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Re: Poor Form? (fwd)
---------- Forwarded message ----------
Date: Sat, 14 Feb 1998 16:16:07 -0600
From: Chuck Curran <ccurran-at-execpc-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Poor Form? (fwd)
-----Original Message-----
From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Saturday, February 14, 1998 2:46 PM
Subject: Re: Poor Form? (fwd)
>
>
>---------- Forwarded message ----------
>Date: Fri, 13 Feb 1998 23:44:56 -0500 (EST)
>From: richard hull <rhull-at-richmond.infi-dot-net>
>To: Tesla List <tesla-at-pupman-dot-com>
>Subject: Re: Poor Form? (fwd)
>
>At 10:16 PM 2/12/98 -0700, you wrote:
>>
>>
>>---------- Forwarded message ----------
>>Date: Thu, 12 Feb 1998 11:07:30 +0000
>>From: "Gregory R. Hunter" <ghunter-at-mail.enterprise-dot-net>
>>To: Tesla List <tesla-at-pupman-dot-com>
>>Subject: Poor Form?
>>
>>Dear Folks,
>>
>>Thanks for answering my query about sonotube. I've seen it before
>>at construction sites, I just didn't know it was called "sonotube".
>>
>>One writer has suggested that this may be a poor choice of coil
>>form. Is cardboard tube lossy or something? For low RF losses, I
>>would think well-sealed cardboard would be nearly as good as air, and
>>superior to PVC.
>>
>>Greg
>>
>>Dreaming of Megavolts in East Anglia, UK
>>
>>
>Some folks claim OK results with cardboard. I have measured Q's of
unsealed
>cardboard resonators and found them the worst of all form materials tested.
>PERIOD!! We did a complete series of tests on one of our video report
tapes.
>
> With small coils you will not really lose all that much. Wood forms
>turned out to be the second worst form material. PVC turned out to be
>rather good! The best is styrene, Teflon, or the ultimate would be a
>polyethylene storage tank. Ed Wingate uses this for his current magnifier
>driver. Except for the terrible wood and paper based products, I really
>believe the coil form material choice is another coiling non-issue. Just
>keep the form material as thin as possible and make sure it is a modern
>plastic product! All the losses in any form are purely dielectric losses.
>Choose it as you would choose a capacitor dielectric to operate in the
>50-500khz range with low losses.
>
>Richard Hull, TCBOR
>
Richard, All:
Just as a tip for anyone looking for a source for a polyethylene storage
drum. I was able to obtain 7 drums made of high density polyethylene from
by brother in-law, who manages a prison laundry (He is not a prisoner!).
These containers held a liquid detergent and are perfect cylinders 22.75" in
diameter by about 33" tall. These are 55 gallon drums and 32 gallon were
also apparently available, but I didn't get any measurements from these. I
would guess as many of us scrounge at neon sign shops for transformers, a
stop at a hospital (or prison) laundry may also provide for some great
materials.
These HDPE drums can not be glued in any manner that I am aware of. The top
and bottom lids are inertia welded into place and I found that they can be
"WELDED" together by using a 200 watt soldering iron. After carefully
aligning the drums, I simply dropped the big soldering iron through the drum
bung hole, mounted on a long stick and melted the bottom of one to the top
of the other, using 16-18 joints. I then wacked the heck out of the
assembly and nothing even came close to failing. The assembly basically
ends up with internal stiffening from the drum lids. The lids do have to be
trimmed and the joint filled in. I trimmed mine with no trouble, but I
won't be doing the "body work" until it warms up around here. The wall
thickness is about 5/16" on these units, in case anyone is wondering about
that point. I'll be posting more on this attempt later this spring. The
moral here is not to go to prison or the Hospital for Tesla materials, but
some handy materials are available out there if you keep looking for them.
That old saying about not what they are, but what they can be----
Chuck