Gear Transmission System Design of Huanrong Zhang

ES3C2 Gear Transmission System Design Introduction Gear transmission has a wide range of uses in mechanical engineering. Vehicle gearboxes are an important application of today's gearing. The gear set can change the direction and magnitude of the force, thereby simplifying and solving problems encountered in engineering. I used MASTA software to design and analyze the gear set.

Further research and discussion will be conducted in this report.

Design Specifications My student ID is 1692726. By the calculation method given, the data in the table below can be obtained.

Input torque = 169 Nm / 2 =84.5 Nm Input speed = 2726 rpm

Input torque (Nm)

Input speed (rpm)

Duration (hours)

84.5

2726

100

Table 1 Design Data by Student ID

Ideation A two stages gearbox with three shafts form a triangle in the x-y plane view.

The shaft

1 and shaft 2 are in a straight line in the x-y plane view. The angle between stage one and stage two is -75 degree. All shafts are 1.5 mm module. width. Stage two has 70 mm face width.

2.64:1(103/39) for stage two.

Stage one has 30 mm face

2.64:1(87/33) for stage one and

Figure 1 Main view and Side view (x-y)

Figure 2 Oblique view

Design Improvement and Evaluation First, I used the data from the examples for testing. I found that the results obtained were far from ideal. I got data shown below.

Figure 3 First result

When the total gear ratio is 7, the closer the gear ratios of the two stages are, the smaller

the volume and mass occupied. So I use 2.64 as the gear ratio for each stage. （2.64 is approximately equal to the square root of 7.） Then I used 30 and 79 as pinion number of teeth and wheel number of teeth, respectively.

I set the two stages to have the same gear ratio, number of teeth, module and face width.(2.64, 79/30, 2, 20) The sizes of bending safety factor and contant safety factor have become much closer.

Figure 4 Second result

I left the stage one’s number of teeth unchanged and changed the value of stage two’s number of teeth to 87/33. I found that bending safety factor became smaller and contact safety factor hardly changed. Then I left both stage one and two’s number of teeth unchanged and changed the value of module. I found that the results did not change.

Then I left the other data unchanged and only changed the face width of stage two. I found that both factors of stage two became larger.

I first determined that when stage one’s number of teeth and stage two’s number of teeth were 87/33 and 103/39, respectively, bending safety factor and contact safety factor were closer.

Figure 5 Third result

Then I increased the factor of the design by expanding face width. The figure below is the result I finally got.

Figure 6 Finally result

Placing three shafts on the same plane takes up a lot of space. So I set an angle to properly place the three shafts to reduce the space occupied.

Figure 7 Distribution of horizontally arranged axes

After that I started to consider whether I could design three stages. Although the three stages can make the gear ratio of each stage smaller, it also means that the radius ratio becomes smaller, which makes the gear volume smaller. However, in order to ensure the safety factor, it is necessary to ensure a sufficiently large face width, which means that a longer shaft is required. When there is one more stage, the results caused by factors will be more difficult to calculate, which requires a lot of time to verify. In the future, specific calculations and analysis of more than two stages will be performed.

Discussion The ratio of shaft 1 over shaft 3 = 2726 / 391.5 = 6.963 By calculation we can get a speed ratio of 6.963, which is very close to 7. This proves

that the design meets the design requirements.

Figure 8 Shaft speeds

By the formula given,(cantilever bending theory for bending stress and Hertzian approach) we can find that Stress is equal to 1366.6901 Mpa. The average of the experimental results is 1370.4645 Mpa. The two results are close, but the result of the formula calculation is relatively small, which may be due to insufficient accuracy in the calculation process.

Figure 9 Bending Analysis

Figure 10 stresses of gear set 1

Figure 11 stresses of gear set 2

Figure 12 Power flow of shaft 1

Figure 13 Power flow of shaft 2

Figure 14 Power flow of shaft 3

Figure 15 Power flow of load 2