I did some more work planning out my ideas for the sand mirror. At this point, I am only going to build a 1 x 6 vertical grid of fans and have a simple interaction to trigger a series of fan events, whether that be timed delays between each fan starting up or a system of valves opening to allow air to pass down a tube. Hopefully play testing will reveal how well simply a lone fan behind the sand wall might work, in which case, I could put a joystick in front of it for folks to interact with.
Below you will see the system diagram. I plan on using a ULN2003 to control the 30 mm fans.
Bill of Materials
For the bill of materials, the fans are going to be the most costly by far, relative to any of the other materials. For this reason, I am hoping play-testing may reveal that using one powerful fan that say, rotates in the X and Y axis behind the sand, might be an alternative to the 6 fans.
Below is the short-term timeline and work list:
Fri Nov 16th - Laser Cutting cardboard frame
Sat Nov 17th - Acquire 6 fans from local hobby shop
Fan Testing, PVC fitting
Mon Nov 19th - Build 1x6 fan and test
Mon Nov 26th - Further testing and interaction design
Thur Nov 29th - Final Tweaks and touches
Here is my current to do list and my thoughts and unsolved mysteries thus far.
build box for sand
measure fan width and match PVC to fit
make PVC pieces
laser Cut cardboard
3D print valves to control air flow
Challenges at the moment:
finding, sourcing, and testing a strong enough fan at a small enough size - duct fans for hobby RC jet planes may be the ticket…
focusing the air into small areas - PVC pipe w straws inside
the larger each fan’s size, the larger the grid will be which means using more sand
accelerating and decelerating the fan quickly to get the desired responsiveness - 3D print valves?
getting a smooth rate of falling sand
getting a consistent pattern of falling sand - perhaps different grades of sand would be better
I should add that I bought a 50lb bag of from Home Depot cause that was the smallest amount on offer. I did some initial testing and found that a computer fan was much too small, unless there was very little sand being used. I found a larger size 6” personal fan that seemed to work better, although the wind pattern was not very accurate. I held a smaller bucket of sand over this fan and saw that the fan was effective. However, the sand had quite a bit of dust coming off of it.
I described the situation to my roommate and he recommended that I wash the sand. Foolishly, I acted like I knew how to go about that and devised my own way which involved a large piece of fabric, about the size of a shower curtain, that I got from the Soft Lab scraps and the utility sink in the shop. It took about two hours to do all 50lbs which was probably overkill, but I was already at it so why not?
Then I had to DRY the sand… First I tried to leave it in that small red bucket overnight by the radiator, which I thought was so smart. But when I came back in the morning, not hardly a dent had been made and the sand was still damp. So I brought my car to school to get the sand and take it home to dry. This took a few days of spreading it out over a heating blanket covered with clear plastic. Perhaps my roommate would have had a better solution, but I have what I need now so…