TCBA founder, Harry Goldman and the TCBA logo

TCBA - Tesla Coil Builders Association

Devoted to the construction, operation and theoretical analysis of the Tesla coil

TCBA Volume 10 - Issue 1

Page 7 of 18

Input - Output

Q. John H. Couture's letter (Volume (9,#2) stated that “Grounding of the secondary is no guarantee of freedom from 60 Hz shocks...There is a possibility of a spark jumping from the primary to the secondary. This would produce a dangerously high 60 Hz current in the secondary.” As you know, an Oudin secondary is directly connected to the primary. Does this mean that an Oudin coil is unsafe?

A. All electrical devices, whether high voltage or not, should be considered unsafe. Mr. Couture's advice regarding the danger of coming in contact with an energized secondary should not be dismissed. It is my opinion, however, that a properly grounded secondary (Tesla or Oudin) presents an opposition to the flow of 60 Hz currents. This, I believe, is due to the high impedance present in the secondary coil.

The dangers that are present when in contact with a high frequency coil secondary, even if properly grounded, depends upon upon a number of factors. Under no circumstances should a person in contact with an energized secondary touch or even approach the primary coil or a grounded object. And one should not make a habit of taking a discharge from a high power Tesla coil secondary as the charge density may be large enough to be painful. OK, so you've seen the pros do it. However, even the pros have been known to make fatal mistakes. The last thing I want to read about in the morning newspaper is of a TCBA member going to that “Great Laboratory in the Sky.” Tesla and Oudin coils are far from harmless. A careless move while handling a coil of sufficient power can result in a painful, if not fatal, shock. I speak from experience. Ask me about it sometime.

Q. How does one properly ground the secondary of an Oudin coil?

A. The procedure I have always used is to ground the point where the upper turn of the primary connects to the lower turn of the secondary coil.

Q. I have come across an amazing discovery that should be of interest to all TCBA members. A report by W. Morris Jones [PHILOSOPHICAL MAGAZINE, London, January, 1916, pp. 62-65] shows that the best primary capacitance for Tesla coils is about twice the value indicated by the equation L1C1 = L2C2. His paper “On the Most Efficient Primary Capacity for Tesla Coils” supported the findings of Taylor Jones (no relation) in the book THEORY OF THE INDUCTION COIL. Why hasn't anyone mentioned this or applied this valuable data to their coils?

A. I can understand your excitement. The information raised the hair on the back of my head when I first came across it a number of years ago. After reading the papers of Jim and Ken Corum and from conversations with Leland Anderson, it appeared that the papers by W. Morris Jones and Taylor Jones had a serious flaw. I'll address your question by referring to the paper by W. Morris Jones.

The weak part of the experiment can be found in the spark gap. Jones used a single fixed gap set at 1 mm. Although he varied other parameters of the circuit, the fixed gap remained at 1 mm. At this setting, quenching became impossible. Energy continued to flow from the secondary back into the primary. The only way to resolve the problem was to increase the size of the capacitor. Quenching took place when the capacitance was twice the indicated value. As far as I know, maximum potential takes place at critical coupling when the product of the primary circuit equals the product of the secondary circuit. Jones might have come to that same conclusion had he used an efficient and properly set gap.

Q. Mention was made regarding a “Railroad Rife” in a recent issue. The man's true name is Royal Raymond Rife. He made use of a high voltage/high frequency machine that changed the course of diseases. A “Royal R. Rife Report” is available from Borderland Sciences. There is another article on him that is available from Rex Research.

A. TCBA NEWS dedicated Volume 8, #4 to Royal R. Rife. Several publications came out with a similar report after it appeared in TCBA NEWS.

Q. Have you ever found a reference to Nikola Tesla in SCIENTIFIC AMERICAN? I have a complete set from 1/73 and have seen numerous references to Edison. But all references to alternating current systems never lay credit to Tesla. Why is this publication so seemingly biased?

A. Welcome to the “Mystified Order of Tesla Fans.” You might consider writing a letter to the editor and see what kind of a response you get. Keep us informed.

Q. I checked out that photo of the Steinmetz generator and wonder if you have received any input as to why the discharge followed a straight line rather than the natural wavering of a high voltage spark?

A. TCBA has received no input regarding this discussion but I know that it was often a practice in those days to use a length of nichrome wire between the poles or from pole to ground. This trick enhanced the brightness of the spark and made it easier to photograph. I don't know if Steinmetz used this procedure.