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Re: [TCML] Gaps



Hi David,

I've never had an electrode fail due to the epoxy getting hot, but that is likely due to ensuring the electrodes themselves stay as cool as possible under the conditions. I'm not sure what would happen if I were to turn off the airflow (and I'm not about to try it). If the electrodes get hot enough, there's probably a good chance epoxy will become flexible. Don't allow that by ensuring the electrodes stay cool under normal operating conditions. Sounds like you have a good deal of cfm, so chances are your gap will do well. If you get any "browning" of the pvc, the electrodes are running too hot. More airflow is absolutely required (much more).

Take care,
Bart

David Rieben wrote:
Hi Bart, all,

I've often wondered how well that glue
could hold up under the heat and UV radia-
tion over time without significant degridation.
As fas as that goes, I've seen the PVC itself
gradually "brown over" and actually start be-
coming a bit conductive due to the bombard-
ment of UVs from the SG plasma. On my
latest SG driven coil project, I have have
just cut 2 slits in the 6" diameter mounting
PVC pipe and mounted the 1" diameter x
5" long copper tube electrodes (8 of 'em)
to the PVC pipe via the slits with 1/4" x 20
TPI machine screws (and nuts). I think I
saw this idea on someone else's website
but I can't recall where. This does away
with the problem of not being able to pre-
cisely locate the mounting holes for those
of us who do not have access to fine machine
shop facilites and makes for a pretty well infi-
nitely adjustable RQ gap. I simply tighten one
copper tube, trying to insure it's parallel with the
PVC mounting pipe and then slide the next tube
up next to it, using the thickness of a credit card
to space the individual gap. Seven seriesed gaps
of this caliber allow my 14.4 kV PT to just break
down the gap at about the rated 14.4 kV applied
to the gap assembly. I have yet to fire it through
the tank circuit capacitor as I am still waiting to get
one of those bulk buy 6 x 24 spun aluminum toroids
that DC is supposed to be working up next month.
Besides that and driving in a good grounding rod
for RF grounding it, everything else is ready to go!
O yes, I fogot to mention that I am using a ~300
to 400 CFM fan for the forced air cooling of the
SG tubes.

David Rieben


----- Original Message ----- From: "bartb" <bartb@xxxxxxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Saturday, February 23, 2008 3:59 PM
Subject: Re: [TCML] Gaps


Well said Brian!

I remember all the gaps you mentioned. I personally like to epoxy my pipes to the pvc. Reason is that I can accurately set each pipe exactly at the distance I need and perfectly parallel. I tried bolt methods in the past and it's just not the best way to do it. I install one pipe at a time letting the epoxy cure between each pipe installation. I use a feeler gauge between each pipe and let gravity aid the exercise. Not hard to figure out really. It's so easy it's ridiculous. A perfectly symmetrical RQ gap can be built on any given Saturday. Parts needed is your pvc tube, copper pipes, feeler gauge at the spacing wanted, and one tube of clear high temp two part 10 minute epoxy.

Here's 10 steps on how to build a perfect RQ pipe gap (or any type of pipe gap):

Step 1) Mix small amount of epoxy and apply a 1/4" strip along the length of one pipe. Step 2) Mount pipe to pvc (epoxy side to pvc tube) and ensure it is parallel in the pvc tube.
Step 3) Let pipe cure for 30 minutes.
Step 4) Mix another small amount of epoxy and apply again to second pipe. Step 5) Mount pipe next to first pipe (epoxy side to pvc) parallel to first pipe.
Step 6) Insert feeler gauge between pipes and leave it there.
Step 7) Turn pvc tube so that the new pipe is forced onto the first pipe and pvc tube by gravity (~45 deg angle). Step 8) Block pvc tube into position so it doesn't roll and wait 30 minutes.
Step 9) Repeat above steps until all tubes are in place.

Step 10) Install fan, connect wires, run coil, take photos, share photos with TCML.

Take care,
Bart


Brian Foley wrote:
Hi, I built a so called "RQ" gap, pvc with copper tubes inside, i use a computer fan and the top of a pill bottle so all the air is in the gaps or thru the pipes. It works well on my coil. For those of us who have built coils and been coiling for years have found Tesla Coils are as unique as people...what works wonderful for one coil doesnt mean it will make your coil wunderful....there is no perfect size, no one size fits all... there are many designs that built carefully work just fine, once tuned to the parts of that coil....... this style gap seems to suit smaller coills up to several KW or a little more....If you ran and tuned your coil to a simple gap set at 1/4 inch then the spacing you might use would include settings that were less than 1/4 inch and slightly more than 1/4 inch...
Gap distance divided by the number of gaps approximately..
I found the pvc pipe difficult to drill slots so the pipes could be spaced to a certain gap distance......easily done however in a machine shop....Now there are many gaps made with pipes layed out flat, one used staggered or high and low pipes for a shorter overall distance......some glued the end of the pipes to a block of plastic, one even was made on a flexible surface and as the tension was increased the gaps became wider.......interesting and very simple design. My best recommendation, look at a lot of pipe style gaps, decide which is easy to make, and expirement.....you own innovation might be just what your coils needs to be happy....enjoy...Brian F.


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