[Amps] Coupling a blower to an air system socket

[Jim Thomson]

Date: Fri, 15 Mar 2013 20:58:34 +0000
From: Alan Ibbetson <alan at g3xaq.net>
To: amps at contesting.com

Subject: [Amps] Coupling a blower to an air system socket
For minimum airflow resistance for a forced air cooled amplifier it 
would seem the blower needs to discharge in a straight line directly 
into the underside of the valve socket. This leads to a fairly tall 
structure with the blower underneath the RF deck.

What is the "right" way to make the physical connection between blower 
and air system socket? Rigid ducting? Something resilient like rubber? 
Or (what intrigues me) how about a fabric transition duct as shown in 
several places here

http://users.pipeline.com.au/~burst/stc.htm

The "floppy" fabric seems attractive as a way to take up minor (major?) 
misalignment between the blower and RF deck if they are built as 
separate units and should help isolate any blower vibration. A competent 
seamstress (seam-master) would be able to take differences in duct shape 
and size in their stride too.

Has anyone got a feel for the pros and cons of the use of fabric rather 
than more rigid blower couplings?

73, Alan G3XAQ
-- 

Alan Ibbetson
alan at g3xaq.net

##  fabric will work, but why bother?  Mount the blower on the rear apron / panel. 
It will pressurize the compartment anyway, and then do a 90 deg, up through the tube 
socket.   The trick here is..... don’t direct the airflow directly across the socket !  Offset
the blower outlet to either side. 

##  A variation of this is to mount the blower some distance away from the RF deck,
then use flexible 2-3-4-5-6 inch dryer hose  to rear off  RF deck.   The mating
2-3-4-5-6- inch female is then simply  squished a bit, so it’s now an oval shape, and
ditto  with the end of the dryer hose.   Check out stove/ wood stove  fittings too. 

##  a friend did just this on his hb YC-156 amp.    Blower + HV supply are located in the basement,
while the RF deck is on the main floor above.   Top lid on RF deck is solid Aluminum sheet, no vents.
A 2nd dryer hose is attached to the rear panel of Rf deck, this time above the chassis, and not an oval
shape, but round.   2nd hose is fed back down into the basement.   

##  You end up with a loop.  Dead quiet  since blower is one floor below.  No heat in shack either. 
In winter, you can simply exhaust the hot air into the shack.   If you want to see what this all looks like,
you can see pix of it on    http://groups.yahoo.com/group/ham_amplifiers/photos/album/654737392/pic/2052134623/view?picmode=&mode=tn&order=ordinal&start=1&count=20&dir=asc

Later........... Jim   VE7RF