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

2. 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.

3. 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.

4. 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.

5. 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!

6. 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

7. 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

8. The Design
To Supercharger
From Engine

9. 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.

10. 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

11. 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