I considered the wind tunnel a total success as it kept a herd of 3-6-year-olds occupied, let them play and discover what items would fly, and simultaneously was interesting enough that all the parents wanted to play, too.
I built the project organically with no more of a plan then wanting to have kids play with a stream of fast moving air. If you don't want to follow along to see what I did specifically for my setup, here's the summary:
- Consider cardboard concrete forms for projects that require 12-inch diameter tubes
- Desktop fans that fit inside such a tube can't move enough air to be fun
- Not only can an air pump from a bouncy air move enough air to fly all sorts of things, but it produces a collimated stream of air; a leaf blower would probably work just as well.
Step 1: Fans inside a cardboard tube vs. air pump
The air pump came with this bouncy house from Amazon. Check here for my other mod to the bouncy house, an additional safety net.
Step 2: The air pump needs to point in the direction of the tunnel
Step 3: Build a base for the air pump
When you've got a biscuit joiner, all problems look like they need biscuits. Wood screws would have worked just as well.
Step 4: Large Diameter Tube
"That is a big, big, big cloud!"
Despite Corvidae's pronouncement, I wasn't satisfied with the 12-inch diameter tube. We could only get pieces of newspaper to really fly. Anything heavier, if it would fly at all, would circulate in the tube between the fast moving, collimated air stream in the center and the still air against the inside of the tube.
Step 5: Build base for smaller diameter tunnel
The adapter holds the ABS tube above the air pump so objects can be loaded directly into the stream of air. I had a fantasy about using the 12-inch cardboard tube as a magazine full of balls to be launched skyward, but wasn't able to solve the issue of balls jamming.