I’ve been working on building my own polar sand table over the past few years as I’ve moved throughout middle and high school, and I plan on posting a more in depth build topic soon to summarize the couple of years I’ve spent learning. However, before that, I’m curious what people have found as the best sand material.
Right now, I’m using this hamster sand which I saw on one thread at some point. I was hopeful about how fine it was because of the 1-star reviews claiming its fine granularity gave their hamsters respiratory problems! However, I’m worried it 1) may not be fine enough, or 2) may be applied in too thick of a layer to produce fine details. (I’ll try experimenting with different volumes of sand some point this week when I find the time-- which I do anticipate will help the issue)
This also may be because I don’t have LEDs lighting the sand from the side yet, but I’m a tad disappointed with the definition of the design in the sand.
Besides definition, another concern of mine is the “choppiness” of the marble-- this may also be because of having applied too thick a layer of sand which I’ll try varying. Applying a layer of felt beneath the sand definitely helped with the choppiness, but it’s still not perfect:
I’ve heard some people have used baking soda, but I’m worried about moisture collection especially in a very hot and humid Georgia summer. Has anyone found a good source for super fine sand-- or is my current sand just fine? And what could I do to make the motion of the marble smoother and more defined?
Definitely looks too thick. I think between 1/2 and 1/3 the height of the ball is good. Think of a bike tire hitting a curb.
I use baking soda and I live in the desert. But I would encourage you to try it anyway. I don’t think it will ruin anything if it does keep some extra moisture. It may just clump up a little.
One key engineering metric is the “angle of repose”. The shape of the sand particles, as well as the size has an impact on that. You want sharp peaks, so you want a high angle of repose so the sand doesn’t just flatten out. I believe sharper particles leave sharper peaks because they have a higher angle of repose. Round particles have a small angle of repose.
I also used the spare sand from a commercial sand machine in my DIY ZenXY and it didn’t work out well. I think the professional machine has a cloth bottom to let some of the sharper sand pieces push down into the fabric.
I think some other folks a while ago had mentioned a dust used for Chinchillas? I guess its super fine. Now that I think about it, I just started raising chickens and bought some diatomaceous earth, which is also super crazy fine powder. Maybe that might work too?
I have been using baking soda with good results.
Now that I saw that tho after over a year I think it’s time to change it out.
I think your main issue is like Jeff said. Your just a big too deep.
One of these days I will get a chance to put some of my ideas to use for sand leveling etc.
I want to add mini rc vehicles to mine like a Zamboni, tank, and maybe a snow cat with a groomer and a snow blade.
That and maybe a swiped rod you insert then turn 90 deg and drag it along a slot milled in the edge.
Sorry it took me forever to reply— I got a full time job and got busy with school things as well— but I ran some tests last week with different materials/volumes. Thank you all so much for the advice!
This is interesting! I had no idea what it was, and as a side-note, it looks amazing under a microscope! I wonder if the rough pattern gives it a higher angle of repose.
I’ve definitely noticed that lighting makes a huge difference! Unfortunately my current design doesn’t allow for side-lit LEDs since the central slip ring is using all 6 wires. For now I might just add some standalone LEDs from Amazon with those little cheap remotes.
I’ve also noticed how my lines aren’t perfectly straight and a tad wobbly— Maybe my magnet (1 inch scary cube) is too strong or the felt top isn’t ideal? No idea.
I cadded a new design for the table on the job while waiting (yes, onshape has a surprisingly functional mobile app) that’ll allow LEDs easier and will also have a larger drawing radius to actual radius ratio.
Right now I think I like medium volume baking soda or I might try an extra low volume sand.
The felt or clumpy sand could be causing the jagged lines. I’ve seen that before on my table where it hits a “boulder” of sand and is pushed to the side. Baking soda can have clumps, but they disappear after a couple of patterns. You have to watch it closely from the top and bottom to see where the error is. I bet your mechanism is smooth and it is something on the surface. You can also play with the magnet distance.
Thank you! I’ll try the wiper hopefully tonight maybe Saturday. My current design is already at the lowest magnet distance but I could try raising it a hair and see if it helps although I’m not sure if I can raise it much more. I’ll also run a couple patterns on it to see how the clumps break up. Speaking of having a smooth mechanism, I got this neat video a few months ago of the “flowsnake” pattern from Sandify.
I attached a sharpie where the magnet would be to test if everything was working before I built the rest of the table:
I think this looks really cool in itself as an “invisible plotter.” Could make an interesting project with a roll of parchment paper that moves like a cassette tape.
