Fall 2016 Velociraptor (W): Center of Mass

/in , /by

By Aaron Choi (Manufacturing Engineer)

Approved by

-Lam Nguyen (Project Manager)

-Tim Haddadian (Division Manager for Manufacturing)

Table of Contents

Requirements

Level 2-10 The center of gravity on the axis of the head and tail shall be controlled by one servo while being placed over the foot

Introduction

The center of mass is crucial for the design of the Velociraptor. To fulfill the Level 2-10 requirement, the center of mass should be placed over the foot. To observe the center of mass, the SolidWorks model of the design is required.

Library of Density

To observe an accurate center of mass, the mass of each observed through SolidWorks. There is no direct way to edit an object’s center of mass. However, a material can change its mass through density. Figure [1] below shows the example of a custom density for a material. The mass was either given from datasheets or weighed through a weight scale. The GM9 [1] and SG90 [2] mass were given through their respective datasheet. The volume of each Solidworks file were observed through the Measure tool in Solidworks. Then the density was calculated with mass divided by volume. Then the units were converted to match kg/m^3. Certain materials contained their density, such as Birchwood [3].

figure-1

Figure [1]

Density of the 7.4 Li-Po battery.

table-1

 

Table[1]

The table shows the density used for each custom material in Solidworks.

Center of Mass of Velociraptor

From the custom library of densities, the accurate center of mass was found. Then moving the head and tail through Solidworks, the head and tail were shifted at an angle. The angle found was 35 degrees.

figure-2
Figure [2]

The black and white dote represents the center of mass.

Conclusion

In conclusion, the center of mass was observed over the foot at 35 degrees. This was calculated by subtracting 65 degrees, found through Solidworks, to 90 degrees. This meets the Level 2-10 requirement.

 

Reference

[1]  https://solarbotics.com/product/gm9/

 

[2]  http://www.micropik.com/PDF/SG90Servo.pdf

 

[3] http://www.engineeringtoolbox.com/wood-density-d_40.html