EDF Testing

[Rob]

I ran some tests on the 70mm EDFs I have lying around the house (turns out I had far too many squirrelled away) as I'm going to need one for a new plane.
I kind of suspected, and the tests have confirmed, that the more blades in an EDF the lower the efficiency (using the same motor, esc, and battery).
This mirrors what happens when you add blades to a standard propeller set up and why most of us use two blade props.
The Lander blew away the competition as far as thrust per watts, very nice fans, Hobby King also sells them as Alloy DPS (arrived in Lander packaging).
I would also like to test an Eflite or HET 70mm set up. If someone has one they would like tested just drop it off and I'll update the list. Not saying my tests are absolutely accurate but as I use the same test bench, batteries, esc, is will be a fair comparison of EDF systems.

[bdg]

Robert,

That is quite a comprehensive list! Interesting results!

How are you measuring thrust?

Brian

[JohnOSullivan]

Although I don't fly EDF, it is nice to see some practical bench tests on various setups.
I have been doing some similar testing on some Free Flight electric motors and various batteries and props and find them quite useful.

[Rob]

An electronic scale with a built in hold feature, the EDF is on a wheeled cart that pulls the scale. Very repeatable, get the same number within .01 kg using the same set up and fresh battery.
Interestingly the Lander comes in almost exactly as advertised (1.38kg).
http://brchobbies.com/catalog/product_i ... cts_id=656

The HK metal comes in lower than advertised (1.34kg printed on the side of the motor, this is not on their site any more) .

[retiredVTT]

quote, " that the more blades in an EDF the lower the efficiency " ...however, the nicer the sound!

The original edf sent with the 4S powered Squall had only 3 blades, the 3S model had 5 blades.

The sound everybody wants now comes from the 10 and 12 blade units, but as you say, you pay dearly for that sound as these units are drawing upwards of 100 amps at full throttle. Freewing increased the ESC value from 100 amp to 130 amp in their version 2 of the Stinger90.


Bill

[RocketManRC]

Very interesting Robert! Can you post some pictures of your test setup?

[Rob]

Will put some pictures on this evening. Not pretty but works. Greg dropped by and we tried the 12 Blade Change Sun with a different 2650 mAH 6S battery that was slightly overcharged. It drew 1250 Watts and 1.65 kg static thrust. Chews up the power but pulls hard, surprisingly the HK motor only got slightly warm after about a minute on full throttle since it's only rated at 900 Watts.

[Entropist]

Hi Rob,
I found this article some time back and had lost the link. I'm sure you'll find it interesting, especially the distinction between static and dynamic thrust:
http://southamptonmac.org.uk/doc/RS_EDF ... ice_v5.pdf

And check the summary by the same author, 2nd and 4th posts in this thread:
http://www.modelflying.co.uk/forums/pos ... p?th=56241


John

[Rob]

Interesting articles. Bench testing is basically just a way to compare the motor esc combinations under identical conditions to see which give the most thrust for the least watts. They're not very efficient but the 10 blade fans sure sound nice.

[steve]

Can you test this fan unit for me Rob? I am working on a large project