[Amps] High Temp silcone rubber sheet, was chimney material suggestion GI35b

[Will Matney]

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 at somis.org>
>To: "Tomm Aldridge" <KD7QAE at ARRL.NET>
>Cc: <amps at contesting.com>; "jeff millar" <wa1hco at 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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>>>>>
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>>>>>
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>>    
>>
>
>Richard L. Measures, AG6K, 805.386.3734.  www.somis.org
>
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