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Giant Jacob's Ladder Project Answered


Many, a many moon, ago I found an old Popular Science Magazine that detailed how to make one --it was an old issue! Any ways, about 13 years ago when the builder's for our neighborhood left, I took the flag poles from the front office with the intent of making an enormous Jacob's Ladder.

Well, cleaning out some brush I found them again and want to make it again.

I am sure the transformer will have to be huge but I am willing to go forth on this project. Does anyone here have any experience on making a giant one?


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Well, I was hoping someone would have had actually built a larger one. As, when one increases anything in scale certain obstacles are met. Very rarely is anything ever linear.

No, in the limit linearity breaks down, but plenty of phenomena are linear. In this case breakdown field strength, which is admittedly a function of geometry of the electrodes is linear with voltage. Big poles, big gaps, huge voltages. Its inevitable

So, Would the correct equation to calculate the power required for the spark gap be: P = ( L / 1.7)^2 With L being the length. So, for a 5' (60") spark I would need 1245 watts, about 83ma at 15KV.

No way. Free breakdown of air takes (liberal estimate)~25kV per inch, so 60 ", 1.5 million volts, or more than 3 in dry air, with polishes circular electrodes ! That power figure probably assumes ionisation in the channel is complete. Steve

Now we're talking! Some helpful info here. 1.5 to 3 million is a lot. I will have to email the authors of some sites that I have seen. A standard transformer is out of the question at this voltage level. Hee! Even better!

Hrmm... so, you think I can take a small one or the design I saw on here with the copper tubing, and just maintain the proportions, and go big? That's be great!

Absolute gaps drive these things to begin with, once the gap is fully ionised, and is conducting well, its different, but you have to strike the arc to begin with.

How big is "giant"? How long are these poles?

They are about 20' tall on the short side. Possibly 25' end to end.