Stress Analysis Crane Project

Group 7: Job Bedford, Steven Cunningham, Faith Quist

Mass: 6.66 oz

Lift Height: 2.0”


Our crane comprises a triangular base, two primary support arms, and a combination IT beam mounted at an angle to the arms. The servo mounts to the end of this beam. It has a short arm which terminates in a freely pivoting strip of aluminum that hooks onto the weight’s bolt.

Special Features

·         The freely pivoting arm that hooks around the bolt on the weight is essential.  It allows us to mount the servo directly to the beam rather than hanging it lower down, which would require more bolts, making the crane heavier. It also guarantees that the servo’s moment arm remains constant because we do not rely upon the weight sliding along a lifting arm as it moves through 90 degrees.

·         The IT beam is so called because it has two bottom flanges and one small top flange. The idea came about because the strips of metal we had were not of equal thickness. Instead of wasting the extra material and cutting it off, we decided to bend the top flange in order to help resist twisting and bending from left to right.


Servo Analysis

Theoretical Motor Torque: 72 oz-in = 4.5 lb-in.

Length of Arm: 2.12”

Moment Arm: 1.5”

Weight of Load: 1lb

Fraction of Max Torque: