Global Scale Modeller

As mentioned in another post viewtopic.php?f=43&t=21953&start=20#p273662, I made a false statement about my first model. Unintentionally of course. In fact, the bridge model is my second. My first, 26 years ago, was a working, scratch build, Tesla Coil (TC) which Nikola Tesla built in Colorado Springs in 1899.

I decided to build it because much of his experiments in the transmission of electrical power came from this type of coil. I wanted to reproduce his findings, but at a much smaller scale (1/10).
For more information, about the Colorado Springs TC, visit this link https://teslaresearch.jimdo.com/colorad ... 1899-1900/

I no longer have the TC. It was lost in storage from a house fire. However I did have some photographs of the model. Though I still have some of my experimental notes, vital photographs of it working were stolen. This coil was my fifth Tesla Coil. Altogether I built nine variations. Seven were given away, and two were lost (one by fire, and one by misadventure). The following photographs shows the construction of the coil, and some of the equipment (mostly homemade) needed to run it.

Here is the original coil by Nikola Tesla. I bought a copy of his notebook of that period, and the basic measurements of the coil were in it.
The smaller coils within the larger primary coil (fence looking ring) are basically test pick-up coils, put on show for the photograph. they are not part of the actual TC.


To be continued.

I think it would be best to briefly explain how a Tesla Coil (TC) works. It is basically a step-up transformer. That is, a small voltage goes in and a large voltage comes out. However electricity has two major components - voltage and amperage. Since we cannot get something for nothing, and increase of voltage means a decrease in amperage. A good example of a Tesla coil can be found in any car which uses an induction coil for producing spark for ignition. Here 12 volts, from battery goes in and about 10-30 thousand volts come out.

For those interested in the circuit I used:


From the above key, you should be able to identify which piece of equipment fits into the circuit diagram.
TOP: My first Tesla Coil (but not the model I made for this thread).
CENTRE L-R: C1 and C2 (leyden Jar Capacitors); RSP (Rotary Spark Gap)
BOTTOM L-R: NTS and NTp (Neon Transformer (240 VAC to 15,000 VAC)); KS and fuses.


Another view


For the curious, the Rotary Spark Gap is purely for safety reasons. What it does is chop the voltage into pulses of high frequency (2,400 pulses per second).
How is this possible? The balanced disc has 16 blades, rotates at 3,000 rpm, and passes three contacts per revolution. That is (3,000 x 16 x 3)/60 sec = 2400 pulses.
The safety part? The human body's nervous system cannot respond to electricity pulsing faster than 2,000 pulses per sec.

Two more photos. Here I am checking the wiring before initial test of my first TC. The next is a picture of it working later that night.


What you actually see is a single arc, but time exposure captures many arcs or pulses. The gap here is about 500 mm. That is, about 500,000 volts, because it is estimated that 1 mm of arc, in the air, is equivalent to about 1,000 volts.


Next, the scale model...

Having trouble uploading pictures to Photobucket. Will continue later.

The original outer coil was 50 feet in diameter, so the model was 5 feet.
Here is the coil former, made from timber. No metal screws used. All put together by dowels. The outer wall of the ring is thin veneer.


Below, I used matchsticks to keep the wire spacing regular.
Here I am about to wind the primary coil of two turns. Above the primary shows the many turns of single wire for half of the secondary coil. The other half is on a smaller coil former shown below.




The smaller secondary coil. This is placed in the centre of the whole TC structure.


This view shows the TC at near completion.




Unfortunately I have no other photographs of the model. However, here is a page scanned from my note book describing my last experiments with this coil. The results were devastating to the coil, because once it starts leaking (insulation shortages) not much can be done about it unless one rebuilds it. But I did learn a great deal from this model. It worked as Tesla described in his own experiments.


Hope this was an interesting sidestep of scale modelling.

Fascinating! Thanks for sharing.

Your notes at the end add a "mad scientist" quality like Frankenstein's diary.

Hi Rob. Thanks for your response. Come to think of it, it does sound a bit mad.