OT: Request for help with air core transformer/power transfer system

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: David Speck <dave@xxxxxxxxxxxxxxxx>

List,
I know this isn't directly TC related, but I hoped someone with more 
transformer theory experience that I have might lend a hand, with Terry's 
indulgence.  Please feel free to respond privately.

->Sound enough like electricity transmission without wires ;o))  But 
respond direct if not really related to Tesla coils) - T. <-

I'd like to transmit about 6 volts AC at 60 Hz and 250 mA through a glass 
plate about 1/4" thick without drilling a hole in the glass, and without 
making any really esoteric circuitry like a high frequency drive 
circuit.  I don't have a lot of time for experimentation, so I though I'd 
run my idea past you and see what you thought.

I have space to put a 4 1/2" OD flat circular pancake coil (about 1/4" 
thick) on each side of the glass.  I figured I'd run 6 volts from a wall 
wart into the primary, and have a matching secondary directly opposite it, 
on the other side of the glass, from which I'd feed a diode bridge and 
filter cap on the secondary side..  I know similar arrangements are used to 
recharge batteries of implanted medical devices, but I don't know if they 
work at 60 Hz or higher frequencies.  My main concern is making an 
arrangement that will not burst into flames during prolonged unattended 
operation.
Questions are:  Would it be better to have primary and secondary circuits 
with a relative few turns of heavier wire, or lots ot turns of finer 
wire.  I expect that you'd get more inductance, but more resistive heating 
with finer wire, but in the absence of an iron core to corral the magnetic 
flux, I worry about drawing too much current from the wall wart into the 
primary with a few turns of thicker wire.
Is there a way to calculate the optimum number of turns and wire size for 
this arrangement?

Is there any simple arrangement of soft iron wire or sheet that would help 
to constrain/direct the magnetic flux for better energy transfer without 
involved magnetic core fabrication?

Thanks in advance for your thoughts.

Dave