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Basic Types of Gear Transmissions and Gear Ratio Calculation

I. Introduction • A. What is a Gear Transmissions The basic definition of gear transmission is a mechanical system that transfers mechanical energy from one rotating shaft to another through the meshing of gear teeth. The gear transmission system facilitates the transfer of power and motion by ensuring that the teeth of the gears come into contact, enabling the conversion of rotational speed, direction, and torque. • B. Purpose of this Article The purpose of this article is to explore the basic types of gear transmission systems and the methods for calculating gear ratios. By examining various gears such…

I. Introduction

A. What is a Gear Transmissions

The basic definition of gear transmission is a mechanical system that transfers mechanical energy from one rotating shaft to another through the meshing of gear teeth. The gear transmission system facilitates the transfer of power and motion by ensuring that the teeth of the gears come into contact, enabling the conversion of rotational speed, direction, and torque.

B. Purpose of this Article

The purpose of this article is to explore the basic types of gear transmission systems and the methods for calculating gear ratios. By examining various gears such as spur, helical, planetary, and worm gears, we will understand how these gears facilitate efficient mechanical energy transfer in different configurations. Additionally, understanding the calculation of gear ratios is crucial, as it helps engineers optimize the design and matching of gearboxes for specific applications.

II. Basic Types of Gear Transmissions in Small Gearbox


The gear structure inside a small gearbox includes spur gears, planetary gears, worm gears, and helical gears. Each type offers unique advantages for different applications due to their specific structural features. Analyzing these gear types helps us understand their essential roles in small gearbox design, enhancing the overall efficiency and stability of mechanical systems.

Gear TypeAdvantagesDisadvantages
Spur GearSimple design, easy to manufactureNoisy at high speeds, limited load capacity
Planetary GearHigh torque density, compact designComplex design, high cost
Worm GearHigh reduction ratios, self-locking capabilityLow efficiency, high friction,
Helical GearHigh efficiency, smooth and quiet operationMore complex design and manufacturing, higher cost
Baisc Gear Transmission Types

A. Spur Gears

• Definition:The tooth profile of the spur gear is parallel to the gear axis. When two spur gears are meshed, the transmission of power and motion is achieved through the contact of the tooth surfaces. Spur gear transmission is usually used for transmission between parallel axes. It is widely used in various micro gearboxes due to its simple design, convenient manufacturing, high efficiency and low cost.

• working principle of spur gears

M1 = Driving Gear (input gear)

M2 = Driven Gear (output gear)

W1 = Driving Gear Speed

T1 = Driving Gear Torque

W2 = Driven Gear Speed

T2 = Driven Gear Torque

r1 = Driving Gear Radius

r2 = Driven Gear Radius

The angular velocity of the driving gear (W1) and its torque (T1) are transmitted to the driven gear (W2, T2) through the gear ratio. Depending on the number of teeth on the gears, the output torque and speed can be altered. Typically, a gear with more teeth will reduce speed and increase output torque, while a gear with fewer teeth will increase speed and reduce torque.

Mathematically, this relationship can be expressed as:

W1 · T1 = W2 · T2

• How to calculate the spur gear ratio




Gear Ratio Calculation

1. Calculating the Gear Ratio for Each Pair of Gears

The gear ratio between two gears is calculated using the formula:

Gear Ratio = (Number of teeth on the driven gear) / (Number of teeth on the driving gear)

<p><strong>For the first pair of gears (where the first gear drives the second gear):</strong></p> <p><strong>Gear Ratio<sub>1</sub></strong> = 40 / 20 = 2</p> <p><strong>For the second pair of gears (where the second gear drives the third gear):</strong></p> <p><strong>Gear Ratio<sub>2</sub></strong> = 80 / 40 = 2</p> <p><strong>2. Calculating the Total Gear Ratio</strong></p> <p>The total gear ratio of the system is the product of the individual gear ratios:</p> <p><strong>Total Gear Ratio</strong> = Gear Ratio<sub>1</sub> × Gear Ratio<sub>2</sub></p> <p>Substituting the values:</p> <p><strong>Total Gear Ratio</strong> = 2 × 2 = 4</p> <p><strong>Conclusion:</strong></p> <p>In this three-gear system, the total gear reduction ratio is 4. This means that the input speed will be reduced to one-quarter of its original value after passing through the gear system.</p>

B. Planetary Gears

• Definition:The planetary gear system consists of a sun gear at the center, one or more planetary gears that rotate around it, and a fixed ring gear (external gear) that the planetary gears simultaneously mesh with.

• working principle of planetary gears

C. Worm Gears

• Types: Straight bevel, spiral bevel, and hypoid gears

• Applications and unique features

D. Helical Gears

• Structure and functioning

• Pros and cons, and typical uses

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