Original poster: gary350@xxxxxxxxxxxxx
Vanderbelt University did some research on Tesla Coils. The best
length to diameter ratio is 3 to 1 according to them. Research
shows 3/1 is better than 4/1 and that is better than 5/1. If you
are going for absolute maximum output try 3/1 ratio.
I did some experenents with this myself and built 3 Tesla
Coils. The 3 TCs are identical only thing that changes is the
secondary coil diameter to length ratio.
TC #1, 950 turns #24 wire 20.5 inches in length wound on 4" PVC pipe.
TC #2, 950 turns #24 wire 20.5 inches in length wound on 6" PVC pipe.
TC #3, 950 turns #24 wire 20.5 inches in length wound on 8" PVC pipe.
I used the same 15K 60ma neon sign transformer.
I used the same .01 uf capacitor.
I used the same VSVFSG spark gap.
I used the same top load, toroid 14" diameter 4.5" thick.
I built a flat would primary coil for each secondary coil. The
inside turn of each primary was 2" from the secondary coil. Primary
were all would with 1/4" copper tubing, flat wound, spacing 1/2"
center to center, 18 turns each.
The only thing in the circuit that changed was the secondary coil.
The primary coil physical shape had to accommodate the secondary coil.
Spark length increased a few inches with each secondary diameter on
each test. The most noticable difference was the appearance of the
streamers. The larger diameter secondary coils produced Hotter streamers.
The 8" secondary would produce a streamer 6" longer than the 4"
secondary coil in this test.
Next I wound another 950 turns of #24 enamel coated copper wire
right over the 950 turns secondary that I already had on the 8" secondary.
I connected the 2 secondary coils in parallel. Test showed the
streamers were 2" longer. As far as I can tell the 2 coils
connected in parallel reduced the wire resistance thats
all. Naturally the 2 secondary coils diameters are different by
about .0201 inch diameter this might change bandwidth frequency a bit.
Next I wound another 950 turns of #24 enamel coated copper wire
right over the 2 layers of 950 turns wire I already had. I
connected the 3 secondary coils in parallel. Test showed the
streamers were 1/2" longer than before. This does not appear to be
much of an improvement just an extra expense for wire.
My conclusion is 3 to 1 ratio is better. Advantages are, streamers
are longer and hotter. Disadvantages are, the TC is physically
larger, more work required to build it, the secondary coil requires
several times more wire.
I later did some experements with multi layer secondary coils. A 4"
secondary with 2 layers of wire connected in parallel would produce
streamers equal to a 6" secondary with 1 layer of wire. A 6"
secondary coil with 2 layers of wire connected in parallel would
produce streamers equal to an 8" coil with 1 layer of wire.
Hummm.....interesting.
Some of you many remember this post 7 years ago. There are new
people on here that were not here then I thought some of them might
be interested in this.
Gary Weaver