1. Portfolio 2016
Drew René Roche
07515891599
drewroche@hotmail.co.uk
34 Selborne Road
London
N14 7DH
Final Year Design Project

2. Drew René Roche
BEng Mechanical Engineer
Portfolio 2016
During my final year project, I developed a roller based, traction driven, continuously variable
transmission - CVT - system. This consisted of a split-spherical type roller in conjunction with
toroidal input and output disks for the first time. Geometrical considerations such as axle
diameter, bicycle frame ‘dropout spacing’, hub design and chainline have been considered in
regard to the final design within a bicycle.
CVT benefits include, step-less gear changes, quieter operation, reduced maintenance and
high tailor-ability to each potential user. A conducted and revised literature review led to
the development of a design brief and a solution due to a ‘gap in the market’. The initial,
intermediate and final design were produced with regard to the associated aims and objectives
of this project. The 3D CAD designs were undertaken on PTC Creo Parametric.
The outstanding feature of the final design is the theoretical gear range ratio of 1500%,
this far surpasses the current competitors and traditional bicycle transmission mechanisms.
However, this design is infantile and requires optimisation via materials & traction fluid selection,
sealants and geometrical considerations. The CVT application is not restricted to a bicycle,
with potential for development in many motorised chain or shaft driven applications.
Introduction

3. Drew René Roche
BEng Mechanical Engineer
Portfolio 2016
Final Design - Sealed Hub Unit
My design would replace the current
hub on the rear wheel of a bicycle. The
holes on the green casing walls are for
spoke attachments so that this could
be built into almost any rear bicycle
wheel.
A sprocket, of the users choice, would
be rigidly attached to the light blue
stem. The addition of a chain would
allow the bicycle to be powered in the
traditional way.
Changing gear requires all of the
yellow rods to be simultaneously
shifted towards either casing walls in
order to change the internal contact
position.

4. Drew René Roche
BEng Mechanical Engineer
Portfolio 2016
Final Design - Exploded Assembly

5. Drew René Roche
BEng Mechanical Engineer
Portfolio 2016
Final Design - Assembly Inside the Case
Black
Blue
Red
Yellow
Brown
-
-
-
-
-
Wheel axle
Input Toroid
Output Toroid
Shifting Mechanism
Power-tranfer Roller

6. Drew René Roche
BEng Mechanical Engineer
Portfolio 2016
Poster Information
Over the course of the project, I was
asked to design an A3 poster. Mine was
shortlisted to be shown at the Queen Mary
Industrial Liaison Forum to demonstrate the
best projects currently being undertaken
at Queen Mary. The idea was to show the
general working principle or theory of the
project,whilstenablingtheviewertobecome
inquisitive and to allow myself to present
along side it. This design was undertaken
on Adobe Illustrator.

7. Output
Half-Toroid
Input
Half-Toroid
Power-transfer Roller
Continuously Variable Transmission
Applied to a Bicycle
by Drew Roche
Introduction
Bicycle transmission and design hasn’t fundamentally changed since 1909 [1]
Some perceived barriers to cycling are [1]:
- Riding discomfort
- Maintenance
Cycling is very competitive in terms of price and speed for urban journeys [1]
The aim is to encourage more cyclists and to explore the different uses for CVT’s
Working Principle
The input is driven by a chain-drive, as stan-
dard on bicycles, and the output is rigidly
attached to the rear bicycle wheel along an
axle.
Rotational motion is transferred from the input
to the output toroid via the power-transfer
roller.
A reduction in wear and improved efficiency of
this CVT will be due to power transfer occuring
solely via a traction fluid.
Tilting the power-transfer rollers changes the
diameter of the ‘contact point’ from the input to
the output, altering the gear ratio.
dOUT
> dIN
Increased pedal resistance
dOUT
< dIN
Decreased pedal resistance
dOUT
= dIN
1:1 Gear Ratio
Conclusion
CVT benefits to user:
- Infinite number of gears within a range
- Smooth gear changes
- Quiet operation
- Removes maintenance of gears
This is the first combination of half toroidal
type input and output disks with a power-trans-
fer roller resulting in more compact and lighter
half-toroidal type configurations
The market potential is not limited to cycling
Instantaneous
Solid
Traction
Fluid
Traction
Fluid
Power-Transfer Roller
Input/Output Toroid
References
[1] ROY, R. (1983) ‘Design:Processes and Prod-
ucts’1st
ed. Open University Press
[2] CISMON (2013) ‘Santotrac in CVT’
Adapted from [2]
dOUT
dIN
dIN
dOUT
dIN
dOUT
Drew René Roche
BEng Mechanical Engineer
Portfolio 2016
Poster Design - A3