Alfa Fan motor and power testing :D - RC Groups
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Oct 31, 2005, 11:40 PM
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roccobro's Avatar

Alfa Fan motor and power testing :D

The Alfa EDF's have become the "new wattage" in that they are bringing in alot of new EDF fliers with their simple, fun to fly depron planes. And like the Wattage F-86 and Mig the Alfa can be hopped up with a variety of motor and battery combinations. The TP PL's are poplular and the Himax 2025-5300 on 3s is the most common setup with a respectable output.

Although the plane is "just foam" and the fan unit isn't "perfect", I have undertaken the chance to try alot of different motors in the Alfa fan unit. There are other brand fan combos that might fit an Alfa power junkies bill, but I wish to keep this motor power upgrade testing "stock" in that the new Alfa owner won't be ditching the expensive fan unit out of a kit that only comes only in a fan/plane combo.

A motors ability to spin at an rpm under a given load is a function of its torque ability. Generally, the larger the motor can diam, the greater its ability to create torque than from another motor of the same length or weight. A lower Kv motor puts it's torque band in a lower rpm, and with light weight lipos bursting from the market, adding another cell to up a low Kv motor to EDF use is easy and economical. High V/ Low A setup are also fun in that a proper motor battery combo coupled together make for a powerful setup, that sometimes has a weight loss and lower cost benefit from the smaller capacity batteries and lower (lighter) rated ESC's needed.

The alfa fan is designed for a speed 300 motor, but has room in the motor tube to be machined open for a larger Mega 16/x/x series motor to fit. The 16/7/x series is a great compact powerhouse, and actually weighs less than the Himax 2025 motors. You can buy a premachined Alfa fan housing and a reamed rotor adapter from All my New Mega motors over the years have come from Randy at and these two tested here were no different. Both shops offer excellent service, and in Randy's case, shipping is really fast. Although HobbyLobby is the sole US importer of Alfa stuff, you CANNOT order spare fan parts unless it's special order with a 6-8 week wait for delivery! The good news for a new EDF nut with his Alfa bird can take his fan unit and open up the fan motor tube themselves, and drill out the "adapter" to fit the Mega's 3.2mm shaft.

Another Mod that can be done to increase the serviceablility of the fan unit, and aid in fan balance is to drill and tap the rotor adapter for two 2.5mm setscrews. This eliminates "glueing" the loose fit rotor button on the motor shaft, that usually leads to an out of balance rotor. Tower Hobbies has tap sets for a great price, and they can be used to drill and tap the adapter in less than 5 minutes. 2.5mm setscrews can be bought from or from any GWS shop that sells replacement EDF-55/64 impeller adapter setsrcews.

Enough background, here is a screen shot of data for where I am at in my "testing". I hope to complete it to my satisfaction this week. Tomorrow should be dedicated to the 16/7/3, and then back to the Himax 4200 with a proper inlet lip. WOW, what a difference an inlet lip makes on this fan. In the process of my testing, I have found a "need" to try out some hacker motors since Philpops and Zimmerman have upped the Alfa anty in this thread.

Just to be clear, this is all static testing. While EDF *generally* don't unload in the air under regular flight, ones fan/motor combo might make different thrust readings based on many things. Inlet and outlet in my testing shows a BIG difference, and a podded installation as I am testing will have different "thrust" readings than from a unit inside a fuse. One key thing to watch is the RPM. And EDF's ability to make power (thrust or efflux) is dependant on it's rotor rpm. There are other factors that can affect "thrust" but anmost every install will be different. Again, RPM is an important reading in measuring an EDF units performance.

If you see any flaws in my data or post, please help us all out and provide the correct information. I am not perfect, and won't stake my life on my equipment. They are just the average brands of average tools other modellors have and use.


Last edited by roccobro; Nov 03, 2005 at 02:13 PM. Reason: Updated the chart
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Oct 31, 2005, 11:49 PM
EDF rules... :)
AirX's Avatar
Good information Justin..

Eric B.
Oct 31, 2005, 11:58 PM
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roccobro's Avatar
This is some pix of the 2025-4200 during a run. The RPM's were fluctuating at that moment...

Nov 01, 2005, 12:01 AM
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roccobro's Avatar
Some pictures of the Mega 16/7/4 on 4s with the inlet lip

All the clamps on the fan base was to keep it "grounded". The whole fan and stnd took flight to the ends of the wire lengths the run before it. Took a while to get up the nerve to run it again.....

Nov 01, 2005, 12:02 AM
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Thanks Eric. had to get some pictures up. In automotive forums, no time slips= lies.

Yes, I will try to get a better lit pictures. They looked good on the camera at the time!

Nov 01, 2005, 05:34 AM
who dares wins
like2fly!'s Avatar
thanks justin,

after seeing zimm's vid im definately going to swap the mp jet motor (dull). they had 15amps with the hacker b20 15L (3700kv) and 4s PQ XP 1800.
so i was trying to work out a 20Amp 4s set up to use with 4s TP Prolite2100 (same weight)
just checked mega site, the 16/7/4 is 4420kv, wow, youv'e saved me a mistake buy, i was guessing a kv for the 20amps. was going to get something around 4000.

16/7/4 looks the trick with the 4s 2100 prolite, also thanks for tapping tip etc

so from your data, i now guess would be about 22A/13.6v~300watts if in your static test

PS wow! see what you mean, Huge difference with inlet lip and outlet!! are the 4s2p PQ cells the same in both tests (just one doesn't say 12C, maybe XP?? just in case, i guess not though, i see you add exit then both and last with 2p cool, thanks again)
Last edited by like2fly!; Nov 01, 2005 at 05:57 AM.
Nov 01, 2005, 07:36 AM
Model Designer
keven64's Avatar

Very interesting results...

( Did you bother with the screen shot program I recommended ? )

Nov 01, 2005, 01:50 PM
Permanently Banned
good effort.
Nov 01, 2005, 03:05 PM
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Thanks like2fly for pointing those problem out. The packs are all the same, with the same born on date. I have 6 12C PQ4s1p 1800's, and just keep two parralleled for discharging and charging, and others single. When running static, there is no airflow and I wanted to do two things. 1) Keep the packs cool (for their safety) and 2) keep them cool for powers sake as ever time I ran up a 1p pack to 20 A, the watts in increased as the pack temp shot up and put out more juice! 1P pack would actually put out more watts than the 2P setup which is very counter intuitive in my experience. The diff is kinda null and void with the voltage staying higher with the 2p packs. It all comes out in the wash.

Keven- I did use your your software. Thanks!

Hackers just might need to be tested in the future.

Last edited by roccobro; Nov 01, 2005 at 03:17 PM. Reason: No, I didn't mean to type I "cook" my packs . :p
Nov 01, 2005, 03:17 PM
Permanently Banned
another great test would be stress test, AKA the
longevity of the fan under those powerloads.
For sure, this fan is very loud even with the MPJ 25/25 and 3S
Nov 01, 2005, 03:42 PM
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Here is a respectable chart that shows the thrust to rpm relation for the Mk1 and Mk2 Alfa fan units.

Thanks goes to What_The?! for the chart.


The AF109 just beeped. Next up is the 16/7/3!
Nov 01, 2005, 03:58 PM
Renaud Ecalle Wannabe
spit's Avatar
Sorry to barge in on your thread roccobro but what's the inlet lip you refer to on your spreadsheet? The peformance difference seems significant when present. I just got done putting my sabre together and any helpfull hints to get the maximum peformance out of this this bird would be appreciated. thanks
Nov 01, 2005, 04:42 PM
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No problem Spit, feel free to "barge in" whenever.

The inlet lip I am using was made yeserday from styro foam. It is just a rounded inlet lip, 6mm wide that goes around the inlet of the fan. This smooths out and transitions air from around the immediate area in front of the fan for easy "ingestion". In a ducted installation like yours *generally* an inlet lip is not necessary. If there is a step in diameter (enlarging) of the ducting right before the fan or if the ducting is bigger than the ID of the fan housing, you'd want to make some sort of "ramp" or inlet to smooth the airflow heading in. Ideally, the design of the ducting you would like to have would be like Klaus describes here

I don't have an Alfa plane to measure or critique, but I have heard there is gaps around the fan unit that could allow air to flow past (or blown forward) of the fan. This is not conducive to maximum performance (unless it was intentionally designed to couteract some other design problem). By taking the time to make a proper sized outlet ducting (and inlet). performance can be upgraded for "free" in that no more watts are needed to reap this lost power. Remember, turbulant air is harder to convert to propulsion and conversely can decrease air velocity (efflux) if it does not have a continually smooth duct to escape through once past the fan.

Nov 01, 2005, 05:05 PM
Begin with end in mind...
power's Avatar
Tap tap tap..... got that 16/7/3 cooking yet I am waiting to see the numbers in comparison to my Microfan setup. This is good stuff Justin thanks for taking the time.

Nov 01, 2005, 05:55 PM
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Mike-Yes I got the testing done, but my screen capture is caput! So here are the numbers:

16/7/3- G2 TP 3s2p1900- 12.5V init V- 28A/10.2V init (28A/10.5V peak)- 294W- 53.6K- 17oz's/480g thrust

16/7/3- PQ 12C 4s2p 1800's- 16.7V init V.- 38A/12.5V-64k rpm- 25oz/700g thrust
second run with warm batteries for pictures
16/7/3- same 4s2p- 43A/13.1V- 563w- 65k rpm- 28.5oz's/800g thrust. Motor 145*F and batts 110* after run.

These pictures are the PEAK after a Warm-up run of motor and first set of data collected lasting at least one minute constant. There is a big jump in performance (that I still will record conservatively) even though it ran for at least another 1 minute while I took pictures ( saw 840g at one point but didn't last). Also note, the stand needed an additional weigh from a bag of screws to stay down. The whole fan stand would twist after 50K rpm and would hold it there. I think I should do some swirl tests after the power #'s are all done (4200 motor gets the inlet lip next). I had originally noted in another thread how little twist the Alfa fan stator vanes actually had compared to my Wemo mini and micro, GWS EDF-40/50/55/64's, WPF, SFTF from England, and kamdax fan unit. Other extrapolations can be made from this observation but more testing would be needed.

I will update the screen shot with the new information when I get my comp playing nicely once more.


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