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Old 23rd September 2005, 02:25 PM   #11
furly is offline furly  Canada
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After a visit to the local hardware store, I think I will use a roll of Aluminum stock. I have a small piece of perf that i can use as a stencil to drill the holes into the stock myself. If I do all 4 stators at once then it shouldn't take too long to do. I can get 50'x12" for $40. The stuff is flimsy enough to be rolled length wise but it should stay nice and flat on the frame of the speaker.


Quote:
Originally posted by I_Forgot

I don't think they would make a very efficient speaker because you need to allow some space between them which means the area they present to the diaphragm will be relatively small, like using a large mesh screen for a stator.

I_F
I guess this means my idea of using the aluminum fly screen wouldn't be a good idea?
Too bad, it was only $9.99!!!

furly
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Old 23rd September 2005, 02:31 PM   #12
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Quote:
Originally posted by Brian Beck
I_Forgot, a caution that you may have already considered:
I was reminded of this concern by a device I have. It is an air-ionizer/cleaner. It uses a weak high voltage supply connected to a small exposed rope of interleaved carbon fibers that is wrapped around a plastic insulator. Here the designers were using the high curvature properties of the carbon fiber to create coronas. And it works. You can hold your hand nearby the rope and feel the electric “wind”.
I think you have conductive coated plastic fibers in that device.

Real carbon fiber material, whether it is just roving or cloth, is too hazardous to be put in a home environment without having a binder like epoxy or polyester resin completely covering it. CF cloth is made of coarse tows consisting of 3000 or more actual carbon fibers bundled together. Individual fibers are very stiff for their diameter and will break and fly off as "dust" (actually needles) from simple handling/flexing. The dust is very sharp because of the small diameter of the fibers (the 3000 fiber tow is maybe 0.1 mm diameter) and is a severe irritant to skin and mucous membranes. I have inhaled those little ******s a couple times and the coughing fit they induce would make them suitable for use as nonlethal crowd control weapons.

CF cloth should be handled with gloves, long sleeve shirts, a dust mask, and eye protection. The dust is conductive and will cause all sorts of problems if it gets into electronic devices.

Your point is valid. It remains to be seen whether the resin in the composite would control corona. It's just one more reason to build a test panel.

I_F
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Old 23rd September 2005, 09:54 PM   #13
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Quote:
Originally posted by furly
I guess this means my idea of using the aluminum fly screen wouldn't be a good idea?
Too bad, it was only $9.99!!!
furly
It might work fine. Many people have used window screen attached to fluorescent light grids for stators. The grids provide the mechanical stability that the screen itself lacks.

At $10 it is certainly worth a try.

I_F
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Old 24th September 2005, 05:14 PM   #14
Lucius is offline Lucius  United States
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I've done some googoling and the C/F composite looks interesting.
I'm thinking about a 6" panel mounted in a plywood baffle to get
some bass out of this width.
You can get pre-pregnated panels, .014"x6"x48" for under $50
a pair. Or even cheaper if .007" thick. Drilling the holes in a panel
this size might not be daunting and minimal dust in case the GF
with asthma walks in my small condo, or worse if one of the cats
jumps in the act....
Would .007" or .014" thickness be stable in a panel this size?
Otherwise you can get them thicker but bigger $$.

Lucius
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Old 25th September 2005, 06:00 PM   #15
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AFAIK, pre-preg panels are CF cloth that has been wetted with epoxy. They are shipped frozen to keep the epoxy from setting. I don't know where you would get something like that in onesy-twosy quantities- they are usually used by CF plate and tube manufacturers who buy in quantity.

What you will get is probably a rolled up piece of epoxied cloth packed in dry ice. You'll need to roll it out flat on a surface that the epoxy won't bond with and it would probably be a good idea to have a similar flat surface to put on top of it and squeeze it flat. Pre-preg stuff is used when minimizing the weight of the final composite part is important. That isn't really a concern here, so why pay extra for it?

If you're going to that much trouble you may as well just buy a yard of CF cloth and a quart of epoxy/polyester resin to mix yourself. It will cost less, and if you have a problem you'll have plenty of material to start over with. One running yard of CF cloth is usually 36" x 48-50" depending on the manufacturer.

I_F
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Old 25th September 2005, 09:19 PM   #16
Lucius is offline Lucius  United States
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Quote:
AFAIK, pre-preg panels are CF cloth that has been wetted with epoxy. They are shipped frozen to keep the epoxy from setting. I don't know where you would get something like that in onesy-twosy quantities- they are usually used by CF plate and tube manufacturers who buy in quantity
"THE GRAPHITE STORE"...Also a good source for graphite powder, rods and a graphite
conductive spray. The panels are shipped with 1 face prepared for gluing.
You have a point on getting the fabric. Even if the panels are gift wrapped, someone
like me is likely to make a goof..Site is here....

http://www.graphitestore.com/cat.asp/spcat_id/2

Lucius
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Old 26th September 2005, 06:07 AM   #17
Lucius is offline Lucius  United States
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Quote:
What about using CF rods to build the stator?
An array of small carbon fiber rods arranged horizontally would make for an interesting look. And couldn't one bow the rods to make a curvilinear panel?
What would the effect of pushing sound around these cylindrical surfaces be?


Cody
My posts in this thread are about panels, but the site I noted has solid rods
which might be a more efficient. You wouldn't have to go with what seems
to me a complicated crate & wire jig. Keeping my small system simple I would
go with the straight hoizontal look. Any simple ideas?

Lucius
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