Gears: Gear Ratio and Input
SOLID MECHANICS
TUTORIAL – GEAR SYSTEMS
This work covers elements of the syllabus for the Edexcel module
21722P HNC/D Mechanical Principles OUTCOME 3.
On completion of this short tutorial you should be able to do the following. •
Describe the different types of gear systems.
•
Describe a simple gear train.
•
Describe a compound gear rain.
•
Describe three types of epicyclic gear boxes
•
Solve gear box ratios.
•
Calculate the input and outputs speeds and torques of gear boxes. •
Calculate the holding torque on gear box cases
It is assumed that the student is already familiar with the following concepts. • Angular motion.
• Power transmission by a shaft.
All these above may be found in the pre-requisite tutorials.
© D.J.Dunn
1
1.
INTRODUCTION
A gear box is a device for converting the speed of a shaft from one speed to another.
In the process the torque T is also changed. This can be done with pulley and chain drives but gears have advantages over these system. A good example is that of winch in which a motor with a high speed and low torque is geared down to turn the drum at a low speed with a large torque. Similarly, a marine engine may use a reduction gear box to reduce the speed of the engine to that of the propeller. Other examples are motor vehicles, lathes, drills and many more. The diagram shows a typical winch that has a reduction gear box built inside the drum.
Figure 1
This tutorial is not about the design of gears but it should be mentioned that there are many types of gears, each with their own advantages. Here are some examples.
Figure 2
Gears are wheels which mesh with each other through interlocking teeth. Rotation of one wheel produces rotation of the other with no slip between them. The shape of the gear teeth is important in order to produce a smooth transfer of the motion. The most common shape is the INVOLUTE gear form but it is not our task to study this here.
TUTORIAL – GEAR SYSTEMS
This work covers elements of the syllabus for the Edexcel module
21722P HNC/D Mechanical Principles OUTCOME 3.
On completion of this short tutorial you should be able to do the following. •
Describe the different types of gear systems.
•
Describe a simple gear train.
•
Describe a compound gear rain.
•
Describe three types of epicyclic gear boxes
•
Solve gear box ratios.
•
Calculate the input and outputs speeds and torques of gear boxes. •
Calculate the holding torque on gear box cases
It is assumed that the student is already familiar with the following concepts. • Angular motion.
• Power transmission by a shaft.
All these above may be found in the pre-requisite tutorials.
© D.J.Dunn
1
1.
INTRODUCTION
A gear box is a device for converting the speed of a shaft from one speed to another.
In the process the torque T is also changed. This can be done with pulley and chain drives but gears have advantages over these system. A good example is that of winch in which a motor with a high speed and low torque is geared down to turn the drum at a low speed with a large torque. Similarly, a marine engine may use a reduction gear box to reduce the speed of the engine to that of the propeller. Other examples are motor vehicles, lathes, drills and many more. The diagram shows a typical winch that has a reduction gear box built inside the drum.
Figure 1
This tutorial is not about the design of gears but it should be mentioned that there are many types of gears, each with their own advantages. Here are some examples.
Figure 2
Gears are wheels which mesh with each other through interlocking teeth. Rotation of one wheel produces rotation of the other with no slip between them. The shape of the gear teeth is important in order to produce a smooth transfer of the motion. The most common shape is the INVOLUTE gear form but it is not our task to study this here.