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Questions regarding variacs & protection

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Jrz126

Mon Mar 27 2006, 04:44AM

Registered Member #242 Joined: Thu Feb 23 2006, 11:37PM
Location: Erie PA
Posts: 210

I found these guys on ebay:

which are the ones Im going to be running.

infinitum

Mon Mar 27 2006, 11:32AM

Registered Member #307 Joined: Sun Mar 12 2006, 06:41AM
Location:
Posts: 37

Jrz, could you tell me if they run well when you get them (ie, not exploding)?

Jrz126

Mon Mar 27 2006, 03:31PM

Registered Member #242 Joined: Thu Feb 23 2006, 11:37PM
Location: Erie PA
Posts: 210

I have them all ready to go. but its going to be awhile before my TC is up and running.
I believe these were on the list of good caps, so Im assuming they will work.

infinitum

Mon Mar 27 2006, 08:36PM

Registered Member #307 Joined: Sun Mar 12 2006, 06:41AM
Location:
Posts: 37

Ok, if they were on the good list I'll go ahead and order them now (they are quite cheap, too). Thank you for the heads up, Jrz.

infinitum

Fri Mar 31 2006, 09:38PM

Registered Member #307 Joined: Sun Mar 12 2006, 06:41AM
Location:
Posts: 37

Ok, I have a question about rotary spark gaps:

I plan on building a static spark gap first, and then later a RSG.

When I do build the RSG, what type of material should I use for the rotor? I plan on using an 1800 rpm motor. A lot of designs use G-10, but it is very expensive. I've seen some other designs using sheets of Lexan...would this be acceptable for the 1800 rpm speed I'm running at?

Can I use rounded brass screws/nuts for the electrodes?

What should I bolt the motor to? A sheet of lexan?

I've seen some designs talking about capacitors for the motors, and others call for no capacitors at all...do I need capacitors for my motor? And if so, what do they do?

Thank you!

edit:

And if Lexan is acceptable, would a 1/4" thick piece of Lexan be sufficient for a rotor?

Part Scavenger

Sat Apr 01 2006, 01:11AM

Registered Member #79 Joined: Thu Feb 09 2006, 11:35AM
Location: Arkansas
Posts: 673

I like to use laminated pieces of formica, I had a bunch and it works very well. Some other stuff I have seen used are acrylic and plexiglass. I wouldn't use these, because they are brittle and will shatter if they broke. I chose formica, because I had some laying around and it is very tough. Secondly, it won't shatter; it tears. I have run it at 15000 RPM with no problems. It doesn't melt either.

I was wondering also about plywood? Any potential it will have will be directly across the bolt, so trace-through shouldn't be a problem. Has anyone else used it? I don't want to recommend it without knowing, but I think it would work. Especially at 1800 rpm.

BTW, I think Lexan is acceptable, but I've never used it. I've just seen other people's setups. I don't know about 1/4 inch though. Like I said, I've never used the stuff.

You can use brass screws. There is one design that uses brass allthread and acorn cap nuts for the electrodes. Just make sure they can't come off.

The motor mount can be anything. I used a 2x4. The motor shouldn't be at a high potential, so it doesn't matter.

The capacitors could either be for starting the motor, or for current limiting. I don't think you'll have to worry about this. If it needs a capacitor, it will come with one.

Tips for a successful RSG:
1. Shield the rotor. If one of those nuts happens to come off, it might hit someone. Especially on a ASRG when you are running very fast.

2. Balance! The best way is to run the rotor and mark a line. Then make sure the electrodes are directly opposite each other.

3. The best way to make the rotor perfectly round is to cut it close, and then hold a file against it while running.

4. Laminations are a good thing. If one section fails, you'll have several more to back it up. Another reason I used formica.

Hazmatt_(The Underdog)

Sat Apr 01 2006, 03:49AM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

There is some discussion on the subject of rotaries in the archives. I have mentioned construciton technique that will get you on your feet using a drill press, eyeballing, hand routers, and some basic tools, and get there with about 1% if you're good.
I wouldn't use plastic unless you know your electrodes won't crash. But do some reading, its all out there. :)

vasil

Sat Apr 01 2006, 09:50AM

Registered Member #229 Joined: Tue Feb 21 2006, 07:33PM
Location: Romania
Posts: 506

If you use plastics, use thick. Thicker = less vibrations i suppose. And multiple electrodes = low speed.

Here is my wheel for a future RSG

http://www.geocities.com/gemaria_ro/rgs.html

Desmogod

Sat Apr 01 2006, 01:55PM

Registered Member #139 Joined: Sat Feb 11 2006, 11:01AM
Location: Perth, Western Australia
Posts: 358

Just make sure the plastic is thick enough, flying bolts and shards of plastic are probably rather detrimental to your continuing health.

infinitum

Sat Apr 01 2006, 06:22PM

Registered Member #307 Joined: Sun Mar 12 2006, 06:41AM
Location:
Posts: 37

Ok, I'll go with some nice thick lexan.

Is it ok if I use a square for the rotor instead of a circle? It seems that cutting a perfect circle would be a lot more difficult than cutting a perfect square.

I have a question about secondaries, too. I see some people seal the ends of the PVC pipe to prevent internal arcing or something? Do I need to do this [seal the ends]?

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