Drive system and Fly/Drive gearbox

Drive System for the Transition flying car

Role: system lead

Mechanical Engineer, Installation and Test Engineer

Led the design of the drive power transmission system of the Terrafugia Transition "roadable aircraft" prototype including light-weight shifting Fly/Drive gearbox

Established requirements definition down to the part level; lifetime and reliability requirements varied greatly between components involved in flight systems and those in drive systems only.
Designed and optimized all components using FEA and fatigue analysis.
Created detailed part drawings, liaised with local fabrication vendors, assembled, installed and tested all components on aircraft.

Successes:

Shiftable fly/drive gearbox supplies 100 hp continuous to propellor or 40 hp continuous to the wheels through a belt driven CVT.
~200 drive hours on gearbox and drive system
~50 flight hours on gearbox

Drive System Scope

CAD side view of Drive System located in vehicle.

Early Sketches

Notebook sketches and calculations for gearbox components.

CAD: Gearbox Side View

Cross-section of gearbox shows slide spline U-Joint drive shaft interface on left and propeller mounting flange on right.

CAD: Gearbox Top View

Cross-section shows gear arrangement for right-angle power take-off for drive system. Two crown gears provide forward or reverse power when one or the other is engaged. CVT primary pulley mounted directly to upward facing splined shaft.

FEA: Drive Load Optimization

Stress analysis of "Wheel Slip at Gross Weight" load case to optimize case material removal.

Bearing Calculations

Spreadsheet analysis of bearing lifetime based on expected spread of driving loads, vehicle lifetime and required bearing reliability.

FEA: Propeller Drive Ring

Stress analysis of spline interface between propeller drive ring and main drive shaft for 100hp, max torque case. Max stress targeted for infinite fatigue life with a factor of safety of 1.5.