Spark Gap Tesla coil not working

[chingyg]

Hey:

I recently decided to build a spark gap Tesla for the weekend, how ever i have encountered some difficulties.

It is powered by a 555 timer flyback driver, the output of the fly back charges a round abt 10nF homemade cap from tin foil and transparency sheets. The spark gap is 5mm and the primary has 10 turns.

The secondary has 250turns and is 300mm tail with a diameter of 22mm. The topload is a 15mm sphere.

Calculations shows the system should oscillate at about 6MHz.

When turned on the spark gap fires violently and very loud. the primary cap also makes an audible noise. However the secondary wont even arc to RF ground

What could be wrong with the setup?

Thanks in advance.

 

[BrownOut]

Show your calculations. A picture would help, as the physical arrangement is crutial to Tesla coils. Also, it would help to know what the actual frequency of your secondary is. You'll have to measure it with a signal generator ( another 555 project )

I'm not a Tesla Coil expert. I only know the basic principles involved, but I'll try to help.

 

[chingyg]

i used the calculators on this site DeepFriedNeon - Tesla Coils
Will get a picture soon.

 

[BrownOut]

I wanted to see how you arrived at your frequency. Linking the site with a bunch of inductance calculators doens't help. Oh well, maybe someone else has the time to figure it out.

 

[chingyg]

the top load has a capacitance of 2.8pF (50mm sphere)
The secondary is 300mm long, 22mm wide and has 250 turns
using the formula for air core inductor the inductance is 100uH
and the self capacitance is 2pF

using the LC formula the resonate frequency is about 6.5MHz