[pure-silver] Re: air pump for Devere 108S
- From: Georges Giralt <georges.giralt@xxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Sat, 12 Jan 2008 09:07:09 +0100
Shannon Stoney a écrit :
I have a Devere 108S (which I've talked about a lot on this list). It
is an old, huge, cranky machine, with a very noisy motor attached to it
that pulls air through the head.
Hi Shannon !
I hope I'm not too late on this one ...
You have been said that the noise is/may be due to ball bearings. It is
a possible cause of the noise, best to be checked.
But, in another post you state that the negative move quite like a flag
on the wind if the door isolating it from the condenser/lighting stage
is not well closed.
This lead me to think that your blower is a little bit on the overkill
side and that the air that goes in has no way to go out... So "it
bounces back" and impose a stress on the motor making it vibrate more
than planned and make noise.
My little knowledge on cooling thing is that you can make it without
noise (well quite), provided that the air coming in goes out as freely
as possible.
If you get fans with blades designed to be quiet, you will like it and
spend more time in the darkroom.
Here is my suggestion :
1) measure the opening of the vent on the head where the previous fan
goes in.
2) look at the opposite side of the head and ask yourself if there is an
opening of an equal surface to let the air out. If yes, my first
hypothesis is wrong. If not you've to make one.
When done I suggest that you buy one fan (like the one planned for
computer venting) made by a reputable maker in it's silent grade (or
medical range). PABST comes to mind, but there are others in the USA.
Then when building your darkroom, make a support for this fan ( a small
box will do into which you will accommodate the small 5 and 12 V
computer power supply), a loose foam filter in the intake a and a
metallic grid to prevent fingers to be caught by the blades) then a
small length of flexible tubing will direct the air to the head to
prevent fan vibration to get to the head and you'll be done.
IMHO, enlargers makers are not good at cooling their stuff : my Durst
Laborator 1000 has a tiny lighthouse and can accommodate a 300 W bulb.
As it is painted black inside, to can become very hot if you use the 300
W bulb. To vent this, they have made a very clever device to make music
: the top of the box has two slots 1/2 inch with and 3 inches long. But
to prevent light to escape and ruin contrast on prints, on the inside
they are closed with a thin sheet of steel. The fan does suck air from
the lamp house. Air comes from the two upper openings, causing the metal
sheet to act like a flute... Tuning the air flow, you can adjust tone to
a B or D tone... Go figure ! Of course, if you revert the air flow, the
pressure force the metal sheet to close and the whole head vibrate as
the incoming air column vibrate due to it bouncing back and forth... So
it either noisy or useless.
This may explain why Durst did not sell the fan in large quantity and
people sticked to the 150 W light bulb which is the upper limit before
venting.
Just my 2¢ ;-)
Oh, BTW, I would be delighted to see plans of your darkroom !
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