[Amps] Centrifugal Blowers

Thu Jan 27 10:34:00 EST 2022

From: Byron Tatum <bjtatum1 at att.net>
To: Amps Group <amps at contesting.com>
Subject: [Amps] Centrifugal Blowers
Message-ID: <2012770418.1476844.1643242299355 at mail.yahoo.com>
Content-Type: text/plain; charset=UTF-8

Hello-? ?Anyone in our group have knowledge of replacing the motor on a
centrifugal cooling blower? I have been rebuilding a few RF decks made in
the 1970's by Scientific Radio for the SR-416A transmitter. These RF decks
are a copy of the Eimac W6PO 144 Mhz design using 8877 tube. They use a
Kooltronics blower with 5" wheel and square outlet with mounting hole
centers 2-5/8" apart in a square pattern. I have bearing noise and
vibration in a few of my motors. The motors are sealed bearing Kooltronic
#7162-082 type U62, 115 VAC @ 1.55 amp, using 4 ufd capacitor. 2850 RPM at
50 Hz, 3400 RPM at 60 Hz.? ? After looking at prices of replacement
blowers/motors I was shocked. Can I replace the bearings in these motors?
Or just buy new motors somewhere? I really do not need the performance of
these blowers, the transmitters were running at 1 KW 24/7 and I am just
doing SSB/CW. Sure could stand to reduce the blower noise some.?
?Thanks,Byron W5FH?

##  Phone / contact  Kooltronics and ask them if the bearings can be
replaced..and if they stock them.  I believe a special bearing tool is
required to remove / install them.   They might also be able to replace em
for you.  They are nice folks to deal with on the phone.   German
EBM-Papst blowers, like what's used on the Ameritron amps, indeed, have
replaceable bearings..as does the old  Rotron  CX-33, used on many FM
broadcast stations.  The CX-33 is still rebuildable, even though out of
production for years.

I had several CX-33 blowers, with the cap start, these were 230 vac single
phase types..and tried them on my small 0-240 vac @  5 amp variac.  Worked
superb.  I could dial it up anywhere from a crawl to full bore..and
everything in between.  Then ran em for extended hours..at intermediate
speeds, with no degradation, or heating etc.  A metal finned resistor can
also be used to slow em down.

Dayton blowers have a huge catalog online.  They revamped their blower line
up a few years ago, and the new versions all have ball bearings, no sleeve
bearings..and the new style / design motors only draw  1/2 as much current.
Available in flanged or unflanged.   Detailed dimensions, including flanges
etc, etc, online.

I bought 4 of the ebm papst blowers..to replace the oem drake blowers, in
my 4 x L4B's.  These are the same ones used in the ameritron  AL-1500  8877
amp.  On that ameritron amp, they offer 3 x speeds, by changing taps.  IE:
3 x different voltages fed to the  120 vac blower.   Max speed, and 2 x
slower speeds.   Max speed used for RTTY / FM. Lower 2 are for ssb / cw
etc.

I bought mine from Digikey. Mouser also sells em. The Baffling part is...
the 230 vac version is one helluva lot cheaper than the 115 vac version,
like almost 1/2 price, go figure. I never run the drake amps on 115 vac, so
it's a moot point.

I have seen too many blowers getting tossed... simply from a bad bearing.
A freq drive will also work to slow em down.  Chinese variable freq drives
are cheap..and actually work good.

I also use ebm papst  deluxe  EC ( electronic commutator)   115 vac
version  blowers.  With a 10 k pot wired in, the speed can be changed from
1/2  rpm, to max rpm.  These are  70 cfm @  1.2"  high pressure types, used
on 3CX-3000A7 tubes.  It also has a tachometer output, and bearings are
field replaceable.  Beauty of the EC motors is... they draw a miniscule
amount of current, like just .4 amp on high speed...and only .12 amp on low
speed.  Don't even  run luke warm.

Jim   VE7RF