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Re: rotary gap electrodes


I use 12" x 2" x 3/8" aluminum bar on each side of my rotary break
wheel with 1/8" tig welder tungsten rods in the aluminum bar as
stationary electrodes and 8/32 stainless steel screws on the 2 x 3/8"
thick sandwiched lexan(180 degrees wrt each other neutralizes warpage
effects-makes it nice and flat and strong) rotar wheel (12" diameter).
The aluminum bars become hot to the touch after 2 minutes of cw coil
operation but not too hot to touch.  As Richard Hull pointed out
to me recently, acrylic is dangerous to work with as it can shatter
into sharp shards.  That is why I remade my break wheel out of lexan.
The tungsten rods get very hot.  They will melt the plastic.  That is why
I used aluminum bars.  I used 1" x 3" long brass rods on my first attempt
and melted the tungsten rods after 20 minutes of cw coil operation.
The stainless steel screws on the break wheel never got warm and wore
very little.

                                        Barry

 ----------
|From: "tesla-at-poodle.pupman-dot-com"-at-PMDF-at-PAXMB1
|To: Benson Barry; "Tesla-list-subscribers-at-poodle.pupman-dot-com"-at-PMDF-at-PAXMB1
|Subject: Re: rotary gap electrodes
|Date: Thursday, August 22, 1996 6:06AM
|
|<<File Attachment: 00000000.TXT>>
|From Esondrmn-at-aol-dot-comTue Aug 20 22:29:17 1996
|Date: Tue, 20 Aug 1996 17:12:44 -0400
|From: Esondrmn-at-aol-dot-com
|To: tesla-at-pupman-dot-com
|Subject: Re: rotary gap electrodes
|
|In a message dated 96-08-19 00:39:59 EDT, you write:
|
|<<
| Greetings,
|
| I'm asymptotically approaching the state of rotary gap construction known
| as completion.  I thought I would ask for others input before proceeding.
|
| The design of my rotary has two 1" thick 14"x14" pieces of plexiglass to
| hold the bearings and act as side shields.  The stationary electrodes are
| going to be mounted to the plexiglass and poke into the box where the
| disc is rotating.  I am using 1/8" tungsten TIG welding rods for
| stationary electrodes.  The input power will be less than 10KVA.
|
| My questions are: How much cooling of the stationary electrodes do I
| need to do?  Will putting the W (tungsten) rod into a piece of 5/8" brass
| rod 2" long be enough to prevent the rod assembly from getting so hot
| that it melts the plexiglass?  I have also considered some sort of
| non-thermoplastic insulator to surround the brass.  Another option is a
| 1" rod of Al with the W rod in it.  The Al could have cooling fins turned
| on it too if necessary.  I don't figure ohmic heating will be much of a
| factor, but the arc will be hot and so heat the electrodes.
|
| Any input would be appreciated.
|
| Chip >>
|
|Chip,
|
|I have my stationary tungsten contacts mounted in 1" x 1" copper blocks that
|are about 3" high.  These are then mounted in nylon blocks for insulation and
|the nylon is mounted to the steel base.  I would say you will need some heat
|sinking although I don't know how much.  The ends of the tungsten rods do get
|hot enough to melt!
|
|I use 5/16" dia. tungsten because that is what the welding shop had - used
|for TIG welding.
|
|Ed Sonderman
|