[Collins] Boat Anchor Fans

[John W. Harden, Jr.]

I use a 110VAC muffin fan on top of my KWM-2A that draws air OUT of the
final amplifier compartment...I have used this technique for years, and it
works quite well..The unit runs rather cool.

73,

John, W4NU
Atlanta
(K4JAG 1959 to 1998)

Garey Barrell wrote:

> Air flowing through a piece of equipment carries dust particles with
> it.  These particles tend to stick to things, either through oils,
> dirt or electrostatic attraction.  Anything that increases the
> _amount_  of air flowing through the device, increases the amount of
> dust  _available_  to stick to things!   Aside from an electrostatic
> filter cleaning all air admitted to the cabinet, the only choice is to
> periodically open up the cabinet brush the accumulated dust loose and
> suck it up with a vacuum.
>
> The brand of fan, or the voltage it runs on, have nothing to do with
> the amount of dust deposited; only the volume of air that is moved.
> As Ray says, if you suck air out, then other air is going to flow in
> behind it.  More air out, more air in to replace it!
>
> With equipment that is designed for convection cooling, (MOST of our
> gear,) the most efficient way to reduce the internal operating
> temperature of the ENTIRE piece of equipment is to "encourage" this
> convection.  This typically consists of a small fan on TOP of the
> unit, EXHAUSTING the hot air within the cabinet UP and AWAY from the
> unit.  Obviously, if the equipment is sitting under a shelf (usually
> supporting still more equipment!) then the next best scenario is a fan
> attached to the back of the cabinet blowing the hot air out that way.
> We are not looking for "forced air cooling", but merely to get the
> warm air out of and away from the cabinet.
>
> Air cooling is a SYSTEM.  Consideration is given in the design process
> to get heated air out of the cabinet in some specific way.  Any add-on
> that does anything other than "encourage" the designed cooling system
> is operating at reduced efficiency.  A fan isn't necessarily "more
> efficient blowing than sucking."  The only thing that affects the
> amount of air moved by a given fan is "back pressure", or resistance
> to airflow.   Again, any air that is "blown" out the front has to be
> "sucked" in the back.  Pesky physics rules.
>
> One last example and I'll shut up.   (If anyone has actually read this
> far.....)    The Drake TR-7 has a "cooling system" for the final
> amplifier.  The SYSTEM was designed for the fan to "suck" air out the
> back, and that is what Drake recommends.  Some after market "experts"
> insist that the fan must be reversed to blow in because everyone
> knows.......   Not true.  The final is way overspec'd, so it will work
> either way, but actual measurement of the heatsink temperature shows
> that it runs cooler with the fan blowing "OUT" the back.
>
> 73, Garey - K4OAH
> Atlanta
>
> ----- Original Message -----
> From: "Ray V." <w2ec@attglobal.net>
>
> > Dave,
> >
> > Are you saying this "Boatanchor Cooler" fan system creates a total
> > vacuum inside the Collins gear? I would think that if the fan is an
> > exhaust system, removing air from the Collins gear, then external
> air
> > would have to re-enter the Collins gear to replace what is removed.
> I
> > would think that, unless the COllins gear is fully enclosed within a
> > filtering system, then whatever air re-enters could bring with it
> the
> > dust, etc. How does the "Boatanchor Cooling" system filter the
> incoming
> > air to replace the exhausted air?
> >
> > I use the exhaust method as well, a simple $3.00 115vac muffin fan
> > sitting on top of my KWM-2 and KWM-2A over the HV section drawing
> air up
> > and out, with little rubber bumper feet for protection of the case
> > surface. This keeps the rig totally cool but of course I do keep an
> eye
> > on the insides for dust buildup etc.
> >
> > 73, Ray  W2EC
> >
> > David Knepper wrote:
> >
> > > The fans that are part of the "Boatanchor Cooler" system are
> exhaust fans
> > > that take warm air from inside the Collins and exhaust it outside
> the unit.
> > > No dirt, etc. can get inside the Collins as a result of the fan.
> > >
> > > Jose, you need to turn your fan around!
> > >
> > > David Knepper - W3ST
>
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