The ball is from an old computer mouse, with the rubber coating removed (you could use a marble as well). A crafty person should never throw perfectly good stuff in the trash. Just hang onto it, and eventually you'll find a new use for it down the road!
With some parental help, this can be a kid-friendly project. Building a solid table with a functioning paddle assembly requires some basic woodworking skills, and may be fairly difficult without proper guidance and appropriate tools. But once the paddle assemblies are in place, just about anyone can build ramps and jumps or anything else they can imagine for the upper part of the table. To me that's where the real fun lies--creating various obstacles and then seeing a ball bounce around all over and through them, somewhat under your power.
This is a great project for parents and kids to take on together!
Please check out the video at the end of the instructable to see it in action.
Step 1: Table top
This should be a helpful guide though, to show you how it can be done.
The table top is a piece of melamine which used to be part of a large router table top. It had numerous screw holes in it that I filled with putty. The dimensions are 36" by 20", not including the sides. The sides are 3/4" plywood that was ripped into 2 1/2-inch wide pieces.
The sides are attached to the piece of melamine with screws. To get a precise fit, it is very useful to use clamps to position the sides to the melamine, and then drill pilot holes into which you drive your screws.
A piece of two by four was screwed to the back to give the table its tilt.
Step 2: Paddles
With the paddles still clamped together, I carefully drilled a 5/16" hole through the pivot corner of the paddles.
I used scrap wood to create two small blocks with a hole drilled about halfway through to fit a 5/16" dowel. These blocks were attached to the paddles with a hinge made from denim. The hinges were attached with hot glue. See the photo below for details.
I then drilled a hole and added a screw eye right in the middle of the backside of each paddle.
Once I had the paddles in place, I realized that the ball would slip when struck, so I cut a large rubber band in half and used spray adhesive to attach the pieces to the paddle faces to give them some grip. For ease, this should be done at this point rather than once the paddles are attached to the table as shown in the photo.
Step 3: Paddle mechanism and mounting to table
The bolts are loose enough that the paddles pivot easily, but tight enough that they don't rock or wobble. There are washers under the paddles to give clearance from the table.
To get accurate, precise holes in the table, I measured the distance I wanted and used a nail punch to create a starting hole for the drill bit.
Please examine the photos to see how everything fits together. I used hot glue to connect all the wooden pieces and dowels and knobs. Rubber bands are attached to the screw eyes in the backs of the paddles and to a dowel attached to the table. This creates resistance, and springs the paddles back into place after you strike the knobs outside the table.
The forward motion of the paddles is stopped by the knobs against the outside of the table, so I had to adjust the length of the dowels accordingly prior to gluing the knobs on. The knobs were drilled out partway to fit the dowels. Thick craft foam provides a cusion for the knobs.
Other parts of the table were added with hot glue. Dowels in the table were glued into drilled-out holes.
Step 4: Ball launcher
The brown stuff is thick craft foam which cusions the knob from impacting the table too hard.
I had to create a ball launcher track over the top of the right hand paddle stick. This was made from a thin piece of wood and some single-ply cardboard, and a few little blocks of wood underneath to support it.
Please examine the photos to see how this works. You will need about an 8-inch piece of dowel, depending on how big your spring is. The knob was drilled out about halfway through to match the size of the dowel I used (5/16").
Get all the pieces together and test fit before you glue anything up. You will most likely need to sand various parts until they fit the way you need them to.
Step 5: Other table parts
I was especially proud of the rubberband bouncy thingies above the paddles! They work very well.
Notice that I drew all over the table top to lay out where things were to go. Doing this helps make sure everything is lined up and symmetrical.
Step 6: The fun stuff!
The loop is made from and old plastic bottle. I detailed the making of that more (in photos), because it was a little more tricky. Everything else is mostly cardboard.
Once the paddles and launcher are working properly, you can go nuts with the top half of the table. You can make whatever you can think up.
The nice thing about melamine is that hot glue sticks to it well, but you can pop it off (or scrape it off) quite easily. If an item you've glued down doesn't work well, or is positioned wrong, you can remove it without too much hassle. I will probably make some changes and move things around on mine, but you get the idea.
This was fun to build, and is really fun to play with.
Check out the video!
Step 8: Various improvements
First, I needed higher outside walls. The added side sections are made from 1/2" plywood, and the back is 3/4" particle board. (That's just what I had lying around.)
I wanted a better launch ramp with some sort of random ball-placing mechanism. I came up with a "Plinko"-style pegged board, which sends the ball a different direction each time. This was made from 3/4" MDF, with 1/4" dowels glued into holes I had drilled in the MDF.
I mounted the plinko board to the back wall with scrap pieces of wood, leaving enough clearance for the ball to still roll around underneath.
Then I added a nice big scenic ramp and a half-loop with a spinny-wheel thingy at the top. All of these things were made with cardboard, poster board, masking tape, and hot glue.
I'll probably add more stuff someday. (It's a work in progress.)
If you can think of any other non-electronic, waste-product-derived obstacles that would improve this, be sure to leave a comment.