A good linear setup can be easily made with a Radio Shack 3 volt DC motor, a square 1/8 inch styrene tube, and about 5 inches of 256-threaded rod. Cut an inch of the styrene tube and pressing it onto your motor, making sure the shaft still rotates. Now you simply start screwing the threaded rod into the other end of the styrene tube. Isn’t it cool how the threaded rod taps the styrene for you? For a real good hold, use modeling or crazy glue to hold it in place.
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