I had been thinking of building this for a long time (ever since I saw Bruce Shapiro’s Sisyphus at the Maker Faire in New York), and finally got to finish it this weekend. I’ve used a CoreXY gantry running on VSlots. On its own, the magnet moves smoothly; however, the ball at the top is not smooth at all. It moves in spurts. Not sure what the problem is and how to solve it. Would love to have smooth motion like this:
Any ideas/suggestions?
A good strong magnet in the right pole orientation, the correct size ration between the ball and magnet, and the smallest gap possible. Also try baking soda instead of sand.
I have attached 3 strong disk magnets - what would be the best ratio? I have tried various sizes of balls, including a permanent magnetic ball; the smaller ones were the worst. The large was better, but not perfect.
Have a look at my parts list for the Zen.
I had tried 15 or so magnets and 4 ball sizes.
Mine roll smoother when I use a thinner layer of baking soda as well. Thicker layers increase drag, increasing hysteresis. Moving faster also helps keep the roll going, at the risk of dropping it when moved too fast.
Thanks - will try a larger magnet. I guess mine is too small.
Thanks Ryan and Bill - was finally able to get nice smooth movement.
Some people use soft material (like felt) on the floor of their tables to assist with smooth movement. Have any of you guys tried this?
Also I’ve seen small magnetic cylinders used instead of spheres. Seems like the key is get the most amount of magnetic force.
Does the medium used (eg bicarb soda vs fine sand) make a big difference? I imagine less friction is better.
My thoughts on this.
Felt adds thickness which is not good, I think smooth movement is had from correct magnet to ball size ratio. I / We tried many to get this right.
We use a cylinder magnet and a regular ball, a mag ball will not work.
I find baking soda holds much higher detail and is much less noisy. Sand crunches and is sorta low resolution.
Thanks Ryan, that makes sense. What is wrong with a mag ball?
Do you mind sharing your ball/magnet sizes?
The info is linked on the Zen page.
If you have a magnet and a magnet ball it will not roll, it tries to get dragged and did not work well for me.