An assignment for Swinburne University.

1. Top Gears
Creativity Journey
MEE30003 Machine Design
Kellen Huang 100674007
Brendan Cooper 101094169
Dylan Hill 101122248
Dexter Archibald 101126949

2. Mind Map
GearboxDesign
Gearbox Design
ComponentsGear Types
Spur
Helical
Gears Housing
Requirements Limitations
Move 10kg load
Fast
Compact Material
Motor
Motor
Bevel
InternalWorm
Rack and Pinion
A4 sheet size Acrylic
Shape and size
Mounting
Locking mechanism
Gear Arrangement
ParallelPerpendicular
Concentric
Assembly
Quick and easy

3. SCAMPER
Substitute - different gear ratios, different gear arrangements
Combine - combine different features from different ideas
Adapt - adapt ideas from literature review resources
Modify - design changes to reduce size, increase efficiency
Put - use it to drag different masses and hobby drivetrains
Eliminate - eliminate unnecessary features and flaws
Rearrange - seek more efficient and compact gear arrangement

4. Properties of Acrylic
Table 1: Average physical and mechanical properties of acrylic
Property Value Units
Density (ρ) 1160 - 1220 (1.16-1.22) kg m-3 (g cm-3)
Young’s Modulus (E) 2.24-3.8 GPa
Yield stress (σy) 52.8-72.4 MPa
Tensile strength (σt) 48.3 - 79.6 MPa
Compressive strength (σc) 124 MPa
Shear strength (𝜏) 62 MPa
Static coefficient of friction (μs) 0.20 -
Kinetic coefficient of friction (μk) 0.15 -

5. Ideal Gear Properties
➔ High strength-to-weight ratio
➔ High surface hardness
➔ High bending strength
➔ Low surface friction
➔ Low rotational inertia
Balance of these often required

6. Acrylic vs Metal Gears
Acrylic Metal (eg. cast iron, steel)
Advantages Disadvantages Advantages Disadvantages
Light Cannot as easily be
engineered for surface-
bending strength balance
Surface-bending strength
balance achieved
through alloys, heat
treatment and oil
quenching.
Dense
Inexpensive Usually mated with iron
or steel pinion
Usually mated with metal
pinion
↑ strength, ↑ cost
High teeth deflection -
effective load sharing
between teeth in contact
High teeth deflection -
exposed to internal
friction heating at high
rotation
Poorer teeth deflection -
protected from internal
friction heating at high
rotation
Poorer teeth deflection -
less effective load
sharing between teeth

7. Motor Properties
At max efficiency
● Efficiency(%): 49.6
● Power (W): 5.96
● Speed (RPM): 9679
● Torque (G.CM):60
● Current (AMP): 2
At max power
● Output (W): 6.44
● Speed (RPM): 7845
● Torque (G.CM): 80
● Current (AMP): 2.6

8. Types of Gears
Eliminate gears difficult to be
reproduced using acrylic

9. Types of Gears
Eliminate gears difficult to be
reproduced using acrylic
=
Uniform cross sectional area
parallel to face plane
=
1 - Spur Gear
2 - Internal Gear
3 - Rack and Pinion

10. Fixed Axis System
Pros
❏ Compact and easy to install
❏ Mass can be decreased
❏ Highly reliable
Cons
❏ Produce a lot of noise when operating
at high speeds
❏ Large stresses on teeth
❏ Limited centre distance

11. Internal Gear System
Pros
❏ Large reductions in compact space
❏ Load shared between gears
❏ Longer gear life
Cons
❏ Gearing must be accurate (complex
manufacturing)
❏ Noisier operation
❏ Driving and driven member must be
concentric

12. Rack and Pinion
Pros
❏ Converts rotational motion directly to
linear
❏ Small pinion required
❏ Less backlash and greater feedback
Cons
❏ Mechanically inefficient
❏ Can only work with certain levels of
friction
❏ Under constant wear

13. Gear Arrangements

14. Preliminary Design Idea

15. Preliminary Design Idea

16. Preliminary Design Idea

17. Preliminary Design Idea

18. Literature Research so far
Title Main Points Reference
Kinematic
Geometry of
Gearing
- Summarises designs of gears (pros/cons)
- Goes through teeth design
Donner, D. B., 2012. Kinematic Geometry of
Gearing. 2nd ed. West Sussex: John Wiley & Sons.
A new approach
for polymer gear
design
- Mainly focuses on polymer gear production
- Does summarise relationship between critical load the
wear rate
Mao, K., 2007. A New Approach for polymer
composite gear design. Wear, 262(1), pp. 432-441.
Acetal gear wear
and performance
prediction under
lubricated running
conditions
- Analyses relationship between surface wear and critical
load
- Compares tooth design with critical load performance
Mao, K., Hooke, C. J. & Walton, D., 2006. Acetal
gear wear and performance prediction under
unlubricated running condition. Journal of Synthetic
Lubrication, Volume 23, pp. 137-152.
An investigation
on the thermal
and wear
behaviour of
polymer based
spur gears
- Compares the effect torque and rpm has on wear
behaviour
- Analyses effect of reducing teeth ratio on wear
Singh, P. K., Singh, A. K. & Siddhartha, 2018. An
investigation on the thermal and wear behaviour of
polymer based spur gears. Tribology International,
Vol 118, pp. 264-272.