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