In this instance, bringing the pipe up to the fins at the bottom should
work. The pipe ID is 3.998" and the tube's OD is 3.945". If you wanted
to bring the pipe up over the fin body, you should use pipe/tubing just
slightly larger in ID than the fin bodies OD. Even though the air temp
is only about 110 deg. F., the anode temp can get to 200 deg C, or 392
deg. F max at the anode connector. This heat is then dissipated by the
fins. It could cause softening if the pipe is touching the fin body, I'm
not sure. Some other steel tubes can run hotter than this. Plus there's
the RF rating of the plastic. If it'll withstand a microwave test on
high heat for about 1-2 minutes, it should be ok.
What I've been looking at is using a fish-paper type tubing. Fish paper
is a rag type paper with a clay mixed in. It's heat rating in
transformers and other electrical components is good and the
flammability is really low. A good stiff piece of fish paper could be
made into a tube easily, then glued making a good chimney. I know fish
paper can withstand 350 deg F. easily as this is the temp transformers
are baked.
Will Matney
K7RDX wrote:
Hot water PVC works perfect with the GS-35b(At hf) and shows no sign of
melting even at full output for an extended period of time. Four inch fits
the tube cooler and I have used this type chimney in my amp here for four
years with no problems.It`s also a lot nicer than trying to brew something
from a sheet of plastic,etc.I have not tried pvc at vhf/uhf....Has anyone ?
Jim,K7RDX.
----- Original Message -----
From: "R.Measures" <r@somis.org>
To: "Tomm Aldridge" <KD7QAE@ARRL.NET>
Cc: <amps@contesting.com>; "jeff millar" <wa1hco@adelphia.net>
Sent: Saturday, October 23, 2004 11:09 AM
Subject: Re: [Amps] High Temp silcone rubber sheet,was chimney material
suggestion GI35b
On Oct 23, 2004, at 9:02 AM, Tomm Aldridge wrote:
Also, go to your local Target, Wal-Mart, etc cooking department and
you will find Silicone baking sheets which are approx $10 / sq ft and
fairly stiff so making a chimney should be easy. Other options from
the same area of the store are Silicone cutting "boards" and Silicone
trivits (hot pads). All of these will make respectable HV insulator
material as well I would think.
Another way to go is to mod a round plastic food container with a
snap-on lid that is microwave oven safe: cut a hole in the bottom with
a dedicated (to plastic cutting), conical soldering iron tip, glue the
box to the chassis with silicone rubber, let cure for 24-hrs, cut a
hole in the lid that will snap on over the anode. // note: the
typical air temperature that comes out of an anode cooler is about
110ºF less than the softening point of such plastic.
Tomm Aldridge wrote:
I believe you can get it from McMaster-Carr online.
jeff millar wrote:
This question reminds me. Who supplies the red high temp
(silicone?) rubber sheet used in chimneys on some of the commercial
amps?
jeff, wa1hco
Manuel R. Alonso / KC4MNE wrote:
Hello
Could PVC pipe be used for a chimney? If not were could I find a
suitable
material?
4" is perfect for the GI35b tube?
Thanks
KC4MNE
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