|Nov 11, 2010, 03:36 PM|
The AFA 68mm EDF Unit
After seeing some one else’s post regarding some of the new 64mm fan and motor units being sold by www.RC-Castle.com, I decided to peruse the site to see what else they had.
In addition to the new 64mm units, AFA has also come out with some interesting 55 and 68mm edf units.
In my quest to find some suitable 6S 2200 edf set-ups, I acquired 2 Neu 1112/1.5Y (kV=2350) motors, based on testing an Ultrafly 4024 6S motor (stated kV=2400) and the online edf calculator http://www.s4a.ch/eflight/fancalc_e.htm. Both gave results of around 35-40 amps of most popular fans on 6S. The Ultrafly motor pulled 37 amps on 6S 2200 with no thrust cone and 40 amps in a wm400 MKII with thrust cone. Alas, though, the Ultrafly motor started to melt the winding insulation and, despite its claim to be a 6S motor, is not. Enter the Neu 1112/1.5Y.
Given that all the information I had about needing a 2400kV motor for 6S operation at about 40 amps, I figured the Neu is just what I needed. Imagine my surprise (anger) when the Neu 1112/1.5Y pulled 66 amps in the WM400 MKII and over 50 amps with a HET 6904 rotor. I had learned the hard way that the Ultrafly 4024 actually has a kV around 2150-2200 and the edf calculator was woefully inaccurate.
Ok, back to the AFA 68mm fan. From the webpage, it seemed to have significantly less blade area than the Eflite, HET and WM400 MKII rotors I currently had. I figured, “well, maybe it’ll work and I won’t have to sell the Neu”.
As you can see by the pictures, the AFA 68mm fan has a fiberglass reinforced 3-bladed “sickle”-shaped impeller mounted in a fiberglass reinforced, 4 stator housing. The housing has both mounting rails and 3 lugs spaced 120° apart that can either support the inlet ring or mount the housing to a bulk head.
The 3-bladed impeller has a very small hub that was recessed towards the front; not the back as in most other mainstream fan designs. To balance it required some blue p[painters tape, as well as relieving the backside with a drill bit to get it to balance. The impellor is held in the motor shaft by a collet and hexagonal thrust washer. The back of the rotor has a hexagonal recess to register with the thrust washer.
The housing has good rigidity with the motor tube being able to accommodate any 28mm motor. The 29mm diameter Neu, however, needed the motor sanded out about .5mm to accommodate it. One thing that I was impressed with is that the angle of attack of the stators increase from the housing to the motor tube. I suspect this was done for better swirl recovery. Also with the mounting lugs, the top and bottom are not perfectly parallel, but get slightly thicker from back to front. I have one of their 55mm fans and those lugs do the same thing. I have no idea why.
So how does it run? On initial tests with the Neu 1112/1.5Y I was getting 35 amps and around 800 watts with no thrust tube. Thrust was 51 ounces which translates to 1.81 g/watt. Not bad. I was also a little worried it might “grenade” on me, but it held together quite well. After all, there’s not a lot of mass to it. Installed in my HET F-20 with a thrust cone the amps were 40 and watts almost 900. The Neu barely got warm. Most importantly the fan runs in the amp range I was looking for, roughly 20C max for 6S 2200 packs.
I’m happy I took a chance on it, as I now have a system that allows me to use my 2200 packs in a comfortable amp and watt range, while giving me 4+ minute flights, depending on throttle management. Other suitable motors may be the ARC 28-37-3, Mega 16/25/2, F5D, or HET 2w-25. I have not tested any, but they’re around the same kV.
As for others wishing to use this fan on 4S, you’re on you own. Though, expect amps to be 15-20 less than a HET 6904.
PLEASE NOTE: The pictures were taken after I ground off one of the lugs on the housing and contoured the inlet lip for installation in the HET f-20, so the pictures aren’t “out of the box”.
I hope you find this helpful,
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