[SML] Extremely low profile air caster?

[Joe Dunfee]

I was in a rehearsal, when at the end of a dream sequence, the director 
asked the character to "float" away as the dream faded.  He said 
ideally, she would just move backwards, without walking. But he just 
asked her to walk backwards smoothly.

That got me wondering if it was possible to do.  In this case, the 
actress is actually starting out kneeling, so she can simply stay 
kneeling, so she is well braced if a platform pulls her.  However, to 
not look like she is on a platform, the platform would need to be very 
low profile.

I 1st though of just dragging a piece of 1/4" ply, or linoleum, perhaps 
with Teflon on the underside if really necessary.

Then, I thought of air casters.  The commercial heavy-duty ones are 
designed with what looks like a bicycle inner tube.  But, they also tend 
to lift the platform a few inches as the "inner tube" inflates. Then, I 
thought of the standard air-puck that is used to demonstrate Bernoulli's 
principal, when the moving air creates a lower pressure, so the puck 
actually adheres to the table surface. The flowing air also reduces 
friction to near zero.  So, the air puck is both levitated, and also 
held down.

Those air pucks have nothing more than just a flat surface on the 
underside. So, they are very low profile.  But, a quick test using a 
large wood circle was unsuccessful. Though, the air pressure for the 
number of square inches should have lifted the disk. But so there are 
other issues. I imagine the air pressure needs to overcome the weight of 
the disk by the surface area of the air inlet.  But, even lifting the 
disk a bit to help the process didn't get it to float.

My air source was a very old CPAP machine (that helps people breath at 
night).  It provides up to 0.26 PSI at a pretty high flow rate, and most 
importantly, is very quiet. Newer ones all have security built in, so 
that it takes a password to set the pressure.  So, I am looking for a 
reasonably affordable source for just the fans, so I won't have to 
scavenge for them.  Note that these are brushless, so they would need a 
motor controller.

Any air-puck experts out there?  I am sure a lot of people in theater 
would love to see an extremely low profile air-caster.

-Joe