ultimax

as im thinking of building one (but it will have to wait a bit because im busy at the moment) anyway... why is ultimax's sparks not as long as in other photos (google searches' date=' other websites etc)???

 

basically what im trying to get at is what are THE most essential thing(s) for me to have to obtain maximum length sparks?[/quote']

 

My toroid's sort of small, and the coil was connected to a mysterious ground wire in the lab, not a proper ground roud. Come December, my coil will have a traditional, larger toroid, and I'll be testing it at home with a copper stake in the ground. I can't say I'll get bigger sparks, but I'm hopeful

 

As for the Crookes Tube photo, the sparks are short because I placed the tube near the coil

Hi YT,

I was in the garden the other day and noticed the lightning rod's ground strap terminating at what appears to be a solidly constructed stake pounded into the ground. Was wondering if I could make use of that instead of pounding another stake into the ground. That would save me some time and money.

It's just a thought. If it doesn't work well I can always go back to the ol' fashion way.

are you on the top floor and the last connection to the strap??

 

if not then NO WAY do it! it`ll radiate upwards and out too' date=' at best you`ll get TVI for several 100 yards, I live on the the 13`th floor (the top floor too) and I still cause probs if I use it

 

cold water plumbing seems to work alot better for some reason [/quote']

I would only change one variable at a time. First I would find the best number of primary turns then I would mess with the spark gap.

Hi Lance' date='

well I fiddled arnd with the spark gap length and blew a capacitor haha. Thank god I had spares, and that the rest of the bank was unaffected

I've tuned it somewhat and have gotten another inch or two. I think I'll leave it at that. Next, I'll try it with a proper ground connection. What do you think of hooking hte coil up to the lightning rod's ground strap? Good idea? Or bad idea?

Here's another photo:

[img']http://web.singnet.com.sg/~shuhuang/tesla_maltese_cross.jpg[/img]

It looks great ultamax.

 

I'm sure you have already done this but did you tune it? Make sure to adjust the spark gap distances along with changing the primary turns. I think that even with a crapy ground you should be able to get larger sparks than that. Also keep in mind that your input was only around 9.5kv when you tested it.

 

Sorry I can’t be more of a help than that.

so how should it go? More turns = wider gap? What's the relationship between gap length and increasing the length of the primary?

hey you've already been a great help. thanks a lot!

Hi YT,

thanks for the compliment!

I'm probably gonna go ahead with the traditional toroid. Just to make sure it's not the toroid which is the obstacle to having longer sparks.

I'm prob gonna redo the spark gap...again. My Prof pointed out that the rubber tubes I used to strap the aluminium rails down may lose their elasticity with time. I'm prob gonna cut my casing horizontally into 2, and sandwich the rails between them. the 2 halves will be joined by a plastic hinge on one side, and maybe leather or a piece of vinyl on the other. I'll also shift the fans to the top of the housing so that they're blowing down onto the fans, thru the gap. Right now most of the air is blowing across the bottom of the rail. Only a bit makes it thru the gaps between them. So who knows ... maybe quencing will be better and we'll see bigger sparks?

I'm also gonna take the coil home and borrow a variac from the lab. I'm suspicous of the ground connection we used in the lab. I'm not sure where it's from, or what it leads to, but I wanna try running the coil with a good ol' copper stake in the ground!

Shu

P.S. How good is an average coat of polyurethane? I'm trying to get my gap to spark in the middle, rather than the ends, so I'm thinking of dipping both ends in polyurethane? As it is, the sparks are sort of shielded from the air flow by the plastic supports they rest on.

WELL DONE!!! )))

 

I`m impressed! nice pics too.

 

1. no idea how to calculate it (I use trial and error method as I hate maths).

 

2. the shape isn`t all that critical in my experience' date=' so long as it`s smooth without sticky outy bits

 

2. it doesn`t matter and the airflow will be the same either way. I prefer your method anyway, the fan doesn`t get any heat, Ozone or NOx gasses through it, extending its life

 

3. the Ground is essential, the better the ground the better the results (up to a point) a 3m or 5m copper pipe in the earth wont make any diff on a small coil, 1 meter would be plenty. as for indoors the cold water pipe is the best ground you`re likely to get, make sure it`s not tank fed water though, by law all Kitchen cold water supplies have to be direct, so there`s your best bet

 

again, Well Done that man![/quote']

Hi everyone,

tested my coil out in school today and it worked right away, much to my relief. Here are some of the specs of my coil :

Transformer : NST, 15kV, 30mA

Diameter of secondary coil: 90mm

Diameter of magnet wire: 24 AWG, 0.51mm

Number of turns: ~883

Toroid: 2 aluminium wok covers joined together with aluminium tape.

Estimated dimensions: 310mm in diamter, 210mm in height.

(I'm probably gonna construct a traditional toroid as I can't calculate the capacitance of this toroid, and I'm not sure if it's any good in the first place)

Inner diameter of primary coil: 140mm

Diameter of copper tubing: 1/4"

Spacing between coils: 1/4"

Number of turns: 13-14

Spark gap:

Number of electrodes: 7

Material used: Aluminium curtain rails

Spark gap: ~1.5mm between each rail, ~9mm in total.

Cooling mechanism: 80mm computer fans, blowing into the spark gap housing, rather than sucking air out.

Total construction time: ~7 days from start to finish.

Photos:

My coil in the lab. Note the atypical toroid.

The spark gap. I removed the last rail as I needed a wider spark gap. The fans limited how far I could go with 8 rails. So I now have 7.

Performance:

The good news is, everything worked from the start. There was some arcing on the capacitor bank because of a poorly soldered connection, but that was soon fixed. Other than that, the coil generated a good amount of noise, ozone and streamers.

The transformer was connected to a variac, and we never went above 150V (the transformer's rated at 240V).

After the initial satisfaction of having everything work, discontent took over. My prof was very happy with the streamers, but seeing how other coils using similar NSTs have generated sparks 2-3 times the length of what I saw today, I was somewhat disappointed haha.

It's funny that we didn't run the coil "as is" ie. without an electrode at the top of the toroid. So I don't know if breakouts are possible from the toroid. But anyway, max streamer length of the day was abt 200-250mm. Maybe 180mm's a more conservative estimate.

Here are some pics! My 1.3 megapixel camera is really bad with shots in the dark, so pls excuse the quality. It barely captured the streamers!

QUESTIONS and improvements.

Yes, more from me! The general question is (as if it isn't already obvious haha), how do I improve spark length? Where do I start? Is there a methodical approach?

More specific questions:

1. How do I calculate the capacitance of this atypical toroid?

2. WOuld a traditional doughnut shaped toroid work better?

2. DOes it matter if the fans blow into the spark gap housing, or suck air out (the traditional way). I find there's more air flow with the former than with the latter.

3. How impt is using a stake in the ground as the RF ground? Does the length of the stake really matter? Like 3m VS 5m?

We were in a lab (on the 5th storey of a building) so we hooked the coil up to a ground wire. I have no idea where it's connected to, but it definitely wasn't from a socket. Anyway, if you don't have access to a patch of dirt/grass, what's the best ground to use?

thanks!

Shu

Hi YT,

what exactly is an earth strap? The RF ground connection from the secondary coil?

thanks!

Please Please Please' date=' do NOT FORGET your Earth strap!!!!

 

a good solid Ground connection is essential! A) for good coil performance and B) for safety of local equip AND your coil! )

 

all the best dude, and I really hope everything pans out nicely for you )[/quote']

Lance, YT,

I've finished building my coil! It took me ~5 full days from start to finish but it's done! I'm testing it in school tomorrow. Hopefully it'll work. Will post pics soon. Maybe a video too!

THanks for all your help guys. You guys have been wonderful and were really forthcoming with answers and suggestions! Can't say the same for some coilers I emailed for help ...

hey sorry I've got (yet) another question.

There are a couple of metal screws directly under the primary coil. The deck that's supporting the primary coil is in turn supported by 4 PVC pipes. I'm guessing the screws won't affect anything because the deck's insulated from the ground by the PVC pipes). Am I correct? thanks!

Hi Lance,

thanks for your help as always....I really appreciate it.

1. I applied the polyurethane in haste (because it was late at night) so I'm afraid I didn't cover all the wood, or the coat was too thin.

I've got my copper pipes resting on the chipboard. There's a layer of epoxy holding everything together so hopefully that'll absorb the heat and spare the wood. I've also got 2, 8mm fans an inch away from the copper pipes. That should keep things cool.

2. Can't find any sort of flex-tubing greater than an inch and half in diameter. I know I'm not searching hard enough, but I haven't the time haha. I think i'll go with the bowls. The fact that everyone's using aluminium this and aluminium that got me concerned so I wanted to double-check with you guys first.

3. I'll prob leave an inch and a half. If the coupling's poor, I'll raise it...somehow. Have to figure that out

I think most people use a multimeter for measuring saltwater caps.

 

1. Will the spark be raised above the board? Normally the only reason wood becomes conductive is when it starts to burn and caramelizes. So as long as the gap is above the wood and there’s no chance of it heating you should be alright. Also' date=' if you coated with polyurethane first I don’t see why it would be a problem. My first primary was on a piece of round particle board and I never had any problem with it.

 

2. What’s wrong with the normal 6" ducting? I don’t think steal will be a problem. YT uses a toroid that’s just two steel bowls wielded together. (Correct me if I’m wrong)

 

3. This is really hard to predict. The problem is that if you cut the bottom off and get smaller sparks you can’t to go back to the other coupling. 2" seems a bit high though. You may want to cut a very small bit off at a time after you finish everything else and see how it affects performance.

 

 

 

 

Good luck![/quote']

Hi lance,

so how do coilers estimate the capacitance of salt water caps? Is there a method? How many bottles do you start with? Or is it completely trial and error?

I've got a couple quick questions abt the coil i'm building now.

1. WOOD. I rebuilt my spark gap and at 2 in the morning, I wasn't thinking straight. I cut the board used to hold the copper pipes out of chipboard. It was dry, and it had 2 coats of polyurethane. In the morning, I realised that wood can actually be a conductor of electricity at high voltages! Do I have to be concerned abt this? Everything sort of fits together perfectly so I really don't want to be dismantling anything. Besides, I epoxied everything together....

2. Toroid. Ok...the toroid I built looks like crap. It's uneven, and pretty creased up. It's almost embarrassing to look at (considering the amt of time spent on it!). I want to build another one, but I haven't had any luck finding 4" drain hose (my neighbourhood hardware shop says they're no longer popular so they're no longer stocked) or 4" aluminium duct (DIY isn't big here, so you can only get such items from a contractor).

I did, however, see 2 metal dishes the other day. Put together, they form a perfect toroid with a lip. I was thinking of joining the 2, and grinding the lip away. However, all toroids I've seen seem to be made from aluminium. The dishes are made from stainless steel probably. What's your opinion on this.

3. Primary coil. I made a flat primary coil then realised something - when winding the secondary coil, I had every intention of making my primary an inverted cone. So I started winding my secondary coil abt 3-4" from the bottom of the form. With my flat primary, the secondary coil only starts 2" above the primary. Again, should I be concerned? How does this affect "coupling"? I can easily saw off a few inches but I don't want to do more work than necessary.

OK that's all for now guys. I'm pretty excited. My first coil's looking good. I hope it works though - a lack of proper tools has resulted in parts which don't fit together accurately. But I've been working on it non-stop for 4 days now so let's hope everything works out ...

That should be fine.

 

I’m not sure about the calculator for saltwater caps. I think there are some for normal plate caps but I have never come across any for saltwater. I think it would be pretty hard to make a calculator for saltwater because of all the different types of bottles

hey i used zinc plated wire to extend the leads of my caps. Is that OK?

Exactly.

Just be sure to do extensive testing before you present your coil. Wouldn’t want it to fail at the last minute.

 

Does the coil have to be compact? Saltwater caps take up quite a bit of space.

I'm prob gonna fire it up in the lab with my prof present. I want to make sure I've got all the connections right, and I do not overlook a problem which could blow something up, or be a hazard.

Anyway, he liks trouble-shooting things so even if it doesn't work I'm sure he won't penalise me. Besides, he knows that I'm not an electrical engineering/science student in the first place (i'm actually a history major haha).

I may make a saltwater cap for the professor during the hols, just to demonstrate the point that everyday materials can hold a huge amount of charge. I came across a tesla coil (I think the owner's name is Greg) on a website and he used 52 beer bottles for his tank cap and it worked really well. Seeing those pics was pretty inspirational. THe prof is also big on using everyday materials for science experiments, esp for this class. He gave me proper caps this time round because he wanted something neat and robust. BTW, to answer your question, no the tesla coil doesn't have to be compact. As long as I can transport it to sch by car, and it's sturdy, it can be of any size.

Abt saltwater tank caps, is there a formula used to calculate its capacitance?

Hi Lance!

Just want you to know I really appreciate all your advice. It's great being able to talk to someone abt specific questions/concerns I have. Websites are great, but talking to someone with experience is always much much better!

The general wire you use is only critical if you plan on making the coil compact. The insulation is what’s important' date=' not the thickness. As long as there is half an inch between wires then there’s no problem. If there is less than then I would look for some high voltage wire. It doesn’t not have to be labeled as 'high voltage' wire though. You can experiment with different wire types and your NST before making your coil.

 

Also I didn’t even think about this till YT mention it but you could also try making your own caps. I have had a lot of success with salt-water caps.[/quote']

 

Ok I've got some 1.5mm core wire lying arnd. I'll probably use that then. So you're saying at this voltage, I don't have to worry abt factors like resistance etc. impeding my coil's performance? And heavy duty HV cable is only useful for its insulation, rather than it's conductivity?

 

Abt salt-water caps, I may try this one day. For the time being, my prof wants something that's neat and durable, something that he can keep for future demonstrations

Oh yeah 2 more questions!

1. Should I be very particular abt how smooth my secondary coil form is? I'm using PVC pipe which I've varnished with polyurethane. Unfortunately, it's sort of bumpy. Not very bumpy, but if you run your fingers around the pipe it's certainly not smooth. I suppose that is to be expected with paintjobs done with a brush, but is that a big deal? I'm gonna sand the surface a bit before I start winding as most coilers recommend but I doubt it'll be as smooth as the unvarnished PVC.

Also, I'll be varnishing the coil once I'm done with it. Should I sand each layer down too. Or leave it be? Should I be concerned abt the smoothness?

2. What sort of wire should I use for the general wiring of my tesla coil. It's hard to get specialist wire around these parts, and HV wire tends to be very expensive. I read that regular AWG 12-14 wire is good enough. Is this true?

thanks!

Hi Lance,

thanks for your suggestions. I'll talk to my prof about this.

Can I mix capacitors of different ratings together? Or do they all have to be identical?

Copper wire is fine. They should not heat up as long as you don’t use thin wire. You may want to use thicker wire on the bank it self though.

Ok just to make sure, what's your definition of thin? I've got AWG #22 copper wire. Is this too thin?

Hi Lance,

thanks for your reply!

If you use a resonant size capacitor bank then it will draw more[/i'] current from you’re NST (meaning larger sparks). However some people will tell you that this can damage your NST. I think the LTR bank is really for other types of power supplies. NSTS are extremely robust and I have never had a problem with damaging then. My bank is resonant.

Ah ok .. that makes sense. But will a LTR value result in better performance? Most coilers say that's the second benefit of using a LTR value.

Do NOT use the capacitor configuration you mentioned. The peak voltage of your transformer is more than 20KV. Not only that but you should probably

have a voltage rating of much higher than that. Would it be possible to get

Hmm ... how does one calculate the peak voltage of a transformer? How many volts extra should I prepare for?

any more caps? Do you have to return the caps intact? If those were the only caps I had I would use two strings of 14, which is only 22.4KV; NOT good! My 12-30 NST easily destroys an 18KV bank. You can probably get away with that configuration as long as you don’t run it for an extensive amount of time.Tesla coils are extremely hard on caps because of the high ac frequency and the low resistance of each discharge.

I could get more capacitors. That's not a problem.

What configuration would you recommend?

Because you’re using an mmc the wire type is not all that important. Individual caps will not have enough power to melt any wire/solder. Just don’t use ultra-thin wire.

Can I use regular copper wire (exposed)? Will it heat up?

thanks a lot!

I'm building my first coil and I need some advice. It's for sch so they're providing most of the components. I'm getting a 15kV 30mA 50hz NST from them (suggested by my prof) and they've given me 30, 1600V 0.047uF capacitors for my MMC.

Using WinTesla, the resonant capacitance for this transformer is 0.0064uF. I've read stuff abt how coilers should use a Larger Than Resonant Cap value, 1.5 times that of the resonant. That means the LTR value is 0.0096uF.

How should I configure my capacitors? Having 2 parrellel strings of 10 caps in series will give me a capacitance of 0.0094uF. Is this ideal?

Also, the leads which came with the capacitors are really short. I need to extend them so that I can solder the caps together. What type of wire should I use? Or will anything be OK?

Should I also space the capacitorss a certain distance from each other? Will the leads arc?

Thanks!

Shu