Friday, May 8, 2015

Money, money, money...

I bought some round telescoping tubing from McMaster-Carr, hoping that it would give me tight tolerance fittings, but it doesn't.  The tolerances are crappy, like 1/8" difference in ID and OD.  I'm hoping to retry the linear model with 4 ft long tubing, and also possibly a new rotational valving model with the following changes:

  • Tighter tolerance tubing
  • Have the outer tube holes all facing upwards, and the inner tube with the helical holes
  • Use 1/16" holes instead of the 1/8" holes I used in the original prototype
I'm just going with my gut on these changes, that they might improve the performance and appearance of the effect.  The problem with swapping the helical holes into the inner tube is that it requires the inner tube to rotate, and the inner tube is connected to the gas supply.  Rotating it by 90 or 180 degrees should be possible as long as the hose is long enough.  I looked at gas swivel joints, but they're really expensive.

On the other hand, I found a really cheap source of solenoid valves on Alibaba, like less than $10 a valve.  The shipping is expensive (from China) but if I decide to go with these in bulk, it's pretty tractable.  I think testing a system with about 10 valves along a 4 foot line might be actually quite doable from a cost and complexity standpoint.  I was thinking this would be prohibitive, but really, I think $3000 in valves isn't actually that much in the grand scheme of things.   I had also originally thought this would require me to to build several independent lengths with holes and their own inputs but I want to try simply attaching them under a square U-Channel with holes drilled at intervals.  It would depixelate the effect but still be pretty simple to build.  The control logic becomes much more complicated, but control logic is in some sense the easy part: one controller per edge, and a central controller.  Not that big a deal.

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