The final bits.

Hi. This must be the last job on my Tesla Coil build. I need to make an earthing point on the main Tesla coil body. Most of the earth leads in my Tesla are connected to the earthing point on the neon transformer. These are

1. Connection to the strike rail underneath the primary coil perspex covering disc.
2. Connection to the lower terminal on the secondary coil.
3. Connection to the central rail on the Terry filter.

So I need to connect this point to my earthing plate on the conservatory wall. I could just run a wire from the earth plate through one of the vent holes in the Tesla base to the earth terminal on the neon transformer. The problem with this solution is that it would be impossible to remove this lead as the ring terminal needed on the end of the wire will not pass through the vent hole. Even if I enlarge the vent hole it would still involve removing one of the perspex walls of the base unit to attach/detach this wire.

After some thought I decided to fit an earthing point on the outside of the back perspex wall of the main Tesla unit. This would consist of 2 copper terminal lugs, one mounted inside, one mounted outside, connected through the perspex by a M6 bolt.

Above is the hardware for the terminal, I will probably replace the stainless M6 bolt with a homemade copper stud but will need to procure an M6 die first.

I made a small lead that finishes in a ring terminal to connect to the new earth point. I fitted the lead to give me a better idea where to site the hole for the terminal.

Marked up the point to drill the 6mm hole. I drilled the hole freehand, there were no obstructions and it was pretty easy to keep the drill at right angles to the perspex.

Result was a nice neat 6mm hole. My OCD placed it on the centre with the vent holes and level with the end of the neon transformer.

Here's the hardware fitted. I used 2 of the copper lugs from Alan at teslastuff.com. These are the best quality electrical lugs I have seen.

The terminal was connected to the short lead from the neon transformer earth point and the perspex sidewall replaced. Job done.

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Winding the Secondary Coil for the second time.

The new secondary coil form has been sat in my homemade coil winder for long enough. It's time to start winding.

In my last post I gave the new stats for the replacement coil. The only change I have made is to start the windings 4.5cm from the base of the coil rather than 4.0cm. This change is just to allow a little extra room at the base of the coil to accomodate the copper plate that will act as the lower electrical connection. This will mean with the same number of turns (1050) the windings will finish 0.5cm higher, 8.3cm from the top of the coil.
 Before starting the winding I thoroughly cleaned the outside of the coil with meths to remove all traces of grease. I ran a line of masking tape around the coil with the top edge of the tape exactly 4.5cm from the base of the form. This would ensure that the windings would start exactly level with the base of the form. I measured 67.2cm (total height of windings required) from the top edge of the tape and marked this point on the form with a small pen dot. I would coil tightly up to this point then loose coil to the top of the form.
Well almost ready to start. Not quite. This time there's no help available..... and believe me, its better to have an extra pair of hands when winding a coil especially if you are relying on human resources to tension the feed wire and direct the winding wire onto the coil. Manual winding requires both hands, one to feed the wire (left in my case) and the other hand to push the coils together either with a non scratch implement or the back of your finger nail. This means you have no free hands if you need to stop (or start) the winding motor. My winding motor is powered by a variable power supply on the bench the winding jig, not exactly "to hand". I would need some way to switch it on/off remotely.
Bingo. Idea.

I plugged the power supply into one off those remote control mains switches. This one is a cheap as chips version from Maplin similar to the one linked.

Here's the little controller. I can either have it close to hand or even put it on the floor and press the off button with a press of a toe.

The winding wire end was clamped under the head of one of the white plastic bolts that holds the base coil end in place. You need to have a plan in place to clamp the wire end tight when you finish the windings, I decided to clamp it with the same method as the start, using one of the bolts that holds the top coil end in place.

Time to turn.

Well it took about an hour and went pretty well. Stopped just once when I realised I had left the door open. Two kittens and turning a tesla secondary coil are not compatible. Here's a quick vid of the finished coil. I have put on a couple of coats of insulating varnish. Still needs another couple of coats.

I am really happy with the finish. The varnish has a better finish than on my first coil. Next up is a few more coats and then fitting the copper plate electrical connection at the base of the coil.

If you like this blog you can show your support by one or all of these. 1. +1 my blog and email it to a friend. 2. Follow me.... It's good to know someones interested. 3. Leave a comment.... All are appreciated.

Starting on the Primary Coil

Spent the last few weeks decorating the lounge, those of you who have followed my blog may have spotted the rather flowery decor in some of the pics, for this I apologize but can now confirm that the decor is a little more up to date. Now onto the primary. As per the original plans from Tesslastuff.com I acquired a fifty foot length of 1/4' copper tubing. This can be sourced from many places, I picked a well priced listing on ebay from a seller with a healthy feedback score.

I have spent a long time deciding on the final design of the primary coil, the plans from Tesslastuff.com give you the basic idea and all the correct measurements but, as usual, I wanted to enhance the design with my over engineering. After reading several blogs and coil build diaries there seemed to be two ways to help prevent primary coil strikes (streamers hitting the primary coil- not good). Firstly to fit a ground rail around the primary and secondly to completely cover the primary with a non-conductor. So I decided to do both.

Above is my solution to covering the primary coil. It's a 5mm thick perspex disc with an external diameter of 900mm and an internal diameter of 170mm. The cut-out allows the secondary coil to pass through and as this disc is prominent I want it to be aesthetically pleasing so paid extra for the inside and outside edges to be polished. Here's another pic to give you an idea of the disc size next to the tesla base (room still with old decor).

I would also need some way of supporting the copper tube spiral of the primary. Most people used strips of plastic with evenly spaced cut-outs with accepted the coils of the primary. The coils were secured with glue or by zip ties. I didn't like the idea of glue cos of it's general messiness which doesn't go well when combined with lovely clear perspex. The other option of zip ties just didn't look that good. The best looking install I saw was to use nothing to hold the coils in place. The coil passes through holes drilled in the supports, very neat but a lot harder to achieve. I ordered the material needed for the supports.

These were 8 pieces of 250mm X 30mm X 10mm clear perspex with the top and bottom edges polished.

Second Thoughts

After deciding to upgrade to a 6" secondary coil I got on the phone to Trent Plastics to order the relevant pieces of perspex. These consisted of a 810mm length of 150mm diameter clear acrylic with a 3mm thick wall and two 144mm diameter 15mm thick clear acrylic discs which will be inserted inside the ends of large tube and form the top and base of the secondary coil. I normally deal with a guy called Levi who is always on the ball, I was a little concerned that the discs would not be a good fit inside the 150mm tube due to variations in wall thickness that occurs in extruded acrylic tube so I asked Levi to check the fit of these discs inside the large tube. Three days later and a long cardboard covered tube turned up. I checked the fit of the discs and they were a perfect close push fit inside the large tube.

The above pic shows the 150mm diameter tube, it still has the protective plastic film and I have added masking tape so I can mark the position of the 8 4mm holes that will accept the M4 nylon bolts to locate the top and bottom perspex end caps.

Here are the 2 end caps. They are sitting on a 12mm thick 500mm clear acylic disc which will be the base for the primary coil. The disc on the left is for the bottom of the secondary coil and will be secured to the primary coil base by 8 M8 40mm Nylon bolts. You can see I have already marked the disc for drilling.

The holes need to be drilled to 6.8mm and then tapped for the M8 bolts. This means the bolts will be captive in the secondary coil base which is needed as there will be no access to the bolt heads once the secondary coil is assembled.

Assembled so you get the idea.

The base disc will attach to the secondary coil tube by 8 X 20mm M4 nylon bolts which will be located equidistant around the circumference at a height of 7.5mm.

Starting to get worryingly large!!

First layer plastic surgery

Spent a couple of hours in the garage drilling the various mounting holes in the base. 4 X 6mm holes for the neon transformer and 16 X 4mm holes for the Terry filter, the emf filter and the mains connector module.

Another 12 X 4mm holes were needed to mount the 10x10mm perspex square rod that runs around the perimeter of the base.

These 10x10mm perspex rods provide a means to screw the side panels onto the base.

Looks a bit like ORAC

I have decided to enclose the whole assembly with clear 10mm perspex. Maybe this may help prevent strikes but mainly I just think it will look good. I will have to sort out some ventilation, perhaps a fan mounted in one of the perspex walls, not sure yet. For those of you who remember Blakes 7, I can't help thinking about ORAC as I envisage the finished enclosure.

I am using 10mm square rod as seams on the inside of the side walls which allows me to bolt the box together rather than glueing.

Our glass dinning table made a great flat surface to align the side panels.

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Multi Mini Capacitor MMC

Today I started on the MMC (multi mini capacitor). The capacitors had arrived from Teslastuff.com a few weeks earlier. The MMC is built up of 40 capacitors, 2 banks of 20 caps in series connected in parallel. Each capacitor is rated at 0.15uf at 2000v as per the original Teslastuff plans.






A bag of 20 capacitors for the first layer of the MMC. This layer would be mounted on a 8mm thick 320mm by 220mm clear perspex board.







The board was covered in masking tape and marked out for drilling.I drilled 1.75mm holes for the cap legs (40 in total), some 4mm holes for mounting onto 1" ceramic stand-offs and 2 6mm holes for the copper lugs. After marking out I attached an identical piece of perspex to the back so I could drill both layers at the same time.







After drilling I mounted the 20 caps to the first level. I twisted the adjacent caps legs together and then laid the bleed capacitors across each cap before soldering.







Also soldered in some copper wire to create the series links between the rows and a couple of terminal loops on the ends.







Above is the first layer completed. The 5 support uprights are 12mm diameter perspex drilled and tapped to accept 4mm bolts. Now for the second layer.






The finished article.






Very pleased with the end result.






Will also be easy to add more layers in the future.






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Terry Filter finished

More brass bolts arrived today plus another parcel from Teslastuff.com






I had been looking for some copper or brass electrical lugs for ages. I wanted some that looked a little vintage, similar to the ones used by Alan at Teslastuff in his Tesla coil plans. I didn't have any success and they weren't for sale on Teslastuff.com so I emailed Alan who replied "How many you want?" I ordered plenty as I'm sure I will use more throughout the rest of the build and the price from Alan was very reasonable.






I used five of the lugs and replaced the 2 nylon bolts through the outside safety gap insulators with brass bolts. Also completed the wiring, think you will agree, the finished filter looks amazing.

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Terry Filter comes together

Covered the 200mm x 320mm x 5mm black acrylic Terry Filter base with a coating of masking tape which will protect against scratching while drilling and allows me to mark up all the holes. After a trial placing of all the Terry Filter components the board was marked for drilling.



The main pcb and the 2 long resistors will be mounted on 1" high ceramic stand offs which require 4mm holes. The completed Terry Filter module will also be mounted on 1" stand offs, 6 in total. With the board marked up I watched the pretty uneventful start of the British grandprix then made my way out to the garage to drill out the holes.



The board was placed on a flat piece of ply offcut for drilling which prevents the drill bit from damaging the back of the acrylic as it emerges.



When drilling lots of varying size holes I find it useful to mark hole diameters on the work. After drilling the masking tape was removed to reveal a pristine piece of black acrylic with clean tidy mounting holes hopefully in the right places.



First trial fit of the components goes well, all holes line up nicely.



Still waiting for some brass bolts and copper lugs to enable the final assembly.



The safety gap ceramic posts are held in place by 65mm nylon bolts that screw through the base and up into threads in the brass balls. I may change to using metal bolts as the nylon bolts flex and do not hold the safety gap assembly as firm as I would like.



Next job is to make the electrical connectors between the pcb, resistors and terminal posts.



Think it turned out pretty good.

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Terry Filter Safety Gap

Today I picked up a parcel from the local Royal Mail depot. Inside was four long awaited 60mm bolts (should have been 8), least I can make a start on the safety gap. First I need to tap 2 holes through the 2 1" brass balls obtained from Teslastuff.com. The holes need to be 5mm which is the size required if tapping out to M6 with 1.0mm threads. The pic below shows how I mounted them for drilling.









I screwed in the bolt to the existing tapped hole to help me drill at 90 degrees to the existing hole. The bolt also prevented the brass ball spinning in the chuck jaws during drilling. It was easy to find the centre point for drilling as I could spin the work in the chuck to show any mis-alignment. After drilling with the centre drill I drilled a 5mm hole completely through each ball.









Next I tapped the holes out to M6 1.0mm threads. Note the plastic jaw covers on the vice to prevent marking my balls!!!









I then polished my balls by mounting them onto a threaded stud held in the chuck and spinning them up against various grades of emery cloth.









The finished articles almost ready to mount on ceramic insulators on the Terry Filter.









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