We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Thomas Prufer saying something like:
the same time.
I stand corrected. Yes, they can be very effective on a small airflow, as long as the plate is well finished and has some partial sealing at the edges, I suppose.
I'd guess at the orifice size being about 1mm and a flare on their top end - not too many, although it would be easy enough to calc how many would be needed for a given airflow and weight of top plate plus bike.
The pressure drop at the orifice needs to be some significant proportion of the total pressure drop... It's something like exactly 2/3 at the orifice, 1/3 at the gap for a given gap and load. (It could be 1/3 and 2/3, but this is Usenet so I can handwave airily). This gives maximum stiffness. And channels and flares are there to give the baring a chance to lift up if it's down under load...
But once it's going, it should be perfect. I know from unloading stacks of large melamine-coated particle board sheets: given a lift, let them drop, and the air stuck between them lets them just glide off the stack. (Then they slide off and become very heavy...)
Would need the bikes to be on centrestands though, which still leaves g/f unable to use it easily... and the Vmax is right at the (300 Kg) max weight limit :o( - I think it needs to be big enough for both wheels and sidestand to rest on it, which means about 6 feet diameter!
-- Dave H. (The engineer formerly known as Homeless)
"Rules are for the obedience of fools, and the guidance of wise men" - Douglas Bader
I'm not sure if they still do, but Mullard Blackburn used compressed air "floaters" to allow one man to move some REALLY f*ck off big engines. And I mean BIG engines. Those destined for ships and whatnot. The air didn't seem to be blasting out anywhere like I expected it too, but I reckon the whole idea would be a bit OTT for a garage turntable doobrie.
How closely you can approximate this depends on your leakage around the edges of the plate. There's no reason why the bearing itself actually needs any air to flow at all. Most of them have flow-based airflow control rather than a simple pressure drop though a fixed orifice.
As the airflow neded is likely to be some factor of the ratio between the circumference and the area (and of course the bike weight) then the bigger the turntable is, the easier it is to do.
The practical limit is likely to be the need to make a rigid turntable, such that it doesn't flatten out and grind at one spot under a wheel. At the same time, the edge sealing skirt need to remain in contact and avoid opening up a leak.
The usual way of arranging this on a commercial air-mover back in the Space Age was to use a spiral rather than a disk. It lost the benefit of beneficial circumference / area scaling laws, but then the potential forces are huge anyway and they just don't need to be big. What it did provide instead was a more flexible support that didn't need perfect alingment over a perfect floor. The spiral deformed under load and was effectively conformal.
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