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Re: spark gap muffler?

Original poster: "Christopher Boden by way of Terry Fritz <twftesla-at-qwest-dot-net>" <chrisboden-at-hotmail-dot-com>

I've been working this week on designing/building the brunt of the new SRSG 
for Marks arrival this weekend (hence being at the motor shop yesterday to 
get the cradle).

Since the SRSG will be used in close proximity to studens/public it has to 
be bombproof.

Since the SRSG will be used often in a completely darkened room, it has to 
be light tight (or very close).

Since the SRSG performance will suffer in it's own self-generated atmosphere 
it has to be vented/cooled.

Since the SRSG is frightfully loud it has to be acousticly shielded.

All of this accounts for a serious pain in the gluteous to design.

I took one of the old 6~7' tall racks we had handy and got thinking. The 
rack is a mid 40's~60's job, and once owned by the USN. It's on nice 4" 
casters, has an exhaust fan in the bottom, solid sides of rather thick 
steel, and a set of slide-out rails about knee high.

I'm mounting the motor assembly on the rails (in a custom welded mount). The 
motor mount is made of large, thick pieces and is within the same 
superstructure as the stationary electrode mounts. The motor, electrodes, 
and everything are a completely isolated module that mounts at 4 points on 
the rails. The torque of the motor causes everything to turn, not just the 
motor so that everything stays in alignment.

The motor module is mounted on the rails and can be slid out for 

inside the rack the walls will get a layer of sheetmetal, with a "Blast 
Zone" shield made in the immediate area around the rotor. This will be most 
likely diamondplate or something else beefy from the scrap pile. We have 12 
electrodes made from 1/2" bolts 1.5" long and loosing one of those at speed 
would be deadly. The cabs on wheels and I don't care what it weighs when 
done as long as it's safe.

I'm welding in a plate above and below the gap. The "Blast Zone" will be 
only about 2 or 3' tall. From the bottom of the rack to about 12" over the 
rotor. I'm removing the fan and replaceing it with a "Squirrel Cage" blower 
pumping into a piece of flex duct (using the plastic, otherwise some damn 
fool will steal it to make a toroid, maybe even me). This will blow outside 
or whereever.

There will be a opening in the interior shield to allow air in, but won't 
let light/debris out (small channel in a z shape, same as is used for the 
door of a photolab).

The interior of the entre rack is lined with Acoustifoam, it's a cheap (when 
you only need a little for a rack,if you need to do a room then plan on 
spending $$$$$).  It works VERY well for controlling sound, 4" is definate 
overkill for a rack, but it will work I'm sure.

There will be a 4 wire cable running from the control cab to the SRSG rack. 
2 wires carry 120VAC -at- 15A for the blower. 2 wires carry 0-130VAC -at- 20A for 
the SRSG motor. There will be an emergency off button on the rack to disable 
power to both motors in the event of a problem.

This is definate overkill, but it's a fun project and I like to tinker :). 
The only downside to it is trying to keep the leads short. I can't see any 
way to do it with this setup. I CAN see a stack of NSTs sitting in the 
bottom, and caps in the top though. With a couple cables going in, and a 
pair of HV lines going out and having the entire coil system in a single 

now THAT's a neet idea.....hmmmmm

MARK! he he he

btw: We're all getting together this weekend at Sigma-6. Everyone is welcome 
to come down and tinker, there's a LOT of HV stuff going on.
Come and play :)


Christopher A. Boden Geek#1
President / C.E.O. / Alpha Geek
The Geek Group
Because the Geek shall inherit the Earth!

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