a HOW-TO from a newbie to a newbie
A lovely girl (BellaDonna) asked me some time ago to assist her in building a TC like my vitamini. She had a very good understanding and a strong will to design things on her own without understanding to much of the math and physics involved ;-) But she decided to bite through the matter and become a professional in building Tesla coils and so I assisted her via email. A good way to learn where my website lacks on information especially for beginners! We both learned and had a good time. Now she has her own website at Terry's hot-streamer server.
Secondary coil construction:
Seeing as this is my first attempt at winding a secondary coil I thought
it best to practice on something smaller, so of to the kitchen where I found
a small tubalar asprin container, that will do nicely I thought. Back in
my room I looked dispairingly at the bobbin of 0.2mm wire, and with faint
heart plus glasses I started to wind. It soon became apparent that even with
glasses this would be no easy task. Infact it was impossible to get a tight
wind with zero space. OK I know my eyesight isnt 10:10 but seeing that I
dont posess 4 hands, things were just not going right. So time to think on
the problem at hand, lets see
OK lets tackle number one, back to the kitchen, for nibble whilst I think. H'm choc-ice be nice, 10seconds each side then 6 to finish, in microwave. Watchin me choc-ice revolve around in the microwave it occured to me that No.1 may have been sorted. Quick phone call to a microwave oven repair shop confirmed that. Dash out, rush back and in my hand 2 small 240v AC 5/20 rpm motors and at no charge, such a nice guy. One problem sorted, and a new one found, need something to mount this on. More thinking time and a cup of caffine.....
So my first coil is kinda small, but hopefully the 2nd will be larger, with that in mind I rummage in the garage for bits of wood. H'm nice covered chipboard, 6" wide 6ft long and another piece 2" wide 6ft long, that will do nicely. So assuming chippy mode I measure out 3ft on the 6" wide stuff and 2 3ft on the 2" wide stuff. Next I glue/screw the 2" to either side of the 6" forming a long 'U' shape. Next I cut 2 8" lengths from the 6" bit and fasten one to the end of my 'U'. The other is a tight fit in the middle of the 'U' section. Then I mount the motor with on/off switch to the fixed section and drill a small hole in the other section so that it aligns up with the centre of the motor shaft. You'll see why shortly :)
Next problem is coupling the motor shaft to the coil former, so thinks time again.... Fumbling around I came across some co-ax shrouds that fit on BNC plugs giving you cable support, ok u might not have them so a piece of tube suitable size would do just as well. Next I get a gland (type used in electrical cabinets), (or cut down the neck of a plastic bottle) you got to improvise here :) Object being is to find something that 'a' will fit inside the former and 'b' will connect to the motor shaft.
With these 2 parts I push the shroud thru the hole and onto the motor shaft, then slide onto the shroud the plastic gland. Grabbing the coil former I notice one end sealed, into this I make a small hole, pin size, (to be sealed later) and push a needle into it, the other end fits in the movable bit of wood, then slide the open end onto the gland and he presto its support and turns at a constant rate. One good thing is because they are all push fits, they act as a slipping clutch, so they wont stress the wire if I hold it to tight.
Prob 1 sorted :)
No2. Looking around again I find a small card index plastic box about 6x4x4" removing the lid I drill a hole .5" in each side center 1" from the top. next a cut up a bit of dowl (or cane) 8" long and on each end .25" in drill a small hole. Taking the bobbin I hold it in the box and push the dowl thru one hole, thru the bobbin and then the other hole, next 2 paper clips pushed in the little holes of the dowl secure it in postion. Now the bobbin spins easily, too easy in fact, we need friction, another rummage finds some foam rubber cut to side and pushed infront of the bobin provides enough friction to hold the bobbin steady, Prob 2. sorted.
Prob 3 is no real problem, I have a desk top magnifier :)
Waddling back to my room I commence to set up my new toys, the former turns nicely all be it slow at 5rpm but for first time I'll stick with this speed. Taping the wire to one end and using finger and thumb to guide it I commence to 'coil'. Disaster, the wire is so small I seem to have problems getting a tight winding, Did notice one thing, if u switch the motor on/off/on fast it reverses its direction, nice for going back. And the friction on the bobbin prevents the wire loosing when u switch motor off. Another search revels a small piece of fibre glass board about 2mm thick (cardboard would do just as well). With this I fire up the motor once again, only this time I gentle tap the wire on the former to get a tight wind. I found that guiding the wire about 1-2 degrees from verticle allows me great control and the tapping stick gently nudges it into place, also you dont have to worry if u miss a bit as you can get it on the next revolution. Only one thing I need now, well two actually, caffine and music :) then of we go....... easy peasy :)
ps btw I dropped of a bottle of scotch at the microwave shop, now he's a happy chappy.... :)
back to top of page (TOC)
In this instance I must admit to having no knowledge on building one of these so I took the liberty of following my very good friend Stefan. His instructions and concepts certainly are worth bearing in mind and I find his webby one of the most informative and concise pages on the net.
As in all things I tried to follow the instructions but found that given sizes over here (UK) don't always agree with the author's location so its time to improvise. Don't you just love that word :) This is where you put into the project a little bit of yourself.
Now I am lucky in one respect in that the place I work as available a wide range of talents and skills and always on the look out, I made the most of these. However there is know reason why one could not achieve the same success by doing this alone..
OK, start time. I visited a pipe engineer and asked him for a off cut off 6" dia pipe. He handed me a 8ft length of 160mm saying will this do.. <cough> I only want 5" I replied. Anyway orf I toddle with me pipe. You don't half get some funny looks round here. Next stop was the chippy, smiling sweetly I ask if he can cut this pipe into 2 x 5" lengths and 1 4ft length (always thinking ahead, MKII). Thankfully he obliges, so I return the unused portion. Next port of call is the coil shop, in there I ask for 15" of 2" diameter copper pipe, alas they only have 42mm, (do wish they'd keep to english), Thanking them, I again head for my next port. The tool maker, he's sweet, I ask him if he can cut the copper pipe into 2" sections and also square the edges on the PVC pipe, being a bit cheeky I also ask if he can drill 2 holes into each copper section 0.5" from each end.
Following day I collect my machined parts :) all polished and deburred. Cant wait to get home now :) Looking at the PVC pipe I see no problem in fitting the first tube section, this is to be positioned in the center of the PVC pipe wall, however, positioning the 2nd and 3rd etc. proves to be difficult. Quick revise on Stefans page, h'mm they have to be 0.028 apart, pipes 42mm dia, wall is approx 1mm, how do you calculate the distance apart on a curve??? After many hours I concede defeat on this one, so by girlspower I align the 2nd tube up, mark the hole position and drill two obrounds (there oval holes <g>) offering the 2nd tube in place along side the first one I proceed to set the gap at 0.028. Now to save face I use a compass to set the distance between each centre bolt then rotate 180deg on a pre marked center line and it gives me the next hole position and with the obrounds I have a little to play with.... Each copper pipe is secured by 2 M5 brass bolts with star washers. There the little serrated ones :) These effectively locks the nuts in place (I hope). Isn't technology wonderful :)
So its back to Stefans page for more instructions, I will emphasise you cant ever read to much, after all there is no point in re-inventing the wheel. Now seeing I have 7 copper tubes fixed it seems I need to separate No1 and 7 by some insulating material. At hand I have mackrolon but I guess any perspex type would do. This is secured in place with araldite (2 part epoxy resin). I seem to remember reading about air flow, quick recap..... Back to the pipe place and I again ask for a 50-60mm off cut. this time I get a 6ft length. Not wanting to appear cheeky I decide to cut this myself. Now the gap housing is 5" long and according to instructions (Stefans page) I need at least 3-4" at the bottom for air flow. So with this in mind I cut a 8" length. Next I need a way of mounting the gap 4" of the table.. Back to work <g> there I find some Plexiglas rod (wooden dowel would do), armed with this I head back to the tool man. There he cuts this down into 4x5" length and taps a hole (M3) 0.5" from one end into each one. These are then secured to the bottom part of the large PVC pipe 90deg spacing and provide the required distance from the table, (they also look kinda sexy as well). Next I place the 60mm pipe in the center and araldite it to the mackrolon spacer.
This is where I deviate slightly from instructions, I intend to mount my fan on the top, blowing down, and require as much air flow around the copper tubes as possible. so with this in mind I make a cone out of some thin clear plastic. This is glued to the top of the 60mm pipe and its apex is just under the center fan. I found that opening the fixing holes on the fan to M5 and using M5 self tapping screws it produces a tight secure fit on the 160mm pipe. Another rummage in the kitchen produces some tupper ware containers and by carefully cutting the lids along there edge in a curve shape produce a section that butts against the fan and outside edge of the 160mm PVC pipe. These are held in place by my trusty araldite. Only thing left is to tidy the mains/fan lead and secure it with some adhesive cable tie bases, wallooo job complete.
back to top of page (TOC)
Primary coil construction:
I guess the first thing I had to decide was what shape and form should the fixed base take. One idea that appealed to me was to use a round breadboard, but since I didn't posses one and was reluctant to go and buy one, I had to think again. This time in the garage, so much junk in here I must be able to find something, and sure enough there it was in all its grandeur <g> Let me explain, a few years back I used to breed grass parakeets, in the garage are stored all the wooden nest boxes. One in particular was a nice size with a removable top about 11" square and 1" deep (the top that is, not the box, poor little birds would have to lay down <g>). So grabbing that lid I head for the sandpaper. After quick rub down and a coat of varnish it came up a treat. Fixing me ruler on diagonal corners I mark the center and drill a small hole.
The secondary former was the outer sleeve of the bit I'm holding and it could slide up and down on small ridges. So turning it so the top contacts the board was the intended way of fixing. Before fixing I need to make the former for the primary, seeing I had some makralon left over this was my first choice. I cut 6 of them at a size of 3"x3" to start with then decide to mark the top at a angle, so I measure 1" from the base at one end and intersect the opposite end/top, this gives a nice slope. Having made sure the edges are smooth and square I tape them all together. Next I use a bit of ally (from the garage) and cut to the same size as the others I mark along the slope 12 holes on a 0.2" pitch, then drill each hole 0.125". This is then used as a jig to drill the makrolon, so taping it to my bundle I commence drilling.. walla, formers made.
Next step is to mark the position on the base for the 6 formers, to be at 60deg. uhho, no protractor... h'mm.. Do have a compass though :) So I draw a 3" diameter circle from my center hole, then by trial and error I adjust the compass to give me 6 equally spaced positions on the circle edge. Didn't take to long and now I have my 60deg markers :)
Grabbing my former I proceed to drill a small hole in the base, insert nylon screw and penny washer and fasten this down to the base. For added support I use my trusty araldite around the base/former and a thick coat of varnish inside to seal it.
Next using the araldite again I place a small amount on the base of each former and fix them down on my 60deg markers with the shallow end pointing inwards and at a distance of approx., 0.2" from the secondary former edge. Although the araldite is a 5min strain, it normally takes 24hrs to cure fully, so time for a break, bbl :)
Day2: Next task is to feed 12 turns of my 1.5mm wire through the holes in the 6 formers. I found the easiest way was to unwind a suitable length from the bobbin and feed firstly through the outside hole on one former, then the next etc. until I had one turn. By using forefinger and thumb on each hand gently push/pull the wire through each vacant hole. Must admit the last too turns where reluctant to thread, but being stubborn I got there, remembering to leave sufficient tails at each end.
One job left to do, the safety ring. Thinks time (in the garage). Unable to find any heavy gauge wire my eye turns to the disused freeze, it died a while back when the compressor sprung a leak. Poking around in the back I notice some copper tube about 0.2" diameter and with my faithful wire cutters I snip this away and unwind it from the larger tube. After straightening it and quick rub down with sandpaper it looked like new. Now for something to support it.
Remembering my former was 3" at the outside edge I looked for something that I could cut down to 4" to use. Sure enough in the bird cages were some wooden and plastic perches. The wooden was rounded .5" dowel and the plastic were oval, but underneath the plastic ones they was a groove running the full length which looked a suitable size to fit the mackrolon edge. So plastic it is then. Cutting them down to 4" was rather easy and drilling a suitable sized hole for the copper pipe was a piece of cake. carefully applying araldite to the opposite end to the hole and also in the grove, I put them in place on the vertical edge of each former, such that the holes are parallel to the primary turns.
Another 24hr wait :)
Last job is to carefully feed the copper pipe through each of the holes in the perches I made yesterday, was a bit fiddly, (left long tails again), but useful as the next time I make a primary I will mark out small slots. Still its all done now. One primary completed :) Ooops neally forget, that end of the copper pipe is cut off so as to leave appox., .5" space from the start position, ie we dont want a complete turn do we :). Job done. A point worth noting, its best not to use enamel covered wire, right job getting it of those small turns, next time I'll got for tinned copper or small bore copper pipe, just a thought :)
back to top of page (TOC)
The first problem I had was what kind of material do I have around here that is suitable. I played around with a cardboard tube, the sort you get in paper towels. On this I cut a lot of 'V' slits down one side and formed it into a circle, wasn't that successful tho. Next I tried it with hose pipe, that worked but was a tad small. In the garage I found some odd bits of neoprene tubing, the sort with the reinforcement, looks like a cross hatch pattern inside. That worked well, but again it was a bit small. Further routing produced a box of 'electroflex' that's a flexible conduit for protecting electrical wiring around machines. In the box was some 0.75" dia and some 1.5" dia and what's more they were long enough. So a quick recap on Stefans page produce a typical dimension to form. I tried the larger one first and that wasn't too bad, although 3 hands would have been easier. Anyway I forced the ends together and with some plastic tape I managed to join them. Because 'electroflex' as ribs I cut and wrapped 6" lengths of tape around the flex thereby gradually smoothing the surface. When it was near smooth I placed it to one side and attacked the smaller one. This one was quite adamant that it did not want to join with itself and in the end I had to resort to the power of fast acting glue. Guess who won :) So having made both ends meet so to speak I wrapped the outside as the other one to get a fairly smooth finish. In the garage I had some aluminum sticky sided tape, the sort they put round windows for alarm systems, two reels infact 1" and .5" wide. Cutting them into small strips 1-2" I placed them over the tape and smoothed them down with the back of a spoon, guess where I read that :). Next was to trim down some 3ply to make 2 small discs that would be a pressure fit inside the toroids and then cover them with plenty of the ali tape. Only need to drill a hole in the center of each and they done. Attaching them together and then to the secondary was a right headache, even after reading and re-reading anything I could find. In the end I opted for 'Stefans' approach with the 35mm container. lid on the Toroid and base upside down on the coil. What a job it was to get that nylon screw through the end of the former inside and the nylon nut in the container. Got there in the end tho. And after plenty of varnish poured in each, (one at a time) to provide an effective seal. The cap was bolted to the smaller Toroid and a nut on the other side, and then the larger Toroid on top of the screw with another nut to hold it in place, the screw was a stainless steel one and the object being to connect both toroids together to the 35mm lid. (Now I may be in error in doin that, we'll have to wait and see). The secondary wire at the top was loose wound up the container and over the lip. Held in place with the plastisized tape. One more thing to do was to place strip of ali foil on the inside lid, object being to connect with top of the secondary turn. Ah yes, don't forget to remove the enamel before you bend it over. Having covered the top nut on the Toroid I smoothed it down best I could with more ali tape. Now all that needs doing is fitting them together, but not just yet.. You'll see why later :))
BellaDonna now has her own website at Terry's hot-streamer server, so please look there for aditional information on her projects!
back to top of page (TOC)