Stress Analysis Design Project 2014
Yudi Chen, Vikram Iyer, Jason Lee
We made a standard square tower centered on the 6x6 aluminum base plate. Horizontal members were added to space the vertical beams correctly. Cross members were added for stability.
We added triangular supports for the arm to reach out enough to allow the arm to go through the larger hold in the barrier. Triangular supports because through analysis, this was the strongest design.
The arm consists of two T-beams that were connected at the servo end by another T-beam. T-beams are strong in bending but weak in torsion. Tubes are strong in torsion but are difficult to make with the materials available. To accommodate this weakness, we put two T-beams in parallel and connected them at the two ends. This increases the J (area moment of inertia for torsion) to reduce the amount of torsion.
Attached on the servo is a 6 in of delrin as a lever arm. At the end is a loop made of aluminum that can rotate perpendicular to the rotational axis of the servo arm. On the other end of the lever arm is a counter weight to help lift reduce the amount of torque the servo has to provide.
How everything works together:
The supports are spaced out enough to provide the arm a large enough moment to counter act the moment created by the weight and the servo. The arm itself will resist twisting during the lift. While the tower holds everything up.
Fraction of servo’s
maximum torque needed to theoretically lift:
About 50% of the motor’s torque is theoretically required to lift the weight.
Theoretical lift height:
Assume linear relation between torque and angle
Arm: This simple design was strong and was very easy to make, it was just two aluminum strips bent into an L shape and held together with screws.
Overall, we are most proud of the fact that our final design handled bending and twisting very well, with a very small amount of deflection.