Re: [ATM] Fan locations & function for a 32

[Richard <cnc@cncservo.co.uk>]

Hi Bob,

Tuesday, January 30, 2007, 5:19:36 PM, you wrote:

BD> should the fans suck the air down and vent out the back of the box

Yes, that has been the consensus of opinion of the list when the
subject has been discussed in the past. Bigger fans run slower than
small fans and cause less noise and vibration (even for greater air
flow) and so are preferred. Personally I would go for three or four
120mm fans to give a linear flow down the tube of around 6"/sec. Use a
good quality quiet fan that is known to be well balanced in
manufacture, like the Papst 4412 F2G/L or the 4412 F2G/LL which is
slower and quieter still at the expense of air flow. Make sure they
are resiliently mounted, regardless. If you use standard fans you will
have to turn them off for all but very low power work. Some people
advocate always turning them off during observation but I've not found
it necessary since switching to the Papst fans with Sintec bearings.

We have the Computer "Modders" with their search for silence to thank
for the availability of almost silent, vibration free fans rather than
the great lumps of noisy metal of yesteryear. So look for those models
in PC enthusiast suppliers, not hardware shops, and be as picky about
fans as you would be about eyepieces.

Papst 4412 F2G/L
Flow 55CuFt/min
Speed 1600RPM
Noise 26dBA
1.3 Watts at 12 Volts DC
Size 120x120x25mm

Papst 4412 F2G/LL
Flow 41 CuFt/min
Speed 1200RPM
Noise 18 dBA
12 Volts DC
Size 120x120x25mm

Both models can be run happily at half voltage.
-- 

Best regards,
  Richard in the UK

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