Re: Information Unlimited BTC30 coil

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Mike <megavolts61@xxxxxxxxx>

I'm not sure you'd wish to use fewer turns for this, but simply 
replace their 'hybrid' primary with some 1/4 inch copper 
tubing....there's many ways in which to create separators to keep the 
spacing right.....  I just looked at the specs and wonder why anyone 
would spend $400 to build such a small coil.   Go to a sign shop and 
get a used 15/30 NST (I got about 10 once just cuz I told them I was 
teaching some science to kids hehe).  They cannot reuse the ones when 
they replace a sign by code, so they accumulate a lot of them.   They 
seemed happy to get rid of them.   The wire to build such a secondary 
for this BCT30 coil can't cost over about $20.   The caps....buy the 
geek group ones and make your own...spark gap...get some tungsten 
welding rods and cut them.....I've copper plated tungsten using cheap 
copper sulfate and a dash of battery acid, then soldered them to 
copper tubing...If you are clever enough...you just built this $400 
coil for about $100...or LESS.  Oh, and that optional  8" by 
2"  toroid....I'd suggest the aluminum heat riser tubing from an auto 
parts store.
Mike (the king of scrounging and dumpster diving).
original poster: jhowson4@xxxxxxxxxxx

We are building the BTC30 coil during physics class at school.  I was
wondering if there was any way to make it better.  I also read some
where that it had a run time of about 45 seconds is that true.
i was going to re-make the primary coil on it so i could tap it at a
lower turn which i can't do now because of the way it is made.  I am
not sure on how to go about calculating the inductance since it is a
weird primary design.