Tesla Frisbee!

Tesla Frisbee!

Did ya know that a Frisbee is a Tesla Turbine???

Some years ago I made a flying saucer... well a tiny one from used foam plates!  All I did was cut 3 holes near the center of one plate that left 3 beam structures strong enough to keep the center of the plate rigid.  Then I trimmed another plate to remove the outer curved section.  I glued toothpick sections as standoffs to hold the two plates about 1/8" apart.  I put a little tape in the center to reinforce it and glued a longer toothpick section through center holes so that the shaft stuck out a little ways on the bottom.  I glued a little scrap plastic cylinder that had a nub on one side onto the toothpick on the underside.  Voi la!  Flying saucer!

I took another plastic scrap tube a little bigger than the one on the saucer and cut a channel on one side big enough for the saucer cylinder nub.  The second cylinder was glued to a small electric motor shaft to be the saucer impeller.  when the saucer hub was placed on the motor shaft the nub in the slot imparted rotation to the saucer but let it fly up when it had sufficient lift.

I put the motor on a variable power supply and fired it up!  The first thing I noticed was that just a Tesla said, there was no need to finely machine or balance the rotor... it self-centered as soon as a sufficient spin rate was reached.  As I turned up the juice the little saucer gained rotational speed, nicely lifted off and floated across the room!  It had a very stable flight but had a penchant for ending up behind heavy funiture!!!  HaZah!

"What does this have to do with Frisbees???" I hear you thinking!  Well I always noticed how Frisbees fly better when they are spun fast, but I just thought it was because they were gyscopically more stable and thus moved through the air better.  Well, that might be some of it, but I think there is more!

A Tesla Turbine uses no blades but rather spinning disks with holes near the center.  Air or any other fluid can go through the inner holes and move along the surface.  The fluid adhears to the surface of the disk and viscosity couples the surface fluid to the near fluid.  If the turbine is driven, the fluid flows outward, sucking more fluid in through the central holes and out the edges.  Conversely, if pressurized fluid is ducted to the edge it will spiral (which ever way you start it) toward the center holes to exit and will spin the disk, imparting torque to the central shaft.

The flying saucer plates form  a very light, efficient Tesla Turbine by sucking in air from above which creates lift and by shooting the air out from the upper disk's under surface and the lower disk's upper surface, which hits the downward curve of the upper plate, producing more lift.  The under side of the lower disk also shoots some more air out to hit the upper plate lip which might create some more lift but also creates a low pressure zone under that disk that probably cancels that lift... oh well...

However, that is not the case with the upper surface of the upper disk!  It also throws air out and contributes to the low pressure near the center above the saucer for more lift.

Ah, but back then I forgot about the Coanda effect!  Thomas Young (1800) and Henri Coanda (1910) described this effect which causes fluids to follow a curved surface... it is adhesion and viscosiy again - see?  So, not only does the upper air fly outward, it is bent downward by the upper surface of the downward curving upper plate.  (Go ahead.. read that sentence 3 more times... ... ... got it?).

So my recent Frisbee epiphany is that both the under and upper surfaces of the Frisbee are functioning like a Tesla Turbine to create actual lift!  The under surface throws air out which is directed down by the downward curve at the Frisbee edge.  Also the upper surface throws air out which is deflected down by the downward curving upper surface via the Coanda effect!

Ain't science fun! Nois.

frisbee impeller (scary stuff!)
Tesla turbine helecopter (the link in this article is broken!  I searched for other links and they are all broken... hummm...)
Coanda Effect