The doorknob capacitors you need must be "high energy" or "pulse rated" - these use a low dissipation dielectric and thicker metalization system that make them capable of handling repetitive high-current oscillatory energy pulses. Standard DC, or "filter" capacitors, will not survive for very long in this circuit. You may need to connect several in parallel so that they can handle the heavy tank current in the hairpin circuit. These capacitors are often found as surplus parts (often removed from pulsed lasers) on eBay for more reasonable prices. They are typically made by MuRata (N4700 series) or TDK (UHV or FHV series). Here are some examples that are currently available on eBay:
: Thanks for your very informative reply! I looked at the book you
: mentioned. I don't have that one. I only have, "Tesla's experiments
: with Alternate Currents of High Potential and High Frequency,"
: "Tesla The Lost Inventions," and Tesla coil Secrets." None
: of these make any specific mention of the hairpin device, but I have seen
: enough to understand the concept.
: I am currently trying to source these *doorknob* capacitors. The closest I
: have found from a local supplier is referred to as a multi-layer ceramic
: capacitor. These have voltage ratings from 15kv up to 50kv, but cost over
: $AU100 each!
: I will let you of any experiment results. I have always been hampered by
: the lack of availability of these high voltage caps. I know I could have
: attempted constructing some myself, but have not had the time or access to
: a vacuum pump to get al lthe air out of them.
: Anyhow, thanks again for your reply.
: Beers and cheers,
: --Previous Message--
: Hi Geoff,
: Tesla's Hairpin is described in chapter 28 of Thomas Commerford Martin's
: book, "The Inventions, Researches and Writings of Nikola Tesla, with
: Special Reference to his Work in Polyphase Currents and High Potential
: Lighting". In the "Impedance Phenomena" section (pages 338
: - 340). You probably already have this book in your personal library, but
: if not, you can download a copy in various formats from the Internet
: Archive site: <a href="http://archive.org/details/inventionsresear00martiala">http://archive.org/details/inventionsresear00martiala</a>
: Tesla's hairpin is actually a 3/4 turn rectangular inductor with two long
: sides and one short side at the far end. Tesla then connected a pair of HV
: capacitors, one to each end, of the inductor. The opposite ends of the HV
: capacitors were connected to a HV source and a spark gap - similar to a
: classic Tesla Coil "balanced" primary circuit. Each time the gap
: fired, the LC circuit formed by the inductor and caps would ring at their
: characteristic frequency. The RF voltage across any two points between the
: parallel wires would range from 0 (at the far end) to the peak supply
: voltage at the near end. You can easily duplicate Tesla's experiment by
: using a pair 1/2" copper pipes and fittings. Here's is an example of
: the inductive loop and spark gap built by one researcher:
: <a href="http://imageshack.us/photo/my-images/684/cimg2885p.jpg/">http://imageshack.us/photo/my-images/684/cimg2885p.jpg/</a>
: You can use pulse-rated 30 - 40 kV ceramic doorknob caps in series with
: the lines to form the LC circuit.
: BTW, you may find that Tesla's hairpin is sometimes described as being the
: same as Lecher lines. In reality, the two are actually quite different.
: Tesla's hairpin simply demonstrates the effects of inductive impedance at
: comparatively low RF frequencies (typically 100's of kHz - 10 MHz), and
: the effects do not require a stable frequency source or precise tuning. An
: example (from a "free energy" researcher) can be viewed here.
: Just short-circuit the far end of the line instead of leaving it open.
: Lecher lines (see <a href="http://en.wikipedia.org/wiki/Lecher_lines">http://en.wikipedia.org/wiki/Lecher_lines</a> ) are
: actually balanced transmission lines that are driven at much higher
: frequencies (100's - 1000's of MHz), usually from CW sources. The far end
: of the lines can either be open or short circuited. Sometimes a sliding
: short circuit may be used to "tune" the lines to a given
: frequency or to measure an unknown frequency. When excited from a
: UHF/microwave source, standing waves form one (or more) nodes and
: antinodes at various points along the lines.
: BTW, neither Tesla's hairpin OR Lecher lines require invoking
: "radiant energy", "longitudinal waves", or
: "scalar waves". The high frequency phenomena demonstrate simple
: physics of inductive reactance (Tesla's hairpin) or simple transmission
: line reflection and standing waves (Lecher lines).
: Please let me know the results of your experiments.
: I hope this helped and best wishes,
: --Previous Message--
: G'day Bert,
: Recently I have been reading about a thing called the Tesla hairpin
: circuit, or the stout copper bars arrangement. I have never heard of this
: before in over twenty years of Tesla research and *fiddling*.
: Best I can find is something to do with radiant energy and, it would seem,
: a short form of wireless power transmission.
: Have you heard of this description, and if so can you direct me to simple
: plans and explanation of the concept.
: Beers and cheers,