Aluminum Crane for Stress Analysis Course
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Goal: Develop a crane from Aluminum 6061 sheet metal to carry a load of 2lb consistently along a smooth cylindrical post using a standard servomotor.
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Theoretical Servo Torque Calculation:
We calculated the torque of the servo by attaching a rigid lever arm onto the servo, measuring the lever arm distance, and the force applied by the servo on the edge of the lever arm. Then multiplying F*d, we found our servo’s max torque to be 3.99 in-lbs. This is approximately 1.12 times the assumed maximum torque. We originally planned to have a lever arm around 1 in long, which would use up only 50% of the servo’s max torque, but later found out that the arm of our crane was too short to allow for that. We then used a longer lever arm, two inches long, in the hope that it would be more reliable in lifting the weight.
Theoretical Lift Distance Calculation:
Considering that our theoretical torque calculation was around 3.99 lb-in and the length of our lever arm was approximately 2 inches, the distance over which the weight should have theoretically moved, given the angular rotation of the
Results: Crane was one of the lightest at just over 12 ounces. The lifting distance was consistently between 3-4 inches which surpassed the 2-inch minimum.
End connection for crane used moment arm with weighted advantage at back (counterweight). The clipping mechanism was made to be moldable so we could adjust the arms weighted positioning with relation to the base in order to reduce twisting along the long edge of the crane. The truss along the length helped reduce deflection at the tip of the arm with allowed us to get maximum lift. The primary problems came from misalignments since the I beam design was used with the intention of having forces in line,