The arm is made from 1/8" thick Aluminum sheet and a bearing hub is fitted to each end of the arm. The arm end mounts are machined from 1" thick Aluminum plate and 1/4" diameter stainless steel rods are fitted as pivots for the arm bearings. The rods are held in place by 4-40 set screws in the arm end mounts. Spacers made from brass tubing keep the arm centered in the end mount. A 6-32 swivel link was attached to the lower bearing hub- this is what the geared servo pulls on in order to raise the arm. A notch was milled in the lower arm end mount to allow clearance for the pull rod and swivel link.

There is a threaded rod on one side of the arm that is attached to each end mount with swivel links- this forms a parallel linkage that keeps the upper arm end mount level as the arm raises. The cannon has an Aluminum plate fitted to the inside bottom and the upper arm end mount is attached to the bottom of the cannon with two 6-32 bolts.