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Engineering

Crane

The purpose of this project was to build the lightest crane that could lift a one-pound weight the highest without deflecting and touching the bounds.

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Duration: 15 hours
Team Members: 3
Skills Applied: Mechanical Systems Analysis
Tools Used: Drill, Drill Press, Metal Shears

The purpose of this project was to build the lightest crane with a motor and lever arm at the end that could lift a one-pound weight the highest without deflecting and touching the bounds. This project was done in a team of three.

Theoretical Servo Torque calculation:

  1. Object Weight: 1 lb = 16oz
  2. Max Torque: 57oz – lb
  3. Theoretical Maximum Arm Length: 57/16 = 3.56 inches
  4. Real Arm Length = 2 inches
  5. Theoretical weight lift:  2 inches
  6. Theoretical torque output necessary:  32 oz-in

Theoretical Lift distance

  1. Assuming there is neglectable deflection on the structure:
    1. According to the geometry:
      1. The distance from the pivot point is 2 inches
      2. Assuming the turning angle of the servo is 90 degrees
    2. The distance of lifting would about:

sin(45) * 2 * 2 = 2.83 inches

  • Assuming we were able to use the full 57 oz-lb.

Theoretical Loading Calculations:

  1. Length of the triangular arm = 26 inches
  2. Size of the base = 6” x 6”
  3. Normal distance between lifting hook and clamp = 12 inches
  4. Calculation of torque that the triangular truss produce on the base:

            26” x 1lb = 26 inch-lb

  1. The max force that the clamp should supply on the far end clamp is:

            26 inch-lb / 6 inches = 4.333 lb

Discussion:

  1. Discrepancies that occurred:
    1. The material that links the base to the triangular truss buckled significantly during testing.
    2. The mounting setup for the motor actually prevented the weight from being raised further.
    3. There was not much space to attach the motor, so it is in a very small area.  Therefore, we did not have a long enough lever arm for the counterweight to be effective.
  2. Consequences of discrepancies:
    1. The linkage buckled significantly and the end attachment to the motor deflected about 1 inch.  In turn, the servo did not lift the weight as high as it should have.
    2. Due to the mounting setup, the servo is not able to continue turning after lifting 1 inch.

The arm for the counter weight was too short, rendering the counterweight more ineffective.  Therefore, to have more of an effect, we added a larger counterweight and ended up adding a lot more weight onto the system. Overall, this design could have been much more successful.