[Amps] Bag-o-meter calcs in US units

[Jim Thomson]

Date: Wed, 13 Apr 2011 17:16:00 -0500
From: "Jeff Blaine" <keepwalking188 at yahoo.com>
Subject: Re: [Amps] Bag-o-meter calcs in US units

Now THAT is out of the bag thinking!  Brilliant.

73, Jeff AC?C
www.ac0c.com

###  The only part you have not factored in is...... the blower takes  time to get to max speed., nor resistance of
the bag opening up.  I think the folks in the UK years ago were using those dry cleaner bags.   The dry cleaning folks will
probably give u a few.... minus the hole through the top !    Even then,  your results  will err on the side of caution, since the
actual time to inflate the bag will be slightly faster, IF the blower was already up to speed. 

later... Jim   VE7RF 





-----Original Message----- 
From: Jim Barber
Sent: Wednesday, April 13, 2011 3:14 PM
To: AMPS
Subject: [Amps] Bag-o-meter calcs in US units

Not to run it into the ground, but does this look right?
(in US units)

. Construct a duct of heavy paper to match/mate the air output duct on
the amplifier, tape it to a US-standard 33-gallon trash bag

. Flatten the bag to eliminate as much trapped air as possible

. Fire up the amp and allow the blower to come up to speed

. Stuff the paper duct onto the amplifier output duct (get as good a
seal as possible) and simultaneously start the watch

. Stop the watch at the point where the bag is fully inflated

So assuming it took roughly 2.5 seconds to inflate the 33-gallon bag:

(1) 33 gallons * 0.13368 = 4.414 cubic feet

(2) 2.5 seconds / 60 = .0417 minutes

(3) 4.414 / .0417  = (is roughly equal to) 106 cubic feet per minute (CFM)

Seems like the very short inflation time would reduce the practical
accuracy of the measurement for larger amplifiers, but you could
certainly get a rough number. Very useful.

73,
Jim N7CXI

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



------------------------------

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


End of Amps Digest, Vol 100, Issue 53
*************************************