Mechanical Engineering Design Project

MECH 390

Gears

Tutorial - 4

Group Name:No. Student ID Name Signature12345

Criteria Performance

Attitude Attendance Knowledge Creativity Total

Grade (%)

❑40

❑40

❑40

❑40

❑40

❑200

The main contribution of this tutorial is to help students become familiar with different types of gears

and understanding broad concept of gear design. In the last decades, gears have evolved from wood,

cast irons and steels to a diversity of alternative materials. Manufacturers have been using gears for

power transmission since long time ago. Further, they can be applied between two shafts which are

parallel, collinear, perpendicular and intersecting, perpendicular and nonintersecting, inclined at any

arbitrary angle and etc.

It is crucial to understand the difference between vehicle and marine transmissions. Thus, the function

of the vehicle transmissions is to change the ratio of engine rpm to wheel rpm several times so that your

car can accelerate from a dead stop to a desirable cruising speed in a relatively short time and run at

that speed with a high degree of efficiency. On the other hand, marin transmissions serve three entirely

different purposes: engaging the engine from the propeller, allowing for reverse (counter clockwise)

rotation of the boat, and setting the ratio of engine and propeller RPM.

The most common examples of the gears are Spur, Helical and Bevel. Hence, it is crucial to know the

advantages and disadvantages of the mentioned gears for the amphibious cars.

In this project, you have to carry out some detailed investigations regarding the following objects that

are described vividly:

1- A brief history of gears

2- Understanding fundamental and different principles of gearing for both vehicle and marine

transmissions

3- Recognizing gear trains and how to calculate ratios

4- Identifying different gearing system, relative advantage and disadvantages among them

5- Discovering gear parameters (geometry parameters) such as number of teeth, form of teeth,

size of teeth and etc.

6- Distinguishing various ways that gears can be used in motion system and how they are

assembled for both environments

Also, you need to determine the following parameters:

1) Velocity Ratio (rpm)

2) Output Speed (rpm)

3) Output Torque (Nm)

4) Direction of the gears (clockwise / counter-clockwise)

5) Design and analysis for a gear box (the double -reduction helical gear set) shown in figure-1 has

to be determined. The gear box is required to transmit 20 hp with input shaft speed at 1800

rpm. The gear box output shaft speed is required to be at 205 rpm - 210 rpm. The first pair of

gears, gears 1 and 2, have a normal diametral pitch of 6 T/in, 25 o helix angle and a normal

pressure angle of 20o. The second pair of gears, gears 3 and 4, have a normal diametral pitch of

10 T/in, 30o helix angle and a normal pressure angle of 20o. The center distance between gears 1

and 2 is required to be 4.78 inch and between gears 3 and 4 to be 3.92 inch. The smallest and

the largest number of teeth for the gear box have to be between 15T and 55T, respectively.

Determine gears geometry and calculate all force components for pinions, 1 and 3.

Perform only bending stress analysis for pinions, 1 and 3. Explain all assumptions and

constraints in your analysis. Specify any table(s) and figure(s) you use in the analysis.

To gain practical engineering experiences, according to standard regulations, you can have your own

assumptions for number of teeth, size of teeth, degree of precision required and etc.

Note that you are supposed to use your support documents, class materials, previous tutorial

information and the mentioned above hints to complete this tutorial.

Figure 1: The Schematic of a Gear box