Testing the WM600 (part 2) - RC Groups
Thread Tools
Sep 03, 2004, 05:37 PM
Registered User

Testing the WM600 (part 2)

At the middle of July I had to interupt the tests of my new EDF because of private reasons and the demise of the employed MEGA MINI 7 (a brushed motor).
I received a new motor the other day and will now carry on with my test program shortly (still with the original fan rotor). A new rotor for the MEGA with 10 winds is also on the way - but that may take some weeks.
Someone here in the forum (Hi Stu, are you reading?) suggested that I should check the motor efficiency, since there are no data available.
Going through a lot of storage boxes I found this little gadget which I will use shortly to do exactly that. It's a torque balance which I used years ago to measure and optimize prop-motor and gearbox arrangements. But it will also do without the gearbox. I only have to find some motor support clamps.

Have fun with fans

Sign up now
to remove ads between posts
Sep 03, 2004, 07:36 PM
The blade numbers go up to 11
stumax's Avatar
Klaus, good to see you back into it! How does your torque balance work? I'm gonna have to make up something for myself as well, as I no longer have access to the lovely Schenke dyno they had at my old job. I have a torque stand I used in the old days when I flew F3D. It was just a motor mounted on a freely rotatable shaft with a rigid pendulum and a scale and pointer to indicate the torque reaction. I may instrument it up by putting an angle encoder on the shaft then I can log the readings.

Sep 04, 2004, 08:58 PM
Registered User

Efficiency of MEGA MINI 7

Hi Stu (and anybody else interested...)

today I did measure the MEGA MINI 7 (replacement).
Surprise, surprise!
I cut down an old Graupner prop just to have the right resistance at ~20,000revs as with the fan. I measured power in and torque and rpm.
The average of five measurements over a time span of about two hours ( to allow to cool down in between) and many intermediate measurements for lower powers, indicates an efficiancy of 0.58. The best individual value was 0.59, the worst 0.56.
I will fit the motor to the fan tomorrow (later today) and do some more testing of the WM600 as it stands.
If the motor's eff. is really as low as that, my fan is even better than I calculated originally (0.82). But we will see.
This is getting quite exiting!

Have fun with fans

Last edited by winmodels; Sep 04, 2004 at 09:00 PM.
Sep 04, 2004, 11:06 PM
The blade numbers go up to 11
stumax's Avatar
Klaus, try a shorter arm to get a higer force on the scale. As it is, with 1gram resolution and only 12 grams force (is that correct?) the final power calc can be in error by around +-4% (ie 12 grams could be between 11.50 or 12.4999. I'd also try a bunch of different props to get a power curve rather than one reading especially as you're not really using the full range of your scale. Either way, your fan sure looks like it's very efficient! BTW, do you have access to a digital voltmeter and current transducer? You really should measure the voltage across the motor terminals as those long leads will be dropping some voltage. Hope you don't mind me nit-picking - data acquisition was one of my specialties at my former job.

Now, when do we see 1kW thru the fan?

Sep 05, 2004, 07:24 AM
Registered User
Hi Stu

it was already quite late last night so I didn't include the whole story.
This 12gr has to be viewed with the figures on the A and V meters, 5V and 9A = 45W - that's the lowest end of the scale at 7750rpm.

The highest figures were: 16V 32A 130gr and 21500rpm (I redid the high numbers several times - the scatter is negligable)

Yes, you are right with the meter across the motor terminals. I have done that in the past, but the differences are very small as long as the wires are appropriately sized (2.5sqmm) for the load (32A max) and not too long.

It took quite a while to get the prop to the right diameter (cut and balance in small steps). I wanted to have the same load as the fan at the same revs. My reasoning behind that is, that as long as I represent the same load as the fan at the previously (in July) measured test then I would get the motor efficiency at those conditions. If you load it lighter the eff. goes up.

If I find it necessary I may invest in some fancy transducers and data acquisition software. But foremost is the making of the fan.

Have fun with fans

Last edited by winmodels; Sep 05, 2004 at 07:27 AM. Reason: typos
Sep 05, 2004, 06:11 PM
Registered User

That's it! - 87% eff. for the whole EDF WM600


I spent a busy afternoon playing with the WM600.
The result is very satisfying - the best so far!!

Going through the results for now I can only give the top figures:
voltage 15.4V, current 32A, motor eff. 0.63, shaft power 312.5W, rotational speed 23800rpm, static thrust 1000gr = 9.81N = 35.3oz, air exit velocity ~55m/s = 120mph,
Total EDF efficiency = 0.87 - 87% (includes duct losses), fan (rotor and stator) efficiency = 0.91 - 91%.

Maximum power was restricted by the power supply at A max = 32A.

There is no significant whirl left at the exit, as can be seen from the (non) rotating star and the tufts.

Now I start thinking about serious production.

A comprehensive analysis of the measured data will follow shortly.

Have fun with fans

Sep 05, 2004, 06:17 PM
Registered User
The last picture shows fan ccoling fan between test runs.
At the "high" power end about 200W are converted into heat and I didn't want to risk the failure of the previous episode. The highest measured temperature was 52 deg.C on the outside of the motor tube.

Sep 06, 2004, 03:25 AM
Registered User
have tou any idea how much you will be charging for these fans klaus. I am very excited about the efficiency levels you have managed to achieve! Its great to see someone furthering the possibilities of edf like this! keep up the good work!
Sep 06, 2004, 05:17 AM
The blade numbers go up to 11
stumax's Avatar
Awsome, Klaus! Have you changed the IGV since last time? I remember there was a bit of swirl left behind in the previous tests. As good as it is at c.300W, I still think you need to put 1kW thru it. BTW, what's the fan swept area? What's the outlet dia?

Sep 06, 2004, 12:29 PM
wood basher
nhoj62's Avatar
are u using a brushed or brushless motor in this thing, because 15.4v is abit high for a normal brushed motor, unless u got one like an astro. do u have a pic of the motor before u put it in the fan?.
an as stumax says wot are the physical dimensions of the thing?

cheers klaus keep up the good work!

Sep 06, 2004, 12:55 PM
If you switch to a 0.80 efficient brushless motor, not only can you put in more power to the fan, you should also see a 2.56 gram/watt specific thrust of the the whole package. That would be nice, considering most setups are running closer to 2.0 g/w electrically.
Sep 07, 2004, 03:27 AM
Registered User
so we should be able to expect 2.5kg of thrust per 1000 watts input? where did you get these figures gfcermac ?
Sep 07, 2004, 08:23 AM
Registered User
Originally Posted by stumax
Awsome, Klaus! Have you changed the IGV since last time? I remember there was a bit of swirl left behind in the previous tests. As good as it is at c.300W, I still think you need to put 1kW thru it. BTW, what's the fan swept area? What's the outlet dia?Stu.
Hi Stu

yes, I "tweaked" the trailing edges of the stator blades a bit, as much as possible without dismanteling the whole assembly. Saves me obviously to make new rotor blades immediately - though the revs are still higher than I wanted. The ratio Va/U for the same airflow has some bearing on the rotor efficiency. So there are still some points to be gained.

At the moment I'm limited to the 500W el.power - at least with this motor.
But I have already some parts for No. 3, so I think I will make a preproduction version with the MEGA AC n 22/30/3.

Have fun with fans

Sep 07, 2004, 08:48 AM
Registered User
Originally Posted by sukhoiboi
have tou any idea how much you will be charging for these fans klaus. Buck
Hi Buck

that's the ten thousand Dollar question.

But in the end it will be more or less in the $ 250 region.
Compared with the competition however you will get a better value for money, e.g. thrust nozzle (two lengths available according to your build), an inlet duct, as shown on the drawing, which gets the inlet down to a circular cross section of 70mm and not a fan annulus, and higher efficiency.
I have been thinking to accompany each of my EDFs with a printed version of the article series which has been started in Q&EFI so that the customer can get aquainted with the theoretical background and can see for himself what to do and what not.
Here are again two pictures with technical data for the WM600

Have fun with fans

Sep 07, 2004, 08:58 AM
Model Designer
keven64's Avatar
Would a Hacker B50-18L go in that fan, Klaus ?


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Trainers part 2 JimJ Beginner Training Area (Aircraft-Electric) 3 Sep 15, 2001 12:31 PM
Jim Bourke's Moving Sale Part 2 -- Brushless motors jbourke Aircraft - Electric - Airplanes (FS/W) 1 Aug 07, 2001 02:00 AM
Hornet CP .... finally ... part 2 cyhyam Electric Heli Talk 90 Aug 05, 2001 09:40 PM
MIA's 12" House FLY Sub-Micro! NEWS!!! (Part 2) MicroRotors Electric Heli Talk 10 Jul 27, 2001 03:19 PM
The Twin Jet CG and Down Elevator Mystery - Part 2 rltucker Foamies (Kits) 9 Jun 29, 2001 10:26 PM