This document discusses designing a gear system to lift a weight of at least 8kg up 0.5-1m. It needs a torque density and gear ratio of at least 40. A planetary gear system was considered but requires precise placement. A worm gear was also considered but is inefficient. The final idea is a compact progressive gear reducer to achieve the required ratio without failure. The system will be laser cut from acrylic and assembled by hand to lift the weight with string or cable.

1. Gear boys
BY JOSHUA CLARKE (TEAM LEAD), TOM GAVEN AND YI HING TEE

2. The Problem
 A Weight of at lest 8Kg must be lifted up .5m to 1m
 Motor Max Torque efficiency is 5.886E-3 N.m.
 The gearbox must be space effective and Torque dense as possible
 Prototyping/production limitations. Must comprise of a A4 worth of Acrylic, or
two if necessary. With only two or one iterations respectfully and Will be
Assembled by hand, Joined by super glue, and the weight pulled up by string or
cable.
 Parts are laser cutter from the A4 of Acrylic, except for the shafts.
 Acrylic Average tensile strength is 70MPa

3. The Problem - Output
 We decided on a pulley attached to output shaft
 At minimum, using the 6mm rod as the axle we need at least
8kg*9.81m/s/s*0.003m = 0.235N.m output torque
 This means a total gearing ratio of 0.235N.m/5.886E-3N.m = 40
 Can increase the force from the pulley by increasing its radius, ie by making a
larger diameter drum for it to roll around

4. The Ideas

5. Planetary Gear System
 A Very Torque dense design, but requires the parts be precisely placed in order to
keep the loading balanced between the gears.
 Attaches easily to drums or chain/belt systems.
 Can be used as a configurable system based on with gears are “locked” or free to
rotate/move.
 The use of multiple gears, makes the system stiff allowing precision movements
to be done, but are less power efficient compared to a normal gear train.
 Planet gears are held equidistant by an arm, producing this arm, would be
wasteful of material, if it needs to rotate

6. Worm Gear
 High Torque density
 Difficult to machine
 Inefficient

7. Gear Train – Final Idea
 Must find a way to make the required total gear ratio of at least 40 in as compact
a manner as possible without failure
 This can be achieved in some sort of progressive reducer