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Ping Pong Ball Insulation

(It's a fair assumption that a ping pong ball can withstand an internal vacuum, so...)
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Insulation made from evacuated ping-pong balls, with closed-cell foam concave rhomboids or caltrops (depending on the packing lattice) in the gaps.

Available as solid blocks, sheets and loose.

FlyingToaster, Nov 21 2017

Vacuum Brick Insulation [xaviergisz, Nov 21 2017]

I have no idea what that person's doing, https://www.youtube...watch?v=skN8ixHxzgM
but it involves a high-vacuum ping-pong ball, so... [FlyingToaster, Nov 22 2017]

Wanted: Vacuum Dirigible Service Tech Centrifugal_20vacuum_20balloon
[sqeaketh the wheel, Nov 23 2017]

Wanted: Vacuum Dirigible Service Tech Wanted_3a_20Vacuum_...le_20Service_20Tech
[sqeaketh the wheel, Nov 23 2017]

[link]






       //It's a fair assumption that a ping pong ball can withstand an internal vacuum//   

       Oh dear. Fell at the first hurdle.
bigsleep, Nov 21 2017
  

       Eh ?   

       A little googling around says pingpong balls can withstand 70m depth pressure, so 1bar is hardly going to bother them.
FlyingToaster, Nov 21 2017
  

       You are trying to equate 7 over 1 bar with 1 over 0 bar.   

       If you could do this, your lighter than air insulation would be pretty cool. Flammable, but cool ... and lighter than air.
bigsleep, Nov 21 2017
  

       I doubt it would be LTA. But 2 - 1 bar is the same as 1 - 0 bar.
FlyingToaster, Nov 21 2017
  

       Think of any springy volume like a football and think of the volumes for 2-1 and 1-0. The 1-0 one is a pancake.   

       The ping-pong balls are not much different when not perfect - a few atoms out of place and pancake it is.   

       1 bar is 14.5 psi, so try sticking 14 pounds or 7kg on top of a ping pong ball to see what happens when any asymmetry develops such as someone tapping a wall.
bigsleep, Nov 21 2017
  

       A football that starts at 2|1 will equalize at half its volume. A football that starts at 7|1 will equalize at 1/7 its volume. A football that starts at x|0 will be a pancake.   

       Good thing it's not a football and won't collapse under a measly 1bar differential.   

       I'm pretty sure I could put 14pounds on top of a pingpong ball and, even though it's a point contact instead of a full square inch, I doubt it would buckle.
FlyingToaster, Nov 21 2017
  

       I'm with the critics on this one, and I got here too late to be the initial poster, but pending some empirical evidence it's skeptics 2, protagonist 1.
normzone, Nov 21 2017
  

       Consider a hollow sphere with internal pressure of 1 Bar.   

       Increase the external pressure from 1 Bar to 1.1 Bar. The sphere deforms slightly, decreasing its internal volume. At constant temperature, the internal pressure must rise, as defined by the General Gas Law.   

       This change in internal pressure resists the external pressure and the deformation ceases.   

       However ...   

       If the sphere is evacuated, and in a vacuum, then the system is stable. Increasing the external pressure will be resisted only by the shell, as there is no internal gas to compress. Once the shell's strength is exceeded, the sphere collapses.   

       Oh, and you owe us for a new ping-pong ball ...
8th of 7, Nov 21 2017
  

       Reducing something by nothing is way different to taking everything away to get nothing. 1 going down to 0 not 1 - 0
wjt, Nov 21 2017
  

       I think [8th]'s analysis is wrong, as is [bigs]'s.   

       For a thin-walled spherical container like a ping pong ball, the failure mode is catastrophic buckling. Basically, a perfect spherical shell, subjected to a uniform pressure, would withstand a very large force. But as soon as it buckles (for instance, due to one point on the surface being indented by a non-uniform pressure), then it will fail catastrophically - it's the spherical analogue of Euler buckling.   

       With that in mind, if a ping pong ball can withstand 70m of water (about 7atm, or 6atm over internal pressure), it should equally well withstand an internal vacuum in air (1atm). In either case, tapping the ball so as to cause a local deformation would lead to an immediate collapse.
MaxwellBuchanan, Nov 21 2017
  

       //uniform// a) not a reality b) wouldn't the two situations be different because of the variation in populations of pressure elements due to more non element and ping pong interactions. More even pressure?
wjt, Nov 22 2017
  

       [xg] this post is celluloid spheres, not metal bricks. Both shape and material properties are defining features.   

       ---   

       <link> vid of somebody evacuating a ping-pong ball for some unrelated nefarious purpose.   

       Unsurprisingly, it doesn't implode.
FlyingToaster, Nov 22 2017
  

       It's actually a very interesting question as to the failure mode of a spherical container between absolute pressure and relative pressure .   

       Case (a): Sphere is evacuated and sealed, extenal pressure is increased until collapse occurs.   

       Case (b): Sphere is pressurized in equilibrium with its environment and sealed, extenal pressure increased until collapse occurs.   

       Will the failure modes be identical, at the same differential pressure ? This is not a rhetorical question .
8th of 7, Nov 22 2017
  

       Yes, they will.   

       The only difference is that the evacuated ping pong ball will collapse more thoroughly than the air-filled one because, in the latter case, the internal pressure will at some point match the external pressure as the ball collapses.
MaxwellBuchanan, Nov 22 2017
  

       I agree that ping-pong balls generally won't collapse with a vacuum. However I expect that gas will slowly seep through the balls, reducing the insulation effect after a couple months and/or years.
scad mientist, Nov 22 2017
  

       The idea was borne of considering an insulation for a double-wall volume, that would be disposable/recycleable : just suck out the old after ten years and replace with new. Most of the "material" is after all vacuum; materiel-wise not very expensive. Perhaps, like spray-in foam, the spheres could be produced on-site.   

       In the specific case of traditional celluloid ping pong balls, I'm surprised the Borg hasn't chipped in a pastry, given the insulation would start off highly flammable (and mostly immune to fire retardants) and age into a low-yield explosive as the camphor outgassed/sweated out of the nitrocellulose. The new polyester balls aren't quite so interesting.   

       Perhaps glass spheres - slightly thicker-shelled Christmas ornaments - instead. That should last a half-century or so.
FlyingToaster, Nov 22 2017
  

       Is the minimal equipment needed to go from 2 to 1 bar, the same equipment for going from 1 bar downto 0 bar? Of course the equipment that will do 0 bar with do the other. I always thought that you needed better equipment to get a better zero.
wjt, Nov 22 2017
  

       //Will the failure modes be identical, at the same differential pressure ?//   

       If you consider the differential limit, you are effectively studying a membrane between two pressures.   

       <strokes beard/>   

       When the higher pressure pushes the membrane, the pressure on the other side will offer increased resistance, but also the stretched membrane itself will seek to restore the spherical shape.   

       So the two forces at work are the forces in the skin of the sphere and the relative pressure forces either side of the membrane. With a vacuum one side, there is no restorative pressure force. So in terms of comparing 2 with 1 bar and 1 with 0, there is a term in the force equation that has dropped to zero.
bigsleep, Nov 23 2017
  

       //The only difference is that the evacuated ping pong ball will collapse more thoroughly than the air-filled one because, in the latter case, the internal pressure will at some point match the external pressure as the ball collapses.//
MaxwellBuchanan, Nov 23 2017
  

       Why not old unused glass lightbulbs?   

       At some strength, the pingpong ball would resist pressure even if the term goes to 0. 1 atmosphere remains just one atmosphere.   

       If it was a perfect sphere, potentially the plastic pingpongball would be able to resist.
mylodon, Nov 23 2017
  

       The real question here is how would it be to play ping pong with evacuated play ping balls? They would be lighter (in air) than the air-filled ones.   

       By the way, this reminds me of the legendary vacuum blimps, which is what got me into the halfbakery oh so many years ago. Wanted: Vacuum Dirigible Service Tech
sqeaketh the wheel, Nov 23 2017
  

       //Is the minimal equipment needed to go from 2 to 1 bar, the same equipment for going from 1 bar downto 0 bar?//   

       Sealing aside, all that needs be done is supply a force greater than 14.7lb per square inch cross-section of the evacuation hose/pipe.
FlyingToaster, Nov 23 2017
  

       // Sealing aside, //   

       Not an insurmountable problem - after all, it's easy enough to get the basic material for a very nice, warm sealskin coat ... if, that is, you all club together ...
8th of 7, Nov 23 2017
  

       Have you considered kitten?
21 Quest, Nov 23 2017
  
      
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