The arm is a T-beam, formed by joining 2 L-beams using bolts.  The T-beam allows for high second moment of inertia, which would reduce bending.  While a T-beam is weak to torsion, our design intends to minimize twisting moment by having the load as close to the center axis of rotation as possible.

Even though the T-shaped arm is weak to torsion, we still chose it since it's easier to attach extra support to the flat bottom and attach our motor right in the center so that the total force acting down close to the center of cross section

The motor turns a lever arm that is attached to the 1lb weight via a freely-spinning hook.  The other side of the lever arm houses a counterweight to reduce the torque that the motor needed to generate (by our calculations, only 73.7% of its total torque). The counterweight has multiple holes drilled into it for distance adjustment during the testing period.  We ultimately settled with the shortest length in order to not hit the ground when the motor turns to near 90 degrees.

The base is a rectangular prism with an overhang.  The rectangular prism is made using L-beams to prevent buckling.  There is a baseplate for the prism, attached to the rest of the L-beams using L-shaped brackets.  The diagonals of the rectangular prism are supported to prevent distortions. 

The overhang on side is needed to attach the arm by 2 sets of bolts.  This allows the overhang to act as 2 pin supports for the arm.

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After initial testing, we realized that the base itself is not enough to prevent the bending of the arm.  Therefore, we added 2 supports that extends from the bottom of the base, directly into the arm.  These are 2-force members that should cancel out each other in the horizontal forces, but provide vertical force components as additional pin supports for the arm.  In addition, the longest support was raised higher than the arm on purpose so that the arm, when not loaded, would be on a positive incline.  When the crane is under loading, the arm would still deflect downwards, but would remain, for all intents and purposes, horizontal.