Maintenance track wish

As several other users have noted, simple physics makes it inevitable that sand will accumulate at Rho 1.0.

I take issue with a couple parts of this statement. First is the term "simple," and second, "accumulate". The latter is a minor quibble: it's obvious that if the ball's reach is confined to a perimeter, this will result in what I call the "terminal berm" (others have used "windrow"). This ridge does build up over time, but only to a point, which is self-limited by the angle of repose for the silica we use. But my real disagreement is with using "simple" to describe the physics behind devising strategic plowing strategies using a rolling sphere on / through  granular matter. 

It "seems" like it should be easy to create Sisyphus paths that move sand in a desired direction. Most people (including me) intuit that the erase pattern should move sand out when running from Rho 0 to 1, and in when running from 1 to 0. But this is greatly dependent on the tightness of the spiral (how close successive passes are). My empiric experience suggests simple Archimedes spirals have very little net effect on overall sand distribution. I tried several times over the past 20 years to devise an efficient strategy for "plowing" routines, and never succeeded. I'm not saying it is impossible - I'm pretty sure it is. But it's not easy, at least for me. However, dumb luck + paying attention, led to noting that tracks that repeatedly move in and out while precessing around the field, when run from Rho 1 to 0, are very efficient at plowing in toward the center. Case in point: Create a playlist composed of erase then apache. Play it sequentially with repeat on,  overnight.

And yes, during our failed struggle to improve 2-ball reliability, I made several attempts at devising a plow-in track that started in >1 territory, hoping to break up and move the terminal berm into <1 territory - with extremely little success.

Growing up and living in Minnesota, I (along with all my fellow northerners) am very familiar with plows. My take-home from this exercise: rolling spheres make piss poor plows. 🙂

(ps - would love to be proven wrong)

Heh! I grew up 2 blocks from Clancy's Drug Store at 50th & France, and I agree about the spherical snowplow idea.

I don't doubt that you've considered this issue for years, nor that it's a difficult puzzle. Whether we think of physics as simple or not, though, a berm does accrete. (I went with accumulate the first time, so this time I'll try accrete...) I mean, I'm looking at it right now, and this is after only five days of use since the last time I crossed my fingers and hoisted the glass so I could mitigate it. It's not an existential problem, but it does lead to some thin spots at the perimeter, and if you're borderline OCD like me, it's an unscratched itch.

I had in mind a track that emulates the zigzag motion of apache or peon1, but which begins at rho=1.N. I could probably write that track, but I would fumble the part where it avoids the ballpark. Don't you even have an experimental script lying around that you could share? It needn't be a thing of beauty, just a hack to eliminate wrasslin with the heavy glass. (On the smaller table, obviously, it's not an issue.)

I'm a tireless promoter of your product. Anyone who asks gets a ten-minute spiel on its elegance and beauty.  I bought it when I decided to build a DIY automated sand table, and after calculating what I would need to buy, and the hours I would have to invest, it turned out that I could purchase a Sisyphus coffee table for less it would cost to make my own, and into the bargain, yours comes with a body of tracks and a community of trackmongers. I adore the thing. I would never tell anyone "Don't buy it, sand builds up at rho>1!" I just wish I didn't have to lift the glass and remove the ring to return the sand to rho<1.

Bruce might cringe when I say this, but I have smoothed out the sand by shaking or vibrating my 2' side table. I do it by hand, with some sharp pulls or pushes, or some palm thumps. It reminds me of erasing an etch-of-sketch. The pattern gets blurry and if you keep going, eventually disappears, and the edge sand comes in a little. I have pondered coupling the plastic  body of my random orbital sander to a leg to see what would happen. Once could attach it underneath and trigger it from the Raspberry Pi instead of running an erase track, but it would surely distract from the quiet Zen of the table!

I will cringe along with him. It's not practical for a 3 foot table. It's enough of a workout to lift and replace the glass. 

@adambrower Nice! My sensitivity to "accumulate" is that, at least for me, it is a self-limiting problem and becomes acceptably stable (the berm is static in position and height). I usually run long playlists (like the default shipped with new orders) in shuffle mode with repeat on, 24/7. Just got back to our condo in Mpls after spending ~half a year in NorCal. Upon return, my two tables greeted me with perfect fields and lighting. Other's mileage may vary of course. Need for manual sand smoothing depends a lot on what types of tracks you play and if they repeat a lot.

@dithermaster Well, we don't "recommend" such a method - but if you're not too boisterous, it shouldn't cause harm. And I certainly have noted this on clumsy accidental occasions. However, I don't think constant vibration will achieve a level field. When I tried it (way long ago), it resulted in a fractal landscape of branching ravines. Actually pretty cool - but that's different kinetic piece altogether 🙂

Not much snow-shoveling in NorCal, I'll wager. 🙂