This is a delightfully simple instructable designed to teach any random individual on how to make a marble launcher from two cardboard paper towel roll centers. This device also doubles as a satisfactory telescope and megaphone.
Step 1: Hook, Line, and Hotglue
The first step is to affix four hookscrews into the lower end of the tube. We reinforced these by hot gluing the ends to the tube after screwing them in. Generally speaking, make sure that they are spaced out every 90 degrees.
Step 2: Stretching the Issue
Next, we affixed the rubber bands (responsible for the the most fun part of the device--launching) to the hook screws. We found that one band per screw was not enough, so we tied two of them together.
Step 3: Duct Tape Can Do Anything
We then made a simple pouch for the marble to sit in, made of a folded piece of duct tape. No matter where man goes, or what he does, he should always bring duct tape.
Step 4: Mounting the Cannon
The most important part of the cannon is how you mount it. Methods may vary but if you happen to have an L bracket and garage door spring laying around... mount it how you see in the picture. The base is composed of the second tube glued to a circular balsa wood base. Modify and customize as you see fit.
Step 5: THE END.
So there you have it, the most versatile marble launcher known to man is now yours. It doubles as a didgeridoo, quick scope, paperweight, and much, much more. You're welcome.