Instructables

Step 5: Boom Construction

Two identical pieces are needed for the crane. Once you have cut out one of the boom sides you will use it with a router template cutting bit to cut the matching side.

Use the dimensions below to lay out the outline of the boom.  See pictures #1, #2 and #3 below.  Make sure you draw everything through picture #3 before you cut out the boom piece.

Drill holes where shown.  See picture #2 and #3 below.  Use a backing block when drilling to prevent blow-out on the back side of the piece when drilling through.  Both sides of the plywood on many of the pieces will be visible when the project is complete.

Use this completed piece to trace the other boom side piece.

Cut to within an 1/8 inch of the traced outline using a bandsaw if possible.

Clamp the two pieces together and use a pattern routing bit to trim the second side piece to an exact match of the other.

A flush cut router bit (guide bearing on the bottom) can be used.  See picture #4 below. Just put the template piece on the bottom and make sure the router height is adjusted properly so the guide bearing rides along the edge of the piece you are copying.

Copper pipe pieces are used between the two sides of the boom to separate both sides.

Measure the thickness of 3 pieces of the 3/4-inch stock material you are using to determine the length of the copper pipe needed for the spacers.

Cut 8 pieces of copper this length using a standard pipe cutter available at any hardware store. Make sure you remove the sharp edges on the cut pipe with a file or sandpaper.

Use a very fine sand paper, 300 grit or higher, to sand the pieces of copper pipe. Do not worry about sanding or polishing all of the copper pieces perfectly smooth. Just try to sand them to a uniform finish.  Sanding lengthwise is recommended.

Continue using finer grit sandpaper to achieve the finish on the copper pipe that you like.

Stand the pieces on end on a board with screw protruding to spray the pieces with spray lacquer.  See picture #5 below.

Coat the copper pieces with several coats of spray lacquer for a lasting shine.

The copper pipe is installed with nylon spacers inside the pipe to limit the movement in any direction.  Without the nylon spacers the movement of the copper spacers will scratch the inside faces of the boom.  The carriage bolts through the copper pipe are installed with a nylon locking nut on the end.  See picture #6 below.
 
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