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Re: AW: [TCML] Coil pic w/ SRSG
There's a copper disk on the back of the 4" garolite disk. It's the stuff they use for roof flashing. Not so stiff. Can be cut with snips, but makes a messy circle.
I was able to cut it at one point with a fly cutter on my drill press. For some reason I did it once, and it never worked again. Tends to bind with the bit.
I'm using collars on both sides of the tungsten rod. I got the tungsten from McMaster Carr. It's sold as tungsten carbide rod. # 8788A158.
I've actually got all the stuff for a propeller gap but I keep having this nightmare vision of one of those 7" tungsten rods flying loose. Also, I'm wondering how to secure the white plastic to the motor. Seems too "soft" a connection if you don't machine it right. I mean, you're not using a set screw with that, right? What keeps it from coming loose an screwing up your dwell setting?
I will try the dremel on the tungsten.
Well, I disconnected the fan, lowered the strike ring - good results. I also tried stacking toroids - I still have my 12x3, and it put it below my 18x4.5 just to see what would happen. But just laying one on top of the other didn't seem to do too much...
I was able to cut the garolite sheets I got, finally. Got a Jasper circle cutter, as was suggested here on TCML. Got a spiral bit for my router and used it in "plunge cut" mode.
Well, generally I hate spiral cutters. I have a rotozip and I avoid using it on home improvement projects - it just tends to spew wood/gypsum/paper all over kingdom come. The kerf from the blade is quite wide and all that material gets flung outward toward the operator.
The Jasper + spiral cut is basically a rotozip on a jig. Then making another jig to hold down the garolite plate and setting the Jasper Pin in the center - I was able to get it to work. I'm covered in Garolite dust. Used a mask - but mask or no mask, it gets all over and you're breathing it no matter what. And with the Jasper template you need to account for the kerf from the bit. I set mine to make a 7" circle and it came out 6 5/8 (you get the kerf on both sides of the circle - so the diameter is reduced by the bit width x2) Wish I had thought of that before I cut through a 12" square sheet of G10. Alas.
But I'm going to start on the "production" SRSG. Thinking to do a design like the ones on John's website, where each of the rotating tungsten electrodes shorts out the HV supply on both sides - so there's no current flowing through the rotating disk itself.
CHeers,
Joe
On Jul 5, 2010, at 5:20 PM, Gary Lau wrote:
> I cut my tungsten rod using a Dremel tool and the cheap brown (~1" dia,
> fragile) cutting disks. It chewed through the disks pretty quickly, but
> ultimately the disks did the job. I think I finished the job by putting the
> cut rod segments in a drill press (any drill would do) and grinding the ends
> flat with some other Dremel tool grinding bit.
>
> Are your rods tungsten (welding rods), or tungsten carbide? I'm not sure
> that tungsten carbide comes in rod stock, but could be mistaken.
>
> How do you make a secure electrical/mechanical connection between your
> rotating rod segments and the copper ring? Bear in mind that the current
> through the gap peaks at hundreds of Amps, so I'm thinking you need more
> than the casual pressure afforded by having the collars snug against the
> disk and ring. I honestly don't know how others make that connection; I
> just sidestepped that issue by using a propeller gap.
>
> Regards, Gary Lau
> MA, USA
>
> On Mon, Jul 5, 2010 at 1:52 PM, Joe Mastroianni <joe@xxxxxxxxxxxxxx> wrote:
>
>> I agree about the long (2") electrodes. I couldn't get them shorter from
>> McMaster Carr.
>> So I figured I'd get the 2" long ones and cut them.
>> Then I figured out I didn't know how to cut tungsten. I mean - don't you
>> need something harder than tungsten carbide to cut tungsten carbide?
>> Rather than shattering the electrodes, I just put them in as is for now,
>> but I do need to cut them in the final build.
>> Any advice on cutting tungsten rod would be much appreciated - I mean, if
>> the answer is using a hacksaw and a bi-metal blade, I'll just do that...;-)
>> Joe
>>
>>
>> On Jul 5, 2010, at 2:09 AM, Fritz W. Egli wrote:
>>
>>> May I succest that you mount a protecting shield over the (long ...)
>>> rotating electrodes - ? There is some leverage, some centrifugal force at
>>> speed.
>>> Perhaps you can also shorten the electrodes.
>>> Opinion, succestion of a mechanic.
>>> Kind regards, Fritz W. Egli
>>>
>>> -----Ursprüngliche Nachricht-----
>>> Von: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] Im
>> Auftrag
>>> von Joe Mastroianni
>>> Gesendet: Montag, 5. Juli 2010 02:11
>>> An: Tesla Coil Mailing List
>>> Betreff: [TCML] Coil pic w/ SRSG
>>>
>>> Pics of Coil v1.2 -
>>>
>>> New 30ga 22" secondary - wound by Dan M.... New Toroid, bought at
>>> amazing1.com
>>>
>>> 3 deck MMC - each w / 18 series CDE 942C20p15K-F (each shorted with 10M
>>> 1/2W resistor). Same Terry filter.
>>>
>>> Sync motor acquired from Alan in Mn, with 4" garolite wheel. Inserted 4
>> 2"
>>> tungsten rods with collars into the garolite. I actually also acquired
>> from
>>> mota.com a 1/30 hp sync reaction motor (oriental motor) upon which I
>> will
>>> base my next attempt at an SRSG - but Alan's motor came with a mandrel
>> and
>>> so made it easier. Cut a copper disk and epoxied it to the back of the
>>> garolite disk to short out the tungsten rods. If anyone has any methods
>>> for cutting copper sheet other than using a metal nibbler and filing your
>>> brains out, do let me know.
>>>
>>> Gaps are about 1/16". As it turned out, I didn't have to move the
>>> insulators upon which I mounted the stationery tungsten gap rods I had
>> been
>>> using for my static gap. I merely rotated them 90 degrees to point to
>> the
>>> rotor and used taller insulators. So I also left my squirrel cage fan,
>>> which I'm hoping doesn't hurt anything.
>>>
>>> I now don't have to have the variac voltage very much more than 1/2 to
>> get
>>> breakout. I've tried adjusting the phase, but once you've got the disk
>>> dwell dialed in, the phase adjustment is kind of tweakage to get max
>> spark
>>> length (I have found - may be doing it wrong).
>>>
>>> Will take pictures/video of the coil running as well.
>>>
>>> http://yfrog.com/emfcj is the start of the 3 pic series. Only iPhone
>>> pictures (don't own an actual camera...have to get one.)
>>>
>>> Cheers and thanks for everyone's great help, especially John and Gary!
>>>
>>> Best to all,
>>> Joe
>>>
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>>
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