Author Topic: Mounting the Tungsten  (Read 1344 times)

Offline thedoc298

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Mounting the Tungsten
« on: August 28, 2019, 04:08:08 AM »
Got my spark gap rotor disk made and mounted to my syncronous motor.  I am going to be running 120bps so will need to mount 2 toungsten rods through my disk, been looking but how are you guys mounting the rod to the disk. I will be ready for tunning after this bit of information. Thanks again.

Offline MRMILSTAR

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Re: Mounting the Tungsten
« Reply #1 on: August 28, 2019, 04:49:04 PM »
I have seen two methods that are suitable and one that is not IMHO.

One method uses brass bolts as holders. A hole is drilled through the middle for the tungsten rod. Two holes are then drilled and tapped in the 6-sided bolt head to hold set screws. The set screws secure the tungsten. The brass bolt also helps with conducting the current and cooling. A disadvantage is slightly more rotating mass because of the brass bolts. I use this method.

A second method uses round aluminum collars with set screws. One collar is placed on each side of the rotor hole containing the tungsten rod. The collars hold the tungsten rod in place.

A third method that I see used is to just hold the tungsten rod in place with a set screw placed on the periphery of the rotor. This requires a tight-tolerance hole for the tungsten rod and a fairly tight press fit of the tungsten rod in the hole. The set screw threads are tapped directly into the rotor material. I don't like this method because  I don't think it is that secure and can possibly loosen over time.
« Last Edit: August 28, 2019, 04:50:50 PM by MRMILSTAR »
Steve White
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Offline thedoc298

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Re: Mounting the Tungsten
« Reply #2 on: August 29, 2019, 12:38:27 AM »
I have seen two methods that are suitable and one that is not IMHO.

One method uses brass bolts as holders. A hole is drilled through the middle for the tungsten rod. Two holes are then drilled and tapped in the 6-sided bolt head to hold set screws. The set screws secure the tungsten. The brass bolt also helps with conducting the current and cooling. A disadvantage is slightly more rotating mass because of the brass bolts. I use this method.

A second method uses round aluminum collars with set screws. One collar is placed on each side of the rotor hole containing the tungsten rod. The collars hold the tungsten rod in place.

A third method that I see used is to just hold the tungsten rod in place with a set screw placed on the periphery of the rotor. This requires a tight-tolerance hole for the tungsten rod and a fairly tight press fit of the tungsten rod in the hole. The set screw threads are tapped directly into the rotor material. I don't like this method because  I don't think it is that secure and can possibly loosen over time.


Thank you for your time, I have watched videos of your gear, impressive. I guess you and Mads are the only ones on this site that know how to build. I guess it is all about learning what works best. So you have to have a coil to learn. Again thanks for your time.


Offline thedoc298

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Re: Mounting the Tungsten
« Reply #3 on: August 29, 2019, 12:54:15 AM »
I have seen two methods that are suitable and one that is not IMHO.

One method uses brass bolts as holders. A hole is drilled through the middle for the tungsten rod. Two holes are then drilled and tapped in the 6-sided bolt head to hold set screws. The set screws secure the tungsten. The brass bolt also helps with conducting the current and cooling. A disadvantage is slightly more rotating mass because of the brass bolts. I use this method.

A second method uses round aluminum collars with set screws. One collar is placed on each side of the rotor hole containing the tungsten rod. The collars hold the tungsten rod in place.

A third method that I see used is to just hold the tungsten rod in place with a set screw placed on the periphery of the rotor. This requires a tight-tolerance hole for the tungsten rod and a fairly tight press fit of the tungsten rod in the hole. The set screw threads are tapped directly into the rotor material. I don't like this method because  I don't think it is that secure and can possibly loosen over time.


Thank you for your time, I have watched videos of your gear, impressive. I guess you and Mads are the only ones on this site that know how to build. I guess it is all about learning what works best. So you have to have a coil to learn. Again thanks for your time.


I like the first Idea but sounds hard to do without a lathe.. I will probably have to go with the collar till I come up with something else. My wife won't let me buy a machine shop.

Offline MRMILSTAR

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Re: Mounting the Tungsten
« Reply #4 on: August 29, 2019, 05:12:54 AM »
The first idea (brass bolts) doesn't require a lathe but it does require a drill press to precision drill the holes down the middle of the bolts and to drill and tap the set screws. I think either the brass bolts or the aluminum collars will work equally well.

There are a lot of people out there with tesla coil building experience. I think the reason that you don't see more responses is that this is a relatively new forum. I really appreciate that Mads has started it and maintains it. I publicize this forum whenever I can. It will gradually gain more members. You might also trying posting your questions to "pupman.com". This is the original tesla coil only forum. Its an old-fashioned E-Mail based forum and can't accept images or video, only text. But it has been around for at least 25 years and has the foremost tesla coil experts as members. It also has extensive searchable archives. That is the forum that originally educated me about tesla coils.

I also post to facebook just to show what I have built or to see what others have built. I don't use facebook for expertise.
« Last Edit: August 29, 2019, 05:24:23 AM by MRMILSTAR »
Steve White
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Offline thedoc298

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Re: Mounting the Tungsten
« Reply #5 on: August 30, 2019, 12:45:05 AM »
I know their are tons of builders and I will try that site. I do have a drill press. I ordered the collars yesterday and I am going to also try the brass bolts. Can't have to much of this stuff around. Thanks for the idea, one step at a time.

Offline Mads Barnkob

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Re: Mounting the Tungsten
« Reply #6 on: August 30, 2019, 09:27:14 AM »
I would recommend using multiply set screw / pinol screws in each metal collar on each side of the tungsten rod, drilling a hole through the tungsten rod is not just hard but also weakens the rod at its most critical stress point.

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Offline thedoc298

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Re: Mounting the Tungsten
« Reply #7 on: August 30, 2019, 03:42:55 PM »
I would recommend using multiply set screw / pinol screws in each metal collar on each side of the tungsten rod, drilling a hole through the tungsten rod is not just hard but also weakens the rod at its most critical stress point.

I lucked out and ordered the collars with 2 set screws. Got a question, where can I find the blank cores to wind a GDT. Was watching your video on your first sstc and it referenced a GDT which I did not know anything about, watched videos all nigh on the subject . On the one you made (your first sstc) can a single GDT have 4 outputs..? Could not see yours in the video, I only find pictures of 1/2 bridge and would like to see H bridge GDT. Every site I go to looking for cores just talks about them but don't sell them. Sorry for being ignorant on coils, but did not really get serious till I retired. My shop is full of this kind of stuff just waiting to be turned into something.

Thanks for the info. This stuff gets me wound up and can't sleep.

Up date wound my GDT for H-Bridge and works fine. 250K to several megs.
« Last Edit: August 31, 2019, 07:04:13 PM by thedoc298 »

Offline Mads Barnkob

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Re: Mounting the Tungsten
« Reply #8 on: September 02, 2019, 07:38:21 PM »
The first 3 cores in this filtered digikey search is good cores for a GDT: https://www.digikey.com/short/prrr3q

I showed my full-bridge GDT and how to calculate it in the article for my DRSSTC1: http://kaizerpowerelectronics.dk/tesla-coils/kaizer-drsstc-i/
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Offline thedoc298

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Re: Mounting the Tungsten
« Reply #9 on: September 05, 2019, 01:54:58 AM »
The first 3 cores in this filtered digikey search is good cores for a GDT: https://www.digikey.com/short/prrr3q

I showed my full-bridge GDT and how to calculate it in the article for my DRSSTC1: http://kaizerpowerelectronics.dk/tesla-coils/kaizer-drsstc-i/

Kool, Don't know how I missed as I have watched most of your videos. I ordered 3 of the ones you gave the part # for in another video.


Got everthing for final assemble, do have one question. I tried out javatc and after I figured it out it is showing 33ms full time to charge (see pix)

First run is going to be with 15000 60ma and my cap for rotory was 27nf as recommend by tesla map.

Is that normal, though I had seen a different number while I was trying javatc.

Thanks for all your help, made things lot easier. Will do some post soon.

Ran the numbers and the time is correct, so hope that is not to much of a hit. Even all 4 nst its still 16.?ms Just did not notice.
« Last Edit: September 05, 2019, 08:44:49 PM by Mads Barnkob »

Offline jturnerkc

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Re: Mounting the Tungsten
« Reply #10 on: November 28, 2019, 12:50:16 AM »
I've also seen an application where bolts (at least about 2x the tungsten rod diameter) were bored down the center and the tungsten rods pressed in. This allowed for easy gap adjustment as well. I will try to find the source and post a link. This method was used for a static spark gap, but I can't think of any reason it couldn't be employed in a rotary.

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Re: Mounting the Tungsten
« Reply #10 on: November 28, 2019, 12:50:16 AM »

 


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