Planetary Gear

AIM – Motion Study of Epicyclic/Planetary Gear Set using Solidworks Motion

Objectives – Our objective here is to do Motion Study of Planetary Gear Set while doing the following,

• Calculate the required values for the Planet gear.
• Creating 3D models of Sun, Planets, and Ring Gears and a Carrier for Planets.
• Performing motion analysis by rotating the Input parameter at 200rpm.
• Obtain the plot of Angular Velocity of the Output parameter.

1 Modelling –

As per given data in Challenges, we have created solid MODLES of all the Gears, in Solidworks 2019 with the help of Toolbox.

• Calculations –

As per the values give –

Table – 1.1

We need to calculate the values for X_1, X_2, X_3, X_4.

Now, as we know that m =    (which is nothing but Thickness of Tooth)

So, we have X₁ = 35mm X₃ = 115mm now, for Planet gear we need pcd which we will get from Sun and Ring gear, i.e. = 115-35 = 80mm now as we need only one gear, the distance should be halved i.e. = 40mm so X₂ = 40mm and similarly X₄ = 16

Table 1.2

• Gears and Planetary Carrier –

We have just need to use Toolbox and select ANSI Metric standard, and just create 3 Gears of above configuration.

For Carrier we have to design it Sketch and 3D model of which, is shown –

Fig – 1.1

2 Assembly –

In order to perform Motion Study, we have created Assembly consisting of 4 Planet Gears one Sun gear, one Ring Gear and a Planetary Carrier.

2.1 Part Description –

• 1 Carrier (Red)
• 4 Planet Gears (Yellow)
• 1 Ring Gear (Blue)
• 1 Sun Gear (Green)

2.2 Assembling the Parts Together –

Basically, we need two parts in such a way that all parts can rotate and the planet gears can Slide along a plane.

In order to do that we have to fix the DOF (Degrees of Freedom) which are not needed, there are in total 6 Types of Degrees of Freedom –

• 3 Translation Motion (Along X, Y and Z Axis)
• 3 Rotary Motion (Along X, Y and Z Axis)

Now as we require only one DOF i.e. Rotation along Y Axis (Considering that the Sketch is Done on Top Plane) so we need every other DOF to be Fixed. So, for that we have used Mates (Co-Incident and parallel)

So, in order to do that, following steps are followed –

Fig – 2.1

1. We need to fix the sliding motion along X and Y and Z axis, we will do so by selecting the axis and use Coincide mate with FRONT and TOP plane (This Fixes 2 Sliding Motion and 1 Rotating Motion)
2. Rest, we need to fix the one more Sliding and Rotating motion i.e. along Right plane, consider the figure shown,

Fig – 2.2

3. As shown above, this fixes 1 Sliding and 1 Rotary motion, now we have only one Rotary motion which is Free i.e. along Y-Axis.

4. Doing the same with Planet Gears but instead of the fixing those at the origin we need to assemble it with the carrier consider the figure below.

Fig – 2.3

As it can be seen, we need to give Coincide mate between Planet and the Carrier Shaft so that it Stays Concentric with the carrier as well as it will not slide back and forth along the shaft. This was possible by selecting the EDGES of both the parts.

5. Doing the same thing with Sun and Ring gear but this time we need to place these gears at offset from the Right plane, consider the image shown.

Fig – 2.4

This way our parts are assembled, which satisfies the motion of gearing.

3 Motion Study – 

Now in order to perform the Motion Study, we need Solidworks Motion “ENABLED”.

We need to perform motion study for the Angular Velocity of the Output Gear. For that we are having the table

Table – 3.1

Now on the basis of the table we have to fix the part and do the motion study, one of which is shown below,

Case – 1

I/p = 200 RPM

I/p Part = Sun Gear

Fixed Part = Ring Gear

Follow the steps explained from next page.

Fig – 3.1

Step 1 – We need to select Motion Study and Motion Analysis as shown in Fig – 3.1 and then tap on the icon which is shown in the figure.

Fig – 3.2

Step 2 – We need to apply a Motor to the Input (i/p) gear entering a value of 200 RPM to the  SUN GEAR (Green) as shown in Fig – 3.2.

Step 3 – In order to run the Motion Study successfully, we need to apply contacts, tap on the icon as shown below

Fig – 3.3

Step 4 – We need to select all the bodies which comes in contact with each other through which the power is being transmitted. Observe Fig – 3.4 we can either select individual part or just click and drag out the mouse icon selecting whole part, this will allow us to give all the contacts in a single run.

Fig – 3.4

Step 5 – After giving contacts we need to set Frames per Second, this basically means how many frames will Solidworks will captured as a DATA or VALUE per second, e.g. if we have selected 10 RPM so that means Motor will rotate 360° for 10 times so that makes 3600° so in order to catch every degree we will need 60 frames per second (1 rpm = 0.0166 fps),so now if we have 200 RPM the fps requirements will go very high which will result in the heavy calculation, load on CPU and will require significantly more time to calculate. So here we have selected 200 fps, which will make the Motion Study smoother and more fluent when in working condition.

Fig – 3.5

Step – 6 Now we will plot the graphs for the output by selecting the Results > Velocity>Angular Velocity, and then select the output part. Follow as shown in Fig – 3.6.

Fig – 3.6

4 Conclusion –

For given tasks we have performed the following –

• Angular Velocity of Output gear.

4.1 Results for Case 1 –

Fig – 4.1

Above figure shows the angular velocity of O/P (Carrier) on the basis of graph we can see that initially the graph is at 0 which defines it is at rest and as the simulation goes on it tries to reach at speed max speed, the wavy feature shows the variation of the Rotation which, as time passes is consistent, as time passes by, variation of rotation is near about 0 to 2 deg/sec. as it can be seen from graph it is around 279 to 281 deg/sec.

Now our input parameter is 200 RPM so the output is increased till 280, so this is because of Gear Ration between Sun and Planet Gears.

4.2 Results for Case 2 –

Fig – 4.2

Above figure shows the angular velocity of O/P (Carrier) on the basis of graph we can see that initially the graph is at 0 which defines it is at rest, the wavy feature shows the variation of the Rotation which, as time passes is consistent, as time passes by, variation of rotation is near about 0 to 2 deg/sec. as it can be seen from graph it is around 921 to 923 deg/sec.

Now our input parameter is 200 RPM so the output is increased till 922 deg/sec, so this is because of Gear Ration between Ring and Planet Gears.

4.3 Case 3 –

Fig – 4.3

Above figure shows the angular velocity of O/P (Ring) on the basis of graph we can see that initially the graph is at 0 which defines it is at rest, the wavy feature shows the variation of the Rotation which is not getting consistent as time passes by which is because of the Backlash between Planet and Ring Gears now this Backlash doesn’t affect that much in other cases because in those cases Carrier was fixed whereas in this it is fixed.

Now our input parameter is 200 RPM so the output is increased till 392 deg/sec, so this is because of Gear Ration between Ring and Planet Gears.

Link to view this model is given Below

 https://drive.google.com/drive/folders/1kb_S8wowZbQRZzBeWG-YOTjyfXZZqC6W?usp=sharing