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teslacoolguy

Wed Apr 09 2008, 01:31PM

Registered Member #1107 Joined: Thu Nov 08 2007, 10:09PM
Location:
Posts: 792

Hi. I am starting to build a rsg and i was wondering and i made a dosk with 1/2" plexiglass but i am starting to have second thoughts about it because i am afraid that the electrodes will start to melt the disk as they heat up. I was wondering if that is going to be a problem or will plexiglass stand up to the heat because i also am going to have a blower quenching system so im sure that will help with the heat also but i want your opinion if anybody has done this before of id i should find a better material.

Cain

Wed Apr 09 2008, 02:33PM

Registered Member #624 Joined: Tue Apr 03 2007, 07:50AM
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Posts: 59

i have a nylon disk (made from a chopping bored) and she seems to hold up fine although i haven't run it for long runs as yet (from the short runs i has done only the stationary electrodes heat up WAY before the flying ones show heat)...

make the disk quite large and use more electrode will help to keep em cool as will keeping the electrodes a little bit longer than normal..

but this will make balancing a little bit more difficult (i use brass screws with spacer nuts and domed end caps to keep them uniform lengh)

Steve Conner

Wed Apr 09 2008, 02:51PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

The only recommended materials for RSG rotors are fabric reinforced phenolic (sold as Tufnol etc.) and glass reinforced plastic (sold as Garolite, FR4, G-10, "Electrical fiberglass", etc.)

For all other materials, you're on your own as far as safety is concerned. Nylon, plexiglass, lexan, chocolate cake etc. all soften with heat: the recommended materials stay strong. They're expensive, but how much would you pay to get that 1/4" bolt removed from your forehead?

Ultra7

Wed Apr 09 2008, 03:01PM

Registered Member #1157 Joined: Thu Dec 06 2007, 12:11PM
Location: Houston, TX
Posts: 307

Before you go and start building an RSG, read Terry Blake's site on RSG's

I built mine around his propeller ARSG using the blower fan motor out of one of the microwaves I scavenged. It works very well, I did not have to spend too much money on the materials, and it was EASY!!!

Mine looks like this one.

Enjoy.

Kizmo

Wed Apr 09 2008, 03:22PM

Registered Member #599 Joined: Thu Mar 22 2007, 07:40PM
Location: Northern Finland, Rovaniemi
Posts: 624

I made my SRSG disk from plane grade plywood :) It is 5mm thick and has 10x 0.5mm layers. It is very, very strong material

HV Enthusiast

Wed Apr 09 2008, 03:42PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
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Posts: 3068

As Steve said, the only material to make your disks out of should be phenolic based materials, and G-10 or derivatives.

Also, Terry Blakes propellar gap is EXTREMELY dangerous, although it works well and is very easy to make. If you do make a propeller, you need it to be completely shielded inside a container. Actually, all rotary spark gaps, especially those made with brittle tungsten, should be enclosed to prevent fragments from inflicting bodily harm!

teslacoolguy

Wed Apr 09 2008, 04:05PM

Registered Member #1107 Joined: Thu Nov 08 2007, 10:09PM
Location:
Posts: 792

I am going to make a tufnol disk to and test both.

Ultra7

Wed Apr 09 2008, 06:28PM

Registered Member #1157 Joined: Thu Dec 06 2007, 12:11PM
Location: Houston, TX
Posts: 307

Dr. Shock wrote ...

Terry Blakes propellar gap is EXTREMELY dangerous, although it works well and is very easy to make. If you do make a propeller, you need it to be completely shielded inside a container. Actually, all rotary spark gaps, especially those made with brittle tungsten, should be enclosed to prevent fragments from inflicting bodily harm!

Agreed, but I don't believe that the propeller is any MORE dangerous than a disk RSG, if made properly.
My gap gets placed in a nice, old, metal clad beer cooler.
Well over 100 runs and no catastrophes as of yet.

A Tungsten welding rod is the material I use for the propeller, and the stationary electrodes are 9AWG copper ground wire held in place with bolts. My reasoning was that give the high heat element to the propeller, and the low heat to the copper, that way I could easily replace the outers, while keeping the expensive tungsten doing what it does best. . . resist heat.

HV Enthusiast

Wed Apr 09 2008, 06:56PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

wrote ...

Agreed, but I don't believe that the propeller is any MORE dangerous than a disk RSG, if made properly.

A propellar is a lot more dangerous. A RSG uses short electrodes, and moves at slower speeds, usually because it has either 4, 6, 8 (or even more) electrodes.
A propellar gap uses a relatively long tungsten electrode as the "propeller" which also moves much faster since in its simplest form is 2-spoke propellar. Its much more dangerous because of the higher speeds, the fact its more fragile in nature, and if an electrode does make contact with a stationary electrode, you are going to get much more schrapnel and possibly even long splinters of tungsten that can wreak some serious havoc.

Andyman

Wed Apr 09 2008, 09:35PM

Registered Member #1083 Joined: Mon Oct 29 2007, 06:16PM
Location: Upland, California
Posts: 256

Keep that thing low to the ground when running, too. I can't imagine what would happen if that propeller somehow slipped out of the arbor. It could end up through someones leg, or worst case, someones head. *shivers*

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