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Old Apr 20, 2011, 04:13 PM
HAL... Open the damn doors!
jfetter's Avatar
Miramar, Florida
Joined Jul 2007
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EDF Test Data, Thrust, Efflux, Amps... Anything I am missing?

So yes, another test thread and yes, I expect it to sink into oblivion Steve.

Truth is I just got a decent test stand (from RCWarez, great stand, you'll be seeing more of it in the future!) and I want to start putting up numbers for 120mm (and larger) EDF's. The issue is, I want to do it in a way best comparable to what others have done but not if it means optimizing it with a bell or special exhaust tubes. What I am after is a way where we can simply compare data without really caring if it's the BEST any particular fan can do, after all, it's about how they perform in relation to each other.

I will be testing the VioFan, VioFan ~2, Shubi 94 HDT and Vasa 120 to get the ball rolling and short of Thrust, Efflux and Amps, does anyone really care about other measurements? Obvisously I will state what Voltage the EDF is running and if asked, will test with alternate Voltages but I'd like to simply use NO bell and NO exhaust unless this is a major issue. At most I'd like to use a thrust tube only, a 1 foot pipe @ 70% fan diameter for the exhaust. What is the concensus on this, does anyone want to make a case for or against any particular test criteria?

Steve, I'd like you to weigh in, given your testing has been perhaps the only testing to span multiple vendors and products and to me seems un-biased. Is there a set of criteria you found "mandatory"? I don't care if the thread languishes, the intent is to provide data, as sweet or ugly as it may prove to be for the various fan vendors. I also won't sweeten the results, whatever they are in the stand with the exhaust only, that's what you'll see, raw data, head-to-head with no "enhancements" to make anyone look better than anyone else...

Note: I plan on modifying this post to include the test data in Excel format, so you won't have to search...

Jack
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Old Apr 20, 2011, 04:58 PM
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RPMs and air density! please.
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Old Apr 20, 2011, 05:05 PM
EDF all the way!
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Gilbert, Az
Joined Jun 1999
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Sounds good Jack.
Bob
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Old Apr 20, 2011, 05:08 PM
HAL... Open the damn doors!
jfetter's Avatar
Miramar, Florida
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Originally Posted by crypto666 View Post
RPMs and air density! please.
RPM, good point but does it matter, after all, it will turn the same for you as for me with the same Voltage, no? Air density, as in barometric pressure?

Jack
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Old Apr 20, 2011, 05:13 PM
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St.Catharines, Ontario
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^^^^he may also be asking about your height above/below sea level, since this will affect readings achieved by testing in different locations.
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Old Apr 20, 2011, 06:05 PM
The blade numbers go up to 11
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Sydney, Australia
Joined Aug 2002
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Jack, you have to use some sort of inlet lip. The idea behind testing a fan is to try to simulate how it will perform inside an aircraft but remove the effects of the ducting. The only way to do this properly is with a proper bellmouth, but a 6" long duct with a large (at least 20mm) radius at the front will do. A bellmouth will stabilise the flow by virtue of the fact that the area is reducing, and so the velocity inside it is increasing, so you get smoother flow (similar to what you'll get inside a good inlet duct) and the accelerating flow will help reduce the boundary layer thickness. Sure, in a real installation you will have significant BL thickness, but it varies from model to model and from airspeed to airspeed, so best to thin the BL as much as possible. Do a test without any form of inlet lip and you'll see what I'm talking about. The short duct is to allow the flow to stabilise before entering the fan. The numbers you'll get will be no indication of how the fan really performs, the current draw will be 10-30% lower and thrust up to 40% lower. I also don't use an exhaust, just use nothing. You can scale what the thrust will be by multiplying it by the expected exhaust area as a % of FSA, ie an 85% area exhaust will give you about 85% the static thrust of 100%. That's just a rough number but close enough. When you test, make a measurement of temperature and relative humidity, as they affect air density greatly, and the load on the fan will be pretty much proportional to the air density. Finally, be prepared to spend lots and lots of time testing, you'll be amazed at how much time it takes to run a repeatable set of tests on a fan.

Stu.
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Old Apr 20, 2011, 06:59 PM
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I look foward to your testing, as i don't trust any of those guys across the pond that have been doing this for years.
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Old Apr 20, 2011, 07:10 PM
Michigan
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Sounds good.
I'll throw my XPS fan in the mix if you like.
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Old Apr 20, 2011, 07:50 PM
HAL... Open the damn doors!
jfetter's Avatar
Miramar, Florida
Joined Jul 2007
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Quote:
Originally Posted by stumax View Post
Jack, you have to use some sort of inlet lip. The idea behind testing a fan is to try to simulate how it will perform inside an aircraft but remove the effects of the ducting. The only way to do this properly is with a proper bellmouth, but a 6" long duct with a large (at least 20mm) radius at the front will do.
Any easy way to create that 20mm radius? Could I use this, no radius but will it be close enough to even out the air flow?

Jack
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Old Apr 20, 2011, 07:52 PM
HAL... Open the damn doors!
jfetter's Avatar
Miramar, Florida
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Originally Posted by Scott9146 View Post
Sounds good.
I'll throw my XPS fan in the mix if you like.
Which fan (motor)? How many cells are you planning on running?

Jack
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Old Apr 20, 2011, 08:02 PM
shut up & fly
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United States, FL, Miami
Joined May 2001
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cereal bowl is cheaper, cut to fit.

the lips make a huge diff
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Old Apr 20, 2011, 09:01 PM
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St.Catharines, Ontario
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that's a fan-tastic idea. gonna have to try that one day.
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Old Apr 20, 2011, 09:12 PM
Michigan
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Quote:
Originally Posted by jfetter View Post
Which fan (motor)? How many cells are you planning on running?

Jack
I have the Orignal XPS with the gold Screamer motor. I was planning on 12s, but maybe 14s based on the reading i have been doing.
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Old Apr 20, 2011, 10:03 PM
HAL... Open the damn doors!
jfetter's Avatar
Miramar, Florida
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Originally Posted by hoser View Post
cereal bowl is cheaper, cut to fit.

the lips make a huge diff
Awesome! Plus this will give the Wife something new to be mad at me for, stealing tupperware!

Jack
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Old Apr 20, 2011, 10:04 PM
HAL... Open the damn doors!
jfetter's Avatar
Miramar, Florida
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Quote:
Originally Posted by Scott9146 View Post
I have the Orignal XPS with the gold Screamer motor. I was planning on 12s, but maybe 14s based on the reading i have been doing.
I'd like to see the numbers on that, seems to be some back-and-forth over the actual data...

Jack
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