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Old Feb 15, 2015, 07:19 PM
FireHawx
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It seems these 8blade 70mm are the new thing? How do they sound?
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Old Feb 15, 2015, 09:21 PM
chuck
santa barbara, CA
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Originally Posted by FireHawx View Post
It seems these 8blade 70mm are the new thing? How do they sound?
funny u beat me to the same question.................... very interested in that one.
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Old Feb 15, 2015, 09:26 PM
chuck
santa barbara, CA
Joined May 2009
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Originally Posted by bps View Post
I have a small collection of 70mm fans and decided to do some primitive testing to compare the ones I have. Here are the fans I tested;

Change Sun 12B with Turnigy 2855-2800 630 watt motor found here http://www.hobbyking.com/hobbyking/s...ner_630w_.html

3S 33 amps and 380 watts
4S 45 amps and 627 watts

FMS 70mm 8B fan and 2845-3000 found here
http://www.motionrc.com/fms-f-4-phan...p/#spare-parts

3S 40 amps and 440 watts
4S 52 amps and 675 watts

Eflight Delta V-15 5B and BL15-3600 motor found here
http://www.horizonhobby.com/airplane...ed-fan-efldf15

3S 27 amps and 305 watts
4S 41 amps and 614 watts

Batteries used were Turnigy Nano Tec 2.65A 3S and 2.2A 4S rated at 25-50c

These tests were rather crude without any kind of ducting or any intake rings. All it does is to compare the 3 fan units under similar conditions. Just thought some might be interested in these numbers. I would love to have some thrust figures to share but I do not have the capability yet.
problem is w/o the intake ring each fan reacts differently so the comparison may be skewed . really need the ring on there.
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Old Feb 15, 2015, 09:28 PM
bps
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Originally Posted by chas650r View Post
funny u beat me to the same question.................... very interested in that one.
The 8b has less of a jet sound than the 10 or 12b but much quieter than the 5bs are.
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Old Feb 16, 2015, 12:02 AM
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it is not actually about how many blades, it is the "Blade to gap Ratio" that makes the sound difference. A "low" blade to gap ratio - like where a blade is equal to the gap between them for eg. - does not give the 'solid wall of air whoosh'.
4,5,6 blades, and Wemo EVO 9 blade, are all low blade to gap ratio. And I expect the FW 8bl is also.

Note there are now 10,12,13,14 blade 70mm fans with 'high' blade to gap ratios now. All these types are more in the region of 95%+ blade, to the 5% gap. All are CS (Changesun).... or renamed/made for XRP....
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Old Feb 16, 2015, 03:43 AM
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the new 8- bladers...

Quote:
Originally Posted by chas650r View Post
funny u beat me to the same question.................... very interested in that one.
+1

8 blades seem to come into fashion, witness the HSD 75mm Viperjet, very good performance it seems, judging from the RC Informer videos etc., and pretty good sound
wouldn't mind it if they are a bit more efficient than the Change Suns (and, possibly, cope with less ideal circumstances in the ducting, and some FSA reduction in the exhaust.
haven't seen the 8-blade on sale anywhere except motion rc, shipping to Europe would be way too expensive, if I can get it in Europe or at a fair price incl shipping via Asia I'll give it a try...

EDIT: interesting what Motion RC writes: as of 9/2014 it should come with the V2 Alphajet (and F4 Phantoms) of FMS, but checking the description of the Alpha Jet at Motion, there is still the 10-blader mentioned. I remember thinking that 3000kV on 4s for a 10-blader is quite a lot, and certaiinly too much for a 2200mA lipo - and possibly for the motor if the lipo can deliver. So FMS had a problem at hand, and they apparently solved it with this 8-blade fan (lower load compared to the 10-blader). They could also have gone with a 2500kV motor - maybe the 8-blader has some other benefits?

hey, there's an alloy 8-blade 70mm rotor at HK (that's the one I would like - in plastic...)
http://www.hobbyking.com/hobbyking/s...Fan_Rotor.html
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Old Feb 17, 2015, 10:48 AM
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The description says they changed from 10 to 8 blade in order to gain extra battery life.

For the life of me none of these guys are into the science of fluid dynamics when it comes to EDFs...

.... instead of changing the horrible ducting (mostly made for 5 blade and 7 blade rotors) in these jets they just change the rotors and think the efflux and or the static thrust will increase.... or the energy in will decrease...

The total energy out (static thrust and efflux relative to bench numbers) on the multi bade fans (10 - 14 blade) coupled with the CORRECT ducting AND plane design yields results just as good as the 5 - 7 blade rotors....

Rainer said it best about a couple of weeks ago...

Most if not all the ducting in our CURRENT edfs models seem to be made for 4 - 7 blade fans (sic)...
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Old Mar 25, 2015, 04:55 AM
bps
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I am currently looking at better EDFs for the Me262. In reading through this thread looks like a inexpensive set up might be the CS12b with Turnigy 2855-2300 on 4s. At under 50 amps if I am reading this correctly sounds good. Inputs?
http://www.hobbyking.com/hobbyking/s...dProduct=71747
Thanks
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Old Mar 25, 2015, 05:03 AM
bps
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Found this on e-bay. Has anyone tested this fan?
http://www.ebay.com/itm/70mm-Ducted-...tem418475aeb4#
Thanks


70mm Ducted Fan Set 12 Blades EDF With Electric Motor kv2600 all Tested Balance



Specification:
Rotor Diameter:70mm
Outer Diameter:75mm
Weight:180 g
Propeller:12 Blade Propeller
Apply to Battery:3s-4s
Apply to ESC:60A
Motor:Brushless Motor 2839 2600kv
Maximum Current: 35-49A
Thrust: 1.1-1.4kg
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Old Mar 25, 2015, 05:23 AM
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Quote:
Originally Posted by bps View Post
I am currently looking at better EDFs for the Me262. In reading through this thread looks like a inexpensive set up might be the CS12b with Turnigy 2855-2300 on 4s. At under 50 amps if I am reading this correctly sounds good. Inputs?
http://www.hobbyking.com/hobbyking/s...dProduct=71747
Thanks
I 've used the 2855-2300kv on the 10Blade extensively on both 4S and 5S.

I believe it would also work well on 4S only for the 12B.
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Old Mar 25, 2015, 05:25 AM
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Quote:
Originally Posted by bps View Post
Found this on e-bay. Has anyone tested this fan?
http://www.ebay.com/itm/70mm-Ducted-...tem418475aeb4#
Thanks


70mm Ducted Fan Set 12 Blades EDF With Electric Motor kv2600 all Tested Balance



Specification:
Rotor Diameter:70mm
Outer Diameter:75mm
Weight:180 g
Propeller:12 Blade Propeller
Apply to Battery:3s-4s
Apply to ESC:60A
Motor:Brushless Motor 2839 2600kv
Maximum Current: 35-49A
Thrust: 1.1-1.4kg
First time I've seen this one. Doesn't seem to be a ChangeSun or XRP.

This is probably a better choice.

http://www.x-flight.com.hk/index.php...&more=&lang=en
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Old Mar 25, 2015, 05:32 AM
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from what i've read, around 3000kv seems to be the general order of the day on 4S, so you might be better off with the 2800kv version (that's what i use on my 4S-powered freewing F16) - i suppose it might depend how draggy the airframe is?
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Old Mar 25, 2015, 06:21 AM
bps
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Thanks for the input. I want to keep the amp draw as close to 100 amps as possible Pipe Dream??
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Old Mar 25, 2015, 06:30 AM
bps
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Originally Posted by anlucas View Post
First time I've seen this one. Doesn't seem to be a ChangeSun or XRP.

This is probably a better choice.

http://www.x-flight.com.hk/index.php...&more=&lang=en
That looks good at only 56 amps. Thanks
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Old Mar 25, 2015, 10:00 AM
chuck
santa barbara, CA
Joined May 2009
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the kv must vary a lot on the h/k 2300........... mine even w/ a very good low ir battery would only draw 40 amps on 4's . thrust was to low for the weight of the system , seems a better setup for 5's. 2600-2800 kv has worked better for me .
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