $1,230 * Based on 1,000 units produced

Conclusion Superchargers cost about $2,500 A CVT will at least double the power output from the supercharger For car enthusiasts the benefits (i.e. outrunning the cops to avoid a ticket) far outweigh the drawbacks and justify the investment Note: this is NOT for soccer moms