Well here we go with the build of the replacement secondary coil. Rather than jump straight in and build an identical secondary with thicker gauge wire and hence less turns I decided to do a little more homework on secondary coil designs. One thing had always concerned me with the design of the first secondary I built. This was the termination of the ends of the coil inside the secondary form. The top and bottom copper tails pass through small holes drilled in the wall of the secondary form and make electrical connection through the top and bottom end caps.
The pic above shows the top electrical connection on the old secondary coil. You can see the copper tail clamped into the lug underneath the perspex cap. A very neat set-up but nearly every knowledgeable Tesla site I have seen strongly advises against this. The only one who seems to prefer this method is Alan at
teslastuff.com who has had great success with this design. My final decision on the design of the new coil was strongly influenced by a page at
www.capturedlightning.org. Stefan really seems to know his stuff when it comes to design and build of secondary coils so I decided to proceed using many of his recommendations.
The overall length and diameter of the new coil form was the same and again it would be made from 150mm diameter 3mm thick clear acrylic tubing with top and bottom caps in 15mm thick clear acrylic. The new secondary will mount to the existing 8 mount holes in the tesla base unit so the secondary base cap is an exact copy of the original. If you want to see the original post showing construction of this you can find it
here.
The pic above shows the new secondary coil form with the top and bottom caps in place.
Here is a close-up of the bottom cap of the secondary showing the 8 nylon bolts that pass through mounting holes in the primary coil support disc. The central hole is 10mm in dameter and will only be used to thread the whole form onto my winding jig. After winding the hole will be permanently sealed by a turned acrylic peg turned (very successfully) on my lathe.
The peg is a really close fit and the flat area will provide a good surface to be bonded with Tensol 12.
Above you can see a trail fit of the peg. Obviously it will be fitted on top of the base cap. The coil form is now ready to wound on the winding jig. However, not tonight, time for a quick spin in the new RCZ. Spot the new wheels.
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