[Amps] 3D Printed ABS Plastic for Chimneys?

[Jeff AC0C]

There's not an issue with RF as you suspect assuming the pigments or any 
additives in the ABS are not RF conductive - but the heat is a problem. 
Pure ABS is a low temp material and that tube is going to melt that about 
the first time you warm it up.  And ABS resin with common additives is still 
going to have a melt temp (HDT) way too low.

The safe bet is to use automotive silicon turbocharger hose.  You cannot 
melt it and it's not RF conductive.  About $20 for a 1' length of 4" at the 
performance car parts jobber near you.

73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie

-----Original Message----- 
From: Dieter Kedrowitsch via Amps
Sent: Wednesday, November 23, 2016 1:19 PM
To: Amps at contesting.com
Subject: [Amps] 3D Printed ABS Plastic for Chimneys?

Having been bit by the home-brew 3D printing bug I've been considering 
designing and printing my own cooling chimney for a GS-35B HF linear 
amplifier I built a few years ago.  Currently the chimney is an 
off-the-shelf Coleman lantern globe that loosely sits over the heatsink, so 
I'd rather use something that's more of an exact fit to ensure all my 
cooling air is forced up through the heatsink rather than around it.

I've read that styrenes like ABS make pretty good RF insulators, better in 
fact than Delrin or acrylics, so I'm curious to know if anyone has any input 
on the feasibility of using a 3D printed ABS chimney for high-voltage HF 
use?  I use high quality pure ABS filaments so I suspect it should be fine. 
Does this sound like a safe bet or would I be best to avoid trying it. 
Obviously the amp has copious mounts of protection built-in, but I'd rather 
avoid any potential for fireworks if possible.

This particular amp and runs about 4KV on the plate and is capable of 1500W+ 
so obviously the ABS chimney would be exposed to extremely high voltages. 
For specifics on the amp itself, I documented my build a little bit here: 
http://www.w3drk.com/wordpress/?p=208
Thanks and Cheers!
W3DRK


_______________________________________________
Amps mailing list
Amps at contesting.com
http://lists.contesting.com/mailman/listinfo/amps