The power supply can put out 30,000 volts, so there must be about 2" space from the primary to secondary.
The secondary diameter is about 13". So the primary inside diameter needs to be 17".
To have sufficient tuning range for various capacitors, there should be 16 turns.
If copper water tubing is used, the primary would be as follows:
Flat-spiral made up of 16 turns
1/2" diameter pipe to handle the power
17" inside diameter
41" outside diameter
120 feet of copper tubing
That's gonna be big, heavy, and hard to make thing. Try bending 1/2" copper tubing in a nice spiral.
Primary coils can also be made with metal strip. 1.25" spring-bronze weatherstrip is easy to get.
Flat-spiral made up of 16 turns
1.25" spring-bronze weatherstrip about 0.01" thick
0.25" thick x 0.75" wide polyethylene foam strip (sticky on 1 side)
(McMaster-Carr #93565K75)
17" inside diameter
26" outside diameter
100 feet of brass strip
Get your own spring-bronze weatherstrip
MUST HAVE: DC gearmotor with 1/2 inch chuck. 17" diameter form
to wind on.
AC variac (note paper clips) with power rectifier and foot-controller.
UL approval still pending.
100 feet of 1.25" spring-brass weatherstrip and 0.25" polyethylene foam (sticky on 1 side)
for spacing.
Jerri and Lauren supply extra hands to help get this thing together.
Who says girls don't do Tesla stuff?
Spin the wheel, guide the various stuff, stick the foam on, keep it going on straight.
There ya go. Now what to do with this rather fragile spiral.
How about a quick and simple base for everything. Two sheets of
1/2" polyethylene cut for putting together.
Here is the base and the primary (held together with tape).
Looking good.
All together. Still need to figure out how to keep the spiral
from going SPROING. Maybe tomorrow. Hehe.
Here are some of the final specs and some measurements:
Inside Diameter: 17"
Outside Diameter: 25.5"
Total Turns: 17.8
Spacing: 0.25"
Height: 1.25"
Total DC Resistance: 0.2 ohms
Total Inductance: 0.242 mH
WinTesla Predicted Inductance: 0.283 mH
| Turns | mH |
| 1 | 0.002 |
| 2 | 0.004 |
| 3 | 0.008 |
| 4 | 0.014 |
| 5 | 0.021 |
| 6 | 0.030 |
| 7 | 0.039 |
| 8 | 0.051 |
| 9 | 0.063 |
| 10 | 0.077 |
| 11 | 0.093 |
| 12 | 0.110 |
| 13 | 0.128 |
| 14 | 0.148 |
| 15 | 0.169 |
| 16 | 0.192 |
| 17 | 0.216 |
| 17.8 | 0.242 |
Starting from the inside