I came up with this design as a way to re-invent the classic marble drop toy. By using a piece of plywood for the back you vastly simplify the construction.
I designed my toy to have two parallel tracks for the marbles to follow. This increases the noise, it increases visual interest, and most importantly of all, it allows your kids to have races. Finally, I added a bell to my design. Again, this adds to the noise, and more noise is good in a marble toy! There is also the idea that each marble gets to ring the bell as it arrives at the "finish line" of the racetrack. Marble track pieces can be nailed or glued very easily to the flat back. If you like, this is a great project to have your child help you build. You can have fun coming up with different marble track layouts.
Step 1: Option: Video Tour
This is one project where I think you really need to see it in action (and hear the noise!) in order to properly appreciate it fully. So please, watch at least the first 30 seconds of the youtube build video, and then you can come back and read the rest of this article.
Of course, if you would prefer, you can watch the entire video build.
Step 2: Bell + Catch Basin
First buy your marbles.
I picked up a pack of 9/16" diameter chromed steel balls from Lee Valley Tools.
You can also find Chrome Steel Balls at Amazon.com
I also recommend buying your bell before construction, as it's size will affect other dimensions. When I built my toy, I was able to buy a brass counter/desk bell kit at Lee Valley. It's no longer available there, but you can find desk bells (or counter bells) at office supply stores. (Here is a link to Brass Desk Bells at Amazon.)
The 2nd photo shows the disassembled bell. The base + clapper is screwed down to the bell base, and then the hemispherical bell is threaded onto that.
Step 3: Track
Here are some photos of building track. I made my track out of 3/4" wide by 1/4" thick stock. Three pieces are glued together to make the U-shaped track. This long piece can than be cut down to the shorter pieces that are arranged to make up the different parts of the racetrack.
Keep aside some of the 3/4" wide stock, and it can be cut down to short pieces and glued in to make the end pieces for the various track segments.
Step 4: Notched Track
I also made some notched sections of track. This can be done either with a dado blade set to 1/4" width, or by repeated cuts over a regular saw blade. The notches cause the balls to make a sort of rat-a-tat sound as they roll down.
Step 5: Notched Base
I set the plywood back into a notch in the base. You want a pretty thick piece for the base, to give some weight to the racetrack, so that it does not easily tip over. You could cut that with a dado blade and fit the back into the slot. I did this a different way. I did not have a thick piece for the base, so I glued together two boards. But I first ripped one narrower, glued the two pieces together. Then I added the back board and a piece on the back of the base, and glued and clamped it all together.
Step 6: Start From the Bottom
You need to start at the bottom with laying things out. The reason for that is simple: you need to ensure that the marbles will drop nicely into the catch area.
This is an iterative process: Clamp some track in place, drop the marble through it, make sure it works, make any necessary adjustments, and then mark the location and add glue and clamp it permanently in place. Now repeat.
You could use nails from the back to fasten the track into place. However, you need to ensure that the nails do not poke through the relatively thin sides of the track!
Repeat this process all the way up the board, clamping, testing, and gluing your track pieces into place. I made two basically identical tracks. Each track has the same elements, though not entirely arranged in the same order. As well, one set of track was made with walnut and the other with ash, to give a nice visual contrast.
Unfortunately, I don't have photos of the track partially assembled. I do have a couple of sketches with a few basic dimensions. I think the idea and process is more important than precise dimensions, as I would hope that every track is going to be a bit different.