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Which fan?

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#1 tag1260

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Posted 13 October 2013 - 09:56 AM

Looking to find the best fan for a dob. Quietest, most airflow, smoothest running and such. Is there a difference between them or are they all about the same.
Thanks

#2 careysub

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Posted 13 October 2013 - 10:27 AM

Although all fans with the same air flow will cool the same, they are not all about the same - there is a wide variety of sizes, speeds, and bearing designs.

Larger, slower fans are quieter than faster ones. Keep the speed below 1500 rpm. If dimensions allow a 120 mm very slow fan is nice. Not knowing the size of your scope it is hard to recommend something particular, but check this out for advice on CFM ratings:
http://www.fpi-proto...r/fanselect.htm

The best bearings are hydrodynamic or magnetic bearings, they are vibration-free and will never wear out. There are a bunch of different names manufacturers use for these suspension technologies - it is perhaps easier to avoid ones with the descriptions of "ball", "sleeve", "rifle", or "oil" (though look for bearings containing "hydro", "magnetic", "barometric", "flux", or "fluid" in their descriptions).

Additional vibration protection can be had by using an elastomeric mount - suspending with rubber bands is popular, but gluing the fan on to small blocks of foam is very good and may be easier.

A good place to shop for fans, with a vast selection, good prices, and an excellent search system is NewEgg:
http://www.newegg.co...3?Tpk=case fans

(A bizarre "feature" of many fans is having an LED, it seems that many nerds/geeks are attracted to the bright flickering light - either avoid these or plan on removing it.)

#3 kfrederick

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Posted 13 October 2013 - 10:27 AM

http://www.frozencpu...30/Akust_Rev...

#4 JM La Galette

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Posted 14 October 2013 - 02:14 PM

It is often said the best fans for astro are the most quiet ones (less vibration).
I've chosen the Noiseblocker UltraSilentFan-XL2 (120mm) for a 16". I'm sure 80mm would have been OK as well.

Jean-Marc

#5 SACK

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Posted 17 October 2013 - 08:12 PM

I was very happy with this FAN . I compared it to another brand, i had them up for sale once as you know tag, and airflow, vibration, noise was a world better. Also comes with a fan speed control.

#6 Redstone2

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Posted 18 October 2013 - 10:58 AM

Here is a two speed fan: http://www.newegg.co...N82E16835608005
Nice and smooth for me.
Noctua makes 120mm (and larger) fans.

#7 tag1260

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Posted 06 November 2013 - 12:17 PM

Here's what I ended up getting.
http://www.newegg.co...N82E16835220059
I'll let you know how it works when I get it mounted and try it out but it will be a while until then.
Thanks

#8 Dr. Hoover

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Posted 25 November 2013 - 10:11 PM

This thread very much interests me, and has helped convince me that I should install a fan on the scope that I am building. Most of the fans suggested in this thread appear to be made for computers, which have their own power source that the fan can be attached to. How would you get power to the fan on a telescope, particularly if it is not near a power outlet?

#9 azure1961p

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Posted 26 November 2013 - 06:12 PM

I use 12v DC fans. I power them off a 6v boxy flashlight battery. If u go to a tattoo supply store you can get a cheap power source to regulate the voltage from zero to 18. I don't recommend over six for vibration/quiet reasons. Anyway the tattoo machine power source had for a scant $30 converts AC to DC so u can run your fans plugged to an outlet as well.

Pete

#10 dag55

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Posted 27 November 2013 - 01:16 PM

I used a low noise- low rpm 12v dc fan for cooling the primary as well as a smaller fan located across from the primary for removing the boundry air from off the face of the mirror, I hooked them up to a potentiometer to control the speed and yes get the slower rpm models with the bearing types described above are the best. Also I mounted the fans with navcom rubber bushings between the fan mount bracket, you can get the navcom rubber from an archery pro shop as it is used for reducing vibration in bows. I also used a low density plastic such as 55 gal. blue plastic barrels are made of, very tough and easy to work with and it doesn't transmit vibration as much as metal or hard plastic does.
Dane

#11 rlmxracer

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Posted 27 November 2013 - 02:27 PM

Here's what I ended up getting.
http://www.newegg.co...N82E16835220059
I'll let you know how it works when I get it mounted and try it out but it will be a while until then.
Thanks

You might be disappointed by that fan. It only flows the same amount as the stock 80mm fan. I originally got a similar one only looking for the quietest fan with no regard to the amount of airflow. Yes it was vibration free but even mounted in a baffle it seemed to take forever to cool my 10" dob. After learning that $20 lesson I purchased a fan with a great combo of flow vs noise. http://www.newegg.co...N82E16835103061
It's rated at 69cfm and 19db. I got the one with red LEDs thinking it was behind the mirror it would be ok. Wrong, I had to clip the wires to the LEDs.
Now at 12v my mirror is cooled in about 20min with a baffle and Deleo ring to direct the airflow around the mirror. I bought an AC adapter with selectable voltage and the fan will run on 6/9/12 volts. When observing I usually run it at 9v. Good luck.

#12 rlmxracer

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Posted 27 November 2013 - 02:48 PM

Also here's some light reading on the subject. http://www.cloudynig...5594403/page...

You can see pics of my set up on pg11, but there are many others that are way nicer looking lol.

#13 tag1260

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Posted 08 December 2013 - 08:03 PM

OK guys. I went and picked up the 120mm fan and now by my design, I can't use it as it's too big. I'm looking to go with 80mm but have a completely different sort of question.

I see fans listed as PWM. What does that mean and can I use one.

Thanks

#14 rlmxracer

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Posted 08 December 2013 - 08:50 PM

Pulse width modulation is a way to control fan speed.
http://www.coolerguys.com/pwmfans.html
You sure you can't run a 120mm fan? That's a big mirror to cool with a 80mm.

#15 tag1260

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Posted 08 December 2013 - 09:29 PM

I don't think I have room for that large a fan. I have a 90mm, which is the same size as the stock fan on my Antares scope, and it looks to be about the perfect size. Only thing is, I don't see a reasonably price quality 90mm anywhere, although I'm still looking.

Thanks for the info on the PWM. I take that we don't have any way to control one? Or do they take a controller?

Thanks again

#16 rlmxracer

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Posted 09 December 2013 - 12:57 AM

You could use one of these between the battery pack and the fan.
http://www.amazon.co...p/B00CGXJSNY...

#17 Víctor Martínez

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Posted 09 December 2013 - 05:31 AM

I installed this:
http://www.bequiet.com/en/casefans/259






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